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We have demonstrated the successful production of titanium phosphate glass microspheres in the size range of ~10-200 µm using an inexpensive, efficient, easily scalable process and assessed their use in bone tissue engineering applications. Glasses of the following compositions were prepared by melt-quench techniques: 0.5P2O5-0.4CaO-(0.1 - x)Na2O-xTiO2, where x = 0.03, 0.05 and 0.07 mol fraction (denoted as Ti3, Ti5 and Ti7 respectively). Several characterization studies such as differential thermal analysis, degradation (performed using a novel time lapse imaging technique) and pH and ion release measurements revealed significant densification of the glass structure with increased incorporation of TiO2 in the glass from 3 to 5 mol.%, although further TiO2 incorporation up to 7 mol.% did not affect the glass structure to the same extent. Cell culture studies performed using MG63 cells over a 7-day period clearly showed the ability of the microspheres to provide a stable surface for cell attachment, growth and proliferation. Taken together, the results confirm that 5 mol.% TiO2 glass microspheres, on account of their relative ease of preparation and favourable biocompatibility, are worthy candidates for use as substrate materials in bone tissue engineering applications.

The physical and chemical processes of formation of new compositions based on hollow glass microspheres are discussed in the article. The aim – to determine the influence of the structural heterogeneity of hollow glass microspheres of sodium silicate composition on the physical and chemical processes of formation of hot aluminum-matrix materials and coatings based on electric-Sv-AMg5 and Sv-08G2S. Researches are performed by electronic and optical microscopy, X-ray diffraction and electron microprobe analysis. The basis of the laws of formation of the new-metal materials and coatings based on new knowledge about the mechanisms of formation of a liquid phase based on the structural heterogeneity of hollow glass microspheres that can predict the physical and chemical processes at the metal – glass boundary surface. The theoretical researches allow us to establish the distinctive features of the structure formation depending on the method of preparing the compositions, and are aimed at improving their competitiveness. The results are used to predict the mechanical properties of the x-ray and metal-glass materials and coatings for their further use for the manufacture of structures of biological protection of ships and floating structures, for the transportation and storage of radioactive substances.

Thulium-doped (Tm-doped) tellurite glass microspheres are used as laser media. Emission lines at wavelengths near 1975 nm are observed. The onset of laser emission is achieved with 8.6 and 30 μW of coupled pump power and injected pump power, respectively, at a wavelength of 1554 nm. To the authors' knowledge, these are the lowest laser threshold values recorded for a Tm-doped tellurite glass microcavity. Intrinsic Q-factors above 10(6) for the undoped tellurite glass microspheres assert the quality of the fabrication processes. An optical intrinsic Q-factor comparison between Tm-doped tellurite and undoped tellurite microspheres shows that ion absorption is the dominant loss source at pump wavelengths. Lower lasing threshold powers and higher power conversion are observed at longer pump wavelengths in agreement with theoretical models.

Our objective was to determine if glass microspheres impregnated with two radionuclides, (90)Y as source of therapeutic beta emissions and (177)Lu as source of diagnostic gamma emissions can be useful for SPECT imaging during or after application of the (90)Y microspheres for treating of hepatic tumors. The glass-based microspheres labeled with (89)Y and lutetium (YAS (Lu)) or (89)Y and ytterbium (YAS (Yb)) were prepared by the sol-gel process where sol droplets directly were formed to gel microspheres. Results of the neutron activation indicate that such a combination of glass, microspheres allow bio-distribution studies by SPECT imaging with high resolution.

A method for production of porous composites from pyrogenic silicas, whose surface is preliminarily modified with methyl and trimethyl siloxane groups, was developed. In order to diminish shrinkage, glass microspheres and organosilicon compounds were used as modifiers. The total porosity of the composites obtained was 0.28 – 0.55.

Porous-wall hollow glass microspheres (PW-HGMs) are a novel form of glass material consisting of a 10- to 100-μm-diameter hollow central cavity surrounded by a 1-μm-thick silica shell. A tortuous network of nanometer-scale channels completely penetrates the shell. We show here that these channels promote size-dependent uptake and controlled release of biological molecules in the 3- to 8-nm range, including antibodies and a modified single-chain antibody variable fragment. In addition, a 6-nm (70-kDa) dextran can be used to gate the porous walls, facilitating controlled release of an internalized short interfering RNA. PW-HGMs remained in place after mouse intratumoral injection, suggesting a possible application for the delivery of anticancer drugs. The combination of a hollow central cavity that can carry soluble therapeutic agents with mesoporous walls for controlled release is a unique characteristic that distinguishes PW-HGMs from other glass materials for biomedical applications. From the Clinical Editor Porous-wall hollow glass microspheres (PW-HGMs) are a novel form of glass microparticles with a tortuous network of nanometer-scale channels. These channels allow size-dependent uptake and controlled release of biological molecules including antibodies and single-chain antibody fragments. PW-HGMs remained in place after mouse intratumoral injection, suggesting a possible application for the delivery of anti-cancer drugs.

