Wire Filament Research Articles

Sample introduction in gas chromatography using a coiled wire filament

A simple device for field sampling and concentration of analytes for subsequent introduction into an injection port for gas chromatographic (GC) analysis has been developed. It consists of a tiny, coiled platinum wire filament (CWF) that is attached to a retractable plunger wire, which fits inside a syringe needle housing. Sampling is accomplished by dipping the end of the CWF in a liquid sample, which is drawn into the wire coil by capillary action, and introducing it into the injection port either before or after allowing the solvent to evaporate. The CWF can be used with or without a nonvolatile chemical coating. A major advantage of this sampling device is that nonvolatile sample matrix components remain on the wire coil, reducing the required injection port and liner cleaning frequency and contamination of the head of the chromatographic column. The coil itself can be easily cleaned between analyses by rinsing and/or burning off residual material in a small flame. The sampling coil facilitates specifically designed chemical reactions in the injection port, such as thermochemolysis and methylation. Applications demonstrated in this work include: (1) direct introduction of samples with little or no pre-treatment, (2) simultaneous thermochemolysis and methylation of lipid-containing samples such as bacteria and bacterial endospores for analysis of biomarkers, and (3) solid phase micro-extraction (SPME) using temporary wire coatings. The CWF allowed for significant reduction in sample preparation time, in most cases to less than a few minutes. The peak shapes examined for polycyclic aromatic hydrocarbon analytes (PAHs) were significantly better (asymmetry factors <1.3) when using the CWF sampling technique compared to splitless and on-column injection techniques (asymmetry factors >1.3). Extraction efficiencies for SPME (especially for high boiling point components such as PAHs) improved by an average of 2.5 times when using the CWF compared to the performance of commercially available SPME fibers. Coiled wire filaments and GC injection port liners were used for more than 100 Bacillus endospore thermochemolysis methylation analyses without the need for cleaning or replacement.

Structure and High-Field Performance of New ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Wires Fabricated From Sn-Based Alloys

Sn-Ta based quaternary alloys were prepared by the reaction of constituent metal powders. The alloys were fabricated into sheet or rod forms. In addition, Sn-Ti based ternary alloys prepared by melt and cast procedure were fabricated into sheets. Jelly Roll (JR) composites were prepared using Sn-based alloy sheet and Nb sheet, and then fabricated into wires. A Bc2 (4.2 K) of 26.9 T (mid) has been obtained in the JR wire using Sn-Ta based alloy sheet. Thick Nb3Sn layers were formed by the mutual diffusion between Sn-based alloy sheet and Nb sheet. Stoichiometric Sn concentration with no gradient was obtained throughout the Nb3Sn layers, which may be the main origin of excellent high-field performance of the JR wires. Meanwhile, 19 and 37 filamentary Nb3Sn wires have been fabricated using Sn-Ta based alloy rods. An equivalent high-field performance has been obtained in the multi-rod wires as that of JR wires.

Electron capture dissociation in a linear radiofrequency‐free magnetic cell

Electron capture dissociation in a linear radiofrequency‐free magnetic cell

NbTi superconductors with low ac loss: A review

Niobium titanium is still the superconductor of choice for magnets where the field changes rapidly with time. To keep the hysteretic ac losses within bounds, it must be finely subdivided. For practical handling and reliable performance in magnets, it is therefore made in the form of filamentary composite wires, with NbTi filaments embedded in a matrix of copper. Unfortunately, the copper matrix introduces eddy current coupling losses, which must be controlled by twisting and by resistive barriers. To date, the major applications have been in particle accelerators and fusion, where high operating currents are required. To achieve these high currents, the filamentary wires are made into cables. Eddy current coupling between wires within the cable can cause additional ac losses. Problems of non-uniform current distribution between the wires can prevent magnets from reaching their full current, particularly with the largest cables.

Is a flared stent effective for decreasing stent migration in canine prostatic urethra?

