Fused Quartz Tube Research Articles

Mechanism of catalytic subcritical water oxidation of m-nitroaniline and nitrogen conversion by CuCo2O4 catalyst

Catalytic subcritical water oxidation (CSWO) of M−nitroaniline (M−NA) was investigated in a fused quartz tube reactor (FQTR) to determine the effects of reaction parameters on M−NA mineralization rate, total nitrogen (TN) removal rate and nitrogen-containing products distribution. The results indicated that the TN removal rate was only 26.36 % at 200 °C, 200 % excess oxidant and 15 min residence time, while the TN removal rate reached 67.83 % at 360 °C in SWO of M−NA. Compared with SWO of M−NA, the mineralization rate and TN removal rate of CSWO of M−NA increased by about 10 % and 17.83 %, respectively. The main reason is mainly attributed to CuCo2O4 catalyzing the preferential reaction of ·NO2 with ·NH4, hastening N2 generation. Alternatively, the CuCo2O4 catalyst may induce a direct reaction between the nitro and amino groups on M−NA within the benzene ring to form N2. Moreover, degradation pathways and nitrogen migration mechanism of M−NA under SWO/CSWO conditions were proposed. These crucial findings are expected to guide the development of environmentally sustainable catalytic technologies towards addressing significant water pollution challenges.

Catalytic supercritical water oxidation of o-chloroaniline over Ru/rGO: Reaction variables, conversion pathways and nitrogen distribution

To ascertain the reaction variables on o-chloroaniline (o-ClA) mineralization, total nitrogen (TN) removal rate, and N-species distribution, o-ClA was subjected to catalytic supercritical water oxidation (CSCWO) in a fused quartz tube reactor (FQTR). The findings demonstrated that when the temperature, reaction time, and excess oxidant were 400 °C, 90 min, and 150%, respectively, the mineralization rate of o-ClA could reach more than 95%. Moreover, potential degradation pathways of o-ClA in supercritical water oxidation (SCWO) was proposed according to the GC-MS results. TN removal rate is significantly impacted by Ru/rGO, despite the fact that its catalytic effect on the mineralization of o-ClA was not particularly noteworthy. Compared with no catalyst, the TN removal rate of o-ClA obviously increased from 44.1% to 90.3% at 400 °C, 10 wt% Ru loading, 90 min and 200% excess oxidant. In addition, N-species distribution in SCWO and CSCWO were also investigated. Results indicated that the Ru/rGO catalyst could accelerate the oxidation of ammonia-N and convert it to nitrate-N, promoting N2 generation. Finally, the possible N transformation pathway in CSCWO of o-ClA was proposed. As a result, this work offers fundamental information about o-ClA catalytic oxidation removal in the SCWO process.

A reactor for time-resolved X-ray studies of nucleation and growth during solvothermal synthesis.

Understanding the nucleation and growth mechanisms of nanocrystals under hydro- and solvothermal conditions is key to tailoring functional nanomaterials. High-energy and high-flux synchrotron radiation is ideal for characterization by powder X-ray diffraction and X-ray total scattering in real time. Different versions of batch-type cell reactors have been employed in this work, exploiting the robustness of polyimide-coated fused quartz tubes with an inner diameter of 0.7 mm, as they can withstand pressures up to 250 bar and temperatures up to 723 K for several hours. Reported here are recent developments of the in situ setups available for general users on the P21.1 beamline at PETRA III and the DanMAX beamline at MAX IV to study nucleation and growth phenomena in solvothermal synthesis. It is shown that data suitable for both reciprocal-space Rietveld refinement and direct-space pair distribution function refinement can be obtained on a timescale of 4 ms.

Catalytic oxidation of o-chloroaniline in hot compressed water: Degradation behaviors and nitrogen transformation

Catalytic oxidation of o-chloroaniline (o-ClA) in hot compressed water (HCW) was investigated in a fused quartz tube reactor (FQTR) to determine the effects of catalyst, temperature, oxygen stoichiometric ratio (OSR) and reaction time on o-ClA mineralization, total nitrogen (TN) removal rate and nitrogen-containing products distribution. The results showed that o-ClA can be effectively degraded in HCW. With the increased of OSR, retention time and temperature or added of Mn2O3 as catalyst, the mineralization rate of o-ClA and the removal rate of TN increased. Ammonia-N was the main nitrogen-containing intermediate product of o-ClA degradation, however, when the oxidant was excessive, ammonia-N was oxidized to form nitrate-N. Althought the catalytic effect of Mn2O3 on the mineralization of o-ClA was not outstanding, it promoted the removal of ammonia-N from the benzene ring, improved the degradtion of ammonia-N, and inhibited the production of nitrate-N. GC–MS analyzed results indicated that o-chlorophenol was the main degradation intermediate product of o-ClA in HCWO process. Meanwhile, the potential degradation pathway of o-ClA was proposed. This work thus provides basic knowledge about o-ClA catalytic oxidation removal in HCW process.

