High Ti Content Research Articles

Microstructural morphology and crystallographic orientation characteristics of as-cast alloys Ti1.8(VFe)CrNi0.2 + x wt% LaNi5 (x = 2.5, 4, 5, 6, 10)

The performances of hydrogen alloy strongly depend on its microstructural characteristics. And the microstructural morphology, crystallographic orientation, and elemental distribution in alloys represent the internal structural features of crystals. In this present work, the multi-component Ti–V–Cr-based alloys Ti1.8(VFe)CrNi0.2 + x wt.% LaNi5 (x = 2.5, 4, 5, 6, 10) were prepared by the two-step re-melting method and the variation of microstructural morphology, lattice constants which reflect intrinsic characteristics of crystals, and microstrain in the alloys containing a different content of LaNi5 were investigated. The results shows that the crystalline diameters in the solidification microstructures of the investigated specimens dropped continuously along the minor axis and the grain size increased with the increase of LaNi5-content from 2.5 wt.% up to 5 wt.%. Meanwhile, a tendency of crystallographic orientation correlated distinctly with the close-packed [001] and [110] directions and the {110} planes appeared. Moreover, there exhibited the symbiotic relations of coherent interface between the major and minor phases. The preferential growth of elongated-grain in axial direction occurred due to decrease of lattice mismatch at the interfaces in the case of high Ti-content dissolved in the major phase. In particular, it was found that the grains of alloy containing 5 wt.% LaNi5 grew predominantly along the close-packed [001] or [110] directions and the {110} planes and the average of diameter and length of unique elongated-grain reached the minimum of 6.51 μm and maximum of 291.45 μm, respectively, for the high Ti content of 33–42%, mostly 33%, in the major phase, which induced a smallest mismatch and lattice distortion, only a misorientation angle of approximately 1.875°, determined using electron backscattered diffraction (EBSD). In addition, the evidences from the analyses of EBSD suggest that the internal microstrain in the major phase of alloy containing 5 wt.% LaNi5 slightly enlarged, represented as a largest local misorientation angle of 1.9°. It is demonstrated that there is an important influence of the content of LaNi5 on the microstructural morphology and crystallographic orientation in Ti-based alloys and it may act as a method of microstructure regulation of phases in hydrogen alloys.

Effect of boron on isothermal oxidation behavior of a nickel-base superalloy with high Al and Ti contents

The influence of boron on the oxidation resistance of conventionally cast U720Li alloy was investigated at 1130 °C and analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDX) and electron probe microanalysis (EPMA). It has been found that the boron-undoped and -doped alloys all obey a super-parabolic rate law, but the oxidation rate is obviously increased by the boron addition. These alloys all show non-uniform oxidation between dendritic and interdendritic areas due to the serious microsegregation, while the oxide scale morphology of the high-boron alloy is quite different from that of the boron-undoped alloy. For boron-doped alloys, in the initial stage of oxidation the outward diffusion of boron from borides formed in the interdendritic region results in the formation of discontinuous and non-uniform B-rich oxide layers beneath and inside the Cr2O3 layer, while as the oxidation proceeds further boron can also transfer from the B-rich oxide to outer layers which eventually leads to disappearance of the B-rich oxide layers. The formation of B-rich oxide layers destroys the continuity of Cr2O3 layer and decomposition of B-rich oxide layers makes Cr2O3 layer more porous, which significantly reduce the protective property of the Cr2O3 layer and in turn decrease the oxidation resistance. Moreover, the eutectic (γ + γ′) highly enriched in Ti, Al is prone to be oxidized and form a thicker scale than the other regions, and hence the significant increase of its precipitation with boron addition also contributes to increasing the oxidation rate.

The role of titanium on the microstructure and mechanical properties of additively manufactured C300 maraging steels

In this study, C300 metal powders containing two different Ti contents (0.72 and 1.17 wt%) were used to additively manufacture maraging steel samples in both horizontal and vertical directions via laser powder bed fusion (LPBF) technique. The effect of Ti addition on the microstructural and mechanical properties of the additively manufactured (AM) maraging steels was investigated using scanning, transmission electron microscopies (SEM, TEM), and electron backscatter diffraction (EBSD) along with uniaxial tensile and hardness testing procedures. Besides, X-ray diffraction (XRD) technique was employed to identify various phases formed during the LPBF process. The results showed that the horizontally printed Ti-rich samples exhibited higher retained austenite (γ) phase and superior values of hardness and tensile strength, while those ones vertically prepared showed an excellent ductility that could bring benefits in high-cycle fatigue applications. The TEM observations confirmed the presence of CoNi precipitates as well as high dislocation densities in the horizontal high Ti content samples, which are associated with higher strain hardening and tensile strength.