Prostatic urethral stents are effective in relieving obstructions caused by benign prostatic hyperplasia (BPH). However, migration of these stents occurs frequently. To evaluate the efficacy of a flared stent for decreasing the migration rate in comparison with a straight stent in a canine prostatic urethral model. The flared stent (15 mm in diameter and 20 mm in length) was flared up to 19 mm at both ends to prevent migration. A straight stent with the same size was straight without flaring. Both stents were made of a nitinol wire filament and covered with an expanded polytetrafluoroethylene (ePTFE) membrane. The flared stent was inserted in the prostatic urethra of 10 dogs (group 1) and the straight stent in the prostatic urethra of 12 dogs (group 2). Follow-up retrograde urethrography (RUG) was performed 1, 4, and 8 weeks after stent placement. Fisher's exact test was used to compare the migration rate between the two groups. When stent migration occurred during the follow-up period, the same type of stent was inserted again. Three of 10 (30.0%) flared stents migrated into the urinary bladder between 1 week and 4 weeks after placement. Seven of 12 (58.3%) straight stents migrated into the urinary bladder 1 (n = 3), 4 (n = 1), and 8 (n = 3) weeks following placement. The flared stent group showed lower migration rate than the straight stent group, but the migration rate did not reach statistical significance (P = 0.231). After the second stent placement, one of three (33.3%) flared stents migrated again after 4 weeks and two of seven straight stents (28.6%) after 1 week. Although the migration rate was not statistically significant, the flaring of the stent seemed to reduce the migration rate in comparison with straight stents in a canine prostatic urethral model. However, the migration rate of the flared stent was still high, and further developments are required to decrease migration rate.

Preparation of SiC doped In-Situ MgB2 mono- and 7-filamentary wires by continuous tube forming and filling technique

Long lengths of in-situ SiC doped MgB2/Fe mono- filamentary wires with high critical current densities and 7- filamentary MgB2/Nb/Cu/Fe wires with better thermal stability have been fabricated by either continuous tube forming & filling (CTFF) technique or combining both powder in tube (PIT) and CTFF process, respectively. Particular efforts were made in view of the optimization of the manufacturing and annealing processes of the wires. The as obtained wires were sintered under a vacuum furnace at different sintering temperatures and the optimized sintering of the MgB2 wires were investigated by the analysis of optical microscope, XRD, SEM, and the transport Jc measurements. The Jc value in a 8 at.% SiC doped MgB2/Fe mono- filamentary wire is more than 104A/cm2 at 4.2 K and a field of 11 T. While in doped 7- filamentary wire, the similar Jc value (104A/cm2) is obtained at 4.2 K and a field of 7.5 T. Moreover, the n factors are determined to be 33 and 10 at 11 T in the mono- and 7- filamentary MgB2wires with SiC doping, respectively, indicating the possibility to use the as fabricated MgB2 wires in the persistent mode for fields from 0.5 T to 10 T at 4.2 K.

Initiated Chemical Vapor Deposition of Poly(furfuryl methacrylate)

AbstractFuran ring‐functionalized solid surfaces are achieved by the initiated chemical vapor deposition (iCVD) method, a solvent‐free process to form films under mild conditions. The polymerization of furfuryl methacrylate monomer is initiated by a resistively heated filament wire. The functionality of the furan group in the iCVD film enabled Diels–Alder chemistry with 4‐phenyl‐1,2,3‐triazolin‐3,5‐dione (N‐PTD).magnified image

Electromagnetic Shielding Effectiveness of Copper/Stainless Steel/Polyamide Fiber Co-Woven-Knitted Fabric Reinforced Polypropylene Composites

Copper wire and polyamide filament were used as the core yarn, and stainless steel wire was used as the wrapping yarn to fabricate the loop yarns for knitting structure. The nonwoven selvedge served as the core yarn, and the conducting wire was used as the wrapping yarn, to fabricate the weft-inlaid yarn. The rotor twister successfully fabricated a series of conductive hybrid yarns (CHYs). The co-woven-knitted machine successfully fabricated the conductive co-woven-knitted fabrics (CWKFs) with various CHYs. The conducting materials of the hybrid yarn were copper wire and stainless steel wire, taken as the wrapping and core yarn, respectively. The conductive co-woven-knitted fabrics were laminated with various angles in four and six layers and then heat pressed to 2 and 3 mm in thickness. This study investigated the surface resistivity, electromagnetic shielding effectiveness (EMSE) and electrostatic discharge (ESD) attenuation percentage of the co-woven-knitted fabrics and CWKFs reinforced composites.