Hydrogen storage in hollow glass microspheres is a safe and efficient method that is superior to storage in high-pressure vessels. Hollow glass microspheres are cheap, nontoxic, made from recycled glass, and commercially available in commodity quantities. On a weight basis, the storage capacity is greater than that in other methods, with potential storage capacities of 6–10 wt% for microspheres containing 69 MPa of hydrogen. The combination of high storage capacity with rapid response provided by photoinduced hydrogen diffusion in microspheres containing selected dopants offers good prospects for meeting the requirements for a hydrogen source for transportation and industrial applications.

This study examined the utility of sol–gel-derived bioactive glass microspheres (BGMs) as a reinforcement to improve the mechanical properties and biological performance of poly(e-caprolactone) (PCL) polymer. All of the PCL-BGMs composites produced, with a variety of BGMs contents (10, 20, and 30 wt %), showed a uniform distribution of the BGMs in the PCL matrix, particularly owing to their spherical shape and small size. This led to a considerable increase in the elastic modulus from 93 ± 12 MPa to 635 ± 179 MPa with increasing BGMs content from 0 to 30 wt %. Furthermore, the addition of the BGMs to the PCL polymer significantly increased the hydrophilicity of the PCL-BGMs composites, which led to a higher water absorption and degradation rate. The PCL-BGMs composite with a BGMs content of 30 wt % showed vigorous growth of apatite crystals with a high aspect ratio on its surface after soaking in the simulated body fluid for 7 days, resulting in the creation of a porous carbonate hydroxyapatite layer. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.

International audience; Sintering experiments on soda-lime glass microspheres have been performed using spark plasma sintering in the temperature range 485°C-560°C. Samples with relative densities between 64% and 99.6% have been obtained in about 10 min. For almost fully dense samples, the microstructure exhibits an unusual "interface-like" aspect for a glass. The densification mechanism has been investigated. For temperatures below 522°C, densification proceeds by formation of necks between spheres. For temperatures of and above 522°C, it is proposed that densification proceeds by viscous flow, accommodated by plastic deformation of microspheres, and is controlled by diffusion of oxygen anions in the glass.

Factor VIII functions in an enzyme complex upon the activated platelet membrane where phosphatidylserine exposure correlates with expression of receptors for factor VIII. To evaluate the specificity of phosphatidylserine-containing membrane binding sites for factor VIII, we have developed a novel membrane model in which phospholipid bilayers are supported by glass microspheres (lipospheres). The binding of fluorescein-labeled factor VIII to lipospheres with membranes of 15% phosphatidylserine was equivalent to binding to phospholipid vesicles (KD = 4.8 nM). Purified von Willebrand factor (vWf), a carrier protein for factor VIII, decreased membrane binding of factor VIII with a Ki of 10 micrograms/ml. Likewise, normal plasma decreased bound factor VIII by more than 90% whereas plasma lacking vWf decreased the binding of factor VIII by only 20%. Proteolytic activation of factor VIII by thrombin, which releases factor VIII from vWf, increased liposphere binding in the presence of vWf and in the presence of normal plasma. Although factor V is homologous to factor VIII and binds to lipospheres with the same affinity, purified factor V was not an efficient competitor for the membrane binding sites of factor VIII. These results indicate that phosphatidylserine-containing membrane sites have sufficient specificity to select thrombin-activated factor VIII from the range of phospholipid-binding proteins in plasma.

Several radioisotope generator systems exist in which the carrier-free daughter product would precipitate if present in macro amounts at pH levels at which the parent is soluble. Included among these are the {sup 68}Ge/{sup 68}Ga, {sup 90}Sr/{sup 90}Y, and {sup 47}Ca/{sup 47}Sc pairs. This paper reveals that in these systems, chemical separation can be achieved by Fajans adsorption of the radiocolloidal daughter products onto surfaces such as activated glass microspheres at an appropriate pH. This is followed by washing to remove the parent solution and desorption of the daughter crop by acid washes. Investigation of the Ge/Ga and Sr/Y systems demonstrated that this solid-phase extraction method is erratic, but can give daughter yields as high at 89% with separation factors up to {approximately} 10,000 form parent isotope. This method has the potential for producing daughter isotopes with a minimum of metal and organic impurities for labeling cells, receptor binding ligands, and antibodies for diagnostic and radiotherapeutic purposes.

