Small Amount Of Mn Research Articles

Effects of Mn doping on the ferroelectric properties of PZT thin films

The effects of Mn doping on the ferroelectric properties of Pb(Zr0.3Ti0.7)O3 (PZT) thin films on Pt/Ti/SiO2/Si substrates have been investigated. The composition of the PZT and Mn doping level are Pb(Zr0.3Ti0.7)1−xMnxO3 (x = 0,0.2,0.5,1,2,4 mol%). The PZT thin films doped with a small amount of Mn2+ (x ⩽ 1) showed almost no hysteretic fatigue up to 1010 switching bipolar pulse cycles, coupled with excellent retention properties. However, excessive additions of manganese made the fatigue behaviour worse. We propose that the addition of small amounts of Mn is able to reduce the oxygen vacancy concentration due to the combination of Mn2+ and oxygen vacancies in PZT films, forming Mn4+ ions. The interfacial layer between the Pt electrode and PZT films and Mn-doped PZT (x = 4) was detected by measuring the dielectric constant of thin films of different thickness. However, this interfacial layer was not detected in Mn-doped PZT (x = 1). These observations support the concept of the preferential electromigration of oxygen vacancies into sites in planes parallel to the electrodes, which is probably responsible for the hysteretic fatigue.

Addition of Carboxyalkyl Radicals to Alkenes Through a Catalytic Process, Using a Mn(II)/Co(II)/O2 Redox System.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Addition of carboxyalkyl radicals to alkenes through a catalytic process, using a Mn(II)/Co(II)/O2 redox system.

A novel strategy for production of mono- and dicarboxylic acids by the addition of carboxyalkyl radicals to alkenes and dienes, respectively, was successfully developed through a catalytic process with use of Mn(II)/Co(II)/O(2) system. Thus, a variety of carboxylic acids were prepared by the reaction of alkenes and dienes with acid anhydrides in the presence of a very small amount of Mn(OAc)(2) (0.5 mol %) and Co(OAc)(2) (0.1 mol %) under dilute dioxygen.

ＭｎとＮｂを微量添加したＰＺＴ圧電セラミックスの機械的特性

Mechanical properties of PZT ceramics with small amount of Mn and Nb were investigated. The addition of 0.01mol% Mn and 0.02mol% Nb to PZT improved and stabilized their piezoelectric properties. The four point bending strengths of PZT with 0.01mol% Mn and 0.02mol% Nb addition were 85MPa and 63MPa, respectively. And the values of Weibull modulus were 9.1 and 7.8. As for the static mechanical properties, there is no large difference between 2 specimens.But compared with 0.02mol% Nb, the addition of 0.01mol% Mn to PZT doubled the vickers hardness. As to the 0.01mol% Mn added-PZT, the crack length measured by a micro vickers diamond indentor was anisotropic, and the internal stress measured with the microindetation tecnique increased.

Influence of manganese(II), cobalt(II), and nickel(II) additives in electrolyte on performance of graphite anode for lithium-ion batteries

Manganese dissolution into an electrolyte from the spinel LiMn 2O 4 in the lithium-ion cell has been recently investigated. In order to study the influence of the dissolved manganese species on the lithium intercalation/deintercalation into a natural graphite electrode, the electrochemical behavior of graphite was investigated in 1 mol dm −3 LiClO 4 electrolyte solution containing a small amount of Mn(II) by the addition of manganese(II) perchlorate. During the charging process, Mn(II) ions were firstly electroreduced on the electrode around 1.0 V versus Li/Li + followed by irreversible decomposition of the electrolyte and lithium intercalation into the graphite. By microscopic observation of the graphite surface, manganese deposition was confirmed after the charge/discharge test. Due to the manganese deposition, the reversible capacity of the graphite electrode was drastically decreased. Furthermore, the cyclability of the anode was degraded with the amount of the manganese additive increasing. We compared these results with those of the cobalt(II) and nickel(II) additives by dissolving the corresponding perchlorates. Furthermore, we discussed the influence in practical cells based on the consideration of electrochemistry of the deposited metals.

