Tantalum Wire Research Articles

Inflammatory tissue response in human soft tissue is caused by a higher particle load near carbon fiber-reinforced PEEK compared to titanium plates

Titanium as the leading implant material in locked plating is challenged by polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK), which became the focus of interest of researchers and manufacturers in recent years. However, data on human tissue response to these new implant materials are rare.Osteosynthesis plates and peri‑implant soft tissue samples of 16 healed proximal humerus fractures were examined (n = 8 CFR-PEEK, n = 8 titanium). Soft tissue was analyzed by immunohistochemistry and µCT. The entrapped foreign bodies were further examined for their material composition by FTIR. To gain insight into their origin and formation mechanism, explanted and new plates were evaluated by SEM, EDX, profilometry and HR-CT.In the peri‑implant soft tissue of the CFR-PEEK plates, an inflammatory tissue reaction was detected. Tissues contained foreign bodies, which could be identified as tantalum wires, carbon fiber fragments and PEEK particles. Titanium particles were also found in the peri‑implant soft tissue of the titanium plates but showed a less intense surrounding tissue inflammation in immunohistochemistry. The surface of explanted CFR-PEEK plates was rougher and showed exposed and broken carbon fibers as well as protruding and deformed tantalum wires, especially in used screw holes, whereas scratches were identified on the titanium plate surfaces.Particles were present in the peri‑implant soft tissue neighboring both implant materials and could be clearly assigned to the plate material. Particles from both plate materials caused detectable tissue inflammation, with more inflammatory cells found in soft tissue over CFR-PEEK plates than over titanium plates. Statement of significanceOsteosynthesis plates are ubiquitously used in various medical specialties for the reconstruction of bone fractures and defects and are therefore indispensable for trauma surgeons, ENT specialists and many others. The leading implant material are metals such as titanium, but recently implants made of polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK) have become increasingly popular. However, little is known about human tissue reaction and particle generation related to these new implant types. To clarify this question, 16 osteosynthesis plates (n = 8 titanium and n = 8 CFR-PEEK) and the overlying soft tissue were analyzed regarding particle occurrence and tissue inflammation. Tissue inflammation is clinically relevant for the development of scar tissue, which is discussed to cause movement restrictions and thus contributes significantly to patient outcome.

Preparation of nanodiamonds based on phase transformation of vertical sheet under atmospheric pressure

A basic and important way to prepare diamond is to make graphite experience the phase transformation under the high-pressure high-temperature (HPHT) condition. However, this method needs stringent equipment and high investment cost. Recently, we proposed a method to prepare the diamond by phase transformation of graphite at atmospheric pressure with monodispersed Ta atoms. It is found that a phase transformation happens to H atoms under atmospheric pressure, but the role of O atoms has not been investigated. Here, we use tantalum wires as Ta source and heat the filaments to prepare vertical graphene containing Ta atoms in hot filament chemical vapor deposition (HFCVD) system. And then the vertical graphene layers are annealed in oxygen-containing environment, and nanodiamonds are obtained by phase transformation from the vertical graphene under atmospheric pressure. The results show that the sample morphologies are the same as the untreated vertical graphene’s, when the annealed ambient air pressure is at 10 Pa and 50 Pa with oxygen atom content of 1.96% and 2.04%, respectively; TEM tests reveal TaC and graphite but no diamond in these samples . Nanodiamond grains with the size range of 2–4 nm are observed in the amorphous carbon region of samples annealed at 100 Pa and 500 Pa air pressure with oxygen atom content increasing to 2.77% and 3.11%, respectively, indicating that oxidation facilitates the phase change from Ta-containing vertical graphene to diamond at atmospheric pressure. When the air pressure of the annealing environment rises to 1000 Pa with the oxygen atom content of 3.54%, the sample is extensively oxidized and the graphite structure is severely damaged,which means that a large number of oxygen atoms tend to disrupt the graphite structure rather than promote the phase change into diamond. These results supply a way to prepare nanodiamond and show the effect of O atoms in the graphite phase transition at atmospheric pressure.

