Mn Ti Research Articles

Anomalous internal friction associated with the thermoelastic martensitic transformation in a Cu–Al–Ni–Mn–Ti alloy

An anomalous internal friction phenomenon was observed during the reverse martensitic transformation of a polycrystalline Cu–Al–Ni–Mn–Ti shape memory alloy, i.e. negative internal friction appeared during the transformation, when frequency is relatively low due to the interaction between the martensitic variants with positive and negative loss elastic modulus. The latter can be stabilized by applied stress when their orientation is unfavorable for the applied stress because of the constraint of austenite in a single growth direction.

First principles study of the electron structures of CaCu 3Mn 4O 12 and CaCu 3Ti 4O 12

The electronic structures of CaCu 3Mn 4O 12 and CaCu 3Ti 4O 12 are investigated from HF SCF LCAO calculation. In CaCu 3Mn 4O 12, the band and the density of states show a spin asymmetric ferrimagnetic character with a small energy gap. The Mn spin is anti-aligned with the Cu spin, and the total spin moment is 9 μ B. Our calculation correctly reproduces the observed antiferromagnetic insulating character of CaCu 3Ti 4O 12. The gap in the band structure, which is 2.15 eV, reasonably agrees with the experimental value 1.5 eV. The electron density populations at different planes show clearly that the electron density has symmetric character. A tilted Mn(Ti) orbital implies a typical tilted three-dimensional network of MnO 6 (TiO 6) octahedra due to doping of the Jahn–Teller ion Cu. There is no covalency between Ca, Cu and Mn(Ti) atoms. In contrast, there are stronger bonds and somewhat likely covalency between Cu and O atoms, and also between Mn(Ti) and O atoms.

Thermal stability of the martensitic transformation of Cu–Al–Ni–Mn–Ti

The development of new shape memory alloys with high martensitic transformation temperature increases the potential for applications. The development and use of these new alloys depends on the stability of the structure during cycling at high temperatures. If it is possible to guarantee that on alloys keeps the structure during cycling, then the alloy can be used because of the shape memory properties. The aim of this work is to obtain a kinetic model of the forward and backward martensitic transformation of two Cu–Al–Ni–Mn–Ti alloys. Differential scanning calorimetry has been performed in order to establish the kinetic stability of the martensite and the beta transformation.

Dependence of dielectric properties of manganese-doped strontium titanate ceramics on sintering atmosphere

It is shown in this paper that the microscopic mechanism of the dielectric relaxation in Mn-doped strontium titanate (SrTiO 3–ST) ceramics is associated with the off-center displacement of Mn Sr 2 + ions. This was accomplished by studying the dielectric properties and electron spin resonance spectroscopy in combination with X-ray powder diffractometry and scanning electron microscopy techniques in Sr 1− x Mn x TiO 3 ceramic samples sintered in different atmospheres (air, oxygen and nitrogen) at 1500 °C. First, it is shown that manganese is incorporated into the perovskite lattice of ST, preferably as Mn 2+ at Sr sites. However, a small amount of Mn 4+ at Ti sites is also observed when fired in air or oxygen flow. The concentration of Mn Ti 4 + is the highest for sintering in oxygen, but firing in a reducing atmosphere (nitrogen) results solely in the incorporation of Mn 2+ at Sr sites. Correspondingly, the dielectric relaxation observed in Sr 1− x Mn x TiO 3 markedly increases in intensity and slightly shifts towards a higher temperature for ceramics sintered in nitrogen compared with those fired in air or oxygen. All these facts are consistent with a suggestion that the off-center displacement of Mn 2+ ions at the Sr sites of the highly polarizable ST lattice is the source of the observed relaxation behavior.

A novel laminate combined with elasticity and damping

A novel elasticity–damping composite laminate has been developed by explosive welding of Cu–Al–Ni–Mn–Ti alloy and QBe2 alloy. The internal friction of the composite laminate is about 18 × 10 −3 below 125 °C and reaches maximum of 30 × 10 −3 at about 125 °C. The damping behavior of the composite laminate shows obvious amplitude-dependent effect as the amplitude is more than 1 × 10 −4, and frequency-independent effect.