Experimental and Analytical Investigations of Fracture Toughness in Weldments of 6082 Al Alloy

6082 Al alloys are commercial and medium strength alloys, widely used as materials for welded structures. The purpose of this study is to investigate the effects of Mn addition on toughness of welded Al-Mg-Si alloys. To evaluate microstructural effects quantitatively, in-situ SEM observations of crack initiation and propagation behaviors through weldment are carried out. For the consideration of in-situ observation of fracture toughness test, stress field at crack-tip is analyzed using elasto-plastic finite element method (Hereinafter, FEM.) assuming that a crack is near a boundary between a weld metal and heat affected zone (Hereinafter, HAZ.). When small amount of Mn is added, recrystallization is completely suppressed as compared to specimens to which no Mn is added, thereby fibrous grains are kept. On the other hand, recrystallization of HAZ causes drastic decrease in fracture toughness in the case of no Mn addition. With the extension of a main crack, many microcracks are formed at grain boundaries ahead of a crack-tip despite the fact that the stress is relatively low. Such microcracking is not attributed to so-called liquation cracks, but the degradation is caused by the formation of film like Al-Mg intermetallic compounds at grain boundaries. The microcracks are aligned ahead of the crack-tip at an angle of 60 degrees from an initial notch direction. This is attributable to the experimentally-observed direction of the intermetallic compound film, which is also confirmed by the numerical analysis.

Thermal Transport Anomaly Associated with Weak Ferromagnetism in CaMnO3

The thermal conductivity κ( T ), thermal diffusivity α( T ) and magnetization M ( T ) have been measured for sintered CaMnO 3 and La 1- x Ca x MnO 3 in lightly electron-doped region (0.98≤ x ≤1.0). κ( T ) and α( T ) of CaMnO 3 show an anomalous enhancement below the weak ferromagnetic transition temperature T N . The enhancement is rapidly reduced by introduction of a small amount of Mn 3+ ions in La 1- x Ca x MnO 3 . The analyses suggest the possibility that the enhancement comes from the contribution of the heat transport by magnetic excitations.

Catalytic radical addition of ketones to alkenes by a metal–dioxygen redox system

Radical addition of ketones to alkenes catalyzed by Mn(OAc)2 combined with Co(OAc)2 using dioxygen as oxidant was developed; for instance, the reaction of cyclohexanone with oct-1-ene in the presence of very small amounts of Mn(OAc)2 and Co(OAc)2 under air (1 atm) gave 2-octylcyclohexanone in good selectivity; from styrene, a six-membered cyclic peroxide was isolated in good yield.

Aerosol particle chemical characteristics measured from aircraft in the lower troposphere during ACE-2

During the Aerosol Characterization Experiment (ACE-2), filter samples were collected aboard the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Pelican aircraft near Tenerife in June and July of 1997. The flights included constant altitude measurements in the boundary layer as well as profiles up to 3800 m providing detailed chemical information about the composition of the aerosol distribution in the lower troposphere. Three cases with different air mass origins—clean marine air, anthropogenically-influenced air from the European continent, and dust-laden air from the Sahara—were identified. The samples were analyzed by ion chromatography (IC) for ionic species, by combined thermal and optical analysis (TOA) for organic carbon, and by total reflection X-ray fluorescence (TXRF) for elemental composition. Particle composition and size distributions for the range of air masses encountered illustrate links in the chemical and microphysical characteristics of aerosol from different sources. Clean marine air masses were characterized by low particle number and mass concentrations with no detectable metals, while anthropogenically-influenced and dust-laden air had high number, mass, and trace metal concentrations. Anthropogenic sources were characterized by high concentrations of submicron particles and some Fe and Cu, whereas dust particle loadings included a significant mass of micron-sized particles and significant loadings of Fe, in addition to small amounts of Mn, Cu, and Ni. These results showed similar tracers for air mass origin as those found in other measurements of oceanic and continental air masses. Aerosol optical properties were estimated with a simplified model of the aerosol based on the measured compositions. The real and imaginary refractive indices and single scattering albedos differed significantly among the three types of aerosol measured, with clean marine aerosol properties showing the least absorption and dust-containing aerosols showing the most. There were only small differences in optical properties for the two different cases of clean marine aerosol, but some significant differences between the two dust cases. Since measurement uncertainties affect these calculations, we studied the type of mixing and the fraction of absorbing species and found the calculation was sensitive to these variations only for the dust-containing aerosol case, probably due to the small amount of water present. While the optical properties varied little with composition for clean marine and anthropogenically-influenced cases, they showed a strong dependence on variations in particle composition and mixing state for the dust-containing cases.