Compositional Variations of Cr-Spinel in High-Mg Intrusions of the Primorsky Ridge (Western Baikal Region, Russia)

Composition variations of Cr-spinel in high-Mg rocks of the Primorsky Ridge (Western Baikal region, Russia) are reported here. A specific feature of Cr-spinels in ultramafic rocks of the Primorsky Ridge is their noticeably high Ti content (up to 6.5 wt.%) compared to spinels in mantle peridotites. The presence of high TiO2 content in Cr-spinels enclosed in olivine crystals may be a clear indication of the primary magmatic nature of Ti enrichment. Two types of Cr-spinel were identified in ultramafic rocks from all intrusions. Cr-spinels of Type I are enclosed in the inner part of olivine crystals and are homogeneous Al-rich chromites and Fe2+-rich chromites. They are characterized by variable content of TiO2 (1.0–5.3 wt.%), moderately high Cr# (0.7–0.83), and low Fe3+# (0.20–0.34). Cr-spinels of type II occur in the interstitial space and occur as homogeneous and zoned grains with Al-rich chromite and Fe2+-rich chromite cores. Al-rich chromite cores have a composition similar to that of the Cr-spinel enclosed in olivine crystals. Fe2+-rich chromite cores have relatively high MgO (3.8–6.2 wt.%), Al2O3 (8–9 wt.%), and TiO2 (2.6–2.8 wt.%) content, low MnO (0.34–0.52 wt.%) content, and a low Fe3+# (0.25–0.27) ratio.

Synthesis and Characterization of Ti-Nb2O5 Catalysts for Discoloration Reaction of Bromophenol Blue and Indigo Carmine Dyes

This work investigated the photodegradation of bromophenol blue (BPB) and indigo carmine (IC) dye under UV–Visible light using pure oxides of titanium and niobium, as well as TiO2-Nb2O5 oxides containing 0.5, 2.5 and 5 wt% of TiO2, prepared by wet impregnation of Nb2O5 with Ti tert-butoxide under inert atmosphere. The results of XRD and Raman spectroscopy showed the presence of anatase TiO2 phase and T-Nb2O5 phase with orthorhombic structure in the pure TiO2 and Nb2O5 oxides, respectively. The Nb2O5 oxides doped with TiO2 presented a T-Nb2O5 phase, but there was no formation of TiNb2O7. TiO2 anatase was observed in the mixed oxide with higher Ti content (5 wt% TiO2). A zeta potential analysis showed positive surface charge values for titanium oxide and negative for niobium oxide and mixed oxides. The addition of up to 5 wt% of the TiO2 fold the activity of Nb2O5 in the discoloration of both dyes. Pure TiO2 exhibits higher initial activity, which could be related to its positive PZC and higher attraction to sulphonic groups present in the dyes. Despite of the lower initial rate, 2.5 and 5% TiNb catalysts achieved full degradation of the dyes after 4 h of reaction.

Integrating Petrography, X-Ray Fluorescence, and U-Pb Detrital Zircon Geochronology to Interpret Provenance of the Mississippian Hartselle Sandstone, USA

The Chesterian (Mississippian) Hartselle Sandstone is a tar sand exposed in the Black Warrior Basin and southern Appalachian fold belt in northern Mississippi and Alabama. Previous studies disagree about the delivery direction and relative contributions of sediment from the cratonic interior, the Appalachians, and the Ouachitas. The goal of this research is to investigate lateral trends in sedimentary and geochemical properties to provide new details about the provenance of the Hartselle. Samples were collected along a west-to-east transect and analyzed using petrography, X-ray fluorescence (XRF) geochemistry, and U-Pb detrital zircon (DZ) geochronology. Point counting indicated a major cratonic interior source with a minor recycled orogen signal. Sillimanite in the easternmost sample narrows down the potential Appalachian sources to areas of high-grade metamorphism. Petrographic observations suggest both western and eastern sources. The XRF results showed high concentrations of Ti and Mo in the westernmost sample, suggestive of a nearby terrigenous source. All of the samples had similar U-Pb DZ age distributions except for the easternmost sample, which had statistically higher proportions of Paleozoic- and Archean-aged grains (Kolmogorov-Smirnov test: p < .02). For the first time, Eoarchean and Paleoarchean grains were found in the Hartselle, indicating a likely sediment source from the Minnesota River Valley gneisses of the Superior Craton prior to Grenvillian overprinting. Based on integration of all data, we conclude that a large fluvial system draining the continental interior provided a substantial volume of sediment from the northwest. At the same time, a more dispersed drainage basin associated with the Appalachian front contributed recycled orogenic material from the northeast.