Crystal structure and physical properties of Ba2Nb3S8I: A new misfit-layered transition-metal dichalcogenide superconductor

Single crystals of Ba2Nb3S8I have been grown using iodine-vapor transport in fused-quartz tubes. The crystals form as flakes with typical areas of 5–10 mm2 and thicknesses of 5–11 μm. The crystal structure was determined using single-crystal x-ray diffraction with the aid of an APEX II CCD diffractometer. The structure shows trigonal symmetry with space group P31c and lattice parameters a = b = 10.0156(5) Å and c = 25.1414(15) Å. Compositional analysis via x-ray spectroscopy confirms the presence of iodine. Superlattice reflections are evident in x-ray precession images. Measurements of the electrical resistivity reveal a metallic temperature dependence and superconductivity near 1 K. Polycrystalline samples of Ba2Nb3S8I were made in order to have samples large enough for other bulk physical properties measurements. Magnetic susceptibility reveals antiferromagnetism below 275 K. The coexistence of antiferromagnetism and superconductivity is surprising. Specific heat measurements reveal the electronic coefficient γ = 3.95(66) mJ/mol K2. The jump in the specific heat at the superconducting transition temperature Tc (ΔC/γTc = 1.4(2)) and the energy gap associated with the superconducting state (Eg = 0.405(17) meV) agree well with BCS theory.

From Ta2S5 Wires to Ta2O5 and Ta2O5-x S x.

Synthesis routes to forming novel materials are oftentimes complicated and indirect. For example, Ta2S5 has only been found as an unwanted byproduct of certain chemical reactions, and its properties were unknown. However, here we demonstrate the growth of Ta2S5 wires with steel-like tensile strength, which are also precursors for the first controlled synthesis of long, mesoscopic Ta2O5 wires and superconducting Ta2O5–xSx wires. Single-crystal wires of tantalum pentasulfide, Ta2S5, were first grown using vapor transport from polycrystalline XTa2S5, sulfur, and TeCl4 in fused-quartz tubes, where X = Ba or Sr. Crystals form as long wires with lengths on the order of a few centimeters and varying cross sections as small as 25 μm2. They were found to have steel-like tensile strength, and their crystal structure was determined using X-ray diffraction to be monoclinic with space group P2/m and with lattice parameters a = 9.91(7) Å, b = 3.82(5) Å, and c = 20.92(2) Å. Electrical resistivity measurements reveal Ta2S5 to be a narrow band gap semiconductor with Eg = 110 meV, while a Debye temperature ΘD = 97.0(5) K is observed in specific heat. Tantalum pentasulfide wires were then converted to insulating tantalum pentoxide (Ta2O5) wires after calcinating them for 30 min in air at 900 °C. Finally, tantalum pentoxide wires were converted to tantalum oxysulfide (Ta2O5–xSx) wires after annealing them in CS2 vapor for 30 min at 900 °C. The oxysulfide crystal structure was determined using X-ray diffraction to be that of β-Ta2O5. Electrical and magnetic measurements reveal Ta2O5–xSx to be metallic and superconducting with Tc = 3 K.

Decontamination of chilli flakes in a fluidized bed using combined technologies: Infrared, UV and ozone

Abstract An initial study of the combination of IR, UV and ozone on treating raw and artificially inoculated chilli flakes (CF, Capsicum annum L) was assessed using a specially designed fluidised bed system, in a fused quartz tube, using a distributor plate and filtered air, to keep the CF in an air suspension. The untreated samples, as bought, were contaminated with ~1 × 106 cfu/g, they were subsequently autoclaved, and inoculated with Escherichia coli (MG1655). The individual treatments were all effective in reducing the bioburden with log reduction and treatment times ~6 logs (cfu/g) in ≤20 min for ozone (300 mgO3hr−>1); ~7 logs (cfu/g) in ≤40 min, for UV (4 W); and ~7 logs (cfu/g) in ≤20 min, for IR (100 W); for stationary air with ozone, and an airflow of 108 Lmin−>1 with UV and IR treatment. The IR was modulated so that the external tube temperature was 58–60 °C. The treatment order was more effective for the IR and UV followed by ozone, than ozone followed by UV and IR (ozone, 10 min, UV and IR 10 min combined), this was due to the higher intial reduction of the UV and IR (0.80 log (cfu/g)) than with ozone first (0.13 log (cfu/g)). Such decontamination systems could be used efficiently when conveying the spices, just prior to aseptic packaging.