An Investigation of High-Z Material for Bolus in Electron Beam Therapy

Electron beams are frequently used for superficial tumors including: primary skin cancers, surgical scars, cutaneous lymphomas and benign conditions like keloids. However, due to electron beam characteristics the surface dose is 75-95% of the prescribed dose depending on beam energy thus requiring placement of bolus to augment surface dose. Various types of boluses; wet gauge/towel, superflab, superstuff, aquaplast, 3D printed plastics, customized dot-decimal bolus, thermoshield, brass and tantalum wire mesh are commonly used in clinics with variable difficulties that are not perfect. As majority of these devices do not snug to the skin contour and create air-gap that is known to produce significant dose perturbations creating hot and cold spot. The variable dosimetry has cosmetic implications and potentially increased risk of recurrence. A new cloth-like high-Z materials; Tungsten, (Z = 74) and Bismuth, (Z = 83) impregnated with silicone gel are now commercially available which is investigated in this study for bolus purpose. Commercially available, super soft silicone-gel based submillimeter thin Tungsten and Bismuth sheets were investigated for bolus properties in electron beams in the range of 6-12 MeV using 10x10 cm2 applicator. These materials were tested on various body contour for perfect snug without any air traps. Using parallel plate ion chamber measurements were performed in a solid water phantom on a medical linear accelerator machine. Depth dose characteristics were measured to optimize the thickness for surface dose to be 100% for selected electron therapy. Surface dose for a 10x10 cm2 cone for 6, 9, 12 MeV beams were measured to be 75.1%, 80.1% and 86.2%, respectively. Silicone-gel Tungsten and Bismuth sheets produce significant electrons thus increasing surface dose. Based on measured depth dose, our data showed that Tungsten sheets of 0.14 mm, 0.18 mm and 0.2 mm and Bismuth sheets of 0.42 mm, 0.18 mm and 0.2 mm provide 100% surface dose for 6, 9 and 12 MeV beams, respectively without any changes in depth dose except increasing surface dose. The new Tungsten and Bismuth based silicone-gel clothlike sheets are extremely soft but high tensile metallic bolus materials that can fit flawlessly on any skin contour without any air trap or variable thickness or spillage of the water as in conventionally used wet gauge. Only 0.2 mm thick sheets are needed for 100% surface dose without degradation of the depth dose characteristics. These materials are reusable and ideal for bolus in electron beam treatment. This investigation opens a new frontier in designing new bolus materials optimum for patient treatment.

Damage characterisation of tantalum ion source electrodes and reconditioning by wire- and powder-based laser metal deposition

The internal ion source of the Advanced Molecular Image Technologies (AMIT) superconducting cyclotron uses cathodes made of pure tantalum to generate high energy H− ion beams for the production of isotopes for positron emission tomography. During service, the cathodes are impacted by high-energy ions from the plasma. The resulting erosion creates craters that reduce the current density of the extracted beam. The cathodes eventually need to be replaced when the ion source can no longer be activated. This research explores the possibility of repairing the tantalum cathodes used in the AMIT cyclotron through laser metal deposition additive manufacturing. The damaged parts were first characterised by 3D imaging, scanning electron microscopy, and Vickers microhardness to understand the damage mechanisms occurring during service and quantify the extent of the damage. Different repair strategies were then tested employing both high-purity tantalum wire and powder feedstocks and the properties of the reconditioned electrodes were determined. The ability of laser metal deposition to restore the damaged cathodes for use in the AMIT cyclotron has been demonstrated.

The optical diagnosis of electrical wire explosion under a microsecond current pulse.

Electrical wire explosions have many applications in scientific research and industry. Optical diagnosis is a powerful method to clarify the evolutionary process of such explosions. In this paper, an experimental platform was established to diagnose the optical radiation of electrical wire explosions. A low-jitter trigatron switch and its trigger generator were designed to ensure accurate synchronization. The spatial-temporal evolution process and the self-emission spectrum of electrical explosion plasmas from different wires (copper and tantalum) were obtained and analyzed. The optical diagnosis results indicated that the electrical explosion of copper wire was mainly characterized by the inhomogeneity of partial ionization and the rapid expansion of the discharge channel. The spectrum in the early discharge stage of the copper wire electrical explosion was a continuum, and most of the self-radiation spectral lines belonged to Cu I or Cu II. At the later stage of the plasma dissipation process, the continuous spectrum gradually transformed into a line spectrum. The development of the tantalum wire discharge channel was relatively uniform, and the plasma was mainly established in the gas-liquid mixed phase channel of the tantalum wire. The self-emission spectrum of the tantalum wire was always continuous, and the absorption process of line spectrum radiation was distinct.