Characterization and A Preliminary Study of TiO&lt;sub&gt;2&lt;/sub&gt; Synthesis from Lampung Iron Sand

The purpose of this study is to characterize Lampung iron sand and to conduct preliminary experiments on the TiO2 synthesis which can be used for the manufacturing of functional food packaging. The iron sand from South Lampung Regency, Lampung Province that will be utilized as raw material. The experiment was initiated by sieving the iron sand on 80, 100, 150, 200 and 325 mesh sieves. Analysis using X-Ray Fluorescence (XRF) to determine the element content and X-Ray Diffraction (XRD) to observe the mineralization of the iron sand was conducted. The experiment was carried out through the stages of leaching, precipitation, and calcination. Roasting was applied firstly by putting the iron sand into the muffle furnace for 5 hours at a temperature of 700°C. Followed by leaching using HCl for 48 hours and heated at 105°C with a stirring speed of 300 rpm. The leaching solution was filtered with filtrate and solid residue as products. The solid residue was then leached using 10% H2O2 solution. The leached filtrate was heated at 105°C for 40 minutes resulting TiO2 precipitates (powder). Further, the powder was calcined and characterized. Characterization of raw material using XRF shows the major elements of Fe, Ti, Mg, Si, Al and Ca. The highest Ti content is found in mesh 200 with 9.6%, while iron content is about 80.7%. While from the XRD analysis, it shows five mineral types namely magnetite (Fe3O4), Rhodonite (Mn, Fe, Mg, Ca) SiO3, Quart (SiO2), Ilmenite (FeOTiO2) and Rutile (TiO2). The preliminary experiment showed that the Ti content in the synthesized TiO2 powder is 21.2%. The purity of TiO2 is low due to the presence of Fe metal which is dissolved during leaching, so that prior to precipitation purification is needed to remove impurities such as iron and other metals.

In-Situ Crystallization and Continuous Modification of Chromian Spinel in the “Sulfide-Poor Platinum-Group Metal Ores” of the Norilsk-1 Intrusion (Northern Siberia, Russia)

Layers rich in chromian spinel (Cr-spinel) occur in numerous differentiated and layered intrusions. These layers are often characterized by elevated and even economic concentrations of platinum-group-elements (PGEs), but only scarce sulfide mineralization. One particular type of such lithology occurs in the roof parts of the Norilsk-type differentiated intrusions (Russia) and is referred to as the “sulfide-poor PGE ores”. We investigated rocks containing variable enrichments in Cr-spinel, sulfides, and platinum-group minerals (PGMs) from two sections of the upper zone of the Norilsk-1 intrusion, with a focus on Cr-spinel. The rocks are dominated by two lithological types: (1) leucogabbro/troctolitic and (2) olivine-gabbro. Fine-grained (5–100 μm) disperse disseminations with varying modal abundances of Cr-spinel are characteristic for the rocks studied. Those abundances range from scarce mineralization through to very dense (up to 30 vol. % Cr-spinel) cloud-like accumulations. However, compact-grained accumulations and cumulate-like textures, which are typical for chromitites of layered intrusions, are not characteristic for the studied rocks. Instead, the disseminations exhibit chain- and trail-like alignments of Cr-spinel grains, which cross the boundaries between enclosing silicates, and sub-circular arrangements. The study revealed millimeter-scaled patchy distribution of Cr-spinel compositions within a given dissemination with Cr-spinel chemistry being strongly correlated with a kind of the enclosing silicate. (1) In unaltered rocks, plagioclase hosts more magnesian Cr-spinel (Mg# 30–60), while Cr-spinel in mafic minerals is less magnesian (Mg# 18–35). (2) In altered rocks, more magnesian Cr-spinel is hosted by less altered silicates, while strongly altered silicates mainly host less magnesian Cr-spinel. Systematics of trivalent cations exhibits divergent trends, even on a scale of a thin section, and depends on a kind of hosting lithology. Leucogabbro/troctolite lithologies contain Cr-spinel with anomalously low Fe3+ and extremely high Ti contents, whereas Cr-spinel from olivine-gabbro lithologies have moderate Fe3+ and moderately-high Ti contents. It is envisaged that crystallization of Cr-spinel and their host rocks occurred from viscous mingled magmas, which had different compositions and redox state. Subsequent processes involved (1) high-temperature re-equilibration of Cr-spinel with enclosing silicates and (2) post-magmatic alteration and partial recrystallization of Cr-spinel. During these processes, Cr-spinel was losing Mg and Al and gaining Fe and Ti. These chemical trends are generally coincident with those established for other intrusions worldwide, but the upper zone of the Norilsk-1 intrusion seems to possess an exceptional variety of Cr-spinel compositions, not recorded elsewhere.