EPR imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities

New hybrid radiotherapy treatment systems combining an MRI scanner with a source of ionizing radiation are being introduced in the clinic. The strong magnetic fields of MRI considerably affect radiation dose distributions, especially at tissue-air interfaces due to the electron return effect (ERE). Experimental investigation of the ERE within a sub-millimeter thick surface layer is still highly challenging.In the present work, we examine and quantify the magnetic field induced perturbations of dose distributions within a 0.5 mm layer surrounding millimeter-size air cavities by applying electron paramagnetic resonance imaging (EPRI).Air-filled fused quartz tubes (inner diameter 3 or 4 mm) mimic small air cavities and serve as model systems. The tubes were irradiated inside a PMMA phantom by a 6 MV photon beam. The irradiations were performed in the presence or absence of a transverse, magnetic field providing a magnetic field strength of 1.0 Tesla. The spatial distributions of radiation induced paramagnetic defects in the quartz tubes were subsequently determined by applying field-swept echo-detected EPRI and were then converted to relative dose distributions.The transverse magnetic field leads to considerable local dose enhancements and reductions (up to 35%) with respect to the mean dose within the quartz tubes. The experimentally determined dose distributions are in good quantitative agreement with Monte Carlo radiation transport simulations.The results of this work demonstrate the feasibility of field-swept echo-detected EPRI to measure magnetic field induced perturbations of dose distributions within a sub-millimeter thick surface layer at the dosimeter-air interface.

Waste electric and electronic equipment (WEEE) melting and resulting gases processing in microwave field

The recycling of waste electric and electronic equipment (WEEE) is of great interest due to the large amounts of such wastes and to their contents of useful and precious metals. After reaching the end of its service lifetime, WEEE is collected and recycled through various processing methods, depending on the waste type.Pyrometallurgy is currently the most used method for the recovery of the metallic fractions from WEEE such as printed circuit boards (PCBs). This type of processing raises major issues because of the generated gas emissions. The non-metallic fraction of the PCBs, which account for a large proportion (50-70 wt.%), contains brominated flame retardants, thermosetting resin, reinforced materials and other toxic and hazardous organic substances. The combustion of these chemicals during the pyrometallurgical processes may cause serious health-related and environmental problems. In this paper, the treatment in microwave field of the toxic gases resulted from the melting of crushed PCBs has been preliminarily investigated. During the waste melting in a microwave furnace, toxic compounds such as benzene (3.2-6.5 mg×m−3), toluene (15.3-17.8 mg×m−3), ethylbenzene (2.8-5.7 mg×m−3), styrene (21.5-24.3 mg×m−3), m/pXilen (1.4-2.8 mg×m−3), naphthalene (1.1-1.3 mg×m−3) and 1,3,5 trimethylbenzene (15.2-23.5 mg×m−3) have been detected in the effluent gases. The treatment was carried out by passing the resulting gases through a filter fabricated from a microwave susceptor granular material (SiC), placed in a microwave transparent tube (fused quartz, 5 cm diameter). For heating the filter, a number of 3 magnetrons (2.45 GHz frequency and 850 W power each) were mounted outside the fused quartz tube at an angle of 120 degrees and in different geometrical planes. The influence of the process parameters (heating response of the susceptor materials, temperature, gas flow, gas pressure) was investigated. It was observed that the temperature of the filter (i.e. the power density in the microwave susceptor material) has a major influence on the neutralization of the toxic compounds while the gas flow and pressure had a minor influence. At a temperature of 1350-1400°C (power density of 5000 W× kg−1), a gas flow of 150 m3 × h−1 and a pressure of 800-1000 mbar, the content of such substances in the gases was reduced below the legal limits. These results confirm the feasibility of the process of treating the gases resulting from the melting of e-waste in a microwave furnace.

