Mn Ti Research Articles

Giant enhancement of the magnetocaloric response in Ni–Co–Mn–Ti by rapid solidification

Magnetocaloric refrigeration is a solid-state cooling approach that promises high energy efficiency and low environmental impact. It remains uncompetitive with conventional vapor-compression technologies due to lack of high-performing materials that exhibit large magnetocaloric effects in low magnetic fields. Here we report a game-changing enhancement of the magnetocaloric response in a transition-metal-based Ni–Co–Mn–Ti. Mechanically and chemically stable rapidly solidified ribbons exhibit magnetic entropy changes as high as ∼27 J⋅kg−1K−1 for a moderate field change of 2 T, comparable to or larger than the best known materials for near-room temperature applications. The ribbons can be easily manufactured in large quantities and the transition temperature can be adjusted by varying Co concentration.

Enhanced Microwave Absorption Properties of Doped M-Type Barium Hexagonal Ferrites in Ka-band Frequencies

The present study reports the microwave absorption characteristics of La3+-Na+ substituted barium hexaferrites with chemical composition: Ba(1−2x)LaxNaxFe10CoTiO19 and Ba(1−2x)LaxNaxFe10Co0.5TiMn0.5O19 (0.00 ≤ x ≤ 0.25) respectively in Ka-band frequencies. The electromagnetic characteristics such as complex permittivity, complex permeability, and microwave absorption properties were studied using Vector Network Analyzer in 26.5–40.0 GHz frequency band. Dielectric properties showed almost constant variation with increase in frequency. Magnetic permeability spectra observed wavy variation with frequency. Comparing the electromagnetic properties of two series, it is observed that Co–Ti–Mn series observes higher values of electromagnetic properties in comparison to Co–Ti series. For composition x = 0.15 of Ba(1−2x)LaxNaxFe10Co0.5TiMn0.5O19 series, −55.33 dB reflection loss at 30 GHz frequency with −10 dB absorption bandwidth around 3.51 GHz has been observed. Thus, these materials can be employed as effective absorbers for Ka-band microwave absorbers.

Microstructure, superelasticity and shape memory effect by stress-induced martensite stabilization in Cu–Al–Mn–Ti shape memory alloys

In this study, the microstructure, martensitic transformation, superelasticity, stabilization of stress-induce martensite and the corresponding shape memory effect of Ti-doped Cu–Al–Mn shape memory alloys were investigated. The results show that the present Cu–Al–Mn–Ti alloys consist of two types of L21 phases, including Cu2AlMn parent and Cu2TiAl precipitate. The dispersive L21–Cu2TiAl precipitates strengthen the stabilization of stress-induced 2H(γ′1) martensite from L21–Cu2AlMn parent. Thus, all studied alloys show not only superelasticity at deformation, but also shape memory effect after unloading by heating. Consequently, the Cu–12.9Al–8.3Mn–0.5Ti alloy (wt%) possesses the best superelastic strain up to 4.6% and a shape memory effect of 1.5% under a pre-deformation of 11%, while Cu–12.8Al–7.7Mn–2.6Ti alloy (wt%) shows the best shape memory effect up to 2.5% simultaneously showing 1.9% of superelastic strain with a pre-deformation of 10%.

Effects of ZnO/Mn Concentration on the Micro-structure and Optical Properties of ZnO/Mn–TiO2 Nano-composite for Applications in Photo-Catalysis

We successfully synthesized of ZnO/Mn–TiO2 (Mn–Ti) nano-composite for different ZnO:Mn (Zn-M) concentrations. These composites with high photo-catalytic activity derived from TiO2 and Zn-M nanoparticles elaborated by the sol–gel method. The SEM and TEM images indicated that samples reveals well-ordered and good size distribution of particles. In addition, the composite sample showed no aggregation in similitude with the anatase TiO2 sample. The study of optical properties of nano-composites shows that Zn-M nanoparticles caused to increase the optical activity of Mn–Ti composites samples and it established by UV–Vis, photo-luminescence, and photo-catalytic tests. The XRD study exhibited that in ours composites samples with increasing the Zn-M concentration, the particle size increased from 10 to 27 nm. PL measurements suggest that co-emission of a strong luminescence, high yellow emission at 563 nm, at 640 nm and at 774 nm is observed from the Mn–Ti composites samples. The photo-catalytic activity of the prepared nano-composite was examined for the degradation of methyl-orange (MO) by the irradiation of UV light.