The effects of substituting Sn for Ni on the thermal and some other characteristics of NiTiSn shape memory alloys

In this study, the thermal stability and phase transformation of Ni50-xTi50Snx (x = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 at%) SMAs have been investigated. Some thermal, mechanical, and microstructural characteristics were measured using DSC, Vickers microhardness, XRD, and SEM–EDX devices. Calculations, such as grain size and entropy change, were also performed based on the DSC results. It is found that by increasing the amount of Sn in NiTiSn alloy, fragmentation has occurred in the alloy, which may be due to the high concentration of Sn and Ti in the grooves. Furthermore, the microhardness and grain size are in harmony, i.e., the microhardness of the alloys was influenced by the grain size. Additionally, martensite and austenite peaks were shifted to the lower temperature by increasing the cycling process, while the rate of shifting increased generally by adding more Sn element into the alloy.

Effect of Ti Contents on the Microstructure and Mechanical Properties of Ni˗Al˗Ti System

In this work, a ternary system prepared by Ni-Al-Ti mixed powder was synthesized using self-propagation high-temperature synthesis (SHS) process. The weight of the reactant was varied using 3%, 10%, 20% and 30% of the Ti content. The mixtures were compressed in a steel die to form compacted pellets, and subsequently ignited using an external heat source to initiate the combustion process. The synthesized products were characterized using SEM, EDS, and XRD, whereas the mechanical property of the product was measured using a Vickers microhardness test. The identification of the formed phase indicates that Ni-Al, Ti-Al and Ti-Ni systems were formed during the reaction. An increase of Ti content from 3% to 10% improves the density of the synthesized product. Further increase of Ti content to 20% results in the generation of cracks. The addition of Ti with 30% leads to the formation of a porous product. The heat released by the SHS process due to the formation of several intermetallic phases was responsible for the formation of defect products. The highest hardness of the product was achieved in the product prepared by 20% Ti content. However, the higher Ti content than 20% results in hardness reduction. This work shows that the content of 10% of Ti produced a dense and hard product.

Role of carbon in modifying solidification and microstructure of a Ni-based superalloy with high Al and Ti contents

The effect of carbon ranging from 0.014 to 0.071 wt.% on the solidification and microstructure of a Ni-based superalloy with high Al and Ti contents was studied. The results show that the increase in carbon addition significantly increases the size and volume fraction of MC carbides and promotes the change of their morphology from blocky to elongated shape. However, the carbon addition obviously decreases the size and volume fraction of eutectic (γ + γ′) and reduces η phase and borides formation. The change in carbide characteristics is mainly because of the increasing carbide-forming element and carbides precipitation temperature with the increase in carbon which favors the growth of them along the interdendritic liquid film. MC carbides are formed at an earlier solidification stage than the eutectic (γ + γ′). The increased carbide formation consumes more Ti, which delays and reduces the eutectic (γ + γ′) precipitation. The delay of eutectic (γ + γ′) precipitation leads to a deeper undercooling, which significantly decreases the critical Ti concentration for its precipitation. This, in turn, lowers Ti/Al ratio in residual liquids ahead of the eutectic (γ + γ′) and hence reduces η formation subsequently. B and Zr are slightly enriched in the carbides, which are considered during discussing how carbon influences the eutectic (γ + γ′) precipitation.

