Showing papers on "Titanium published in 1995"

Formation and characterization of anodic titanium oxide films containing Ca and P.

Abstract: Commercially pure titanium was anodized in an electrolytic solution that was dissolved calcium and phosphorus compounds in water, and an AOFCP (anodic titanium oxide film containing Ca and P) was formed. It was found that sodium beta-glycerophosphate (beta-GP) and calcium acetate (CA) were suitable for the electrolytes to form the AOFCP having an equivalent Ca/P ratio to hydroxyapatite (HA). The AOFCP was characterized by scanning electron microscopy (SEM), an energy-dispersive X-ray microanalysis (EDX), and X-ray diffraction (XRD). Numerous micropores and microprojections were observed on the AOFCP by SEM. The composition of the AOFCP, which was measured by EDX, changed according to beta-GP and CA concentration, and the electrolytic voltage. Ca and P in the AOFCP seem to be incorporated into the TiO2 matrix from CA and beta-GP in the electrolyte during the anodic oxidation. Despite the existence of Ca and P in the AOFCP, no calcium phosphate peak was detected by XRD, and the AOFCP consisted of anatase and only a little rutile. The AOFCP, whose contents of Ca and P were low, had a high adhesive strength after soaking in a simulated body fluid for 300 days. When the AOFCP having an equivalent Ca/P ratio to HA was hydrothermally heated at 300 degrees C, HA crystals were precipitated on the AOFCP and completely covered the surface.

Implant surface preparation

Abstract: The surface of a device that is surgically implantable in living bone is prepared. The device is made of titanium with a native oxide layer on the surface. The method of preparation comprises the steps of removing the native oxide layer from the surface of the device and performing further treatment of the surface substantially in the absence of unreacted oxygen.

Preparation of transparent tio2 thin film photocatalyst and its photocatalytic activity

Abstract: Transparent TiO2 thin films with high photocatalytic activity were prepared on glass substrates via the sol-gel method from tetraisopropyl titanium ethanol solution containing polyethylene glycol a...

Mechanical properties of the binary titanium-zirconium alloys and their potential for biomedical materials

Abstract: Mechanical properties of titanium-zirconium binary alloys were investigated in order to reveal their possible use for new biomedical materials and to collect useful data for alloy design through a hardness test, a tensile test, and optical microscopy. The hardness of the alloy containing 50% zirconium was approximately 2.5 times as large as the hardness of pure titanium and pure zirconium. Tensile tests showed a similar tendency. No changes between hardness of as cast specimens and as homogenized specimens were observed, nor were changes in microstructures noted. Comparisons between the Ti-6Al-4V alloy and the Ti-Zr-6Al-4V alloy indicated that a titanium-zirconium alloy could provide a base material for a new biomedical alloy. From these results, it was concluded that new alloys for biomedical materials should be designed as titanium-zirconium base alloys. © 1995 John Wiley & Sons, Inc.

Titanium for aerospace: Rationale and applications

Abstract: Titanium and titanium alloys are excellent candidates for aerospace applications due to their high strength to weight ratio and excellent corrosion resistance; titanium and its alloys are immune to almost every medium to which they would be exposed in an aerospace environment. Titanium usage is, however, strongly limited by its higher cost relative to competing materials, primarily aluminum alloys and steels. Hence the advantages to using titanium must be balanced against its added cost. The titanium alloys used for aerospace applications, some of the characteristics of these alloys, the rationale for utilizing them, and some specific applications of different types of actual usage will be discussed herein. This is an extension of References 1 and 2, which reviewed applicaiions of β alloys. These references will provide more details on applications of the β alloys, while the α and α/β alloys are added herein.

Synthesis of Titanium Silicon Carbide

Abstract: Synthesis of bulk titanium silicon carbide (Ti3SiC2) from the elemental Ti, Si, and C powders has been accomplished for the first time, using the arc-melting and annealing route. The effects of various parameters on the phase purity of the Ti3SiC2 have been examined, including the starting composition of the powders, compaction technique, arc-melting of the samples, and temperature and time of anneal. The best bulk samples, containing about 2 vol% TiC as the second phase, were made from Si-deficient and C-rich starting compositions. Based on electron probe microanalysis data from a number of bulk samples, it appears that Ti3SiC2 exists over a range of compositions; the Ti-Si-C ternary section has been modified to reflect this. The purest samples of the ternary phase were obtained by leaching powders of silicide-containing samples in diluted HF, and contained over99vol%Ti3SiC2.

Monocyclopentadienyl titanium metal compounds for ethylene-α-olefin-copolymer production catalysts

Abstract: The invention is a catalyst system including a monocyclopentadienyl titanium compound and an alumoxane component which is highly productive for polymerizing ethylene and α-olefins to produce a high molecular weight ethylene-α-olefin copolymer having a high content of α-olefin.