High Critical Current Densities in SiC Doped In-Situ${\hbox{MgB}}_{2}$ Wires Prepared by Continuous Tube Forming and Filling Technique

20 meters long length of in-situ SiC doped MgB2/Fe, MgB2/Nb/Cu/stainless steel (SS) mono- or MgB2/Nb/Cu/Fe multi- filamentary wires with high critical current densities have been prepared by combining both powder in tube (PIT) and continuous tube forming & filling (CTFF) processes. Particular efforts were made in view of the optimization of the manufacturing and annealing processes of the wires. The as obtained mono- wires were sintered under a vacuum furnace and the effects of the sintering temperature on the properties of the MgB2 wires were investigated by the analysis of XRD, SEM and the Jc measurements. The optimized sintering process was found to be 830degC for 15 minutes. It was shown that the magnetic Jc value of MgB2/Nb/Cu/SS wire reaches 6times105 A/cm2 (10 K, 0 T), while the transport Jc value in this 8 at.% SiC doped MgB2/Fe mono- filamentary wire is more than 104 A/cm2 at 4.2 K and a field of 11 T. The estimated Jc value approaches 106 A/cm2 at 4.2 K and zero field. Further enhancement of Jc in both mono- and multi- wires is expected for improving the filling density of the CTFF + PIT processing.

Influence of Filament Number on Workability and Critical Current Density of Bi-2212/Ag Superconducting Wires

The important merit of Bi-2212/Ag high Tc superconducting wire is to apply cable as round wire geometry. Bi-2212/Ag wires were fabricated in order to develop Rutherford cable for SMES near the future. Various Ag ratio and various numbers of filaments for PIT (powder-in-tube) process were applied to investigate the workability during drawing and to improve critical current property of the wires. In order to find proper working process, we investigated the variation of drawing stress during working. Post-annealing of Bi-2212/Ag wires at various atmospheres was carried out after main heat-treatment in order to increase critical current density. The results of post-annealing in nitrogen were better than that of post-annealing in oxygen. Jc of Bi-2212/Ag wire was increased as increased maximum temperature,Tm , for partial melting until 890degC, and highest Jc was over than 2000 A/mm2. The shape of grain was observed by SEM to investigate Bi-2212 phase formation in filaments. The critical current density increased in proportion to the increase of Bi-2212/Ag wire's filaments number.

Study on thermo-mechanical treatment in fabrication of Bi2212/Ag HTS wire

Round shape Bi2212/Ag wire is isotropic, while Bi2212/Ag or Bi2223/Ag tape has anisotropic characteristics or performances with respect to magnetic field orientation, which is the only HTS wires that can be used to make Rutherford cable to transport high current. In this work, two different Bi2212/Ag round wires with different Ag ratio were fabricated using powder-in-tube method and processing factor at each step was investigated. Double stacked 385 (55 × 7) filamentary wires of various final diameter were heat treated at different melting temperatures. Microstructure after pre-annealing was investigated. Wires which have Ag ratio (silver area/superconductor area) of 0.3 and 0.42 after powder filling show similar critical current density. Higher Ag ratio wire at 0.74 mm diameter heat treated at melting temperature 890 °C shows critical current density of 2750 A/mm 2 at 4.2 K, 0 T.

