In-plane/out-of-plane disorder influence on the magnetic anisotropy of Fe1-yMnyPt-L10 bulk alloy

The random substitution of a non-magnetic species instead of Fe atoms in FePt-L10 bulk alloy will permit to tune the magnetic anisotropy energy of this material. We have performed by means of first principles calculations a study of Fe1-yMnyPt-L10 (y = 0.0, 0.08, 0.12, 0.17, 0.22, and 0.25) bulk alloy for a fixed Pt concentration when the Mn species have ferro-/antiferromagnetic (FM,AFM) alignment at the same(different) atomic plane(s). This substitution will promote several in-plane lattice values for a fixed amount of Mn. Charge hybridization will change compared to the FePt-L10 bulk due to this lattice variation leading to a site resolved magnetic moment modification. We demonstrate that this translates into a total magnetic anisotropy reduction for the AFM phase and an enhancement for the FM alignment. Several geometric configurations were taken into account for a fixed Mn concentration because of different possible Mn positions in the simulation cell

METHODS AND APPARATUS FOR THE OXIDATION OF GLUCOSE MOLECULES

A catalyst comprising Pt-Co alloy, or Pt-Co-Sn alloy or Pt-Co>mn< mixed metal oxides is disclosed to be used as a catalyst for the direct electrochemical oxidation of glucose or other simple sugars and carbohydrates at room temperature. The catalyst can be supported on metal electrodes, graphite electrodes, porous carbon electrodes, or gas diffusion electrodes. An electrode containing this catalyst will be used as the key component in a direct glucose-air fuel cell operating in alkaline media with a good room temperature performance. This catalyst can also be applied as a key electrode material in a glucose sensor to detect glucose concentration in neutral or alkaline medium. The preparation method of the catalyst, optimum composition, and results of glucose sensor and glucose fuel cell applications are disclosed.A catalyst comprising Pt-Co alloy, or Pt-Co-Sn alloy or Pt-ComOn mixed metal oxides is disclosed to be used as a catalyst for the direct electrochemical oxidation of glucose or other simple sugars and carbohydrates at room temperature. The catalyst can be supported on metal electrodes, graphite electrodes, porous carbon electrodes, or gas diffusion electrodes. An electrode containing this catalyst will be used as the key component in a direct glucose-air fuel cell operating in alkaline media with a good room temperature performance. This catalyst can also be applied as a key electrode material in a glucose sensor to detect glucose concentration in neutral or alkaline medium. The preparation method of the catalyst, optimum composition, and results of glucose sensor and glucose fuel cell applications are disclosed.published_or_final_versio

ANALISIS KEKUATAN STRAIN DAN STRESS PADA BAJA PADUAN DENGAN MENGGUNAKAN TENSILE TEST MACHINE

Penelitian ini bertujuan untuk menentukan karakteristik mekanik dan kimia logam baja paduan produksi PT. Petrokimia Gresik dan melakukan analisis kekuatan Strain dan Stress masing-masing logam baja paduan. Data penelitian diperoleh melalui hasil uji kekuatan logam menggunakan Tensile Test Machine dengan besarnya nilai Force dan Strain dan kandungan Peak, besar nilai Energi Eksitasi dan Presentase kandungan unsur dengan menggunakan XRF XL-2 GOLDD berbasis X-Rays Fluorosence (XRF) dan Arc Met 8000 berbasis Optical Emission Spectroscopy. Karakteristik didasarkan pada analisis dari Grafik perbandingan Force dan Strain yang diolah melalui aplikasi Origin50 versi 6.1. Hasil penelitian ini adalah : (1) Kekuatan tarik logam SS 304 adalah 342,20 kg/cm2, SS 310 adalah 260,60 kg/cm2 dan Low Alloy adalah 201,90 kg/cm2. (2) Kekuatan Stress dan Strain dari logam uji SS 304 adalah nilai Strainnya sebesar 11 dengan nilai Stress 3.422 x 104 N/m2 , SS 310 dengan nilai Strainnya sebesar 12 dengan nilai Stress 2.675 x 104 N/m2 dan Low Alloy nilai Strainnya sebesar 6 dengan nilai Stress 2.019 x 104 N/ m2. (3) Pola patahan logam untuk SS 304 berupa patahan getas, logam SS 310 berupa patahan ulet sementara Low Alloy berupa patahan getas (4) pengujian menggunakan Niton XL2 GOLDD(instrument bekerja sesuai prinsip XRF) adalah logam SS 304 ini memiliki Cr 17,96033 %, Si 2,05% , Mn 1,31733% dan Ni 7,703%. Logam SS 310 kandungan Ni 19,3255%, Cr 23,896%, Mo 0,1125%, Mn 1,5115% dan Si 1,0665%. Logam Low Alloy kandungan Ni 0,09%, Cr 0,9%, Mo 0,459%, Mn 0,466333% dan Si 0,088333%. dan Arc Met 8000(instrument yang bekerja sesuai prinsip OES) didapatkan hasil pengujian logam 304 diperoleh komposisi logam yaitu Si 0,588%, Cr 19,378%, Ni 6,973% , C 0,177%, Mn 1,554% dan Mo 0,098%, logam SS 310 diperoleh komposisi logam yaitu Si 1,23%, Cr 29,38%, Ni 15,48% , C 0,78%, Mn 1,44% dan Mo 0,176% dan logam Low Alloy diperoleh komposisi logam yaitu Si 2,71%, Cr 1,11%, Ni 0,27 % , C 1,52%, Mn 0,54% dan Mo 0,32%.