Selective polish process for titanium, titanium nitride, tantalum and tantalum nitride

Abstract: An improved Chemical Mechanical Planarization (CMP) method is provided for selectively removing a layer of metallization material such as tungsten or copper and a liner film such as Ti/Tin or Ta/TaN from the surface of an oxide layer of a semiconductor wafer The method includes removing the metallization and liner layers with a first removal process which utilizes CMP polishing and an alumina-based slurry The first removal process is stopped after the metallization layer is completely removed and before the liner film is completely removed The remainder of the liner film is removed using a second removal process which includes CMP polishing using a neutral pH silica-based slurry which is selective to the liner film

Deflection fatigue of cobalt-chromium, titanium, and gold alloy cast denture clasp

Abstract: The aim of this study was to determine the fatigue resistance of the cast clasps of removable partial dentures. The different commercial types of metals used included five cobalt-chromium alloys, pure titanium, one titanium alloy (Ti-6Al-4V) and one gold alloy (type IV) that was either unhardened or age-hardened ( n =5 per group). The test method used was a constant-deflection fatigue test in which the force required to deflect the clasp for 0.6 mm and the number of loading cycles required to fracture the clasp were determined. The fatigue fracture surface of the clasps was examined with a scanning electron microscope. The results revealed that a fatigue fracture occurred in the cobalt-chromium clasp after approximately 25,000 loading cycles, in the pure titanium clasps after 4500 loading cycles, in the titanium alloy clasp after 20,000 loading cycles, and in the gold alloy clasp after 21,000 loading cycles. The means differed significantly ( p p

Influence of fluoride on titanium in an acidic environment measured by polarization resistance technique.

Abstract: The effect of sodium fluoride on the polarization resistance of titanium was investigated. Titanium plates were exposed to sodium chloride solutions with increasing fluoride concentrations. This was done at pH 7 and 4 at 37 degrees C. The polarization resistance technique was chosen because it is the only electrochemical corrosion test procedure that allows sequential measurements of the same specimen and provides a quantitative basis to estimate corrosion currents unlike measurements of the potential. The results showed a large decrease in polarization resistance with increasing fluoride concentration at pH 4. The polarization resistance at pH 7 remained constant after a slight decrease at a very high value, even with a high fluoride concentration. The results clearly confirm that titanium is attacked by fluoride in an acidic environment. The clinical implications are that fluoride rinses or fluoride gels must have a neutral pH if there is a titanium containing device in the oral environment despite the less prophylactic effectiveness.

Pre-treatment of titanium implants with fluoride improves their retention in bone

Abstract: Fluoride pre-treatment of titanium improved the bone response to this material in the present study. Fluoride pre-treated titanium implants had a four times increased retention in rabbits ulna after four and eight weeks healing periods as measured by a push out technique. Scanning electron microscopic evaluation of the implants revealed that the F-treated implants were partly covered with bone after the push out procedure indicating that an internal fracture had occurred in the bone rather than between the bone and the implant. This was not observed in the titanium control group. It is suggested that the presence of a fluoride coat on the surface of titanium implants stimulates the bone response leading to a connection between titanium and phosphate from tissue fluids. Free fluoride ions will catalyse this reaction and induce the formation of fluoridated hydroxyapatite and fluorapatite in the surrounding bone.

Mechanical and histological investigation of hydrothermally treated and untreated anodic titanium oxide films containing Ca and P

Abstract: In a previous study a new method for forming thin hydroxyapatite (HA) layers on titanium was described. Titanium was anodized at 350 V in an electrolytic solution containing sodium β-glycerophosphate and calcium acetate, and an anodic titanium oxide film containing Ca and P (AOFCP) was formed on the surface. Then numerous HA crystals were precipitated on the AOFCP during hydrothermal treatment in high-pressure steam at 300°C. In this study three types of hydrothermally treated films differing in amounts of precipitated HA crystals and tensile adhesive strength, and untreated films were histologically and mechanically investigated in a transcortical rabbit femoral model for 8 weeks of implantation using light microscopy, scanning electron microscopy (SEM), and push-out tests. Machined titanium and HA ceramics served as control materials. The push-out shear strength and bone apposition of the AOFCP significantly increased after hydrothermal treatment, and were equivalent to those of HA ceramics, although the HA layer on the AOFCP was thin at 1–2 μm. From SEM observation of the pushed-out specimen, it was found that the thin HA layer had directly bonded to bone but the AOFCP had not. The push-out strength of the hydrothermally treated film resulted from the chemical bonding of the bone–HA layer interface, while that of the untreated film resulted from mechanical interlocking force between bone and the microprojections. There was a small difference in bone apposition but no significant difference in push-out strength with the amount of precipitated HA crystals on the treated films. Among the treated films, the film formed at the lowest electrolyte concentration showed the lowest bone apposition because of incomplete covering by the HA crystals, and showed the highest stability against mechanical failure because the adhesive strength was very high at about 38 MPa. Also, the hydrothermally untreated anodic oxide films, whose surfaces were rough as a result of the large microprojections, showed much higher push-out strength and bone apposition than titanium. The good hard-tissue compatibility may be attributed to the surface roughness and the possible inhibition of titanium ion release from the specimen. © 1995 John Wiley & Sons, Inc.

