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Tantalum powder, 60-100 mesh, 99.9%; CAS Number: 7440-25-7; Synonyms: Ta; find Sigma-Aldrich-692824 MSDS, related peer-reviewed papers, technical documents, similar products & more at Sigma-Aldrich

Tantalum powder, 60-100mesh, 99.9 7440-25-7

Tantalum

Interest in soft tissue RadioStereometric Analysis (RSA) is rising. Previous studies have attempted to use this technique to analyse anterior cruciate ligament (ACL) graft constructs, and more recently, the movement of soft tissue as a precursor to RSA follow up of rotator cuff repairs. These methods were either prone to large amounts of marker migration, deemed unsuitable for in vivo use or, where alternative markers such as stainless steel sutures were used, lost the inherent accuracy that makes RSA an attractive tool in the first place. We describe a modification of tantalum marker balls that allows for immediate secure fixation to soft tissue in order to accurately analyse stretch and displacement of soft tissues using RSA. 1.5mm tantalum marker balls were converted to marker beads by pre-drilling with 0.3mm holes, allowing them to be sutured directly to soft tissue. Using an established ACL graft model, the amount of marker micro-motion was then analysed by RSA after cyclical loading between 20 N and 170 N at 25 Hz for 225,000 cycles. None of 40 marker beads loosened or became detached after 225,000 cycles. Mean micro-motion of the markers was <0.1mm. Analysis of elastic stretch, plastic stretch and stiffness of the graft model was possible. This method of attachment of tantalum markers to soft tissue is simple, reliable and provides immediate stability. Although further work is required to establish its suitability for in vivo use, this technique could potentially be used in all areas where soft tissue RSA is of interest.

A new technique for the radiostereometric analysis of soft tissues.

Presurgical devascularization of hypervascular spinal metastases has been shown to be effective in preventing major blood loss during open surgery. Most often, embolization can be performed using polyvinyl alcohol (PVA) microparticles. However, in some cases, the close relationship between the feeders of the metastases and the feeders of the anterior spinal artery (ASA) poses a risk of spinal cord ischemia when PVA microparticle embolization is performed. The authors present their early experience in the treatment of spinal metastases close to the ASA; in 2 cases they injected Onyx-18, by direct puncture, into hypervascular posterior arch spinal metastases situated close to the ASA. Two women, one 36 and the other 55 years of age, who presented with spinal lesions (at the posterior arch of C-4 and T-6, respectively) from thyroid and a kidney tumors, were sent to the authors' department to undergo presurgical embolization. After having performed a complete spinal digital subtraction angiography study, a regular angiography catheter was positioned at the ostium of the artery that mainly supplied the lesion. Then, with the patient in the left lateral decubitus position, direct puncture with 18-gauge needles of the lesion was performed using roadmap guidance. Onyx-18 was injected through the needles under biplanar fluoroscopy. Satisfactory devascularization of the lesions was obtained; the ASA remained patent in both cases. The metastases were surgically removed in both cases within the 48 hours after the embolization and major blood loss did not occur. Presurgical devascularization of hypervascular spinal metastases close the ASA by direct puncture with Onyx-18 seems to be an effective technique and appears to be safe in terms of the preserving the ASA's patency.

Onyx injection by direct puncture for the treatment of hypervascular spinal metastases close to the anterior spinal artery: initial experience.

In response.

A review of the current clinical applications of a variety of percutaneous and endovascular interventional procedures of the extracranial head and neck is presented. After a description of general principles and embolic agents for interventional procedures, management of specific disorders is presented and procedural steps are described for epistaxis, embolization of vascular head and neck tumors, high-flow and low-flow cervical vascular malformations, head and neck trauma and bleeding, radiofrequency ablation and cryoablation of tumors, along with percutaneous biopsy within the head and neck.

Interventional neuroradiology applications in otolaryngology, head and neck surgery.

Re: Fernandez-Fairen M, Murcia A, Torres A, et al. Is anterior cervical fusion with a porous tantalum implant a cost-effective method to treat cervical disc disease with radiculopathy? Spine 2012; 37:1734–41.

Ta-based compounds show Pt-like behavior: Binary tantalum compounds as counter electrodes (CEs) in dye-sensitized solar cells (DSCs) demonstrate Pt-like electrocatalytic activity and competitive photovoltaic performance, matching the performance of DSCs with Pt CEs. The first-principle density functional theory (DFT) calculations provide a strategy for understanding the relationship between the electronic structure and the catalytic activity of CE catalysts in DSCs.

Pt-like behavior of high-performance counter electrodes prepared from binary tantalum compounds showing high electrocatalytic activity for dye-sensitized solar cells.