The primary goal of this project is to demonstrate that hydrogen gas can be rapidly extracted from hollow glass microspheres (HGMS) using a photo-induced heating effect. The results of the project demonstrate that diffusion of hydrogen is readily induced by exposure to light from an IR lamp in transition metal-doped HGMS filled to as much as 5,000 psi with hydrogen gas, which contain approximately 2.2 wt% hydrogen. Doped HGMS in conjunction with optically induced outgassing provide a solution to the traditional limitation of HGMS – i.e., the slow release of hydrogen from HGMS that are heated using a furnace. This information will also be invaluable in designing process changes for future production of HGMS able to hold higher pressures of hydrogen.

Fairly uniform porous microspheres of poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) were synthesized using a particular microporous glass membrane (SPG). Average diameters of these spheres are from 2.5 to 38 μm with the coefficient of variation (CV) around 10%. A maximum specific surface area of 370 m2 /g was achieved. Uniform dispersion of MMA droplets was successfully prepared only when the swelling process reported by Higuchi and Misra was adopted. Two potential applications, one as a packing material for column chromatography, and the other as a carrier of enzyme immobilization, were demonstrated.

Bioactive glass is a promising osteoconductive silica-based biomaterial for guidance of new bone growth. On the basis of several in vitro studies, the material appears able to promote osteoblast functions. In our in vivo study, the osteopromotive effect of bioactive glass microspheres seemed to surpass the osteoinductive action of direct adenovirus-mediated human bone morphogenetic protein 2 (BMP-2) gene transfer in a noncritical size bone defect model. The current study was initiated to elucidate the molecular mechanism behind bioactive glass action with or without adjunct BMP-2 gene transfer. A standardized bone defect of the rat tibia was filled with bioactive glass microspheres and injected with adenovirus carrying the human BMP-2 gene (RAdBMP-2). Control defects were left empty or filled with bioactive glass microspheres with injection of adenovirus carrying the lacZ reporter gene or saline. Quantitative polymerase chain reaction confirmed the expression of the transferred human BMP-2 gene at the defect area at 4 days, but not in intact reference tissues. Bone matrix components (collagens I, II, and III, osteocalcin, osteonectin, and osteopontin) and resorption markers (cathepsin K and MMP-9), determined by Northern analysis, showed a completely different pattern of gene expression in defects filled with bioactive glass compared with control defects left to heal without filling. Bioactive glass induced a long-lasting production of bone matrix with concurrent upregulation of osteoclastic markers, a sign of high bone turnover. Combining RAdBMP-2 gene transfer with bioactive glass decelerated the high turnover, but did not influence the balance of synthesis and resorption. This molecular analysis confirmed not only the highly osteopromotive effect of bioactive glass microspheres, but also the accelerated rate of new bone resorption on its surface. At least in noncritical size defects this impact of bioactive glass seems to saturate new bone formation on its surface and thereby overshadow the effect of BMP-2 gene transfer.

A new encapsulation method was investigated in an attempt to develop an improved palladium packing material for hydrogen isotope separation. Porous wall hollow glass microspheres (PWHGMs) were produced by using a flame former, heat treating and acid leaching. The PWHGMs were then filled with palladium salt using a soak-and-dry process. The palladium salt was reduced at high temperature to leave palladium inside the microspheres.

Dysprosium lithium-borate (DyLB) glass microspheres have been developed as a biodegradable radiation delivery vehicle for the treatment of rheumatoid arthritis and other diseases. Radioactive microspheres of these glasses are intended to be injected into a joint infected with rheumatoid arthritis to safely deliver a localized dose (100 Gy) of beta radiation. Once injected, the microspheres react nonuniformly with body fluids. The nonradioactive, lithium-borate component is dissolved from the glass, whereas the radioactive (165)Dy reacts with phosphate anions in the body fluids, and becomes "chemically" trapped in a solid, dysprosium phosphate reaction product that has the same size as the unreacted microsphere. The glass microspheres lose approximately 80% of their weight after nonuniform reaction (1 day), but the dysprosium phosphate reaction product is slowly metabolized by the body over several months. Ethylenediaminetetraacetate (EDTA) chelation therapy can be used to dissolve the dysprosium phosphate reaction product in vitro in2 h. The dysprosium phosphate reaction product which formed in vivo in the joint of a Sprague-Dawley rat was also dissolved by EDTA chelation therapy in1 week, without causing any detectable joint damage. The combination of DyLB glass microspheres and EDTA chelation therapy provides a unique "tool" for the medical community because it can deliver a large dose (100 Gy) of localized beta radiation to a treatment site within the body, followed by complete biodegradability.