Fabrication of conductive woven fabric and analysis of electromagnetic shielding via measurement and empirical equation

Copper wire and polyamide filaments used as core yarn were wrapped with polypropylene filaments. Identical yarn was utilized for warp and weft to obtain isotropic shielding behavior. Samples were produced with an electronic loom. In the second step, four or six layers of fabric were laminated at various angles in various thicknesses. This study investigates the shielding effectiveness of the various layers of fabric. The screened aperture and wave-transmission-matrix methods were adopted to estimate shielding effectiveness of the fabric and composites and to verify and compare the correlation between measured results and values calculated using empirical equations.

Hydrogen termination for the growth of carbon nanotubes on silicon

Vertically aligned carbon nanotubes (CNTs) are grown on Fe-covered nano-structured Si tip apexes and planar Si substrates. Under the similar condition of a hot wire filament chemical vapor deposition technique, the growth and adhesion behaviors of the CNTs strongly depend on the chemical treatment of the Si surfaces, which determines the predominant chemical terminations. The Si substrates are terminated by hydrogen, or covered by a native oxide layer, or treated with tetramethyl ammonium hydroxide. The former provides an extremely strong adhesion, presumably due to the formation of Si–C direct bonds created in the initial stage of the CNT growth process, whereas the latter adheres poorly, and the third not at all, as revealed by images of scanning and transmission electron microscopy. A related concept of the CNT growth is suggested.

Detection of Hermetic Defects in HTS Wire

There are important applications of HTS in which the wire comes into direct contact with liquid coolants. If the coolant penetrates into the wire filaments through small leakage paths then a catastrophic failure may result upon warming of the wire as the liquid rapidly expands into a gas. It is therefore desirable to have a simple nondestructive test for hermeticity of long lengths of tapes. A number of tests for detecting hermetic defects with an emphasis on their feasibility within a manufacturing context are considered. The most promising technique is a colormetric test using ammonia as a tracer gas. We correlate results from colormetric tests with pressurized liquid nitrogen testing.

High-Field Performance and Structure of&amp;lt;tex&amp;gt;$(rm Nb,rm Ta)_3rm Sn$&amp;lt;/tex&amp;gt;Wires Prepared from Sn-Ta Matrix

Sn-Ta-Cu buttons with enough ductility to be fabricated into thin sheets were synthesized by melting a mixture of Sn+Ta+(Cu) powder. (Nb,Ta)/sub 3/Sn wires have been prepared by a Jelly Roll (JR) process and a filamentary process. In the JR process a Sn-Ta(-Cu) sheet was laminated with a Nb sheet forming a JR composite. In the filamentary process a Sn-Ta(-Cu) sheet was wrapped around thirteen Nb-1.0 at%Ta rods forming a filamentary composite. Both composites were fabricated into wires without intermediate annealing, and then heat treated. The effect of Ge and Ti addition to the Sn-Ta-Cu sheet has been studied in the JR wires. A small amount of Ge addition improves the workability of the sheet, while that of Ti addition enhances appreciably the J/sub c/ of the JR wires. Meanwhile, the 13-core filamentary wires exhibit equivalent high-field performance as that of the JR wires. Present new (Nb,Ta)/sub 3/Sn wires can be fabricated through a relatively easy process, and show attractive J/sub c/ in the field range of 22-23 T at 4.2 K and that of 24-25 T at 2.1 K.

&amp;lt;tex&amp;gt;$rm Nb_3rm Sn$&amp;lt;/tex&amp;gt;Multi-Filamentary Superconducting Wires Prepared by Ta-Sn Powder in Tube Process

Nb/sub 3/Sn multi-filamentary superconducting wires prepared by Ta-Sn powder in tube (TS-PIT) process have been developed. To develop the TS-PIT wire with applicable scale, a two stage approach was examined. At the first stage, two kinds of test wires with single and 19 filaments were fabricated by using 10 kg class billets. The critical current density (Jc) of the single filament wire was 167 A/mm/sup 2/ at 21 T and 4.2 K. Based on results of the first stage developments 50 kg class scale wire with 54 filaments was progressed in the following stage. This wire showed Jc of 136 A/mm/sup 2/ at 21 T, 4.2 K. Beside Jc, RRR and 0.2% yield strength were estimated. From these estimations, it was clear that the wire in the second stage has efficient applicable properties to the high field magnet. In both stage, microscopic analysis were followed for samples and found that over 50% in the sheath area reacted uniformly and the grain size was extremely fine. Through this development, TS-PIT processed multi-filament Nb/sub 3/Sn superconducting wire has been developed to applicable quality and scale.