Sulphur tolerant diesel oxidation catalysts by noble metal alloying

A series of Mn-alloyed Pt supported catalysts were investigated for the NO oxidation reaction applied in diesel oxidation catalysts under sulphur-containing conditions. The observed NO oxidation conversion correlated to the Pt amount in the catalyst under sulphur-free conditions. In the presence of SO2 in the feed, the Pt/Al2O3 catalyst heavily deactivated resulting in the lowest performance compared to Mn-alloyed Pt catalysts. Already small amounts of Mn improved the SO2-resistance significantly. Whilst pure Pt/Al2O3 catalyst deactivates fully within the first 30 min under NO oxidation conditions including 300 ppm SO2, an alloy with a Mn to Pt ratio of 1:1 performed with a remarkable high catalytic stability for the NO oxidation over at least 70 h under continuous testing conditions

Chemical contrast in STM imaging of transition metal aluminides

The present manuscript reviews recent scanning tunnelling microscopy (STM) studies of transition metal (TM) aluminide surfaces. It provides a general perspective on the contrast between Al atoms and TM atoms in STM imaging. A general trend is the much stronger bias dependence of TM atoms, or TM-rich regions of the surface. This dependence can be attenuated by the local chemical arrangements and environments. Al atoms can show a stronger bias dependence when their chemical environment, such as their immediate subsurface, is populated with TM. All this is well explained in light of combined results of STM and both theoretical and experimental electronic and crystallographic structure determinations. Since STM probes the Fermi surface, the electronic structure in the vicinity of the Fermi level (EF) is essential forunderstanding contrast and bias dependence. Hence, partial density of states provides information about the TM d band position and width, s–p–d hybridization or interactions, or charge transfer between constituent elements. In addition, recent developments in STM image simulations are very interesting for elucidating chemical contrast at Al–TM alloy surfaces, and allow direct atomic identification, when the surface does not show too much disorder. Overall, we show that chemically-specific imaging is often possible at these surfaces

Desenvolvimentos de estruturas muitiferroicas de filmes finos de ligas Ni-Mn-Ga e PMN-PT