Comparison of novel shielded nasopharynx applicator designs for intracavitary brachytherapy

PurposeNasopharyngeal brachytherapy is limited in part by the radiotolerance of nearby organs like the soft palate. This study explores several novel shielding designs for an intracavitary applicator to significantly reduce soft palate dose while adhering to the constraints of standard treatment procedure. MethodsThe Monte Carlo code TOPAS is used to characterize each prototype under typical high-dose-rate treatment conditions. Mucosal surface dose maps are collected to evaluate the shields on their dose reduction to the central and soft palate planning points and uniformity in their shielding profile. Practicality with respect to patient comfort and pretreatment imaging is discussed. History-by-history standard deviations are calculated for each simulation. ResultsA design with elliptical tubing containing bundles of tantalum wires provides the most significant attenuation with 39% and 27% dose reduction to the center and soft palate locations, respectively. Another design utilizing miniature lead spheres loaded into a constructed cavity shows 27% and 24% dose reduction to the same locations while providing more uniform shielding and several practical benefits. Both shields are designed to be completely removable for applicator insertion and pretreatment imaging. The mean and maximum standard error of relative dose measurements was 0.36 and 1.14 percentage points, respectively. ConclusionEach shielding design presented in this study provides a novel approach to safely and effectively shield healthy tissue during intracavitary nasopharyngeal brachytherapy. Analysis performed using Monte Carlo suggests that the design using metal spheres most practically shields the soft palate and should be advanced to the next stages of clinical optimization.

DSMC simulation of two-step dissociation-recombination of hydrogen on tantalum surface

The presented work is devoted to the development of new approaches to simulating heterogeneous reactions of hydrogen dissociation and recombination during its interaction with the solid surface within the framework of the direct simulation Monte Carlo (DSMC) method. The DSMC algorithm including a two-step model of hydrogen dissociation is developed. A new technique for simulating heterogeneous reactions within the framework of the DSMC method is proposed, in which the reaction rate constant depends on the gas and surface temperature. The algorithm is verified on the example of a heated infinite tantalum wire placed in a hydrogen atmosphere. The influence of different approaches to simulating heterogeneous reactions on the flux of atomic hydrogen is studied. The results are compared with the results of simulation within the framework of the continuum approach. The developed approaches expand the possibilities of the DSMC method for the study of gas flows taking into account the influence of heterogeneous reactions.

The History of Alloplastic Ear Reconstruction for Microtia.

Microtia reconstruction is a unique and challenging field in reconstructive surgery. In the early 20th century, many different alloplastic materials have been used in an attempt to recreate the fibrocartilaginous framework of the native ear. These materials include celluloid, tantalum wire cage, nylon mesh, polyethylene, and acrylic. The first standard for alloplastic microtia reconstruction, silicone, is one fraught with complications and failures. This alloplastic material is walled off by the host and prone to scar tissue formation and extrusion. Alloplastic microtia reconstruction largely shifts to porous polyethylene, where the results are markedly superior. This is attributed to the porous structure of porous polyethylene, which allows tissue ingrowth. Moreover, the use of the temporoparietal fascia flap for total coverage of the implant has impressively lowered the risk of implant extrusion. However, there is paucity in the literature regarding the evolution of alloplastic microtia reconstruction, especially characterizing historical mistakes, significant technique evolutions, and drawbacks/advantages of materials. This review serves as a guide both to avoid repeating mistakes and to improve outcomes.

Fabrication of 4N5 Grade Tantalum Wire from Tantalum Scrap by EBM and Drawing

Fabrication of 4N5 Grade Tantalum Wire from Tantalum Scrap by EBM and Drawing

Microstructure, hardness and mechanical properties of two different unalloyed tantalum wires deposited via wire + arc additive manufacture

An innovative way of producing large-scale unalloyed tantalum parts, based on the Wire + Arc Additive Manufacturing process, has been developed in this study. Two different unalloyed tantalum wires have been used to deposit 200-mm-long structures in tantalum. The effect of the wire chemistry on microstructure, hardness, porosity, mechanical properties and strain localisation has been investigated. The deposits showed high integrity and excellent mechanical properties, with yield strength, ultimate tensile strength and elongation as high as 234 MPa, 261 MPa, and 36%, respectively. Indeed, yield strength was higher than commercially available tantalum, even though, in this study, the grains were large and had a high aspect ratio. Wire + Arc Additive Manufacture has clearly shown the potential to produce tantalum components with relatively low cost and reduced lead time, thus offering a new robust and viable manufacturing route.

New Findings Confirm Regional Internal Disc Strain Changes During Simulation of Repetitive Lifting Motions

To understand the mechanisms of disc injuries that result from repetitive loading, it is important to measure disc deformations and use MRI to quantify disc damage. The aim of this study was to measure internal disc strains during simulated repetitive lifting and their relation to disc injury. Eight cadaveric lumbar segments underwent a pre-test MRI and 20,000 cycles of loading under combined compression (1.0MPa), hyperflexion, and right axial rotation (2°), which simulated bending and twisting while lifting a 20kg box. The remaining eight segments had a grid of tantalum wires inserted and used stereoradiography to calculate maximum shear strain (MSS) at increasing cycles. Post-test MRI revealed that 73% of specimens were injured after repetitive loading (annular protrusion, endplate failure, or lumbar disc herniation). MSS at cycle 20,000 was significantly larger than all earlier cycles (p < 0.003). MSS in the anterior, left posterolateral, and left lateral regions was significantly greater than the nucleus region (p < 0.006). Large strains, annular protrusion and herniation in the posterolateral regions were found in this study, which is consistent with clinical observations. In vitro strains can be used to develop more-robust computational models for understanding of the specimen-specific effects of repetitive lifting on disc tissue.

