Synthesis Of Ti Research Articles

Synthesis of Ti<sub>3</sub>AlC<sub>2</sub> Powder by High Energy Ball Milling and High Temperature Heat Treatment

Highly pure Ti3AlC2 powder was fabricated by combination of high energy milling and heat treatment with Ti, C and Al as starting materials. The details of reactions and phase evolution in fabrication process were investigated. The results shown that the Ti-Al intermetallics, Ti3AlC2 and TiC were formed in high energy milling. The as-milled powders were heat treated subsequently, and the Ti3AlC2 powder with high purity was produced from the reaction among Ti-Al intermetallics, Ti3AlC2 and TiC at relative low temperature (1100 °C).

Formation of Ti 3AlC 2/Al 2O 3 and Ti 2AlC/Al 2O 3 composites by combustion synthesis in Ti–Al–C–TiO 2 systems

Preparation of Ti 3AlC 2/Al 2O 3 and Ti 2AlC/Al 2O 3 in situ composites was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS). The SHS process incorporates the thermite reaction of Al with TiO 2 into solid state combustion of the Ti–Al–C system. The extent of thermite reaction involved in the SHS process was studied on the product composition and combustion behavior. It was found that for the formation of Al 2O 3, the addition of the Al–TiO 2 displacement reaction into the Ti–Al–C combustion system significantly reduced the flame propagation velocity and combustion temperature, both of which decreased with increasing content of Al 2O 3 formed in the composites. In situ formation of Al 2O 3 and Ti 3AlC 2 or Ti 2AlC was confirmed by XRD analyses. Moreover, the secondary phase TiC present along with formation of Ti 3AlC and Ti 2AlC was reduced when the thermite reaction was involved, implying an improvement in the evolution of ternary carbides. The maximum contents of Al 2O 3 formed in the Ti 3AlC 2 and Ti 2AlC-matrix composites are up to 60 and 50 mol%, respectively, beyond which the synthesis reaction cannot proceed in a self-sustaining manner due to lack of sufficient reaction exothermicity. SEM micrographs of the synthesized composites show plate-like grains packed in a laminated structure typical of Ti 3AlC 2 and Ti 2AlC.

A Novel Approach for the Synthesis of Ti- and Zr-oxo Species as Precursors for Metal Oxide Nanopowder

ABSTRACT Thermal and microwave irradiation treatment of Ti(OPri)4 and Zr(OBu)4 leads to the formation of homogenous and transparent oxo-alkoxy derivatives of titanium and zirconium in a quantitative yield. The oxo-alkoxy derivatives were characterized with the help of FT-IR, NMR, UV, Raman, GC–mass spectroscopy, and elemental analysis. The physicochemical properties of gel differ considerably from their corresponding parent metal alkoxides. Hence, the gel can be considered as an immediate precursor for the preparation of functional metal oxide nanomaterials under mild conditions with control over particle size and its distribution, surface chemistry, and particle agglomeration. The morphology of the metal oxides strongly depends on the nature of the precursor and as well as synthetic methodology.

Synthesis of Ti 1− xSn xO 2 nanosized photocatalysts in reverse microemulsions

The preparation of Ti 1− x Sn x O 2 nanocrystalline photocatalysts in reverse microemulsions is reported in this work. The obtained materials have been characterised by total reflection X-ray fluorescence (TXRF), X-ray diffraction (XRD) and Raman and UV–vis spectroscopies. Very good accordance between calculated and obtained compositions is observed. Undoped TiO 2 prepared in this way crystallises in the anatase phase. Tin-doped anatase is formed with x < 0.05, while both anatase and rutile phases crystallise when x ≥ 0.05. When both phases coexist, a preferential doping of rutile seems to occur. When x = 0.10, a multiphase mixture containing TiO 2(anatase), TiO 2(rutile) and SnO 2 was formed. No significant modification of the band gap is found in any case. The photocatalytic activity of the obtained catalysts is compared employing the trichloroethylene photocatalytic degradation as a test reaction. The beneficial effect of Sn 4+ in the activity of TiO 2 appears to be related to the formation of anatase–rutile mixtures, leading to the highest specific photocatalytic activity in the sample of composition Ti 0.93Sn 0.07O 2, with anatase:rutile ratio close to 3.

Effect of Al on the Synthesis of Ti3SiC2 by Reactively Sintering Ti—SiC—C Powder Mixtures.

