Search results for "TITANIUM"
showing 10 items of 878 documents
Ti-based robust MOFs in the combined photocatalytic degradation of emerging organic contaminants.
2022
Photocatalysis process is a promising technology for environmental remediation. In the continuous search of new heterogeneous photocatalysts, metal–organic frameworks (MOFs) have recently emerged as a new type of photoactive materials for water remediation. Particularly, titaniumbased MOFs (Ti-MOFs) are considered one of the most appealing subclass of MOFs due to their promising optoelectronic and photocatalytic properties, high chemical stability, and unique structural features. However, considering the limited information of the reported studies, it is a hard task to determine if real-world water treatment is attainable using Ti-MOF photocatalysts. In this paper, via a screening with seve…
Influence of Heat Treatment on Fatigue Crack Growth in Ti-6Al-4V Alloy
2011
The paper contains the results of experimental work carried out in order to analyse the initiation and propagation of fatigue cracks in Ti-6Al-4V titanium alloy. The tests were performed on plane specimens with the stress concentrators in form of one-sided sharp notches. The tested specimens were made of the oxygenated Ti-6Al-4V subjected to various variants of heat treatment.
Low-temperature Ti-containing 3:2 and 2:1 mullite nanocrystals from single-phase gels
2007
Abstract TiO 2 -containig single-phase gels with (Al 2 O 3 + TiO 2 )/(SiO 2 ) molar ratios 3/2 and 2/1 were prepared by gelling mixtures of aluminium nitrate, tetraethylorthosilicate and titanium isopropoxide. Gels were fast heated at several temperatures up to 1100 °C. Dried and heated gels were characterized by differential thermal analysis (DTA), magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray powder diffraction (XRD), and scanning and transmission electron microscopies (SEM and TEM). Coupled DTA and XRD results of gels fast heated at 900 °C showed the crystallisation of two mullites as well as a small amount of alumina-silica spinel. 27 Al NMR spectra showed the format…
De novo synthesis of mesoporous photoactive titanium(IV)-organic frameworks with MIL-100 topology
2019
[EN] Most developments in the chemistry and applications of metal-organic frameworks (MOFs) have been made possible thanks to the value of reticular chemistry in guiding the unlimited combination of organic connectors and secondary building units (SBUs) into targeted architectures. However, the development of new titanium-frameworks still remains limited by the difficulties in controlling the formation of persistent Ti-SBUs with predetermined directionality amenable to the isoreticular approach. Here we report the synthesis of a mesoporous Ti-MOF displaying a MIL-100 topology. MIL-100(Ti) combines excellent chemical stability and mesoporosity, intrinsic to this archetypical family of porous…
Influence of operational variables on the photodegradation kinetics of Monuron in aqueous titanium dioxide dispersions
1994
The degradation of Monuron [N′—(4-chlorophenyl)—N, N dimethyl urea] in aqueous TiO 2 dispersions irradiated in the near-UV region has been investigated using a Pyrex batch photoreactor. The influence on the degradation kinetics of pH, initial Monuron concentration and catalyst concentration has been studied. The mineralization of the pollutant was also investigated. Measurements of photon absorbed flows allowed to determine the quantum yield values; they were found to increase by increasing the initial pH of the dispersion.
Scale composition and oxidation mechanism of the Ti–46Al–8Nb alloy in air at 700 and 800 °C
2011
It is known that the oxide scale formed on TiAl alloys is generally composed of a mixture of alumina (Al2O3) and titania (TiO2). The presence of niobium changes the activities of Ti and Al and influences the kinetics of oxidation and oxide layer composition. In this work, the Tie46Ale8Nb alloy was subjected to cyclic oxidation in air at 700 � C (for 2 and 24 h) and 800 � C (for 300 h). Scale composition was analyzed by means of different techniques including X-ray photoelectron spectroscopy, X-ray diffraction and secondary ion mass spectroscopy. The scale consisted of several layers. The outer layer was built of alumina (amorphous or with very fine grains), whereas the inner layer e mainly …
A supported titanium postmetallocene catalyst: Effect of selected conditions on ethylene polymerization
2011
Ethylene polymerization with a titanium complex [N,N-ethylenebis(3-methoxysalicylideneiminato)titanium dichloride] immobilized on the magnesium support with the formula MgCl2(THF)0.32(Et2AlCl)0.36 was studied. In particular, the effects of polymerization temperature, monomer pressure, and polymerization time on the activity of the catalyst and on the polyethylene properties (molecular weight and its distribution, melting point, crystallinity, and bulk density) were evaluated. The findings of investigations prove that the studied supported titanium catalyst is highly active in ethylene polymerization, and its activity increases with increasing temperature and monomer pressure. Moreover, stab…
Investigation of corrosion defects in titanium by positron annihilation
2015
Abstract The positron annihilation method was used to study the formation of defects in titanium samples during their corrosion in the vapor of a 3% HCl solution. In particular, the distribution of defects depending on the distance from the corroding surface and the impact of an external magnetic field on the concentration of vacancies forming during the corrosion of titanium layers close to the surface were determined.
The role of yttrium and titanium during the development of ODS ferritic steels obtained through the STARS route: TEM and XAS study
2018
Abstract Oxide Dispersion Strengthened Ferritic Steels (ODS FS) are candidate materials for structural components in future fusion reactors. Their high strength and creep resistance at elevated temperatures and their good resistance to neutron radiation damage is obtained through extremely fine microstructures containing a high density of nanometric precipitates, generally yttrium and titanium oxides. This work shows transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS) characterization of Fe-14Cr-2W-0.3Ti-0.24Y ODS FS obtained by the STARS route (Surface Treatment of gas Atomized powder followed by Reactive Synthesis), an alternative method to obtain O…
Synthesis and catalytic performance in ethylene and 1-octene polymerization of chlorotitanium(IV) silsesquioxane complexes. Effect of increasing liga…
2016
Abstract The series of titanasilsesquioxanes that differ in a way of binding to the transition metal ( via one, two or three oxygen atoms) and type of nonreactive substituents bonded to inorganic oxygen-silicon cage ( i -Bu, Ph, c -C 6 H 11 ) were prepared by reacting of TiCl 4 with 1 eqv. of the silsesquioxane ligand. Upon treatment with an appropriate cocatalyst, all titanium precatalysts are active in ethylene and 1-octene polymerization and produce from low to high molecular weight polyethylenes and moderately ([ mmmm ] = 44–74%) isotactic poly(1-octene)s. The influence of polymerization parameters, type of cocatalyst and the silsesquioxane structure on the catalytic behavior of the tit…