Quantized conductance was observed in a cation-migration-based resistive switching memory cell with a simple metal-insulator-metal (MIM) structure using a thin Ta(2)O(5) layer. The observed conductance changes are attributed to the formation and dissolution of a metal filament with an atomic point contact of different integer multiples in the Ta(2)O(5) layer. The results demonstrate that atomic point contacts can be realized in an oxide-based MIM structure that functions as a nanogap-based atomic switch (Terabe et al 2005 Nature 433 47). By applying consecutive voltage pulses at periodic intervals of different times, we also observed an effect analogous to the long-term potentiation of biological synapses, which shows that the oxide-based atomic switch has potential for use as an essential building block of neural computing systems.

Conductance quantization and synaptic behavior in a Ta2O5-based atomic switch.

Microstructure and mechanical properties of laser deposited complex quaternary Ti-34Nb-7Zr-7Ta (all wt%), an orthopedic load-bearing implant alloy, has been investigated in detail in both as-deposited as well as heat-treated (β-solutionized and quenched) conditions. The difference in stress-strain behavior of this alloy in the above conditions has been characterized using scanning electron microscopy (SEM), orientation imaging microscopy (OIM™) and transmission electron microscopy (TEM). Compared to the sample in heat-treated condition, the as-deposited sample showed evidence of strong growth related texture. Again in the as-deposited post tensile-tested condition formation of a high density of shear bands, possibly arising from slip localization due to shearing of ω precipitates in the β matrix is observed. TEM investigations also show the presence of lenticular shaped deformation induced ω phase within the shear bands. In contrast, in case of the β-solutionized sample, twinning and the formation of stress-induced plates appears to be the primary mode of deformation. The change in deformation mechanism and thus the tensile property of this alloy could be attributed to the crystallographic texture along the growth direction as well as diffusion mediated isothermal ω precipitates, that cause an enrichment of Nb and Ta in the β matrix, during the laser-deposition process. This is no longer present after the solutionizing treatment.

Laser deposition and deformation behavior of Ti-Nb-Zr-Ta alloys for orthopedic implants.

Control of back bleeding from the hypogastric artery into the aneurysm after endovascular aneurysm repair (EVAR) of a ruptured aorto-iliac aneurysm may be necessary in order to avoid a type II endoleak. It is an emergency situation and selective catheterization and embolization of the hypogastric artery may be time-consuming and more importantly, it has to be performed before complete exclusion of the aneurysm has been established. We describe a plugging and sealing technique that embolizes the hypogastric artery after the exclusion of a ruptured aorto-iliac aneurysm using the embolizing agent Onyx. The mortality rate of the 16 patients treated in our institute with this technique was 25% (4/16) at 30-day and 31% (5/16) at 90-day follow up. One patient had a type II endoleak at one-year follow-up. The EVAR procedure can focus completely on controlling the acute life-threatening situation, with the embolization performed at the end of the procedure.

Plugging and sealing technique by Onyx to prevent type II endoleak in ruptured abdominal aortic aneurysm.

Ta oxide nanotubes (NTs) were formed by the anodization of Ta at 15 V in a solution of concentrated sulfuric acid containing 0.8-1.0 M hydrofluoric acid. To study the initial stages of NT formation, FESEM images of samples anodized for very short times were obtained. The results contradict the existing explanation of the current-time data collected during anodization, which has persisted in the literature for more than two decades. In addition to providing a first-time morphological study of Ta oxide NT formation at very early stages of anodization, we also propose a new interpretation of the i-t response, showing that pores are already present in the first few milliseconds of anodization and that NTs are formed well before present models predict. This behaviour may also extend to the anodization of other valve metals, such as Al, Ti, Zr, W, and Nb.

New insights into the initial stages of Ta oxide nanotube formation on polycrystalline Ta electrodes.

Orbital ultrasound in the selective screening of a dural-cavernous sinus fistula.

Tantalum hydroxide exhibits the ability for the removal of phosphate from aqueous solution. The kinetic study, adsorption isotherm, thermodynamic study, desorption, and foreign anions effect were examined in batch experiments. The kinetic process was very well described by a pseudo-second-order rate model. The adsorption isotherms showed that phosphate uptake fitted with a Langmuir-type model very well, with an increase of PO4(3-) adsorption capacity from 78.5 to 97.0 mg/g when the temperature increased from 298 to 338 K. The negative values of deltaG(0) and the positive values of deltaH(0) indicated that the phosphate adsorption process was spontaneous and endothermic naturally. While the deltaS(0) values obtained were positive, indicating an increase in randomness at the solid-liquid interface during the adsorption. Foreign anions tests showed that the presence of competitive ions cause minimal interference with the adsorption of phosphate on tantalum hydroxide.