Titanium-rich phases in the Earth's transition zone and lower mantle: Evidence from experiments in the system MgO–SiO2–TiO2(±Al2O3) at 10–24 GPa and 1600 °C

Phase relations in the MgSiO3–MgTiO3 and Mg3Al2Si3O12–MgTiO3 systems were studied at 10–24 GPa and 1600 °C using a high-pressure Kawai-type multianvil apparatus. We investigated the full range of starting compositions for the enstatite-geikielite system to derive a P–X phase diagram and synthesize titanium-bearing phases, such as olivine/wadsleyite, rutile, pyroxene, MgTiSi2O7 weberite, bridgmanite and MST-bridgmanite in a wide pressure range. Olivine and pyroxene in run products are characterized by a low titanium content (<0.6 and <0.3 wt% TiO2, respectively) whereas the content of TiO2 in wadsleyite reaches 2 wt% at 12 GPa. The concentration of Ti in MgTiSi2O7 weberite decreases with pressure from 52 wt% TiO2 at 14 GPa to 43 wt% TiO2 at 18 GPa. Two perovskite-type structures (MgSiO3 bridgmanite and Mg(Si,Ti)O3 bridgmanite) were detected in the studied system. MgSiO3 bridgmanite (Brd) is formed at a pressure of >20 GPa and characterized by significant titanium solubility (up to 13 wt% TiO2 at 24 GPa). Mg(Si,Ti)O3 perovskite is formed at a pressure of >17 GPa. The concentration of TiO2 in this phase varies from 29 wt% to 49 wt%. It was found that addition of Ti to the system moves the boundaries of Ol/Wad phase transformations to lower pressures. Addition of Al to the starting material allows us to simulate the composition of natural Ti-rich garnets and bridgmanites. It is important to note that garnet in the Prp-Gkl system is stable throughout a wide pressure range (10–24 GPa). Al incorporation does not affect the distribution of titanium between two types of bridgmanite. It is shown that high contents of Ti stabilize bridgmanite-like compounds at considerably lower pressure than that at the lower mantle/transition zone boundary. Our experiments simulate the composition of natural Ti-rich primary garnet found in eclogite from the Sulu ultrahigh-pressure (UHP) terrane.

Effect of isothermal annealing on mechanical performance and corrosion resistance of Ni-free Zr59Ti6Cu17.5Fe10Al7.5 bulk metallic glass

Ni-free Zr-Ti-Cu-Fe-Al bulk metallic glass (BMG) is regarded as a prospective candidate for practical applications. However, a high Ti content in the BMG causes a sharp deterioration of mechanical performance. Herein, the effects of isothermal annealing on the structure, mechanical performance, and corrosion resistance of the Zr59Ti6Cu17.5Fe10Al7.5 BMG are investigated. The alloy after a short-time annealing at 573 K shows admirable compressive strength and plasticity of 1910 MPa and 12.1%, respectively, which are much higher than 1733 MPa and 4.3% of the pristine BMG. This enhancement was ascribed to precipitation of ultrafine Al3Zr2 nanograins from the BMG matrix. However, the prolonged annealing induces propagation of nanocrystals and decreases free volume in the alloys, leading to the deterioration of mechanical performance. The electrochemical study demonstrates that the BMG maintains good corrosion resistance after the annealing. This work offers an avenue for designing high-performance Ni-free BMG-based alloys.

Tracking crystal-melt segregation and magma recharge using zircon trace element data