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Microstructural study of titanium carbonitride produced by combustion synthesis

The self-propagating high-temperature synthesis (S.H.S.) process, which is promising for the fabrication of ceramic materials, was chosen to elaborate titanium carbonitride materials. The influence of parameters such as nitrogen gas pressure and carbon ratio on the microstructure was studied. A single phase product of Ti(C,N) is obtained for a carbon ratio under 15 at.% and a nitrogen pressure of 36 MPa. The increase of the carbon ratio corresponds to a decrease of the maximum temperature reached during the synthesis. Time resolved X-ray diffraction measurements (TRXRD) with the synchrotron radiation were used to determine the reaction mechanisms. We could observe that the synthesis of Ti(C,N) is preceded by the formation of titanium nitride. This reaction is initiated by the allotropic transition of α-Ti phase into β-Ti. In the final material the presence of sub-stoichiometric phases such as Ti 2N and α-Ti was observed.

Titanium- and zirconium-monosubstituted polyoxometalates as molecular models for studying mechanisms of oxidation catalysis

Recent developments in the application of titanium- and zirconium-monosubstituted Keggin-type polyoxometalates (Ti- and Zr-POMs) as molecular models for studying mechanisms of H 2O 2-based selective oxidation catalysis are reviewed. The similarity in the catalytic behavior of Ti- and Zr-POMs and heterogeneous Ti(IV) and Zr(IV) single-site selective oxidation catalysts is demonstrated. The progress on the synthesis of Ti- and Zr-POMs, studying their interaction with H 2O and H 2O 2, and characterization of the peroxo species formed are surveyed, with special emphasis being placed on the role of protons in the activation of the peroxo species.

Syntheses of Ti- and Al-containing hexagonal mesoporous silicas for gas-phase epoxidation of propylene by molecular oxygen

Ti- and Al-containing hexagonal mesoporous silicas (Ti-Al-HMS) were synthesized through a sol–gel reaction using dodecylamine as a surfactant. All Ti 4+ ions could enter into the HMS framework until Ti/Si = 4 mol% and all Al 3+ ions could enter into the HMS framework until Al/Si = 1 mol% in Ti-Al-HMS after calcination at 923 K for 4 h. The Al 3+ ions at the extra-framework of HMS are much stronger acidic sites than the Al 3+ ions in the intra-framework of HMS. In a fixed-bed catalytic system, Ti-Al-HMS (Ti/Al/Si = 4/1/100 (molar ratio)) showed 47.8% of propylene conversion and 30.6% of selectivity for propylene oxide (PO) for the propylene epoxidation by molecular oxygen at 523 K. The simultaneous existence of Ti and Al in the framework of HMS is very important for improving the PO yield. An epoxide-like intermediate formed from Ti site, Al site and adsorbed O 2 was proposed for explaining the synergy effect of Ti and Al in Ti-Al-HMS for the propylene epoxidation by molecular oxygen. The Ti 4+ ions at the extra-framework had little effect on improving the PO yield, and the Al 3+ ions at the extra-framework greatly decreased the selectivity for PO, because their strong acidity promoted the oligomerization-cracking of propylene. The sol–gel method is more effective than the impregnation method for preparing a catalyst containing Ti and Al for the propylene epoxidation by molecular oxygen. Ti-Al-HMS deactivated rapidly for the propylene epoxidation at 523 K due to the carbonaceous deposits on the catalyst surface. The deactivated catalyst could be regenerated by calcinating in air at 923 K for removing the carbonaceous deposits. Adding a little amount of hydrogen in the feed gas obviously decreased the speed of catalyst deactivation but could not completely suppress the catalyst deactivation. The amounts of the carbonaceous deposits were 2.6 wt% without H 2 and 0.9 wt% with H 2 in the feed gases over Ti-Al-HMS after 3 h on stream at 523 K. The KNO 3 additive could improve the selectivity for PO and the Ca(NO 3) 2 additive could improve the propylene conversion over Ti-Al-HMS for the propylene epoxidation by molecular oxygen.

Synthesis of Ti3AlC2 Powders Using Sn as an Additive

Nearly pure Ti3AlC2 powders have been synthesized by calcining a mixture of titanium, aluminum, and graphite powders using tin powders as additives. Four recipes with different mole ratios of Ti:Al:C:Sn were examined at calcining temperatures from 1300° to 1500°C. The addition of Sn effectively inhibited the generation of thermal explosion when the volume of the starting materials is larger, and considerably reduced the lower‐limit calcining temperature. The nearly pure Ti3AlC2 powders can be obtained reliably on a large scale by calcining the starting materials with a mole ratio of 3Ti:1Al:1.8C:0.2Sn at temperatures from 1350° to 1500°C.

Liquid Reaction during Synthesis of Ti&lt;SUB&gt;3&lt;/SUB&gt;SiC&lt;SUB&gt;2&lt;/SUB&gt; through Pulse Discharge Sintering Ti/Si/TiC Mixed Powders

To understand the synthesis mechanism of Ti3SiC2 through pulse discharge sintering Ti/Si/TiC mixed powders, the shrinkage displacement curves were studied during sintering process. Liquid reaction above Ti-T15S13 eutectic temperature was revealed. The Ti-Si liquid reaction was found not only to have assisted the Ti3SiC2 phase formation but also accelerated its dcnsification. Ti 8 C 5 was found to be the intermediate phase during this liquid reaction stage.