Microstructure and Hardness Evolution during Deformation near Ae3 in a Cr–Mn–Ti Gear Steel

Developing appropriate thermomechanical processing routes for decreasing macrohardness of gear steels without heat treatment has a numerous futuristic applications in rolling industry. The effect of different deformation processes applied to Cr–Mn–Ti gear steel on the evolution of microstructure and hardness are studied by using a thermal simulator. It is found that imposing second‐pass deformation near Ae3 temperature inhibits occurrence of dynamic recrystallization (DRX), and increases stored deformation energy in austenite, which significantly promotes ferrite and pearlite transformation. As a result, the maximum volume fraction of ferrite and pearlite approaches ≈90%, and the corresponding macrohardness decreases to ≈215 HV. The difference of ferrite transformation between different deformation processes is analyzed using a thermodynamic equation by taking into account the stored deformation energy. The present calculations indicate that interval between Ae3 and deformation temperature can only be avoided at lower deformation temperature of second‐pass. This restricts static recovery or recrystallization, and quantities of dislocations that act as nucleation sites are retained before ferrite transformation.

W-Modified Mn–Ti Mixed Oxide Catalyst for the Selective Catalytic Reduction of NO with NH3

A W-modified Mn–Ti mixed oxide catalyst was prepared by the homogeneous precipitation method, which was applied to the selective catalytic reduction of NO with NH3 (NH3-SCR). The introduction of W could broaden the operation temperature window of Mn0.5TiOx, and the Mn0.5W0.1TiOx showed good SCR activity at 150–350 °C (NOx conversion above 80%). The results of characterization demonstrated that W introduction improved the redox ability, inhibited the separated NO/NH3 oxidation abilities, and provided additional Brønsted and Lewis acid sites. When W was added, less NO oxidation to NO2 possibly led to the inhibition of SCR activity at low temperatures, while the increase of NH3 adsorption and inhibition of NH3 oxidation could contribute to the enhancement of high-temperature SCR activity. Meanwhile, the N2O formation in the NH3-SCR over both Mn0.5TiOx and Mn0.5W0.1TiOx mainly follow the Eley–Rideal mechanism, and the introduction of W inhibited the N2O formation.

Magnetic and electronic properties of the ferroelectric-photovoltaic ordered double perovskiteCaMnTi2O6investigated by x-ray absorption spectroscopies

The ferroelectric and magnetic phases of the double perovskite $\mathrm{CaMnT}{\mathrm{i}}_{2}{\mathrm{O}}_{6}$ with $A$-site order have been investigated by soft x-ray absorption and magnetic circular dichroism. All spectra point to a very ionic state of divalent Mn and tetravalent Ti atoms. The effects of the crystal field produced by O ligands around tetravalent titanium and the dissimilar Mn1 and Mn2 sites were investigated. Both the so-called square-planar and the octahedrally coordinated Mn sites spectroscopically contribute in a rather similar way, with little influence by the oxygen environment. Multiplet calculations suggest a small $O\phantom{\rule{0.16em}{0ex}}2p\text{\ensuremath{-}}\mathrm{Ti}\phantom{\rule{0.16em}{0ex}}3d$ charge-transfer component in the FE phase. Magnetic symmetry calculations were performed to determine probable configurations of Mn spins compatible with the acentric $P{4}_{2}mc$ structure and, in combination with the computational magnetic results in Inorg. Chem. 56, 11854 (2017), we have identified the $P{4}_{2}^{\ensuremath{'}}{m}^{\ensuremath{'}}c$ as the most likely magnetic space group keeping invariant the unit cell below ${T}_{\mathrm{N}}$. This symmetry forces the sign of the magnetic coupling along the Mn columns parallel to $c$ to reverse with respect to the coupling between neighboring columns. Below ${T}_{\mathrm{N}}$, the dichroic magnetization loops at the $\mathrm{Mn}\phantom{\rule{0.16em}{0ex}}{L}_{3}$ edge confirm the absence of spontaneous ferromagnetism, although a very small field-induced spin polarization was detected in the sample.