PIXE analysis of muscovite samples from tourmaline bearing granite pegmatites of Southwestern Nigeria

Muscovites from pegmatite bodies from southwestern Nigeria have been characterized by PIXE. The chemical analysis reveals that in these muscovites, the interlayer sites are occupied mainly by K, Fe, Rb Na, and traces of Mg and Ca in the octahedral positions whilst Si, Al, Ti Mn occur in the tetrahedral ones. The low Na/(Na+ K) ratios, low Ti content and enrichment in Rb in the muscovite suggest postmagmatic genesis of the host rocks. The variability in trace element composition may reflect differences in geological environment of emplacement of the pegmatite bodies.

PIXE ANALYSIS OF TRACE ELEMENTS IN HUMAN HAIR OF PATIENTS WITH LIVER DISORDERS

Human hairs of cirrhosis, acute viral hepatitis patients and healthy people in Ulaanbaatar, capital city of Mongolia, were analyzed for the presence of heavy elements by PIXE spectrometry using 2.5 MeV proton beam at the Tokyo Institute of Technology Van de Graaff Laboratory. The samples were dissolved in a mixture of nitric acid and hydrogen peroxide. Then a 20μl aliquot was dropped on a Nuclepore Track-etch Membrane. The IAEA Reference Hair IAEA-086 certified reference material was used in order to verify accuracy of the method and the results were in good agreement with the certified values. To determine the interaction among nine elements in hair, correlation coefficients were evaluated for several pairs of elements. In the group of healthy control, no correlation between elements was identified. Opposite to this, the strong positive correlations were observed for Zn and Ca or Fe ; Mn and Ca or Ti ; Sr and Zn or Fe in the patients hair. In the present study, the mean concentrations of Ca , Ti , As and Sr in Mongolian patients were higher than those in the hair of normal people in Japan, Mongolia, Iran and Indonesia. The levels of Cu , Zn and Mn concentration in hair of normal people were almost the same for all the cohorts.

Coupled Charge-Spin Dynamics of the Magnetoresistive PyrochloreTl2Mn2O7Probed Using Ultrafast Midinfrared Spectroscopy

Optical-pump midinfrared probe spectroscopy is used to investigate coupled charge-spin dynamics in the magnetoresistive pyrochlore TI(2)Mn(2)O(7). We find that the temporal persistence of the photoexcited carrier density is strongly influenced by spin disorder above and below the ferromagnetic Curie temperature. Our results are consistent with a picture whereby spin disorder leads to spatial segregation of the initially excited Tl 6s-O 2p electron-hole pairs, effectively reducing the probability for recombination. This further implies that colossal magnetoresistance in these materials may be driven primarily by Mn t(2g) spin disorder.

Development of metal hydride with high dissociation pressure

The effective hydrogen capacity of Ti 1.1CrMn exhibited the maximum value of 1.8 wt% in the pressure range of 33 and 0.1 MPa at 296 K (dissociation pressure: 11 MPa), and the alloy provided over 10% more capacity than conventional Ti Cr Mn (Ti 1.2CrMn: 1.6 wt%, Ti 1.2Cr 1.9Mn 0.1: 1.3 wt%). At the low temperature of 233 K, the alloy absorbed 2.0 wt% of hydrogen and the hydrogen desorption capacity at 0.1 MPa was 1.6 wt%. The desorption capacity of conventional Ti Cr V was 0 at 233 K due to the low dissociation pressure. The dissociation pressure decreased with the Ti and the Mn contents and was explained by the function of the bulk modulus and the cell volume. According to the Van’t Hoff plots, the standard enthalpy difference (heat of formation) of the Ti 1.1CrMn hydride was −22 kJ/mol H 2. The absolute value was about 10 kJ/mol H 2 smaller than those of LaNi 5 and Ti Cr V. The alloy had sufficient hydriding and dehydriding kinetics. In the pressure range of 33 and 0.1 MPa at 296 K, the alloy absorbed and desorbed 1.8 wt% of hydrogen in 60 and 300 s, respectively. The hydrogen capacity changed gradually over many cycles and that after 1000 cycles was 94% of the initial capacity. Thus, Ti 1.1CrMn can be utilized for a high-pressure MH tank, which contains a hydrogen-absorbing alloy with high dissociation pressure and compressed hydrogen.