Micro-resonators have attracted considerable attention as a potential geometry for photonic devices used in multiplexing, memory and switching. These all-optical-resonators allow light at certain wavelengths to build up in intensity allowing nonlinear effects to be seen for much lower input power than in a bulk material. We report here on microspheres made from gallium-lanthanum-sulphide glass. Spheres have been produced with diameters from less than 1 mum up to 450 microm, and we demonstrate a first measured quality factor of 8x10(4) at 1.55 microm, for a chalcogenide sphere diameter of 100 microm. We also predict an ultimate Q of up to 4x10(10) at 3 microm.

Split-flow thin (SPLITT) separation cells, consisting of submillimeter thick rectangular channels having now splitters at both inlet and outlet ends, were operated continuously using the earth's gravitational field as a driving force to prepare narrow fractions from polydisperse micron-size glass bead populations. Equations arc shown that make it possible to achieve a binary fractionation around a specified cutoff particle diameter by the control of inlet and outlet flowrates. Using a single separation cell, each narrow fraction was obtained by a two step fractionation. one dividing the panicle population around the upper desired limit and the other around the lower desired limit of particle diameters. The clean fractionation by SPLITT cell operation was verified by scanning electron microscopy, which also provided the mean particle diameter and the coefficient of variation for each fraction. The consistency of size distribution results was also examined by steric field-flow fractionation.

This paper reports the first observation of chromatic and intensity optical bistability (OB) in a commercial, active, phosphate glass (Schott IOG-2) microsphere driven by thermal avalanche at room temperature. This is, to the best of our knowledge, the first report of simultaneous intensity OB (at multiple wavelengths) and chromatic OB in a single material.

Purpose: The aim of this study was to fully characterize newly developed radioactive rhenium glass microspheres in vivo by determining their biodistribution, stability, antitumor effect, and toxicity after hepatic arterial injection in a syngeneic rat hepatoma model. The dose response of the tumors to increasing amounts of radioactive 186 Re and 188 Re microspheres was also determined. Methods and Materials: Rhenium glass microspheres were made radioactive by neutron activation and then injected into the hepatic artery of Sprague–Dawley rats containing 1-week-old Novikoff hepatomas. The biodistribution of the radioactivity and tumor growth were determined 1 h and 14 days after injection. Results: Examination of the biodistribution indicated a time-dependent, up to 7-fold increase in Novikoff hepatoma uptake as compared to healthy liver tissue uptake. After 14 days, the average T:L ratio was 1.97. Tumor growth in the rats receiving radioactive microspheres was significantly lower than in the group receiving nonradioactive microspheres (142% vs. 4824%, p = 0.048). Immediately after injection, 0.065% of the injected radioactivity was measured in the thyroid; it decreased to background levels within 24 h. Conclusion: Radioactive rhenium microspheres are effective in diminishing tumor growth without altering hepatic enzyme levels. The microspheres are safe with respect to their radiation dose to healthy tissue and radiation release in vivo and can be directly imaged in the body with a gamma camera. Furthermore, rhenium microspheres have an advantage over pure beta-emitting microspheres in terms of preparation and neutron-activation time. In sum, this novel radiopharmaceutical may provide an innovative and cost-effective approach for the treatment of nonresectable liver cancer.

It was found that modification of the surface of nickel-plated hollow glass microspheres with N-oxide-Cl-alkyldimethylamine causes overcharging of their surface and as a result improves wetting of particles of the solid phase with acrylic latex water-emulsion paint. The conductive paint coatings are characterized by high electrical conductivity. The paint developed can be used to protect people and equipment from electromagnetic radiation.

ER fluids (ERFs) typically consist of a concentrated dispersion of solid particles in a non-conducting base fluid. As a result, particle sedimentation represents a significant problem for many formulations since, in most cases, the particulate phase is of higher density than the base fluid. To remedy this situation, higher density fluids have been widely used in ERFs (ρ > 1.1 g/cc) rather than less expensive mineral oils that display lower densities (0.8-0.9 g/cc). An alternative approach to density "matching" has been explored by Qi and Shaw who have successfully developed ERF particles based on low density, micron-sized hollow glass "balloons" that are polymer coated. These microballons are commercially available from the PQ Corporation and they exhibit an effective density of 0.7 g/cc. Using these materials, it becomes possible to engineer ERF particles that are "neutrally buoyant" in mineral oils by adjusting the coating weight of an ER active polymer on the glass spheres. In this study, a simple solution coating process was developed exploiting the unique surface chemistry of glass which contains -Si-O-Si- and -Si-OH sites capable of hydrogen bonding with hydrophillic polymers. A number of water-soluble ionic polysaccharides were evaluated as coatings because of their ability to form hydrogen bonds with glass surfaces. A synthetic alcohol-soluble polymer, sulfonated polyphenylene oxide, was also evaluated because of its thermal stability and mechanical durability.