The protective role of selenium against cadmium-induced hepatotoxicity in laying hens: Expression of Hsps and inflammation-related genes and modulation of elements homeostasis

The purpose of this study was to examine the potential role of high selenium (Se) diets in alleviating chronic cadmium (Cd) hepatic toxicity in laying hens. In the present study, 128 healthy 31-week-old laying hens were fed a diet supplemented with Se (Na2SeO3, 2 mg/kg), Cd (CdCl2, 150 mg/kg), or both Se and Cd (150 mg/kg of CdCl2 and 2 mg/kg of Na2SeO3) for 90 days. The expression levels of heat shock proteins (Hsps, including Hsp60, Hsp70 and Hsp90) and inflammation-related factors, including nuclear factor-kappa B p50 (NF-κB), cyclooxygenase-2 (COX-2), prostaglandin E synthases (PTGES), interleukin 1-beta (IL-1β), and tumor necrosis factor-α (TNF-α) were investigated. The concentrations of 28 elements were also determined. The results indicated that Cd treatment significantly increased the mRNA and protein expression levels of Hsps and significantly improved the expression of inflammation-related genes. Moreover, Cd addition to the diets resulted in disturbances in the systemic balance of 13 elements, leading to decrease in the concentrations of Cr, Mn, Sr, Ba, and Hg and increase in Li, B, Ca, Ti, Fe, Cu, Mo, and Cd concentrations. Treatment with Se significantly alleviated Cd-induced hepatic toxicity, as evidenced by a reduction in Hsp60, Hsp70, Hsp90, NF-κB, COX-2, PTGES, TNF-α, and IL-1β expression. Additionally, Se and Cd co-treatment alleviated the changes in Li, B, Ca, Fe, Ti, Cu, Mo, Cd, Cr, Se, Sr, Ba, and Hg concentrations, which was in contrast to that upon Cd induction. The study indicated that Se could help against the negative effects of Cd and may be related to the alleviation of Cd-induced Hsps stress and the inflammatory responses along with modulating the element homeostasis.

Mesoporous Mn–Ti amorphous oxides: a robust low-temperature NH3-SCR catalyst

Mn–Ti amorphous oxides prepared by the combinedin situdeposition and freeze-drying strategy exhibited excellent activities and stability in low-temperature NH3-SCR.

Improved NOx reduction in the presence of alkali metals by using hollandite Mn–Ti oxide promoted Cu-SAPO-34 catalysts

Hollandite Mn–Ti oxide promoted Cu-SAPO-34 catalysts exhibited outstanding deNOx performance and excellent resistance against alkali metal poisoning.

Precipitation behavior of Ti in high strength steels

Precipitation behavior of Ti in high strength steels was investigated by means of the equilibrium solid solubility theory. The contributions of Ti content to yield strength were calculated. The calculated results were verified by the hot rolling experiment for C–Mn steel and C–Mn–Ti micro alloyed steel, respectively. The research results show that the precipitates are mainly TiN at the higher temperature. With the decreasing temperature, the proportion of TiC in precipitates increases gradually. When the temperature drops to 800 °C, TiC will become predominant for the precipitation of Ti. When Ti content is less than 0.014% (mass fraction), Ti has little influence on the yield strength. When Ti content is in the range of 0.014%–0.03% (mass fraction), the yield strength of Ti micro alloyed steel is greatly increased, which leads to instability of the mechanical properties of the steel. Therefore, the design of Ti content in high strength steels should avoid this Ti content range. When Ti content is higher than 0.03%, the yield strength increases stably. In this experiment, when added Ti content was controlled in the range of 0.03%–0.05%, the contribution to the yield strength of Ti micro alloyed steel can reach about 92.44 MPa.