Using beam flux monitor as Langmuir probe for plasma-assisted molecular beam epitaxy

We present a simple method for measuring the ion flux from a molecular beam epitaxy (MBE) plasma cell in real time. A Langmuir probe was created by attaching the beam flux monitor to a picoammeter and measuring the current impinging upon the collector or filament wires. This provides a noninvasive, convenient, and direct measure of ion flux at the actual wafer position, yet requires no internal changes to the MBE machine. Quantitative measurements of maximum ion energies and relative ion fluxes are possible. Real-time feedback from this measurement allows rapid optimization of the plasma for the minimum ion flux. This method is applicable to GaN and related materials, but is particularly important for growth of dilute nitrides. This was one of the techniques which led to the longest wavelength GaInNAs(Sb) vertical cavity surface emitting lasers and continuous wave edge emitting lasers on GaAs to date.

Effective properties and micro-mechanical response of filamentary composite wires under longitudinal shear

We propose an asymptotic approach for evaluating effective properties and determining the micro-mechanical response of filamentary composite wires fabricated by cold drawing under longitudinal shear (torsion). Our procedure is based on the homogenization method; a cell problem is solved using the underlying principles of the boundary shape perturbation technique. As the results we derive approximate analytical solutions for the effective shear modulus and for local distributions of the stress field. Developed approach is valid for all values of the components' volume fractions and properties, in particular, it works well in cases when rapid oscillations of stresses occur on micro level (e.g., in the case of perfectly rigid nearly touching inclusions). Analysis of the local stresses allows to predict the effective initial yield limit corresponding to the beginning of plastification of the composite medium. Obtained results are in good agreement with data of other authors.

Microfluidic oscillator for gas flow control and measurement

Microfluidic oscillators were obtained from wall attachment microfluidic amplifiers using a feedback loop from the outputs to the control inputs. These devices can be used as flow meters when the oscillation frequency is proportional to the volumetric flow rate in subsonic and moderately compressible conditions. They can also be used as actuators, for applications involving flow control and/or mixing. The devices, presenting critical dimensions of the order of 280 μm, were fabricated using SU-8 based epoxy photoresist and conventional photolithography. The article shows the results obtained in the experimental device tests with gases (nitrogen, argon, and carbon dioxide). The typical variation of the frequency with volumetric flow presents a range close to thousands of hertz. The oscillation frequencies were obtained using hot wire filament anemometers (in this case with a diameter of 12 μm). The experimental results indicate that the operation of the microfluidic oscillator was a direct function of the length of the feedback loops and of the velocity inside of the interaction region.

Electromagnetic and electrostatic shielding properties of co-weaving-knitting fabrics reinforced composites

The rotor twister successfully fabricated a series of hybrid conductive yarns. Copper wire and polyamide filament were used as the core yarn, and stainless steel wire was used as the wrapping yarn to fabricate the loop yarns for knitting structure. The nonwoven selvedge served as the core yarn, and the conducting wire was used as the wrapping yarn, to fabricate the weft-inlaid yarn. The co-weaving-knitting machine was used successfully in this study to fabricate the conducting co-weaving-knitting fabrics (CWKFs) with the hybrid yarn. The conducting materials of the hybrid yarn were copper wire and stainless steel wire, taken as the wrapping and core yarn, respectively. The CWKFs were laminated with various angles in four layers, and then were heat pressed for 3 mm in thickness. This study examined the surface resistivity, electromagnetic shielding effectiveness and electrostatic discharge attenuation percentage of the CWKFs reinforced composites.