This article deals with the problem of increasing ecological safety, effectiveness and quality of mortars and grouting mortars. It is achieved by introduction of hollow glass microspheres into the cement mortar. Hollow glass microspheres have amorphous walls, which consist of silicon, sodium and boron oxides. The article considers physical-and-mechanical and environmental properties of hollow glass microspheres, the results of chemical, X-ray, microstructure and granulometric analyses of the microspheres are given. The application recommendations for the hollow microspheres are given, the role of microspheres in the process of the lightweight cement mortars and grouting mortars structure formation is noted. The experimental results are presented.

Purpose: To develop a realistic model for the dosimetric distribution and to evaluate biological effective dose (BED) of Praseodymium‐142 (Pr‐142) and Yttrium (Y‐90) glass microspheres in blood vessel within tumor for treating hepatocellular carcinoma (HCC). Methods: Blood vessels filled with uniformly distributed microspheres were modeled and positioned along the central axis of the tumor. Cylindrical blood vessels had diameters ranging from 25.0 to 75.0 μm, while tumor radii were varied from 0.2 to 1.0 cm, based on average values reported in the literature. Physical dose distributions due to a single blood vessel were simulated using Monte Carlo (MCNPX2.6) for large combinations of blood vessel and tumor sizes. HCC doubling times (DT) ranging from 17 to 720 days were used as a parameter in the BED calculations. To quantify the BED coverage throughout the entire tumor volume, a BED volume histogram (BEDVH) was calculated for each nuclide. Results: The physical dose distribution for both nuclides was comparable, e.g. dose per decay of 1.95 × 10−12 Gy and 2.36 × 10−12 Gy were obtained for Pr‐142 and 90‐Y point source at the same point, respectively. Pr‐142 distribution yielded higher BED coverage of the tumor volume for all DT, blood vessel sizes, and tumor sizes. The differences were higher for fast proliferating tumors and smaller tumor and blood vessel sizes, e.g. for 17 days DT, 20 μm blood vessel diameter and 0.2 cm tumor radius, BED coverage of 150 Gy was 48.7 % higher for Pr‐142. Conclusion: Blood vessels modeled within tumors made possible the quantification of the dose range due to a single embolized blood vessel. From BEDVH evaluation it appeared that the biological effectiveness throughout the tumor was sensiμtive to the radionuclide used, tumor sizes, and blood vessel sizes. The work was partially supported by a Ralph E. Powe Junior Faculty Enhancement Award provided by Oak Ridge Associated Universities.

Thrombosis, recurrent fetal loss, and thrombocytopenia are clinical manifestations associated with circulating antibodies that recognize cardiolipin (CL)- or phosphatidylserine (PS)-dependent antigens. Enzyme-linked immunosorbent assays (ELISAs) are generally used to determine the presence and specificity of antiphospholipid antibodies (aPLs). However, the presentation of the phospholipid antigen in the ELISA assay is unknown. In this study, we determined the specificity of three mouse monoclonal aPLs for phospholipid bilayer membranes. These monoclonal aPLs had been characterized by ELISA to have different specificities for CL and PS and were designated BA3B5C4 (CL+/PS+), 3SB9b (CL-/PS+), and D11A4 (CL+/PS-). Bilayers composed of 0-100% PS or CL in phosphatidylcholine (PC) were formed on the surface of 1.6 microns diameter glass microspheres to permit analysis by flow cytometry. BA3B5C4 and 3SB9b bound specifically to both PS- and CL-containing bilayers, and binding increased with increasing percentage of anionic phospholipid. The threshold for PS-dependent binding was 20 mol% PS for both BA3B5C4 and 3SB9b. For CL-dependent binding, the threshold was below 25 mol% CL for both of these antibodies. Binding to PS-containing bilayers was tested as a function of ionic strength for BA3B5C4 and 3SB9b. The ionic strength dependence of the binding suggested that the intermolecular attractive forces between anti-PS antibodies and PS-containing bilayers are predominantly multiple weak electrostatic bonds. D11A4 bound only to bilayers composed of 100% PS and 100% PC, and this antibody did not bind to CL-containing bilayers. The binding specificities of these aPLs to bilayer membranes suggest that, in this system, the conformation of the epitope involving CL, and perhaps PS, is different from that expressed in the routine clinical ELISA. Two of the monoclonal antibodies reacted in this model system at the low levels of PS typically externalized in the plasma membranes of activated platelets, apoptopic lymphocytes, and senescent red blood cells: thus, these surfaces are plausible candidates for the site of pathologically relevant antibody interactions.