Experimental Study on Shock Wave Characteristics of Ammonium Nitrate Ignited by Wire Explosion

Based on high pulsed-power technology, electrical explosion is increasingly utilized to generate shock waves (SWs) with high pressure and short duration. To further magnify the SWs, we have proposed a novel technique by using energetic material (EM) loads. In this paper, we investigated the SW characteristics of ammonium nitrate (AN) powders ignited by the plasma of different kinds of refractory wire explosion. Evident results suggested that compared with $\Phi ~0.5$ -mm wires, $\Phi ~0.2$ -mm molybdenum and tantalum wires were able to finish vaporization, undergo the breakdown and eventually produce stronger SWs. After introducing the AN powders, the peak pressure of SW was scarcely enhanced, while the duration was significantly increased. Moreover, it was implied that various factors would affect the SW characteristics, including the EM charge density, the diameter, and material of metal wire. Finally, a simple plasma ignition mechanism based on multifactors was proposed.

钽铌管棒线制品加工尺寸公差的控制

钽铌管棒线制品加工尺寸公差的控制

Preparation and cutting performance of ultra-smooth CVD composite diamond coated ladder-shape drilling tools

The preparation of ultra-smooth composite diamond (USCD) coated ladder-shape drilling tools is studied. These are produced by growing microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) layers employing the hot filament chemical vapor deposition (HFCVD) method on WC-Co parts. A double hot-wire arrangement apparatus is adopted, the complex shape tool is placed between upper tantalum wires and lower tantalum wires so that all parts of the tool can be coated with diamond. The drilling experiments are conducted for assessing the cutting performances of the MCD and USCD coated tools using carbon fiber reinforced plastics (CFRP) as the workpiece, the uncoated tool is also used in the drilling experiments for the sake of contrast. The results show that the MCD and USCD coated tools exhibit a better cutting performance than the uncoated one, besides, the USCD coated tool displays the best wear resistant. The workpiece is precisely machined with a smooth and bright surface by the USCD coated tool, and there are no defects such as crackle and burrs in the hole exit, the durability of the USCD coated tool and the processing quality of the workpiece have been greatly improved.

Novel Gas Barrier SiOC Coating to PET Bottles through a Hot Wire CVD Method

In an attempt to enhance the gas barrier enhancement of plastic containers such as poly(ethylene terephthalate) bottles, a novel method was found using a hot wire CVD technique, where tantalum wire is heated and exposed to a gas flow of vinyl silane. The resultant SiOC thin film was confirmed to characteristically contain Si-Si bonds in its surface and demonstrate a remarkably and highly practical decrease of the permeation of various gas through poly(ethylene terephthalate) bottles.

Carbon Nanotubes Grown on Metal Microelectrodes for Dopamine Detection

Directly growing of carbon nanotubes (CNTs) on microelectrodes using chemical vapor deposition (CVD) can provide a dense and vertically aligned CNT film. Vertically-aligned CNTs grown on carbon fibers microelectrodes can detect dopamine, but the low conductivity of the carbon fiber may lead to slow electron transfer kinetics and the intrinsic electrochemical activity of carbon fibers makes evaluating the effect of CNT enhancement difficult. In this study, we compared vertically-aligned CNTs gown on metal wires and carbon fibers as microelectrodes. Scanning electron microscopy shows that aligned CNTs can be grown on metal wires, particularly Tantalum and Niobium wires. Using fast-scan cyclic voltammetry, CNT-coated niobium (CNT-Nb) microelectrodes had higher sensitivity and lower DEp values compared to CNTs grown on carbon fibers or other metal wires. The limit of detection for dopamine at CNT-Nb microelectrodes is 11±1 nM, which is approximately five times lower than CNT grown CFMEs. Using Langmuir isotherms to model adsorption/desorption processes revealed that dopamine oxidation is more reversible at CNT based microelectrodes than that for CFMEs. CNT-Nb microelectrodes were useful for monitoring stimulated dopamine release in anesthetized rats. Other neurochemicals could also be detected, including ascorbic acid, DOPAC, serotonin, adenosine, and histamine and the enhancement for dopamine was greater than ascorbic acid at CNT-Nb electrodes. This study demonstrates that CNT-grown metal microelectrodes, especially CNTs grown on Nb are useful for sensitive monitoring of neurotransmitters. Figure 1