Heavy metals in mine soils amended with sewage sludge

In order to reclaim a clay quarry, a topsoil material was mixed with gravelly spoil at different ratios and with various rates of sewage sludge. The influence of three spoil/topsoil ratios (1:1, 2:1 and 3:1) and three sludge rates (40, 80 and 120 t ha−1) on chemical properties of the resulting material was investigated, with emphasis on heavy metal (Fe, Cu, Mn, Ni and Zn) contents. The mixtures topsoil/spoil/sludge were water saturated and incubated for 15 or 30 days in a chamber under controlled conditions. The incubated samples were analysed for pH, total carbon and nitrogen, and total, available, exchangeable and soluble heavy metals. The addition of spoil to the topsoil increased the volume of material available, by utilizing an inert material unsuitable by itself to grow plants. The addition of sewage sludge repaired the disadvantages of the spoil, increasing the pH and the organic matter contents. The total heavy metal contents in the mixtures followed the sequence Fe>>Mn>>Zn, Cu>Ni. All except Cu were within the ranges allowed for agricultural lands. The available heavy metals constituted a small fraction of total contents and decrease with time due to complexation and immobilization processes. The exchangeable and soluble fractions were almost negligible; only small amounts of Mn, Zn and Cu were detected. Therefore, the risk of contamination by heavy metals is insignificant in the conditions investigated. Copyright © 1999 John Wiley & Sons, Ltd.

Temperature dependence of β-phase transformation in Cu added Fe2Si5 thermoelectric material

Abstract The time–temperature–transformation diagrams for the eutectoid decomposition (α→β+Si) in slowly solidified Fe 2 Si 5 alloys with small amounts of Mn and Cu were obtained in the temperature range 873 and 1173 K. The shape of the diagrams can typically be described by the character C. The nose temperature in a binary Fe 2 Si 5 alloy was about 1023 K and increased by about 50 K in the Cu added alloy. The addition of small amounts of Cu drastically shifted the diagram to shorter times. The start of the eutectoid decomposition in the Cu added alloy was more than 240 times faster than that in the Cu free alloy at the nose temperature. The shape of the Si dispersoids formed by the eutectoid decomposition changed from lamella in the Cu free alloy to granular in the Cu added alloy. In the FeSi 2 alloy, the peritectoid reaction (α+e→β) was also enhanced by the addition of Cu. These results suggest that the existence of Si is not significant for the acceleration of the β formation. The kinetic analysis of the β-phase transformation based on the Johnson–Mehl–Avrami equation suggests that the addition of Cu does not change the transformation mechanism but changes the growth kinetics. The size of the Si dispersoids was quite fine when heating below 1023 K.