The practical design of composite material suggests that there is a need for an improved quantitative understanding of the interaction between acoustic waves and microspheres. The multiple scattering method is used to investigate the sound attenuation of the viscoelastic polymer containing hollow glass microspheres. Then the dynamics of the hollow glass microspheres is investigated by reference to the elements of the scattering matrices. It shows that the dilatational vibration of the microsphere plays a key role in the sound attenuation within the viscoelastic polymer composite at the quasistatic region. The thinner glass shell undergoes more severe dilatational vibration and induces more attenuation in the polymer composite.

Using trans-2-butene and hydrogen as the precursor, the glow discharge polymer (GDP) films are successfully coated on glass microspheres with diameters of 350—400 μm and thicknesses of 2.5—3 μm by the glow discharge polymerization technology. Glass/GDP microsphere is heated to test its thermal stability, whose process is the same as the D2 gas charge procedure. The chemical structures, the thermal stabilities of the GDP films, the morphologies of glass/GDP microspheres are characterized by the FT-IR, TG, stereoscopic microscope and X-radiography technology. The Results show that the C/H and C C in GDP films decrease as pressure increases. Their thermal stabilities are better, and the adhesion between GDP film and glass microsphere is enhanced when the GDP coatings are fabricated at lower pressures.

The use of hollow glass microspheres in syntact foam plastics with organosilicon binders is described. The physicomechanical and thermophysical properties of the heat-insulating materials obtained are investigated.

We present experimental results on an all-optical, thermally-assisted technique for broad range tuning of microsphere cavity resonance modes to arbitrary probe wavelengths. An Er:Yb co-doped phosphate glass (Schott IOG-2) microsphere is pumped at 978 nm via the supporting stem and the heat generated by absorption of the pump light expands the cavity and changes the refractive index. This is a robust tuning method that decouples the pump from the probe and allows fine tuning of the microsphere's whispering gallery modes. Pump/probe experiments were performed to demonstrate thermo-optical tuning to specific probe wavelengths, including the 5S1/2 F = 3 to 5P3/2 F' = 4 laser cooling transition of 85Rb. This is of particular interest for cavity QED-type experiments, while the broad tuning range achievable is useful for integrated photonic devices, including sensors and modulators., 20 pages, 5 figures. To appear in Japanese Journal of Applied Physics

Glasses used in photonics research and industry are required to be homogeneous and stable. Our study of chalcogenide microspheres indicates that significant deterioration can take place at the surface of such micro-optics in a few years at normal environmental conditions. Chalcogenide glass (Ga2S3:La2S3, 70:30 (GLS)) microspheres of order one hundred microns in diameter have been focused ion beam (FIB) milled and imaged to show material and morphological changes at the surface. Such microspheres are used as whispering gallery mode cavities for micro-sensors, for devices in optical communications and, with rare earth doping, for micro-lasers. It is the optical quality of the glass at, and near, the surface, that is most important in these applications. With the surface corrosion shown, the Q of a whispering gallery mode resonator based on such a microsphere will reduce dramatically over time. More generally, the result may have significant implications for the production, storage, and usage of uncoated chalcogenide micro-optics. The FIB technique emerges as an additional tool for characterizing glass morphology and homogeneity.

Compact microspheres with high-quality (Q) whispering gallery modes are required for many applications involving liquid immersion, such as sensing nanoparticles and studying resonant radiative pressure effects. We show that high-index (1.9 and 2.1) barium titanate glass (BTG) microspheres are perfect candidates for these applications due to their high-Q (∼10(4) in the 1100-1600 nm range) resonances evanescently excited in spheres with diameters of 4-15 μm. By reattaching the spheres at different positions along a tapered optical fiber, we show that the coupling constant exponentially increases with thinner fiber diameters. We demonstrate the close to critical coupling regime with intrinsic Q=3×10(4) for water immersed 14 μm BTG spheres.

Plasma spheroidization exploits the high temperature and high enthalpy available in the thermal plasma jet to melt irregularly shaped powder particles and quench them to get dense spherical particles. Plasma spheroidization is a versatile process and can be applied to metals, ceramics, alloys and composites to obtain fine spherical powders. Radioactive microspheres incorporated with high energetic beta emitting radioisotopes have been reported to be useful in the palliative treatment of liver cancer. These powders are to be prepared in closer range of near spherical morphology in the size range 20-35 microns. Inactive glass samples were prepared by heating the pre-calculated amount of glass forming ingredients in a recrystallized alumina crucible. The glass was formed by keeping the glass forming ingredients at 1700°C for a period of three hours to form a homogeneous melt. After cooling, the glass was recovered from the crucible by crushing and was subsequently powdered mechanically with the help of mortar and pestle. This powder was used as the feed stock for plasma spheroidization using an indigenously developed 40 kW plasma spray system. Experiments were carried out at various operating parameters. The operating parameters were optimised to get spheroidised particles. The powder was sieved to get the required size range before irradiation.