Catalytic Combustion of Vinyl Chloride Emission over a TiO2–MnOx Catalyst

TiO2–MnO x catalyst samples with different Ti/(Ti + Mn) molar ratios (2:3, 3:4, 4:5, 5:6, 6:7 and 1) prepared by the citric acid (CA) sol-gel method were studied in the catalytic combustion of vinyl chloride (VC) emission. The effects of preparation conditions and operation parameters on the catalytic performance of TiO2–MnO x were investigated. The catalyst samples were characterised by N2 adsorption, X-ray diffraction (XRD) and H2-temperature programmed reduction (H2-TPR). In the catalytic combustion of VC over TiO2–MnO x, products containing HCl, CO2, and H2O were obtained and there were no by-products such as chlorohydrocarbons and chlorine. The TiO2–MnO x catalyst with the molar ratio of CA/Mn/Ti = 0.30:0.20:0.80 showed the best catalytic performance and had better operating flexibility over the ranges of gas hourly space velocity (GHSV) of 15000–100000 h−1 and VC concentration of 0.05–2.00%. The temperatures at 50% conversion (140 °C) and at 99% conversion (220 °C) were achieved at a VC concentration of 0.1% and GHSV of 15000 h−1. XRD characterisation indicated that only the characteristic diffraction peaks of TiO2 with the anatase structure appeared and no characteristic diffraction peaks of MnO x species appeared for the TiO2–MnO x catalyst. XRD and H2-TPR results indicated that Mn ions were incorporated into the TiO2 lattice to form a Ti–Mn–O solid solution, which enhanced the reactivity of active oxygen species on the catalyst surface and thereby promoted the catalyst activity.

Promoting effect of Mn and Ti on the structure and performance of Co3O4 catalysts for oxidation of dibromomethane

Co3O4 catalysts modified with Mn and Ti, prepared by co-precipitation method, were used for catalytic oxidation of dibromomethane (CH2Br2), a model molecule for brominated volatile organic compounds (BVOCs). Addition of Ti or Ti+Mn distorted the crystal structure and led to the formation of a Co–O–Ti solid solution. The addition of Mn further enhanced the surface acidity and redox ability of the catalysts. Co–Mn–Ti exhibited the highest activity with a T90 of approximately 234°C and the highest selectivity to CO2 at low temperatures. Additionally, Co–Mn–Ti showed good stability for at least 30h at 500ppm CH2Br2, 0 or 2 vol% H2O, 0 or 500ppm p-xylene (PX), and 10% O2 at a gas hourly space velocity of 60,000h−1, and the final products were COx, Br2, and HBr, without the formation of other Br-containing organic byproducts. This high catalytic activity was attributed to its high specific area, high surface acidity, and strong redox property. Furthermore, the synergetic effect of Co, Mn, and Ti made it superior for CH2Br2 oxidation. A plausible reaction mechanism for CH2Br2 oxidation over Co–Mn–Ti catalysts was proposed based on the analysis of the products and in situ diffuse-reflectance infrared Fourier transform spectroscopy results.

Mineral composition of alkaline lamprophyres of the Tomtor massif as reflection of their genesis