Using Raman spectroscopy and a fused quartz tube reactor to study the oxidation of o-dichlorobenzene in hot compressed water

A fused quartz tube reactor (FQTR) and Raman spectroscopy were employed to investigate the decomposition of H2O2 and o-dichlorobenzene (o-DCB) in hot compressed water (HCW). The results showed that o-DCB can be effectively degraded in HCW, and exhibited applicability as a powerful tool to quantitatively and qualitatively analyze O2 and CO2 using Raman spectroscopy combined with an FQTR. The decomposition rate of H2O2 reached 95.4% at 8 min, and it completely decomposed after 23 min at 400 °C in the closed heating system. When the oxygen stoichiometric ratio (OSR) increased from 50% to 200% after 90 min at 400 °C, the degradation rate of o-DCB significantly increased from 67.5% to 100%. The conversion data for the kinetic analysis of o-DCB indicated that the reaction followed pseudo first-order kinetics and exhibited reaction rate constants of k0.5 = 0.00782 s−1, k1.0 = 0.01412 s−1, k1.5 = 0.02675 s−1, and k2.0 = 0.03509 s−1, respectively.

The Chemistry of Phospholipid Binding by the Saccharomyces cerevisiae Phosphatidylinositol Transfer Protein Sec14p as Determined by EPR Spectroscopy

The major yeast phosphatidylinositol/phosphatidylcholine transfer protein Sec14p is the founding member of a large eukaryotic protein superfamily. Functional analyses indicate Sec14p integrates phospholipid metabolism with the membrane trafficking activity of yeast Golgi membranes. In this regard, the ability of Sec14p to rapidly exchange bound phospholipid with phospholipid monomers that reside in stable membrane bilayers is considered to be important for Sec14p function in cells. How Sec14p-like proteins bind phospholipids remains unclear. Herein, we describe the application of EPR spectroscopy to probe the local dynamics and the electrostatic microenvironment of phosphatidylcholine (PtdCho) bound by Sec14p in a soluble protein-PtdCho complex. We demonstrate that PtdCho movement within the Sec14p binding pocket is both anisotropic and highly restricted and that the C5 region of the sn-2 acyl chain of bound PtdCho is highly shielded from solvent, whereas the distal region of that same acyl chain is more accessible. Finally, high field EPR reports on a heterogeneous polarity profile experienced by a phospholipid bound to Sec14p. Taken together, the data suggest a headgroup-out orientation of Sec14p-bound PtdCho. The data further suggest that the Sec14p phospholipid binding pocket provides a polarity gradient that we propose is a primary thermodynamic factor that powers the ability of Sec14p to abstract a phospholipid from a membrane bilayer.

Multichord optical interferometry of FRX-L’s field reversed configuration

A 0.633μm laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC’s) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star capacitor bank at the Air Force Research Laboratory. The interferometer probes a fanned array of eight chords through the FRC midplane, measuring the line integrated free electron density via its effect on optical phase shift relative to eight reference beams as a function of time. The reference beams are given nominally identical optical paths, except that they are folded for compactness and given an 80MHz higher optical frequency by use of a Bragg cell beam splitter. After the beams are recombined, interference results in 80MHz electromagnetic beat waves with dynamic phase shifts equal to those of the corresponding optical probes. Quadrature mixing of the electronically monitored light is then performed with rf components. Noteworthy features of the interferometer’s design are the unique compact folding scheme of the reference paths, inclusion of a fused quartz tube in the reference path similar to that of the FRC’s vacuum vessel to compensate for cylindrical lensing, and transmission of the interfering light via optical fibers to a rf shielded room for processing. Extraneous contributions to the phase shift due to vibration resulting from the system’s pulsed magnetic field, and dynamic refractive changes in or near the fused quartz tube wall (possibly due to radiation heating) are corrected for.

Swelling of fused capillaries in capillary assemblies

This paper discusses the problem of the swelling of a fused quartz tube when it is heated locally. An equation is obtained that describes the viscous-flow kinetics of the melted section of the tube. Studies were carried out of how the maximum swelling diameter of the tube and the time it takes to swell depend on the relative length of the heated section of the tube and on its temperature. The results are experimentally checked when single quartz capillaries swell, as well as when a capillary assembly consisting of blanks for drawing microstructured optical fiber with two layers of air holes is sintered.

