Search results for "Titanium"
showing 10 items of 878 documents
Kinetic studies of two-step polymerization of propylene over a titanium-aluminum catalyst
1997
The influence was studied of the modification of an unsupported titanium-aluminum catalytic system with an internal Lewis base incorporated, via prepolymerization, on the activity of this system in propylene polymerization. In order to clarify the reasons for the activating effect of prepolymerization, comparative studies were carried out on the kinetics of polymerization catalyzed by a titanium system and its prepolymerized counter part. Based on the kinetic model suggested for the polymerization mechanism, the concentration of active sites and rate constants were determined for chain propagation, chain transfer and termination reactions. The following conclusions were deduced: (i) the ini…
XPS and EELS investigations of chemical homogeneity in nanometer scaled Ti-ferrites obtained by soft chemistry
1999
Abstract Nanocrystalline Ti-ferrites with composition Fe 3− x Ti x O 4 with 0≤ x ≤1 are synthesized using the soft chemistry route. Heterogeneities in precipitate and annealed powders are investigated by a combination of XPS and EELS techniques. As-prepared powder consists in particles with spinel structure and grain size of about 15 nm. Due to high reactivity towards oxygen of nanoparticules, a significant amount of Fe 2+ cations oxidize during precipitation, so that precipitated powders present large deviation from oxygen-metal stoichiometry. Moreover precipitated particles are evidenced to exhibit a strong surface titanium enrichment and an iron richer core. Observation of such cation se…
Assessment of the electrochemical behaviour of Nickel-Titanium-based orthodontic wires: Effect of some natural corrosion inhibitors in comparison wit…
2019
Background The aim of this study is to assess the corrosion resistance behaviour of Nickel-Titanium-based orthodontic wires (NiTi) in different concentrations of Sodium Fluoride (NaF) and the corrosion's inhibitory effect of the extracts of some medicinal plants (essential oils, hydrosols and extract). Material and methods In this study we used NiTi (3M) and CuNiTi (ORMCO, 35°C, California) orthodontic wires. The following electrolytes were prepared: Lactate Ringer solution with additions of 0.1%, 0.5% or 1% of Sodium Fluoride and the extracts of different plants: Artemisia, Syzygium aromaticum (Clove) and Celtis australis. Corrosion resistance was studied using anodic potentiodynamic polar…
Tensile strength and impact strength of color modified acrylic resin reinforced with titanium dioxide nanoparticles
2017
Background Poor mechanical properties are among the main limitations of acrylic resins. Addition of titanium dioxide (TiO2) nanoparticles to acrylic resin has been shown to improve its mechanical properties with an adverse effect on its color. Thus, this study sought to assess the tensile and impact strength of a color modified heat cure acrylic resin reinforced with TiO2 nanoparticles. Material and Methods In this in vitroexperimental study, 1wt% TiO2 nanoparticles were added to SR Triplex Hot heat-cure acrylic resin powder and mixed. Pigments and color fibers were also added and 18 samples were fabricated of this paste for tensile and impact strength testing (n=9) according to ISO5271. Ei…
Thermal effects of continuous laser treatment on Ti-6 Al(wt%)-4V(wt%) titanium alloy
2008
A titanium alloy Ti-6 Al(wt%)-4V(wt%) was treated in air by Nd:YAG laser radiation (wavelength of 1.064 %m) in continuous mode. Targets were irradiated globally with different levels of energy (accumulated fluence) at constant power. Different focal lengths and beam displacement velocities were used. Cross section microstructural observations were carried out by scanning electron microscopy. Backscattered electron imaging reveals microstructural modifications in samples. A structural phase transformation of beta (bcc) to alpha prime (hcp) phase was observed. The depth of the transformed zone observed by phase transformation is dependent on the treatment parameters. Conformity between micros…
MOCVD growth of TiO2 thin films on single crystal GaAs substrates
2000
Abstract TiO 2 thin films have been grown on (100)GaAs and (111)GaAs substrates by low-pressure metal organic chemical vapour deposition (LP-MOCVD). Titanium(IV) isopropoxide, Ti{OCH(CH 3 ) 2 } 4 , was used as a precursor and TiO 2 films were obtained without an additional oxygen flux. Scanning electron microscopy (SEM) experiments have shown a well ordered rod-like crystallisation in the films grown on (100)GaAs. This ordered crystallisation was favoured by a high deposition temperature ( T d =700°C). By contrast, no distinct order was observed in the films grown on (111)GaAs substrates. X-ray diffraction patterns revealed a mainly rutile structure for the TiO 2 films deposited on (100)GaA…
Mechanism of Formation of TiO2-Doped Mullites from Heated Single-Phase Gels Investigated by Structural and Microstructural Parameters
2008
An analysis of the microstructure of TiO 2 -doped mullites prepared from monophasic gels thermally treated in the temperature range 900°-1600°C is reported. Two series of gels with nominal compositions 3(Al 2-x Ti x O 3 ) ·2(SiO 2 ) and 2(Al 2-x Ti x O 3 )·(SiO 2 ), in the range 0≤x≤0.15, were prepared. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were used to follow the structural and textural evolution from gels to the final doped mullites. The crystallite sizes and microstrains were determined by linewidth refinements of XRD patterns using the integral breadth method of Langford and the Warren-Averbach analysis. XRD patterns showed the formation of Al 2 TiO 5 and…
Ti-Al Membranes for Microfiltration
2016
Porous membranes made of Ti – 48 at. % Al intermetallic compound was obtained by elemental powder synthesis. These disks can be used as microfiltration membranes due to their low pores size and interconnected porosity. During this study titanium (purity 99.5%) and aluminum (purity 99 %) with low particle size range were mixed in corresponding ratios. The powder mixture was pressed at 500 MPa and the samples were heat treated in two stages. In the first step is the forming of Al3Ti compound by a solid state reaction at a temperature of 640 °C, slightly below the melting point of aluminum. In the second step the Ti-Al compound was formed at the temperature of 1300 °C and the sintering the por…
In vitro preliminary study of osteoblast response to surface roughness of titanium discs and topical application of melatonin
2014
Objectives: To observe human osteoblast behavior cultured in vitro on titanium discs (Ti) in relation to surface roughness and melatonin application. Study Design: Human osteoblasts (MG-63) were cultured on 60 Ti6Al4V discs divided into three groups: Group I: discs treated with dual acid etching; Group II dual acid etching and blasting with calcium phosphate particles; Group III (control) machined discs. Surface roughness and topography of the discs were examined with scanning electron microscope (SEM) and confocal laser scanning electron microscope( CLSM). Osteoblast adhesion, proliferation and cell morphology were determined by means of fluorescence microscopy with Image-Pro Plus software…
Development of dark Ti(C,O,N) coatings prepared by reactive sputtering
2008
Accepted manuscript