Fabrication and characterization of a two-dimensional electron gas in modulation doped ZnTe/Cd1−xMnxSe quantum wells

The II–VI semiconductors ZnTe and CdSe are nearly lattice-matched materials which have a type-II band alignment with a large offset (∼1.35 eV) of conduction band edges. Even though donors in ZnTe create deep levels, we have successfully made two-dimensional electron gases in this system through modulation doping of a CdSe layer sandwiched between n-doped (chlorine) ZnTe layers. In addition, we have fabricated “magnetic” two-dimensional electron gases, where a small amount of Mn is included in the CdSe quantum well, with the aim of studying spin-dependent phenomena in reduced dimensions. We find efficient transfer of electrons into the (Cd, Mn)Se quantum well, even when the doping layer is separated from the well by up to 150 nm of intrinsic ZnTe. By utilizing narrow spacer layers, carrier concentrations of up to 2×1013 cm−2 are demonstrated. Low temperature magnetotransport measurements of nonmagnetic samples indicate a Hall mobility typically in the range 5000–10 000 cm2/V s, but somewhat lower quantum mobilities (∼3000 cm2/V s). In the magnetic samples, while both the carrier concentrations and the Hall mobility are relatively unaffected by the presence of the Mn ions, a dramatic decrease in the quantum mobility is observed.

The crystal structure of λ-Al 4Mn

The crystal structure of the λ-Al 4Mn phase, considered to be closely related to icosahedral quasicrystalline i-AlMn was determined by X-ray analysis. Metallic, hexagonal needles of the λ-phase were obtained by thermal decomposition of a mixture of Al and MnS. The structure crystallizes in P6 3/m with a=28.382(9) A ̊ and c=12.389(2) A ̊ . The volume of the cell is 8643 Å 3 and contains an average of 568.1 atoms. 106.6 atoms (18.8 at.%) are Mn, corresponding to a calculated density of 3.517(6) g cm −3. The final R-values were R u=9.2% and R w=5.9% for 2508 reflections with I>3 σ. There are 66 atoms in the asymmetric unit. 104 positions in the unit cell are occupied with Mn and 482 with Al. 102 Mn have icosahedral coordination and two Mn a tri-capped trigonal prismatic coordination (CN 9). 36 Al atoms have icosahedral coordination, 138 Al have a polar bi-capped pentagonal prismatic, 72 Al have a bi-equatorial capped pentagonal prismatic and 168 Al a mixed capped pentagonal prismatic with CN 13 or 14, 4 Al a CN 16 Frank-Kasper polyhedron, and 52 Al an irregular coordination polyhedron. Six Al positions are partly occupied and five Al positions show disorder with small amounts of Mn. The distance ranges are MnMn 2.689–2.784 Å, AlMn 2.362–2.949 Å and AlAl 2.424–3.414 Å. Additionally, one short distance of 2.180 Å is between two partly occupied Al sites. The structure of the λ-phase is a member of the I3-family, containing the I3-cluster, a fragment of three vertex connected icosahedra. The structure is composed of six chains of fused truncated 1(2)-tetrahedra in the unit cell, aligned along c. The chains are B-type connected via primitive stacked pseudo I13-clusters. A similar arrangement is found in the structure of μ-Al 4.12Mn.

Preliminary Investigation of Manganese-Catalyzed Ozonation for the Destruction of Atrazine

A preliminary experimental study conducted with a conventional bubble ozonation contactor column has shown that small amounts of Mn(II) greatly enhanced the destruction of atrazine by ozone. There is an inversely linear relationship between the dosed Mn(II) concentration and the residual ozone concentration at a specific reaction time. The ozone transfer efficiency into water is greater with the increase of Mn(II) dosage. Hydrous manganese dioxide prepared by reacting permanganate with manganese sulfate, also was shown to be effective in catalyzing the destruction of atrazine by ozone. The efficiency of catalytic activity for the destruction of atrazine caused by preformed hydrous Mn(IV) is slightly lower than the case of Mn(II). A lower residual ozone value using manganese dioxide compared to the case of ozone alone suggests that ozone also may be decomposed by hydrous Mn(IV). However, a commercial MnO2 did not show any catalytic activity for atrazine destruction. The very much greater degree of atrazine oxidation by manganese-catalyzed ozonation compared to ozone alone is speculated to be the result of the generation of highly oxidative intermediate species such as hydroxyl radicals during the reaction between ozone and manganese species.