The Cretaceous Yunshan caldera complex in SE China consists of an unusual coexisting assemblage of peraluminous and peralkaline rhyolites and a resurgent intra-caldera porphyritic quartz monzonite. In this study, we use zircon trace element data to study the compositional differences of zircons from cogenetic magmas and to track the evolution of the entire magmatic system. Our results indicate that the zircons from the peraluminous and peralkaline rhyolites formed from highly evolved compositions with high Hf concentrations and low Ti contents, and low Th/U and Zr/Hf ratios, which are distinct from those of the intrusive porphyritic quartz monzonite. Zircons from the peraluminous and peralkaline rhyolites display overlapping Zr/Hf and Hf, but the zircons from the peralkaline rhyolites have extremely low Eu/Eu* ratios (<0.1) and Ti contents (2.26–13.3 ppm). The lack of overlapping zircon trace element compositions between the volcanic and intrusive caldera units is interpreted to represent crystal–melt segregation processes. In addition, zircon grains from the porphyritic quartz monzonite and a few zircon grains from the peraluminous rhyolite display distinctly bright rims and whole grains in cathodoluminescence imaging, which have high Ti, Zr/Hf, and Eu/Eu*, and are similar to those of zircons from the mafic microgranular enclave within the porphyritic quartz monzonite. We interpret these signatures to reflect crystallization from a relatively hot and less evolved magma indicating a magma chamber recharge event. We further developed a model in which the magmas of the peraluminous and peralkaline rhyolites were successively extracted from a primitive crystal mush by crystal–melt segregation with a rejuvenation of the crystal mush after the extraction of the peraluminous rhyolitic melt, leaving behind residual mushes solidified as porphyritic quartz monzonite. Our study shows that trace element analyses of zircons can effectively be used to pinpoint multiple crystal–melt segregation and melt extraction events as well as magma recharge processes in silicic magmatic systems.

29Si solid state NMR and Ti K-edge XAFS pre-edge spectroscopy reveal complex behavior of Ti in silicate melts

An understanding of the mechanisms of Ti is incorporation into silicate glasses and melts is critical for the field of petrology. Trace-element thermobarometry, high-field-strength element partitioning, and the physical properties of magmas are all be influenced by Ti incorporation into glasses and changes therein in response to changes in composition and temperature. In this study, we combine 29Si solid state NMR and Ti K-edge XAFS spectroscopy to investigate how Ti is incorporated into quenched Na-silicate glasses, and the influence of Ti on the structure of silicate species in these glasses. 29Si NMR shows that in both Ti-bearing Na2O•4SiO2 (NS4) and Na2O•8SiO2 (NS8) glasses, increasing the amount of Ti in the melt results in a shift of Si Q4 peak in the 29Si NMR spectra reflecting Ti nearest neighbors for Si in Q4 speciation. The Ti XAFS results from NS8 glass indicate that Ti is primarily incorporated in [5]-fold coordination. At higher Ti content, there is a shift of the XAFS pre-edge feature suggesting mixing of [4]-fold Ti into the spectra. Combined, the 29Si NMR and XAFS pre-edge data are consistent with Ti incorporation as isolated [5]Ti atoms and the formation of [5]Ti clusters at relatively low Ti concentrations, with no evidence for Ti–Na interactions as suggested by previous studies. As the Ti content increases, the Ti atoms begin to occupy 4-fold coordinated sites interacting primarily with Si in Q4 speciation (no significant Na–[4] Ti bonding). The internal consistency of these two techniques provides a uniquely complete snapshot of the complexity of Ti incorporation in silicate melts and underlies the importance of understanding Ti incorporation mechanisms in natural magmatic systems.

Quantitative Analysis of Microstructures and Strength of Nb-Ti Microalloyed Steel with Different Ti Additions

A quantitative analysis was carried out in the present study to determine the effects of titanium (Ti) addition on microstructures and strength of Nb-Ti microalloyed steel. The obtained results revealed that strength was significantly improved with an increase in Ti content from 0.041 to 0.079 wt pct. The difference in the yield strength between the two steel samples occurred due to the different strengthening effects of grain refinement, precipitation, and dislocation strengthening, among which the grain refinement and precipitation strengthening contributions were dominating. With a further increase in the Ti content, ferrite grains became refined. Consequently, a homogeneous ferrite microstructure was attained for high Ti contents. Moreover, large-sized (Ti, Nb)C particles manifested the Kurdjumov–Sachs (KS) relationship, whereas fine (Ti, Nb)C particles held the Baker–Nutting (BN) relationship; thus, abundant fine nanoscale (Ti, Nb)C particles formed after coiling. Furthermore, the high dislocation density facilitated the precipitation of (Ti, Nb)C particles along dislocation lines.