Mestrado em Ciência e Engenharia de MateriaisLigas de forma ferromagnética em sistemas Ni-Mn-Ga são uma classe recente de materiais activos que podem gerar deformações de até 10% induzidas por um campo magnético por um rearranjo de maclas. Esta e outras propriedades físicas destas ligas têm importância tecnológica. Este trabalho investiga as propriedades de filmes finos de ligas de Ni-Mn-Ga sobre diferentes substratos, incluindo substratos activos (piezeléctricos). Para estudar as propriedades de filmes finos da liga, heteroestruturas sob a forma de Ni-Mn-Ga/substrato foram produzidas por RF sputtering com magnetrão utilizando temperaturas de deposição de 3200C, 3700C, 4000C sobre substratos de Al2O3, MgO, SrTiO3 e PMN-PT. A influência da temperatura do substrato durante a deposição nas propriedades estruturais e magnéticas de filmes finos foi estudada. Além disso, o acoplamento magnetoeléctrico entre Ni-Mn-Ga como filme fino material ferromagnético e PMN-PT como material piezoeléctrico foi investigada. O efeito magnetoeléctrico foi investigado apenas em filmes depositados a temperatura do substrato de 3700C e 4000C. As propriedades estruturais foram estudadas por difração de raios-X, as propriedades magnéticas foram investigadas por VSM, SQUID, e MFM, e o efeito magnetoeléctrico foi estudado por técnica lock-in. A medida estrutural mostrou que os filmes depositados são parcialmente cristalinos e o grau de cristalinidade aumenta como o aumento da temperatura do substrato. Fases austenita e martensita foram observadas nesses filmes. Os resultados da medição magnética mostram que todos os filmes depositados exibem comportamento ferromagnético e o comportamento ferromagnético é favorecido com o aumento da temperatura do substrato. Todos os filmes depositados na temperatura do substrato de 400ºC apresentam temperaturas dev Curie acima da temperatura ambiente: 337K para Ni-Mn- Ga/PMN-PT, 345K para Ni-Mn-Ga/STO e 348K para Ni-Mn-Ga/Al2O3. Nenhuma evidência separada de temperatura de transição estrutural foi observada para nos filmes. Os resultados das medições magnetoeléctricas mostram que as heteroestruturas multiferróicas Ni-Mn-Ga/PMN-PT apresentam efeito magnetoelétrico. O valor máximo medido para a tensão magnetoeléctrica induzida para filmes depositados à temperatura do substrato de 3700C e 4000C são 3.16mV/cmOe e 3.02mV/cmOe, respectivamente.Ferromagnetic shape memory alloys (FSMAs) in Ni-Mn-Ga systems are a recent class of active materials that can generate large magnetic field induced strains up to 10% by twin rearrangement. This and other physical properties these alloys have many technological importance. This work investigates the properties of Ni-Mn-Ga alloy thin films on different substrates including active substrate (piezoelectric). To study the properties of thin films of the alloy, the heterostructures in the form of Ni-Mn-Ga/substrate were produced by RF magnetron deposition system using substrate deposition temperatures of 3200C, 3700C, and 4000C, where the substrates used were Al2O3, MgO, SrTiO3 and PMN-PT. The influences of deposition substrate temperature on structural and magnetic properties of sputtered thin films on the aforementioned substrates were studied. Moreover, magnetoelectric coupling between Ni-Mn- Ga thin film as ferromagnetic material and PMN-PT as piezoelectric material was investigated. The magnetoelectric effect was investigated only on films deposited at substrate temperature of 3700C and 4000C. The structural properties were studied by x-ray diffraction, magnetic properties were investigated by VSM, SQUID, and MFM, and the magnetoelectric effect was studied by lock-in technique. The structural measurement has shown that asdeposited films are partially crystalline and degree of crystallinity increases as substrate temperature increase. Austenite and martensite phases have been observed in these films. The magnetic measurement results show that all films as-deposited display ferromagnetic behaviour and ferromagnetic behaviour improvements are observed as substrate temperature increases. All films deposited at substrate temperature of 4000C exhibit Curie temperatures above room temperature which are 337K for Ni-Mn-Ga/PMN-PT, 345K for Ni-Mn- Ga/STO, 348K for Ni-Mn-Ga/Al2O3. No separate signature of structural transition temperature was observed for all these films. The magnetoelectric measurement results show that a heterostructure of Ni-Mn-Ga/PMN-PT multiferroic exhibit magnetoelectric effect. The measured maximum induced magnetoelectric voltage for films deposited at substrate temperature of 3700C and 4000C are 3.16mV/cmOe and 3.02mV/cmOe, respectively

Elastic and Chemical Contributions to the Stability of Magnetic Surface Alloys on Ru(0001)

We have used density functional theory to study the structural stability of surface alloys. Our systems consist of a single pseudomorphic layer of $M_xN_{1-x}$ on the Ru(0001) surface, where $M$ = Fe or Co, and $N$ = Pt, Au, Ag, Cd, or Pb. Several of the combinations studied by us display a preference for atomically mixed configurations over phase-segregated forms. We have also performed further {\it ab initio} calculations to obtain the parameters describing the elastic interactions between atoms in the alloy layer, including the effective atomic sizes at the surface. We find that while elastic interactions favor alloying for all the systems considered by us, in some cases chemical interactions disfavor atomic mixing. We show that a simple criterion (analogous to the Hume-Rothery first law for bulk alloys) need not necessarily work for strain-stabilized surface alloys, because of the presence of additional elastic contributions to the alloy heat of formation, that will tend to oppose phase segregation.Comment: 10 pages, 8 figures Submitted To Phys. Rev.