The influence of parental melts on the chemical composition of rock-forming minerals of alkaline lamprophyres (monchiquites) referred to as the volcanic series of porphyritic potassic alkaline-ultrabasic rocks was studied in the Tomtor alkaline-ultrabasic carbonatite massif (Yakutia) hosting a unique deposit of Sc-REE-Y-Nb ores. Previous fluid-melt inclusion study showed that these rocks formed from two mixing alkaline-basic melts of different alkalinity. A detailed study of the chemical composition of minerals revealed a repeated irregular zoning in most of phenocrysts, which reflects the influence of different parental magmas and their mixing. It was established that the cores of diopside phenocrysts (Di I) with inclusions of Na-Fe-rich silicate melts have a low Mg-number and low contents of Ti, Al, and Ca and high contents of Na and Mn. The intermediate zones of phenocrysts (Di II) containing inclusions of K-Mg-rich silicate melts show a high Mg-number and are rich in Ti and Al and poor in Mn and Na. Groundmass grains and rims (and, sometimes, intermediate zones) of diopside phenocrysts often have a mixed Di I-Di II composition with slightly elevated contents of Mg, Ti, and Al. Amphibole phenocrysts, like the diopside ones, have both zones with low Mg contents and high Na/K ratios and Mn contents and zones with high Mg contents, low Na/K ratios, and low Mn and elevated Ti contents. Phlogopites are also of two varieties: highly magnesian, with high contents of Si and K and low content of Mn, and lowly magnesian, with low contents of Si and K and high content of Mn. Ilmenite, titanomagnetite, and fine grains of femic minerals are mostly of mixed varying composition. The chemical composition of rock-forming minerals, especially zoned phenocrysts, evidences that they crystallized with the participation of two alkaline-basic melts: Na-Fe-rich silicate melt enriched in Mn and K-Mg-rich silicate melt enriched in Ti but depleted in Mn.

Swelling of improved 16Cr–15Ni–2Mo–Mn–Ti–V–B steel under dose rates from 1 × 10−8 to 1.7 × 10−6 dpa/s

Radiation-induced swelling negatively affects the operability of structural units of fast breeder reactor (FBR) cores. Therefore, search for new and improvement of existing steels for reducing swelling is an important task.Since 2003, type 16Cr–15Ni–2Mo–Mn–Ti–V–B steel has shown a significant increase in radiation resistance due to its improved composition and heat treatment. Specialists of the JSC INM studied swelling of 16Cr–15Ni–2Mo–Mn–Ti–V–B steel with improved composition, data on the maximum swelling temperature, average swelling rate within typical coolant temperature ranges, as well as fast reactor dose rate were obtained.The obtained results are based on swelling measurements using hydrostatic weighing and transmission microscopy. Errors in hydrostatic measurements were examined with involvement of metallography data and selection of immersion liquid.It was revealed that the average swelling rate of improved 16Cr–15Ni–2Mo–Mn–Ti–V–B steel at the maximum swelling temperature is within the range of 0.04–0.14%/dpa. Shifting of this temperature from 460 to 520°C with increase of the maximum damaging dose from 60 to 80dpa (1.3× 10−6 and 1.7×10−6dpa/s, respectively), is observed. At doses below 10dpa and temperatures below 400°C the average swelling rate may reach 0.04%/dpa. At temperatures of about 600°C and irradiation doses below 50dpa the swelling rate does not exceed 0.01%/dpa during the whole period of observation.

Identification of Mn site in Mn-doped SrTiO 3 : First principles study

Abstract Manganese can incorporate into perovskite SrTiO 3 at either on the Sr-site ( A -site) or Ti-site ( B -site) depending on the growth conditions. However, there is no clear explanation on what conditions lead to A -site or B -site occupations and what are the local structures around Mn. In this work, first-principles calculations were carried out to study Mn in SrTiO 3 under different growth conditions. The calculations showed that Mn prefers to substitute for Ti site under a wide range of growth conditions; indicating that the substitution it is difficult to avoid even when one intentionally tries to dope Mn into the A -site. Due to a large size difference, Mn cannot fit in the Sr site. Instead, a charged interstitial Mn has rather low formation energy, especially under O-poor conditions. In addition, Mn i can bind with Sr vacancy which has the compensating charge with a very high binding energy to form Mn i - V Sr complex. Mn i - V Sr has an equivalent chemical composition to Mn Sr . Therefore, one might view Mn i - V Sr as an off-center Mn Sr . In this view point, Mn A -site has a large cation off-centering consistent with experimental observations. We further relate our local structure models with the experiments by calculating the Mn K -edge x-ray absorption near-edge spectroscopy (XANES) spectra associated with Mn Ti , Mn Sr (on regular Sr lattice), and Mn i - V Sr or off-center Mn Sr defects to compare with the measured Mn K -edge XANES spectra. Our results show good agreement with the measured spectra.