Green synthesis of submicron-sized Ti-rich MWW zeolite powders via a novel mechanochemical dry gel conversion in mixed steam environment

In this research, a novel green mechanochemical dry gel conversion method (MDGC) is reported to obtain submicron-sized Ti-rich MWW zeolite. First, titanium and silica sources were milled under milder conditions in a planetary ball mill to construct the uniform SiO2-TiO2 composite powders with higher Ti contents. Subsequently, submicron-sized Ti-rich MWW zeolite powder was prepared via dry gel conversion (DGC) route using the obtained composite under mixed steam environment consisting of water and piperidine. The physicochemical properties of the SiO2-TiO2 composites before and after calcination and corresponding Ti-MWW-MDGC were investigated by XRD, UV–Vis, FT-IR, SEM, XRF, and N2 absorption-desorption. Moreover, Ti-MWW (30)-MDGC exhibited a superior catalytic activity during epoxidation with H2O2 compared with the traditional DGC method, and the conversion of 1-hexene increased from 4.2% to 26.3%. The MDGC method is a promising approach for the green production of various zeolites with higher heteroatom contents, such as TS-1, Ti-Beta and Sn-MWW, etc.

Titanium Ions Play a Synergistic Role in the Activation of NLRP3 Inflammasome in Jurkat T Cells.

Release of titanium ions (Ti ions) frequently occurs around dental implants and, as a consequence, higher content of Ti is typically present in peri-implantitis tissue. Unlike chronic periodontitis, Ti ions may play a role in the development of peri-implantitis. Inflammasomes are multiprotein signal transduction complexes, involved in inflammation and immune response, which lead to the secretion of mature cytokines associated with the progression of peri-implantitis. It is well known that T lymphocytes dominate the immune response in peri-implantitis, but whether Ti ions can impact the assembly of functional inflammasomes in T cells still remains unclear. Here, we observed that the mRNA expression of NLRP3 and CASP1, as well as the secretion of IL-1β, increased after 6-h incubation of Jurkat T cells with PHA and Ti ions. Moreover, measurement by confocal microscopy and flow cytometry assay indicates that Ti ions can promote the production of ROS, while NLRP3 expression and IL-1β secretion are reduced after treatment of Jurkat cells with NAC (ROS scavenger). Taken together, we presently show that Ti ions can activate NLRP3 inflammasome and then promote IL-β secretion in vitro, where ROS may play a mechanistic role in this activation process.

Spalling resistance of thermally grown oxide based on NiCoCrAlY(Ti) with different oxide peg sizes

NiCoCrAlY is usually used as the material to bond-coat in thermal barrier coating systems under high temperatures. Using NiCoCrAlY and adding different amounts of the active element Ti (0, 0.1, 0.3, and 0.5; wt%), the relationship between oxide peg size and thermally grown oxide spalling resistance is ascertained by examining specimens subjected to a cyclic oxidation experiment. Oxide pegs, consisting of a Y- and Ti-rich oxide core and an outer Al2O3 sheath, are formed by Ti and Al successively reacting with oxygen after the rapid generation of Y-rich oxide. The size of the oxide pegs with higher Ti concentrations is on average bigger in the alloy. Severe thermally grown oxide spalling occurred in the 0.5 wt% Ti specimen, but in the 0.3 wt% Ti specimen, it displayed the best adherence with the alloy due to the presence of fine pegs. Cavities existed at the interface between the inner oxide core and outer Al2O3 sheath of larger pegs serve as microcrack sources and further induce severe scale failure combined with the initial interface crack between the scale and alloy.

Synthesis of titanium silicalite-1 (TS-1) zeolite with high content of Ti by a dry gel conversion method using amorphous TiO2–SiO2 composite with highly dispersed Ti species

In this study, we have developed a new method to synthesize mesoporous titanium silicalite-1 (TS-1) with a higher content of active titanium in the framework (more than 5%) than that obtained from the conventional hydrothermal synthesis. The new method combines two methods as follows: (1) a sol-gel method in tetrahydrofuran for the synthesis of TiO2–SiO2 composite with highly dispersed Ti species and (2) a dry gel conversion method for the crystallization to TS-1. This investigation revealed that the dispersion of Ti in the starting materials was quite important to synthesize mesoporous TS-1 with high content of Ti besides dry conversion method. The obtained mesoporous TS-1 with a high content of titanium showed higher catalytic activity in 1-hexene epoxidation than conventional TS-1. This high activity is likely to originate from the high content of titanium in the framework.