Oxidation of high-temperature alloys (superalloys) at elevated temperatures in air. II

In continuation of previous work, the oxidation behavior of three more alloys, namely UHBA 25L, Sanicro 28, and Inconel 690, was studied at high temperatures (600 to 1200°C). The oxidation kinetics of UHBA 25L and Sanicro 28 followed the parabolic-rate law at 800 and 1000°C. At 600°C oxidation rates were very low, while at 1200° C the parabolic-rate law was initially observed, followed by “breakaway.” Both alloys suffered extensive spalling at all temperatures, despite their high Cr contents of about 25% and 27%, respectively. This is atrributed to significant amounts of Mn present. Sanicro 28, with higher Cr, suffered an early breakaway at 1200°C because of the presence of Mo, which forms a low-melting oxide. Inconel 690 showed mixed behavior at 600 and 800°C, parabolic at 1000°C and cubic at 1200°C. Inconel 690 and Incoloy 800H gave the best overall performance for the range of temperature and exposure time under study. This may be ascribed to the absence of Mo, the presence of small amounts of Ti and Al, and relatively small amount of Mn in these alloys.

Growth of willemite, Zn 2SiO 4, single crystals from a Li 2MoO 4 solvent

Single crystals of willemite, Zn 2SiO 4, containing a small amount of Mn 2+ and Sb 3+ were grown between 1300 and 900°C from Li 2MoO 4 solvent by the slow cooling technique, by applying the non-equilibrium phase diagram of the Zn 2SiO 4-Li 2MoO 4 system, which was prepared previously using the quenching method with DTA and XRD analyses. The size (5×5×30 mm) and quality of the willemite crystals obtained were improved by the addition of MnF 2, but these crystals included striations and cavities with a c-axis orientation. Lattice parameters for the a- and c-axes and also the segregation coefficients of manganese and antimony were estimated. The growth conditions necessary for obtaining high quality crystals are described.

Mn3+-Mediated Coupling-Cyclization of 5-Arylpent-1-enes with Active Methylene Compounds by Electrooxidation

Abstract Selective coupling-cyclization of 5-arylpent-1-enes with active methylene compounds was developed by indirect electrooxidation using a small amount of Mn(OAc)2·4H2O to give 1-[2,2-(disubstituted)ethyl]tetralines in good yields.

Carbon—carbon bond formation using manganese(iii) acetate as an electrochemical mediator

Anodic oxidation in a solution containing a variety of olefins and a small amount of Mn(OAc) 2·4H 2O brought about Mn +3-mediated carbon—carbon bond formation, such as efficient carboxymethylation of styrene derivatives to the corresponding γ-aryl-γ-butyrolactones, and selective coupling of active methylene compounds with non-activated monoolefins, unconjugated dienes or 5-arylpent-1-enes.

Novel Carboxymethylation of Styrene Derivatives by Mn3+-Mediated Electrooxidation

Abstract Anodic oxidation in a mixed solvent of acetic acid and acetic anhydride containing a variety of styrene derivatives, small amounts of Mn(OAc)2·4H2O and Cu(OAc)2·H2O brought about a facile carboxymethylation to give the corresponding γ-butyrolactones as the main products in good yields.

Selective Coupling of Non-Activated Olefins with Ethyl Cyanoacetate by Mn3+-Mediated Anodic Oxidation

Abstract Novel carbon-carbon bond formation of non-activated olefins with ethyl cyanoacetate has been developed by anodic oxidation using only a small amount of Mn(OAc)2·4H2O to give selectively either saturated or unsaturated coupling products depending upon the presence of a catalytic amount of Cu(OAc)2·H2O.