Adsorption kinetic and thermodynamic studies of phosphate onto tantalum hydroxide.

Aseptic loosening of all-polyethylene glenoid components remains a limiting factor in achieving long-term implant survival in total shoulder arthroplasty (TSA). This study prospectively evaluated the functional and radiographic outcomes of patients undergoing TSA with a novel, porous, tantalum-backed glenoid component, with a minimum 2 years of follow-up. Porous tantalum-backed glenoid components were used in 19 TSAs in 19 patients. All patients were available for radiographic follow-up at an average of 38 months (range, 24-64 months). Patients were evaluated prospectively using the American Shoulder and Elbow Surgeons (ASES) score and pain on a visual analog scale (VAS). Radiographs were evaluated for component loosening and failure of the porous tantalum backing at a minimum 2 years of follow-up. The mean VAS decreased from 8.6 to 2.9 (P < .0001). The mean ASES score improved from 21 to 70 points (P < .05). Mean active forward elevation improved from 75° to 131° (P < .0001). At latest follow-up, all glenoid components except 1 had complete in-growth of the porous tantalum keel; however, 4 components (21%) failed by fracture at the keel-glenoid face junction. There was an unacceptably high rate of glenoid component failure (21%) due to fracture at the keel-glenoid face junction in this series. The manufacturer has subsequently revised this early design to reduce the risk of failure. The results of this study illustrate that caution should be exercised in the use of novel implants with an unproven clinical track record.

Results of total shoulder arthroplasty with a monoblock porous tantalum glenoid component: a prospective minimum 2-year follow-up study.

Magnetic behavior of the pseudo-binary alloy Hf(1-x)Ta(x)Fe(2) has been studied, for which the zero-field ferromagnetic (FM) to antiferromagnetic (AFM) transition temperature is tuned near to T = 0 K. Our studies show that such composition lies around x = 0.230. Detailed magnetization studies on x = 0.225, 0.230 and 0.235 show thermomagnetic irreversibility at low temperature due to kinetic arrest of the first-order AFM-FM transition. All three compositions studied show a reentrant transition in the zero-field-cooled warming curve and non-monotonic variation of the upper critical field. The region in H-T space where these features of kinetic arrest manifest themselves increases with increasing Ta concentration.

Concentration dependence in kinetic arrest of the first-order magnetic transition in Ta doped HfFe2.

Here we present a surface based on double-layered nanoparticle stacks suitable for spectro-electrochemical applications. The structure is formed on a continuous gold layer by a two-dimensional periodic array of stacks of gold and tantalum pentoxide nanodisks. Reflection spectra in the visible wavelength region showed the multiple-resonant nature of surface plasmon (SP) excitations in the nanostructure, which is in good agreement with simulations based on a finite-difference-time-domain method. The multiple SP resonances can be tuned to various wavelength regions, which are required for simultaneous enhancement at excitation and emission wavelengths. Cyclic voltammetry measurements on the nanostructure proved the applicability of electrochemical methods involving interfacial redox processes.

Double-layered nanoparticle stacks for spectro-electrochemical applications.

A kinetic study of the electrochemical oxidation of syringic acid (3,5-dimethoxy-4-hydroxybenzoic acid) by cyclic voltammetry at treated gold disk was combined with results of electrolyses at Ta/PbO2 anode in order to convert it into potentially high-added-value product. The electrochemical oxidation of syringic acid was carried out in order to convert this compound to 3-O-methylgallic acid. This latter was identified by mass spectrophotometry using LC-MS/MS apparatus. The 3-O-methylgallic acid synthesis was controlled by cyclic volammetry, Ortho-diphenolicdeterminations and DPPH radical-scavenging activity. The proposed mechanism is based on the hypothesis of a bielectronic discharge of syringic acid molecule under free and adsorbed form involving two intermediate cation mesomers. Hydrolysis of the more stable of this last one leads to the formation of the 3,4-dihydroxy-5-methoxybenzoic acid (3-O-methylgallic acid) as a major product. The latter aromatic compound was synthesized by anodic oxidation of syringic acid at PbO2 electrode. The cyclic voltammogram of the electrolysis bath of syringic acid shows that the anodic peak potential of 3-O-methylgallic acid was lower (Epa=128mV) than that of SA (Epa=320mV). And the strongest antiradical activity was detected when the 3-O-methylgallic acid concentration was higher". The electrochemical oxidation using PbO2 anode is a rapid, simple and efficient method tool for a conversion of SA into 3-O-methylgallic acid, a potent antioxidant derivative The electrochemical process consists in a simple transformation of the syringic acid into 3-O-methylgallic acid having a better antioxidant capacity. This result has been justified by cyclic voltametry which shows that anodic peak of 3-O-methylgallic acid is reversible. Furthermore, its potential is lower than that of the irreversible anodic peak of syringic acid to 3-O-methylgallic acid.