The isothermal section of the Gd–Mn–Ti ternary system at 773 K

The isothermal section of the phase diagram of the Gd–Mn–Ti ternary system at 773 K has been investigated mainly by X-ray powder diffraction with the aid of differential thermal analysis. The 773 K isothermal section of the ternary system consists of 11 single-phase regions, 19 two-phase regions and 9 three-phase regions. At 773 K, the maximum solid solubility of Ti in Mn, GdMn 12, Gd 6Mn 23 and GdMn 2 are about 8, 2, 3 and 3 at% Ti, respectively. The homogeneity range of Mn 2Ti extends from about 61 to 69 at% Mn. No ternary compounds were observed in this system.

The isothermal section of the phase diagram of the Dy–Mn–Ti ternary system at 773 K

The isothermal section of the phase diagram of the Dy–Mn–Ti ternary system at 773 K has been investigated mainly by X-ray powder diffraction (XRD), differential thermal analysis (DTA) and optical microanalysis techniques. It consists of 11 single-phase regions, 19 two-phase regions and 9 three-phase regions. At 773 K, the maximum solid solubility of Ti in Mn, DyMn 12, Dy 6Mn 23 and DyMn 2 are about 8, 3, 3.5 and 3.5 at% Ti, respectively. The homogeneity range of Mn 2Ti extends from about 61–69 at% Mn. No ternary compounds were observed in this system.

Crystallographic superstructure of Ti-doped hexagonalYMnO3

We synthesized hexagonal $\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_{3}$ doped with Ti ions and investigated the crystal structure by means of transmission electron microscopy. Superlattice reflection spots with a modulation wave vector $q=\frac{1}{3}{c}^{*}$ appeared for the Ti-doped $\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_{3}$. We found that Ti-doped $\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_{3}$ intrinsically consists of the hexagonal phase and the rhombohedral phase derived from formation of a superstructure with the $3{d}_{001}$ period along the $c$ axis. The hexagonal-to-rhombohedral phase transition results from a change of the stacking manner in Mn(Ti) trimers in Mn(Ti)O layers.

Occurrence and Origin of Andalusite in Peraluminous Felsic Igneous Rocks

Andalusite occurs as an accessory mineral in many types of peraluminous felsic igneous rocks, including rhyolites, aplites, granites, pegmatites, and anatectic migmatites. Some published stability curves for And = Sil and the water-saturated granite solidus permit a small stability field for andalusite in equilibrium with felsic melts. We examine 108 samples of andalusite-bearing felsic rocks from more than 40 localities world-wide. Our purpose is to determine the origin of andalusite, including the T–P–X controls on andalusite formation, using eight textural and chemical criteria: size—compatibility with grain sizes of igneous minerals in the same rock; shape—ranging from euhedral to anhedral, with no simple correlation with origin; state of aggregation—single grains or clusters of grains; association with muscovite—with or without rims of monocrystalline or polycrystalline muscovite; inclusions—rare mineral inclusions and melt inclusions; chemical composition—andalusite with little significant chemical variation, except in iron content (0·08–1·71 wt % FeO); compositional zoning—concentric, sector, patchy, oscillatory zoning cryptically reflect growth conditions; compositions of coexisting phases—biotites with high siderophyllite–eastonite contents (Aliv ≈ 2·68 ± 0·07 atoms per formula unit), muscovites with 0·57–4·01 wt % FeO and 0·02–2·85 wt % TiO2, and apatites with 3·53 ± 0·18 wt % F. Coexisting muscovite–biotite pairs have a wide range of F contents, and FBt = 1·612FMs + 0·015. Most coexisting minerals have compositions consistent with equilibration at magmatic conditions. The three principal genetic types of andalusite in felsic igneous rocks are: Type 1 Metamorphic—(a) prograde metamorphic (in thermally metamorphosed peraluminous granites), (b) retrograde metamorphic (inversion from sillimanite of unspecified origin), (c) xenocrystic (derivation from local country rocks), and (d) restitic (derivation from source regions); Type 2 Magmatic—(a) peritectic (water-undersaturated, T↑) associated with leucosomes in migmatites, (b) peritectic (water-undersaturated, T↓), as reaction rims on garnet or cordierite, (c) cotectic (water-undersaturated, T↓) direct crystallization from a silicate melt, and (d) pegmatitic (water-saturated, T↓), associated with aplite–pegmatite contacts or pegmatitic portion alone; Type 3 Metasomatic—(water-saturated, magma-absent), spatially related to structural discontinuities in host, replacement of feldspar and/or biotite, intergrowths with quartz. The great majority of our andalusite samples show one or more textural or chemical criteria suggesting a magmatic origin. Of the many possible controls on the formation of andalusite (excess Al2O3, water concentration and fluid evolution, high Be–B–Li–P, high F, high Fe–Mn–Ti, and kinetic considerations), the two most important factors appear to be excess Al2O3 and the effect of releasing water (either to strip alkalis from the melt or to reduce alumina solubility in the melt). Of particular importance is the evidence for magmatic andalusite in granites showing no significant depression of the solidus, suggesting that the And = Sil equilibrium must cross the granite solidus rather than lie below it. Magmatic andalusite, however formed, is susceptible to supra- or sub-solidus reaction to produce muscovite. In many cases, textural evidence of this reaction remains, but in other cases muscovite may completely replace andalusite leaving little or no evidence of its former existence.