Co–Ti- and Mn–Ti-substituted barium ferrite for electromagnetic property tuning and enhanced microwave absorption synthesized via mechanical alloying

Substituted barium hexaferrite nanoparticles with nominal composition of BaCo1.0Ti1.0Fe10O19 and BaMn0.8Ti0.8Fe10.4O19 were synthesized by high energy ball milling (HEBM). The effects of Co–Ti and Mn–Ti substitution on their microstructure, electromagnetic properties, and microwave absorptive behavior were analyzed. The samples were structurally characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray analysis (EDX). The M-H loops of the composites were determined with a vibrating sample magnetometer (VSM), and the interaction with the microwave radiation in the range of 8–18 GHz of the nanocomposites dispersed in epoxy resin was measured with a vector network analyzer (VNA). This study suggests that by controlling the grain size and different elements of substitution would give a decrease in coercivity and enhanced values of complex permittivity in order to improve microwave absorption. The dielectric constant and loss were enhanced in comparison to the permeability constant and loss over the entire frequency range. Finally, microwave measurement showed that the substituted barium hexaferrite sample with Co–Ti and Mn–Ti could be used as an efficient microwave absorption material with an appropriate absorption at −31.27 and −26.73 dB, respectively. The predicted absorption and reflection loss demonstrates that Co–Ti and Mn–Ti substitution gives low reflectivity at microwave frequency and is a good candidate for electromagnetic materials for radar wave applications.

Self-Organized TiO₂-MnO₂ Nanotube Arrays for Efficient Photocatalytic Degradation of Toluene.

Vertically oriented, self-organized TiO2–MnO2 nanotube arrays were successfully obtained by one-step anodic oxidation of Ti–Mn alloys in an ethylene glycol-based electrolyte. The as-prepared samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis absorption, photoluminescence spectroscopy, X-ray diffraction (XRD), and micro-Raman spectroscopy. The effect of the applied potential (30–50 V), manganese content in the alloy (5–15 wt. %) and water content in the electrolyte (2–10 vol. %) on the morphology and photocatalytic properties was investigated for the first time. The photoactivity was assessed in the toluene removal reaction under visible light, using low-powered LEDs as an irradiation source (λmax = 465 nm). Morphology analysis showed that samples consisted of auto-aligned nanotubes over the surface of the alloy, their dimensions were: diameter = 76–118 nm, length = 1.0–3.4 μm and wall thickness = 8–11 nm. It was found that the increase in the applied potential led to increase the dimensions while the increase in the content of manganese in the alloy brought to shorter nanotubes. Notably, all samples were photoactive under the influence of visible light and the highest degradation achieved after 60 min of irradiation was 43%. The excitation mechanism of TiO2–MnO2 NTs under visible light was presented, pointing out the importance of MnO2 species for the generation of e− and h+.

Influence of Mn valence state and characteristic of TiO2 on the performance of Mn–Ti catalysts in ozone decomposition

ABSTRACTThe effects of physicochemical properties of Mn–Ti catalysts on O3 conversion were examined. The catalysts were prepared by a wet impregnation method that gave manganese supported on various commercial sources of TiO2. The properties of the catalysts were studied using physicochemical techniques, including Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA). The O3 decomposition tests of Mn–Ti catalysts with various manganese loadings revealed that the 10 wt% manganese catalyst exhibited optimal, excellent activity. The O3 conversion and Mn valence state of the Mn–Ti catalysts were different, depending on the structure of the TiO2 source. Increasing the O/Ti surface atomic ratio in TiO2 increased the Mn3+ ratio. The Mn3+ ratio directly affected the O3 decomposition activity of the Mn–Ti catalyst. When the Mn3+ ratio was the largest, the catalyst showed the highest activity in O3 decomposition. The valence state of Mn exposed to the surface was a critical factor in O3 decomposition by Mn–Ti catalysts.

The enhanced resistance to P species of an Mn–Ti catalyst for selective catalytic reduction of NOx with NH3 by the modification with Mo

The modification of Mn–Ti catalyst by Mo could enhance its resistance to P species.