Synthesis of 3-O-methylgallic acid a powerful antioxidant by electrochemical conversion of syringic acid.

Biomimetic oxygen activation by MoS2/Ta3N5 nanocomposites for selective aerobic oxidation.

In this paper, we investigated the optical and structural properties of the Ag:Ta2O5 nanocomposites. The nanocomposite films were prepared by magnetron co-sputtering of Ta2O5 with Ag chips. The transmission electron microscopy images clearly revealed that Ag nanoparticles were successfully produced by post-thermal annealing of the deposited films. The reflection spectra exhibited the surface plasmon resonance behavior. The photoluminescence (PL) spectra indicated that the Ag:Ta2O5 nanocomposites exhibited larger PL intensity than pure Ag or pure Ta2O5. The PL enhancement is thought to be due to the surface plasmon resonance of Ag nanoparticles. From the spatial intensity distributions that were obtained by solving Maxwell equations using the three-dimensional, finite-difference time-domain method, we found that there was strong confinement of optical field near the Ag nanoparticle. This optical confinement effect makes it possible to exhibit the enhanced PL.

Optical and structural properties of Ag:Ta2O5 nanocomposites.

Hydroxyapatite (HAp) films were deposited on a β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), by metal organic chemical vapor deposition (MOCVD) in order to improve its hard-tissue compatibility. The surface morphologies of TNTZ substrates were changed by acid treatments and mechanical polishing prior to the HAp film deposition. The adhesive strength of the HAp films formed on TNTZ substrates treated with an HF solution increased to twice that of the HAp film deposited on a TNTZ substrate with a mirror-like finish. Complex microstructures with deeply etched grain boundaries, formed on the TNTZ substrates after immersion in the HF solution, were responsible for the increase in the adhesive strength of the HAp film caused by an interlocking effect. The HAp films on TNTZ substrates treated with a H(2)SO(4) solution exhibited lower adhesive strength than HAp films on TNTZ substrates treated with HF solution, regardless of the surface roughness of the substrates. Additionally, acid treatments using HNO(3) and H(2)O(2) solutions did not change the surface morphologies of the TNTZ substrates. The complex microstructures with deeply etched grain boundaries and nanosized asperities formed on the TNTZ substrates are important factors in the improvement of the adhesive strengths of HAp films deposited on TNTZ substrates.

Enhancement of adhesive strength of hydroxyapatite films on Ti-29Nb-13Ta-4.6Zr by surface morphology control.

Ti-10Ta-10Nb alloy is a promising alloy for metal ceramic crowns because of its good corrosion resistance and low cytotoxicity. However, more information is needed on the bond strength between this alloy and porcelain. The purpose of this study was to compare the surface morphology, surface roughness, and bond strength of a Ti-10Ta-10Nb alloy, pure Ti, and a Ti-6Al-4V alloy. Ti-10Ta-10Nb, pure Ti, and Ti-6Al-4V specimens (25 × 3 × 0.55 mm plate) were prepared and then divided into 6 groups (n=8) according to surface treatment. Group P (control group) was polished with SiC paper. Groups S50 and S250 were airborne-particle abraded with 50 μm and 250 μm aluminum oxide powder. Group HCl was immersed in 10% HCl aqueous solution, and Group HF was immersed in 17% HNO(3)/HF solution. Group TiN was coated with TiN. Atomic force microscopy was used to observe the surface roughness of the metal surface. Scanning electron microscopy was used to analyze the surface profile. A 3-point bending test was performed to evaluate the bond strength. Two-way analysis of variance (ANOVA) was performed to compare the roughness and bond strength and statistical differences were revealed by the Bonferroni post hoc test (α=.05). There were significant differences in the surface roughness, surface profile, and bond strength of the Ti alloys according to the surface treatments. The groups with the higher mean surface roughness showed higher bond strength, but surface profile had a larger effect on the bond strength than surface roughness. Moreover, the bond strength of the Ti-10Ta-10Nb alloy was high. Ti-10Ta-10Nb would be more suitable for a metal ceramic crown than pure Ti or Ti-6Al-4V, which have limited use because of their low bond strength to porcelain.

Effect of surface treatment on bond strength of Ti-10Ta-10Nb to low-fusing porcelain.

Biomedical implants are essentially foreign substances within the human body that must survive many years’ exposure to demanding mechanical and physiological conditions. Despite these challenges, metal implants have been widely used to substitute for or rebuild hard tissues such as bones and teeth.

Tantalum

powder, 60-100 mesh, 99.9%

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