Synthesis of Ti&lt;SUB&gt;3&lt;/SUB&gt;SiC&lt;SUB&gt;2&lt;/SUB&gt; through Pulse Discharge Sintering Powder Mixture Containing Coarse Ti

Ternary compound Ti 3 SiC 2 was successfully synthesized by pulse discharge sintering (PDS) for Ti/Si/TiC powder mixtures with different molar ratios, where coarse Ti powder (-0.15 mm) was used. When the molar ratio of Ti:Si:TiC was selected to be 2:2:3, the content of Ti 3 SiC 2 reached 97.8% and density reached 99.0% after sintering at 1450°C for 20 min under 50 MPa load. The Ti-Si liquid reaction occurred above the Ti-Ti 5 Si 3 eutectic temperature at 1330°C is thought to assist the synthesis reaction of Ti 3 SiC 2 as well as densification.

Synthesis of Ti3AlC2 from Ti/Al4C3/C Studied by In Situ Neutron Diffraction

The reactive sintering of Ti/Al4C3/C mixtures at a temperature of 1417°±5°C to form the ternary carbide Ti3AlC2 was studied in situ by neutron powder diffraction. A series of intermediate phases occur during the synthesis process beginning with the formation of β‐Ti, TiCx (x≤1) and Ti3AlC. This is followed by the transition of Ti3AlC to Ti2AlC, after which the Ti2AlC and TiCx react with each other to form the product phase Ti3AlC2.

An investigation of the self-propagating high-temperature synthesis of Ti(Si,Al)2

An investigation of the self-propagating high-temperature synthesis of Ti(Si,Al)2

Titanium hydrazido and imido complexes: synthesis, structure, reactivity, and relevance to alkyne hydroamination.

Treatment of Ti(NMe(2))(2)(dpma) (1) with aniline results in the protonation of the dimethylamido ligands, which are retained as dimethylamines, and generation of a titanium imido complex Ti(NPh)(NHMe(2))(2)(dpma) (2) in 94% yield. The monomeric imido 2 is converted to the reactive dimeric micro-imido [Ti(NPh)(dpma)](2) (3) on removal of the labile dimethylamine donors. The dimer 3 is converted to monomeric terminal imido complexes in the presence of added donors, e.g., 4,4'-di-tert-butyl-2,2'-bipyridine (Bu(t)-bpy) and DME. Compounds 1-3 exhibit the same rate constant for 1-phenylpropyne hydroamination by aniline and are all kinetically competent to be involved in the catalytic cycle. Attempts to use 1 as a catalyst for hydroaminations involving 1,1-dimethylhydrazine resulted in only a few turnovers under the best conditions. Consequently, the chemistry of 1 with hydrazines to generate hydrazido complexes was scrutinized for comparison with the imido species. Through these studies, titanium hydrazido complexes including Ti(eta(2)-NHNC(5)H(10))(2)(dpma) (5), Ti(eta(2)-NHNMe(2))(2)(dpma) (6), and [Ti(micro:eta(1),eta(2)-NNMe(2))(dpma)](2) (7) were characterized. In addition, a terminal hydrazido(2-) complex was available by addition of Bu(t)-bpy to 1 prior to 1,1-dimethylhydrazine addition, which provided Ti(eta(1)-NNMe(2))(Bu(t)-bpy)(dpma) (8). Compound 8 was structurally characterized and compared to Ti(NPh)(Bu(t)-bpy)(dpma) (4b), an imido derivative with the same ancillary ligand set. Compound 8 has a nucleophilic beta-nitrogen consistent with a hydrazido(2-) formulation, as determined by reaction with MeI to form the ammonium imido complex [Ti(NNMe(3))(Bu(t)-bpy)(dpma)]I (9). Analogous pyridinium imido complexes [Ti(N-1-pyridinium)(Bu(t)-bpy)(dpma)](+) (10) are available by addition of 1-aminopyridinium iodide to 1. From the investigations, some conclusions regarding the activity of titanium pyrrolyl complexes in hydroamination were drawn. The lack of conversion of the bis[micro-hydrazido(2-)] 7 to monomeric species in the presence of donor ligands is put forth as one explanation for the poor hydrazine hydroamination activity of 1. This problem was combated in the synthesis of Ti(NMe(2))(2)(dap)(2), which is an active catalyst for hydrazine hydroamination of alkynes.