Dielectric relaxation in SrTiO3: Mn

Dielectric relaxation (activation energy U≈0.03 eV, relaxation time τ0≈5×10−11 s) has been observed in SrTiO3: Mn solid solutions at low temperatures. It is assumed that the relaxation is related to reorientation of the polarons localized at defects of the {Mn Ti 2+ -O−} type and that the deviations from classical thermally activated behavior at the lowest temperatures reached are due to the quantum tunneling mode.

55Mn NMR study in Mn1−Ti As

Abstract The nuclear magnetic resonance of 55 Mn nuclei in Mn 1− x Ti x As has been measured at 4 K. 55 Mn resonance frequency in zero external field is 237 MHz for MnAs of which the spontaneous magnetization at 4.2 K is 3.4 μ B /f.u. Zero field 55 Mn NMR spectra shift at the high-frequency side and they split in three signals by substituting Mn for Ti though the magnetic moment per Mn atom is constant for x less than 0.55. The transferred hyperfine field due to the nearest neighbor Mn moment is estimated to be +21 kOe.

Hydrogen absorption–desorption behavior of zirconium-substituting Ti–Mn based hydrogen storage alloys

Hydrogen storage properties of zirconium substituting Ti–Mn based Laves phase alloys with the formula Ti1−XZrXMn1.4 (X=0, 0.1, 0.2, 0.3 and 0.4) were evaluated by pressure-composition (PC) isotherm tests. Their crystallographic structures were identified by X-ray diffraction (XRD). The experimental results showed that their maximum hydrogen storage capacity (H/M, M=Ti1−XZrXMn1.4) increased with increasing X. The value of H/M for X=0.4 reached up to 2.916 which corresponds to 2.05 wt.% of hydrogen in the hydride, while the maximum reversible hydrogen storage capacity of the alloys appeared at X=0.1. The introduction of zirconium into the alloy did not cause any change in the phase constitution. C-14 type Laves phase was still predominant in the alloy while the lattice parameters a and c increased with increasing content of zirconium substituting for titanium. The introduction of zirconium increased the changes of entropy and enthalpy of hydrogen absorption. Activation tests showed that Ti0.9Zr0.1Mn1.4 alloy could react with hydrogen quickly under the condition of 273K and 9 atm of hydrogen.