Carbon nanohorn doping in MgB2 wire prepared by suspension spinning

Carbon nanohorn (CNH) doping in MgB2 wire prepared by suspension spinning was studied to enhance flux pinning. The mixed powders of MgB2 and CNH with nominal composition of (MgB2)0.95C0.05 were suspended in a mixed poly(vinyl alcohol) solution. The as-drawn filaments were hot-pressed under 20MPa at 200°C for 8h. The samples were enveloped by an iron sheet with a pellet of mixed powder of Mg and B and vacuum-sealed in a fused quartz tube, and then sintered at the temperature ranging from 885°C to 900°C for 2–3h. The superconductivity of the samples was studied by electrical resistivity and SQUID method. Serious deterioration of Tc was not observed for the doped sample. The CNH doping resulted in enhancement of the transport Jc values at 4.2K in high fields ranging from 6T to 10T by sintering at 885°C for 2h. The superconductivity at 4.2K was maintained by applying the field of 14T for the doped sample sintered at 900°C for 3h.

SiC addition for MgB/sub 2/ superconducting wire by suspension spinning

The effect of nanoscale SiC addition on the field dependence of J/sub c/ for MgB/sub 2/ superconducting wire by suspension spinning was examined to enhance the flux pinning. The suspension spinning of commercially available MgB/sub 2/ and SiC powders was examined to fabricate a long superconducting MgB/sub 2/ wire by using the spinning medium of poly(vinyl alcohol) (PVA) or polyacrylonitrile (PAN). The as-drawn filaments were uniaxially pressed under 20 MPa at 200/spl deg/C for 8 h to remove volatile components and connect the MgB/sub 2/ grains. The filamentary samples were enveloped by an iron sheet with a pellet of mixed powder of Mg and B to prevent Mg loss, and vacuum-sealed in a fused quartz tube and sintered. The field dependence of J/sub c/ for the samples was examined at 4.2 K in magnetic fields up to 14 T. The J/sub c/ of the sample was strongly dependent on the spinning medium and sintering condition. Addition of 5 at% SiC in the sample spun by PVA medium attained the maximum J/sub c/ value more than 1000 A/cm/sup 2/ at 4.2 K by applying the field of 14 T.

Fabrication of Mesoporous Polycarbosilane from SBA-15 Templated Polymethylsilane

Mesoporous silica materials have been used as templates for syntheses of carbon, metal and polymer-based mesoporous replicas via nanocasting process. Since mesoporous silica templates have a narrow pore size distribution and uniform wall thickness, the replicas obtained by synthesis using mesoporous silica templates also have nanometersized pores with a narrow pore size distribution. Incorporation of hydrocarbon polymer through polymerization of monomer such as aniline, acrylonitrile, ethylene, methyl methacrylate and phenolformaldehyde within mesoporous MCM-41 could lead to the fabrication of organic nanofibers. Syntheses of mesoporous polymer networks with three dimensional continuity by the replication of mesoporous materials were reported. The preparation of highly ordered macroscopic silicon carbide, mesoporous silicon imido nitride and bimodal porous silicon oxycarbide from liquid preceramic polymer were also reported. In this communication, we report for the first time the preparation of mesoporous polycarbosilane from liquid polymethylsilane as a polymer precursor and SBA-15 as a template. The silica mesoporous material SBA-15 used as a template for synthesis of mesoporous polycarbosilane have been synthesized, following the procedure in the literature. The XRD (Rigaku D/Max 2200 diffractometer) pattern of calcined SBA-15 reflected the formation of high quality SBA-15 with hexagonal symmetry (not shown here). Figure 1(a) shows transmission electron micrograph (TEM, JEOL JEM-2010) image of rod-shaped calcined SBA-15 with the regular channel array in parallel along the crystallographic c-axis. The external morphology of SBA-15 is rod shape with the length of ca. 1 μm and the diameter of ca. 400 nm, as shown in Figure 1(a). N2 adsorption-desorption isotherm of calcined SBA-15 was measured using Micromeritics ASAP2010 instrument (Figure 2(a)). Brunauer-EmmettTeller (BET) surface area was 849 m/g, the average pore diameter, 5.1 nm, total pore volume, 1.073 cc/g, and micropore volume, 0.058 cc/g. The d100 spacing calculated from (100) peak at 1.03 of XRD pattern was 8.6 nm, the unit cell parameter (a0=2d100/ ), 9.9 nm and the wall thickness, 4.8 nm. The agent impregnated to the pore of SBA-15 for the synthesis of polycarbosilane-based mesoporous material was polymethylsilane prepared by polymerization via dehalocoupling of dichloromethylsilane using Na catalyst as following procedure in the literature. The number average molecular weight and the weight average molecular weight of polymethylsilane determined by gel permeation chromatography were 927 and 4120, respectively. The synthesis of mesoporous polycarbosilane was performed using SBA-15 as a host material and polymethylsilane as a guest material. 0.32 g of calcined SBA-15 was dried under vacuum of 10−3 torr. and impregnated with 0.28 g of polymethylsilane dissolved in 0.5 mL of toluene in the glove box filled with nitrogen atmosphere. The resultant composite was put into a fused quartz tube equipped with fritted disk. After removal of toluene under vacuum for 24 h at 160 C, the composite was heated to 250 C at a heating rate of 5 oCmin−1, cured at 250 C for 4 h and heated at 600 C for 2 h in Ar atmosphere. The heat-treated composite was dissolved with stirring for 2 h in 48% HF solution to remove SBA-15 template. The resulting mesoporous polycarbosilane was washed with ethanol/H2O solution and dried at 60 C for 12 h. The yield percentage based on the impregnated weight 3