The preparation of nylon-6/hollow glass microspheres composites by the RIM procedure, leading to a new material with reduced density and increased stiffness, is described. The shear moduli of these composites show a linear dependency on the filler concentration. By means of a modified Kerner equation the shear moduli of the various glass spheres were calculated. A linear dependency between the shear modulus of a glass sphere and its wall thickness is demonstrated. A direct method for the determination of the shear moduli of those glass spheres having a density lower than the matrix material is presented.

Sputter‐deposited platinum coatings on glass microspheres were severely disrupted after a deuterium–tritium (DT) mix was permeated into the hollow spheres under elevated temperature and pressure conditions. Optical, scanning electron microscope, and x‐ray diffraction techniques were used to study the disrupted structure. This characterization, combined with results of separate sputtering experiments and literature information, suggested that hydrogen gas was occluded in the platinum rift structure during the high‐pressure fill process. Subsequent release of the hydrogen pressure resulted in an expansion of the occluded gas; because diffusion rates were too low to relieve the stress concentrations thereby produced, the platinum coating delaminated along weakly bound interfaces. Neither oxygen present within the platinum structure nor water (as a Pt‐catalyzed H2+O2 reaction product) appeared to contribute significantly to this disruption.

The nuclear track technique (NTT) is used to produce porous glass microspheres. The nuclear tracks randomly penetrate the material so that the resultant pores are interconnected. The result of this process is the creation of latent, radiation-damaged regions by the charged particles emitted from the neutron-induced fissioning of 235 U, an isotope of uranium which in trace quantities either naturally occurs in or surrounds the microspheres. The damaged regions, or “tracks” are then enlarged to optically visible tracks with the aid of a light microscope by chemically etching the material. The number of tracks or pores created both at the surface and within the microsphere is dependent upon the neutron fluence used to induce the fission of 235 U, provided that the bulk uranium is constant in the microspheres. Pore diameter is determined by the concentration of the etching solution and the etching time.

Thick platinum coatings on glass microspheres are needed for proposed laser fusion targets. The spherical nature of these substrates, combined with the small dimensions (about 100 μm in outside diameter), makes it difficult to achieve a smooth and uniform coating. Coating problems encountered include a rough surface and a porous microstructure from the oblique incidence and lack of temperature and bias control, “clumping” of the microspheres causing non-uniformities, and particle accumulation causing “cone” defects. Sputtering parameters significantly affecting the coatings include the total pressure, the d.c. substrate bias and the addition of doping gases. Using an ultrasonic vibrating screened cage and an r.f. magnetron sputter gun, we successfully batch coated microspheres with up to 6 μm of platinum, with a surface roughness of 200 nm, a thickness non-concentricity of 300 nm and a density greater than 98% of the bulk platinum density.

Hollow glass microspheres (HGS) for laser fusion targets were fabricated in the system Na2O-B2O3-SiO2 from NaOCH3, B(OCH3)3 and Si(OC2H5)4. Gel powders prepared from metal alkoxides and urea liberate H2O, CO2 and NH3 gases, evolution of which takes place completely at about 500° C. The precursor of HGS is formed by the encapsulation of these gas components in the glass layer formed at the surface of the powder. HGS are produced from the gel powders having both a melting temperature lower than about 1000° C and a viscosity at that temperature lower than 105 P. In the Na2O-B2O3-SiO2 system, the compositions from which HGS are produced are those containing 55–75 wt% SiO2 and 0–20 wt% B2O3. HGS ranging from 100–500μm diameter and 0.5–7.0μm wall thickness are obtained by change of urea content.

Polytetrafluoroethylene (PTFE) coatings are used in many applications and processing industries. With their use, they wear out and lose properties and must be replaced by new ones if the cost of the element so advises. There are different stripping techniques, but almost all of them are very difficult and require strict environmental controls. It is a challenge to approach the process through efficient and more sustainable techniques. In the present work, we have studied the stripping of PTFE coatings by projection with abrasives (1 step) as an alternative to carbonization + sandblasting procedures (2 steps). For this purpose, different types of abrasives have been selected: brown corundum, white corundum, glass microspheres, plastic particles, and a walnut shell. The tests were performed at pressures from 0.4 to 0.6 MPa on PTFE-coated aluminium substrates of EN AW-5182 H111 alloy. Stripping rates, surface roughness, and substrate hardness have been studied. Scanning electron microscopy (SEM) images of sandblasted specimens have also been obtained. All abrasives improved mechanical and surface properties in one-step vs. two-step processes. The abrasives of plastic and glass microspheres are the most appropriate for the one-step process, which increases the hardness and roughness level Ra in the substrate. Corundum abrasives enable the highest stripping rates.