Characterization of Ti–Zr–Mn–V-based Laves phase alloys for MH refrigeration system

Ti–Zr–Mn–V based C14 Laves phase alloys have been developed, aiming for application to the metal hydride (MH) refrigeration system, because of their large hydrogen storage capacities and good plateau properties. The melt-spinning process, which was applied to the manufacturing of some of these alloys, could make the plateau slopes much flatter. In the present work, observations of the microstructures were carried out with regard to both Ti–Zr–Mn–V–Fe and Ti–Mn–V–Fe alloys, which are practical compounds for use in the MH refrigeration system. It was revealed that the segregation of zirconium in the Ti23Zr10Mn46.5V17Fe3.5 alloy and the precipitation of E93 structure oxide phase in the Ti35Mn47V15Fe3 alloy affected their plateau properties. It appears that, in order to improve the plateau property of these alloys, compositional homogenization and lowering of the oxygen are desirable.

Crystal structure and related properties of copper-doped barium titanate ceramics

The influence of copper on the crystallographic phase and the microstructure of ceramics with a nominal composition of BaTiO 3+0.02 BaO+ x CuO (0⩽ x⩽0.02) was investigated. Systematic studies of X-ray diffraction and electron paramagnetic resonance (EPR) with varying doping level and sintering temperature were performed. The EPR data show that Cu 2+ is incorporated into the BaTiO 3 lattice at Ti-sites. Like in the case of other 3d transition elements as, e.g., Mn, Fe or Ni, also Cu decreases the phase transition temperature cubic–hexagonal and stabilizes the hexagonal phase at room temperature. At Cu concentrations ⩾0.3 mol% and at a sintering temperature of 1400 °C hexagonal phase occurs and the microstructure exhibits exaggerated, plate-like grains with grain sizes ⩾200 μm which is typical for hexagonal BaTiO 3 ceramics. Compared to the doping with manganese, copper is more effective to stabilize the hexagonal phase, but its solubility into the BaTiO 3 lattice is significantly lower. Depending on doping level and sintering temperature the EPR data exhibit in the whole temperature range between 40 and 450 K a superposition of two spectra of Cu Ti 2+ which are attributed to tetragonally distorted CuO 6 octahedra in a tetragonal and hexagonal crystal surrounding, respectively. Analogous to the case of Ti Ti 3+ (d 1), Mn Ti 3+ (d 4), Fe Ti 2+ (d 6) or Ni Ti 3+ (d 7), the Jahn–Teller distortion caused by the d 9 electron configuration of Cu Ti 2+ is proposed as the driving force for the phase transition cubic to hexagonal.

Hydrogen absorbing properties and structures of Ti–Cr–Mo alloys

Ti–Cr–Mo alloys show different hydrogenation properties to Ti–Cr–V and Ti–Mn–V hydrogen absorbing alloys with b.c.c. structure. Ti–Cr–Mo alloys have a smaller solid solution range (<0.5 wt.%) than Ti–Cr–V (<1.3 wt.%). In order to understand this difference, crystal structure and hydrogenation behaviors were investigated by X-ray diffraction and pressure–composition isotherms (P–C–T) measurements. Most of the alloys investigated were single bcc phase. The relation of the plateau pressure vs. lattice volume of Ti–Cr–Mo alloys was opposite to Ti–Cr–V and many of conventional intermetallic alloys. The new parameter, the radius of tetrahedral hydrogen site, is introduced. This new parameter gives a linear relationship with the plateau pressure for both Ti–Cr–Mo and Ti–Cr–V alloys. Hydrogen capacity of Ti–Cr–Mo and Ti–Cr–V are the same in a hydrogen to metal ratio basis. Slight addition of V to Ti–Cr–Mo alloys leads to dramatic increase of solid solution range.

Thermal behavior of Mn- and P-containing anodic-spark coatings on titanium

Differential thermogravimetric, and x-ray photoelectron spectral, as well as diffraction, analyses were applied to investigate anodic coatings formed under electric-breakdown conditions in electrolytes containing polyphosphate manganese complexes. It is shown that annealing at temperatures of up to 1000°C does not affect the concentration of elements in coatings, but is conducive to crystallizing Na0.23TiO2-bronze, manganese pyrophosphate Mn2P2O7 , sodium, as well as manganese, titanophosphates NaTi2(PO4)3 and Mn(II)Mn(III)Ti(PO4)3 , respectively.