Synthesis of Ti(C, N, O) coatings by unbalanced magnetron sputtering

Several TiCNO coatings were deposited using an unbalanced magnetron sputtering system. The composition of C, N, O was first studied using GDOS (glow discharge optical spectrometer). The coating properties as a function of oxygen/nitrogen flow ratio were then studied by using SEM, scratch testing and nano-indentation measurement. The tribological properties of the coatings were then investigated using a ball-on-disk setup with alumina balls. The sliding speeds were set at 10, 20, and 30cm/min. The results show that coating properties and performance are greatly affected by the flow rate of oxygen. With oxygen flow rate set at 4sccm during deposition, the TiCNO coating shows the lowest wear rate and friction coefficient among all. Further increase in oxygen flow rate caused a decrease of wear resistance with the increase of friction coefficient. The wear debris were analyzed using Raman spectroscopy. The tribological behavior of the selected TiCNO coating was also compared with other Ti-based hard coatings.

Physical simulation of the effect of sample volume on ignition temperature in the thermal explosion synthesis of Ti+3Al→TiAl3

Semenov's theory of a spontaneous ignition was applied to study the sample geometrical dependence of ignition temperature (Tcr) of thermal explosion synthesis in Ti–75at.%Al cylinder sample in various sizes. By linear-fitting of 2lnTcr+ln(1/r+1/h)∼−1/RTcr plot, the apparent activation energy of ignition process is obtained 169±15 kJ/mol. The kinetic mechanism of the ignition process was also provided.

Self‐Propagating High‐Temperature Synthesis of Ti3SiC2: I, Ultra‐High‐Speed Neutron Diffraction Study of the Reaction Mechanism

In situneutron diffraction at 0.9 s time resolution was used to reveal the reaction mechanism during the self‐propagating high‐temperature synthesis (SHS) of Ti3SiC2from furnace‐ignited stoichiometric 3Ti + SiC + C mixtures. The diffraction patterns indicate that the SHS proceeded in five stages: (i) preheating of the reactants, (ii) the α→β phase transformation in Ti, (iii) preignition reactions, (iv) the formation of a single solid intermediate phase in &lt;0.9 s, and (v) the rapid nucleation and growth of the product phase Ti3SiC2. No amorphous contribution to the diffraction patterns from a liquid phase was detected and, as such, it is unlikely that a liquid phase plays a major role in this SHS reaction. The intermediate phase is believed to be a solid solution of Si in TiC such that the overall stoichiometry is ∼3Ti:1Si:2C. Lattice parameters and known thermal expansion data were used to estimate the ignition temperature at 923 ± 10°C (supported by the α→β phase transformation in Ti) and the combustion temperature at 2320 ± 50°C.

Mechanical‐Alloying‐Assisted Synthesis of Ti3SiC2 Powder

Mechanical alloying (MA) has been used to synthesize Ti3SiC2 powder from the elemental Ti, Si, and C powders. The MA formation conditions of Ti3SiC2 were strongly affected by the ball size for the conditions used. MA using large balls (20.6 mm in diameter) enhanced the formation of Ti3SiC2, probably via an MA‐triggered combustion reaction, but the Ti3SiC2 phase was not synthesized only by the MA process using small balls (12.7 mm in diameter). Fine powders containing 95.8 vol% Ti3SiC2 can be obtained by annealing the mechanically alloyed powder at relatively low temperatures.

SYNTHESIS OF ALLOY Ti − 6Al − 4V WITH LOW RESIDUAL POROSITY BY A POWDER METALLURGY METHOD

The possibility of producing titanium alloy Ti ― 6Al ― 4V with minimal residual porosity from mixtures of elemental powders by the method of pressing and sintering without hot deformation during or after sintering was investigated. Various powder mixtures based on titanium and titanium hydride with alloying additions of either elemental powders having different particle sizes, or master alloys, were studied. It was shown that the synthesis of Ti ― 6Al ― 4V from mixtures of titanium hydride and master alloys is optimal with respect to the attainment of high relative density. In this case the sintered material has density up to 99%, homogeneous microstructure with relatively small (100-120 μm) β-phase grains, and a low concentration of impurities, in particular oxygen, which provide a high level of mechanical properties σ(ten = 970 MPa, δ = 6%).

Electrochemical Synthesis of Ti–Si–B Compounds in Chloride–Fluoride Molten Salts

Metals, semiconductors, and their binary and ternary compounds can be produced by electrolyzing molten salts of the components. For a Ti–Si–B system, reduction potentials of all three elements are close, which significantly alleviates the problem. Using thermodynamic calculations, voltammetric measurements, and electrolysis we demonstrate the possibility of producing metal-like refractory compounds. Binary compounds TiB2, Ti5Si3, and SiB4 and a new ternary compound Ti5Si3B3 are produced electrochemically.