Synaptic vesicles from rat brain were immobilized on glass microspheres covalently coated with poly-L-lysine. Using a potassium tartrate perfusion medium, the vesicular accumulation and methamphetamine-induced release of (L)-3H-norephinephrine could be conveniently monitored in a flow experiment.

The paper deals with the synthesis and characterization of undoped and doped (Bi, Ni and Cr) aluminate glass microspheres with gehlenite (2CaO.Al 2 O 3 .SiO 2 ) matrix. Polydisperse systems of glass microspheres were prepared by flame-spraying technique. All composition were partially crystalline, with gehlenite as main crystalline phases, except undoped composition, where hatrutite is the main crystalline phase. Magnetic measurements showed that gehlenite glass systems are relatively complicated magnetic systems. Magnetic behaviour of microspheres is a function of the temperature, magnetic field and the content of various dopants.

Three poly(amido-amine)s of similar structure in the form of highly hydrophilic crosslinked resins, have been prepared, and tested for their heparin-adsorbing capacity at physiological pH. They showed different capacities, and their capacities were related to their basicities. One of the same polymers was grafted on the surface of glass microspheres. After treatment, it was shown that the microspheres could adsorb significant amounts of heparin. In all cases most of the adsorbed heparin was hardly eluted with saline, plasma, or blood, but could be recovered by eluting with 0.1 M NaOH. The resins were found to have some haemolytic properties, but no haemolysis was observed with the grafted microspheres.

In this study, hollow glass microspheres (HGM) filled polypropylene (PP) composites were prepared by melt extrusion method. In order to understand the effect of structure and physical properties on the performance of composites, the morphologies, tensile properties and thermal conductivities of composites were investigated. The surface of HGMs were modified with 3-(Trimethoxysilyl) propyl methacrylate ( TMSM ) silane coupling agent to improve the compatibility between PP matrix and HGMs. The physical properties of silane modified and unmodified HGMs were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope (SEM). The effect of HGM content and surface modification of HGM on morphological, mechanical and thermal conductivity properties of composites were evaluated. The results indicated that the surface modification of HGM enhance the interfacial region between HGM and polymer matrix. When 20 wt % modified HGM was added to neat PP, the modulus of the composite obtained was 1057 MPa, increasing by 15.1% compared with that of the PP/unmodified HGM composite. However, any positive or consistent effect of surface modification and HGM addition on thermal conductivity of samples can not be observed.

Gehlenite glass microspheres, doped with a different concentration of Bi3+ions (0.5, 1, 3 mol%), were prepared by a combination of solid-state reaction followed by flame synthesis. The prepared glass microspheres were characterized from the point of view of surface morphology, phase composition, thermal and photoluminescence (PL) properties by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and PL spectroscopy. The closer inspection of glass microsphere surface by SEM confirmed a smooth surface. This was further verified by XRD. The basic thermal characteristics of prepared glasses, i.e.Tg(glass transition temperature),Tx(onset of crystallization peak temperature),Tf(temperature of the inflection point of the crystallization peak) andTp(maximum of crystallization peak temperature), were estimated from the DSC records. High-temperature XRD experiments in the temperature interval range 600–1100°C were also performed. The PL emission properties of prepared glasses and their polycrystalline analogues (glass crystallized at 1000°C for 10 h) were studied in the visible and near-infrared (NIR) spectral range. When excited at 300 nm, the glasses, as well as their polycrystalline analogues, exhibit broad emission in the visible spectral range from 350 to 650 nm centred at about 410–450 nm, corresponding to Bi3+luminescence centres. The emission intensity of polycrystalline samples was found to be at least 30 times higher than the emission of their glass analogues. In addition, a weak emission band was observed around 775 nm under 300 nm excitation. This band was attributed to the presence of a minor amount of Bi2+species in prepared samples. In the NIR spectral range, the broad band emission was observed in the spectral range of 1200–1600 nm with the maxima at 1350 nm. The chemistry of Bi and its oxidation state equilibrium in glasses and polycrystalline matrices is discussed in detail.

A refined model of a mid-IR amplifier, constituted by a tapered chalcogenide fiber coupled to an erbium-doped chalcogenide microsphere, is integrated with a global solution search procedure based on particle swarm optimization approach. It is implemented in a computer code in order to obtain an inversion algorithm useful to evaluate the spectroscopic parameters of rare-earth-doped glass microspheres. The rare earth parameters can be recovered by means of the optical gain measurement. The error in evaluation of the erbium lifetime $\tau _{41}$ is