Joining titanium materials with tungsten inert gas welding, laser welding, and infrared brazing

Abstract: Titanium has a number of desirable properties for dental applications that include low density, excellent biocompatibility, and corrosion resistance. However, joining titanium is one of the practical problems with the use of titanium prostheses. Dissolved oxygen and hydrogen may cause severe embrittlement in titanium materials. Therefore the conventional dental soldering methods that use oxygen flame or air torch are not indicated for joining titanium materials. This study compared laser, tungsten inert gas, and infrared radiation heating methods for joining both pure titanium and Ti−6Al−4V alloy. Original rods that were not subjected to joining procedures were used as a control method. Mechanical tests and microstructure analysis were used to evaluate joined samples. Mechanical tests included Vickers microhardness and uniaxial tensile testing of the strength of the joints and percentage elongation. Two-way analysis of variance and Duncan's multiple range test were used to compare mean values of tensile strength and elongation for significant differences ( p ≤0.05). Tensile rupture occurred in the joint region of all specimens by cohesive failure. Ti−6Al−4V samples exhibited significantly greater tensile strength than pure titanium samples. Samples prepared by the three joining methods had markedly lower tensile elongation than the control titanium and Ti−6Al−4V rods. The changes in microstructure and microhardness were studied in the heat-affected and unaffected zones. Microhardness values increased in the heat-affected zone for all the specimens tested.

Plasma diagnostics in pulsed laser TiN layer deposition

Abstract: Time‐ and space‐resolved emission and laser‐induced fluorescence spectroscopic measurements were performed to investigate vaporization and plasma formation resulting from excimer laser irradiation of titanium targets in a low‐pressure nitrogen atmosphere. Measurement series have been done by varying the laser intensity from the vaporization threshold at 25 MW cm−2 up to values of about 500 MW cm−2 typically applied in pulsed laser deposition processing of titanium nitride films. Thus, the transition from thermal evaporation to the high‐density plasma formation process, leading to the production of reactive species and high‐energy ions, was evidenced. An interesting result for the comprehension of the reactive deposition process was the observation of a quantity of dissociated and ionized nitrogen, which is transported with the plasma front in the direction of the substrate.

In vivo corrosion of cobalt-chromium and titanium wear particles

Abstract: Tissue reaction to wear particles from metal implants may play a major role in the aseptic loosening of implants. We used electron microprobe elemental analysis to determine the chemical composition of wear particles embedded in the soft tissues around hip and knee implants from 11 patients at revision surgery for aseptic loosening. The implants were made of cobalt-chromium-molybdenum alloy or titanium-aluminium-vanadium alloy. Histological examination showed a widespread giant-cell reaction to the particles. Elemental analysis showed that the chemical composition of the particles was different from that of the implanted alloys: cobalt and titanium were reduced, often down to zero, whereas chromium and aluminium persisted. Our findings indicate that corrosion is continually changing the shape, size and chemical composition of the implanted alloy. This may alter the biochemical environment of the tissue surrounding an implant to favour bone resorption.

17O and 29Si Solid State NMR Study of Atomic Scale Structure in Sol-Gel-Prepared TiO2-SiO2 Materials

Abstract: Solid state O-17 and Si-29 magic angle spinning (MAS) NMR spectroscopy has been applied to the study of the structure of three Ti-Si mixed oxides and their gel precursors. Gels were prepared by the hydrolysis of tetraethyl orthosilicate (TEOS) and titanium isopropoxide (Ti(OPrn)4). Both one-stage (addition of the Ti(OPrn)4 to the TEOS) and two-stage (partial hydrolysis of the TEOS before addition of the Ti(OPrn)4) procedures were used. Si-29 MAS NMR spectra hardly show any differences between the one- and two-stage gels. All consist of Q(2), Q(3), and Q(4) SiO4 species becoming Q(4) after heat treatment at 600 degrees C. This study shows that O-17 MAS NMR is a valuable tool in the characterization of amorphous oxides and that it is much more informative than Si-29 MAS NMR. O-17 MAS NMR shows that titanium is incorporated only as Ti-O-Si bonds in a two-stage gel, whilst samples that show phase separation alsb have Ti-O-Ti bonds. Ti-O-Si linkages persist until 600 degrees C and in conjunction with the Si-29 NMR data indicate that titanium enters the silica network. The assignment of the Ti-O-Si resonance is confirmed by studying the mineral fresnoite (Ba2TiSi2O8).

Chemistry, microstructure, and electrical properties at interfaces between thin films of titanium and alpha (6H) silicon carbide (0001)

Abstract: Thin films (4–1000 A) of Co were deposited onto n-type 6H-SiC(0001) wafers by UHV electron beam evaporation. The chemistry, microstructure, and electrical properties were determined using x-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and I-V and C-V measurements, respectively. The as-deposited contacts exhibited excellent rectifying behavior with low ideality factors and leakage currents of n < 1.06 and 2.0 × 10−8 A/cm2 at −10 V, respectively. During annealing at 1000 °C for 2 min, significant reaction occurred resulting in the formation of CoSi and graphite. These annealed contacts exhibited ohmic-like character, which is believed to be due to defects created in the interface region.