MgO nanobelt-modified graphene-tantalum wire electrode for the simultaneous determination of ascorbic acid, dopamine and uric acid

ABSTRACT A promising electrochemical biosensor for simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) was fabricated by electrochemical deposition of MgO nanobelts on a graphene-modified tantalum wire (denoted as MgO/Gr/Ta) electrode. The MgO nanobelts and graphene were verified by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical performances of the electrodes were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The CV results show that AA, DA and UA could be detected simultaneously using MgO/Gr/Ta electrode with peak-to-peak separation of 300 mV, 147 mV and 447 mV for AA-DA, DA-UA and AA-UA, respectively. In the threefold co-existence system, the linear calibration plots for AA, DA and UA were obtained over the concentration range of 5.0–350 μM, 0.1–7 μM and 1–70 μM with detection limits of 0.03 μM, 0.15 μM and 0.12 μM, respectively. The modified electrode shows excellent selectivity, good sensitivity and good stability, making it attractive as a sensor for simultaneous detection of AA, DA and UA in biological fluids.

Carbon nanospikes grown on metal wires as microelectrode sensors for dopamine.

Carbon nanomaterials are advantageous as electrodes for neurotransmitter detection, but the difficulty of nanomaterials deposition on electrode substrates limits the reproducibility and future applications. In this study, we used plasma enhanced chemical vapor deposition (PECVD) to directly grow a thin layer of carbon nanospikes (CNS) on cylindrical metal substrates. No catalyst is required and the CNS surface coverage is uniform over the cylindrical metal substrate. The CNS growth was characterized on several metallic substrates including tantalum, niobium, palladium, and nickel wires. Using fast-scan cyclic voltammetry (FSCV), bare metal wires could not detect 1 μM dopamine while carbon nanospike coated wires could. The highest sensitivity and optimized S/N ratio was recorded from carbon nanospike-tantalum (CNS-Ta) microwires grown for 7.5 minutes, which had a LOD of 8 ± 2 nM for dopamine with FSCV. CNS-Ta microelectrodes were more reversible and had a smaller ΔE(p) for dopamine than carbon-fiber microelectrodes, suggesting faster electron transfer kinetics. The kinetics of dopamine redox were adsorption controlled at CNS-Ta microelectrodes and repeated electrochemical measurements displayed stability for up to ten hours in vitro and over a ten day period as well. The oxidation potential was significantly different for ascorbic acid and uric acid compared to dopamine. Growing carbon nanospikes on metal wires is a promising method to produce uniformly-coated, carbon nanostructured cylindrical microelectrodes for sensitive dopamine detection.

Dual hot-wire arrangement for the deposition of silicon and silicon carbide thin films

A dual hot-wire arrangement has been designed and investigated for the deposition of various thin film materials by the hot-wire chemical vapor deposition (HWCVD) technique. Tantalum and rhenium wires were used for silicon and silicon carbide depositions with hydrogen diluted silane and monomethylsilane, respectively. It is shown that the both types of filaments are mechanically stable after alternate depositions of silicon and silicon carbide with a total deposition time of about 80h. Good material quality of the deposited films is demonstrated. By taking advantage of this dual hot-wire arrangement, it is possible to deposit both kinds of thin film materials with the individual optimum deposition conditions in a single HWCVD chamber.

Synthesis of chemical vapor deposition graphene on tantalum wire for supercapacitor applications

This paper studies the synthesis and electrochemical characterization of graphene/tantalum (Ta) wires as high-performance electrode material for supercapacitors. Graphene on Ta wires is prepared by the thermal decomposition of methane under various conditions. The graphene nanosheets on the Ta wire surface have an average thickness of 1.3–3.4nm and consist typically of a few graphene monolayers, and TaC buffer layers form between the graphene and Ta wire. A capacitor structure is fabricated using graphene/Ta wire with a length of 10mm and a diameter of 0.6mm as the anode and Pt wire of the same size as the cathode. The electrochemical behavior of the graphene/Ta wires as supercapacitor electrodes is characterized by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy in 1M Na2SO4 aqueous electrolyte. The as-prepared graphene/Ta electrode has highest capacitance of 345.5Fg−1 at current density of 0.5Ag−1. The capacitance remains at about 84% after 1000 cycles at 10Ag−1. The good electrochemical performance of the graphene/Ta wire electrode is attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene layer. This suggests that graphene/Ta wire electrode materials have potential applications in high-performance energy storage devices.