Field dependence of transport J/sub c/ for MgB/sub 2/ superconducting wire by suspension spinning

The field dependence of transport J/sub c/ or MgB/sub 2/ superconducting wire by suspension spinning was examined at 4.2 K in magnetic field up to 10 T. The suspension spinning of commercially available MgB/sub 2/ powder was examined to fabricate a long superconducting MgB/sub 2/ wire. The as-drawn filaments were pressed and pyrolyzed to remove volatile components. The filamentary samples were then cold-pressed, enveloped by an iron sheet with a pellet of mixed powder of Mg and B or with Mg powder, and vacuum-sealed in a fused quartz tube and sintered. The J/sub c/ of the sample was strongly dependent on the starting materials and sintering condition. Although the transport J/sub c/ value was low such as 4500 A/cm/sup 2/ at 4.2 K and self-field, the J/sub c/ value of more than 200 A/cm/sup 2/ was maintained by applying the field of 10 T.

懸濁紡糸法によるＭｇＢ２線材の作製

Suspension spinning of commercially available MgB2 powder was examined to fabricate a long superconducting MgB2 wire. The MgB2 powders were suspended in a nonaqueous poly(vinyl alcohol) solution. The viscous spinning dope was extruded as a filament into a precipitating medium of methyl alcohol and coiled on a winding drum. The as-drawn filaments were pressed and heated in order to remove volatile compounds. The filamentary samples were then cold-pressed, enveloped by an iron sheet with a pellet of mixed powder of Mg and B or with Mg powders, vacuum-sealed in a fused quartz tube and sintered. The Jc of the sample was strongly dependent on the starting materials and sintering condition. Although the transport Jc value was low, such as 4500 A/cm2 at 4.2 K and self-fields, a Jc value of more than 200 A/cm2 was maintained by applying a field of 10 T. Doping of 5 at% nanoscale SiC resulted in an improvement in the Jc and superconductivity at 4.2 K was maintained by applying a field of 14 T.

Fabrication of MgB 2 superconducting wire by suspension spinning

The suspension spinning of commercially available MgB 2 powder was examined to fabricate a long superconducting MgB 2 wire. The MgB 2 powder was suspended in a mixed poly(vinyl alcohol) solution of dimethylsulfoxide and hexamethylphosphoric triamide. The viscous suspension solution was extruded as a filament into a precipitating medium of methyl alcohol and coiled on a drum. The as-drawn filaments were pressed and pyrolyzed to remove volatile components. The filaments were then cold pressed, enveloped by an iron sheet with a pellet of mixed powder of Mg and B, and vacuum sealed in a fused quartz tube and sintered. The effect of the J c on the starting materials and sintering conditions of the filamentary MgB 2 superconductors was examined. The J c of the sample was strongly dependent on the staring materials. The optimum sintering condition was sample to sample. The maximum J c value of more than 10 4 A/cm 2 at 4.2 K and self-field was attained.

Structural Change of Fused Quartz Tube by Blowing with Hydrogen-Oxygen Flame.

Structural change of OH-free fused quartz tube by blowing with hydrogen-oxygen flame was investigated by optical adsorption. The blowing increased the OH content within _??_500μm from the surface. The maximum OH content was ca. 1100ppm.