SOMED

SnO 2 ceramic is an n-type semi-conductor used in devices such as gas sensors, electrodes for electric glass melting furnaces, photo catalysts for detectors, and solar cells . It has a tetragonal unit cell. This oxide ceramic can be prepared by sintering, but sintered ceramics prepared without proper additives exhibit poor densification and therefore work poorly in aforementioned applications. Investigations on this aspect of SnO 2 ceramic revealed [2] that an addition of 0.5 mol% of CoO into SnO 2 promotes a densification 99% of the theoretical density during sintering at 1400 °C. To explain the promotion of densification in SnO 2 , it is suggested that Co 2+ creates oxygen vacancies in the SnO 2 lattice by substitution for Sn 4+ . It is believed that the vacancies are preferentially created at the surface of the SnO 2 grains, increasing oxygen diffusion at grain boundaries and then promoting densification. The grain boundary precipitates formed by this process have been reported . This paper provides the observation of additional dislocations and other defects suggested to form by the process and to be found on the surface of the grains of thus prepared Co-doped SnO 2 ceramic. The investigated ceramics of SnO 2 containing 0.5 mol% of CoO were prepared by the standard ceramic processing techniques in which sintering was performed at a temperature of 1400ºC in an Argon gas environment.

In order to incorporate magnetostrictive actuators into microelectromechanical systems devices, thin film magnetoelastic materials must have both a high magnetostriction and a low saturation field. This work focuses on the fabrication and characterization of (110) oriented epitaxial FeGa thin films grown epitaxially on Cu on Si. The material in the bulk exhibits a large magnetostriction and in thin film form is here shown to be easily saturated in all in-plane orientations in fields under 500 Oe. Thin (less than 160 nm) FeGa films grow according to a single (110) variant on Cu(100)/Si(100). On the contrary, thick (160 nm) films exhibit multiple (110) variants.

€"e-N fiknr have bean prepared by argon-aitrogen reactive Rp aputtering at a total prerrum o f 6 mTorr, an argon flow rate of 100 standard cubic centimeters per minute (sccm) and a nitrogen flow rate R of 0 to 30 accm. For R l l S =an, littb changea in phase structure and moment ( A v s 6%) were aeen for annealing temperaturea TA s3OO0C. Above 300°C, changes in the phaae structure and moment (Aus 2 12%) were observed.

This paper is primarily focused in studying the effects of nanoclay particles such as montmorillonite on improving mechanical and thermal properties of fiber reinforced polymer matrix composite materials. Basic correlations between polymer morphology, strength, modulus, toughness, and thermal stability of thermoset nanocomposites were investigated as a function of layered silicate content. S2-glass/epoxy-clay nanocomposites were manufactured through an affordable vacuum assisted resin infusion method (VARIM). The nanocomposites are formed during polymerization when the adsorbing monomer separates the clay particles into nanometer scales. Transmission electron microscopy (TEM) and wide angle X-ray diffraction(WAXD) were used to characterize the morphology of the dispersed clay particles. The thermal properties such as onset of decomposition and glass transition temperatures were determined by Thermo Gravimetric Analysis (TGA) and Dynamic Modulus Analyzer (DMA). Mechanical properties such as interlaminar shear strength, flexural properties and fracture toughness are also determined for both conventional S2-glass/epoxy composites and S2-glass fiber reinforced nanocomposites.

Ferromagnetic crystallites of chalcospinel CuCr 2 Se 4 have been synthesized in solution via a one-pot thermal decomposition of metal-acetylacetonate precursors in tri-n-octylamine. The reaction is carried out at temperatures of 300-350 1C in the presence of the cation precursor H 2 Se, formed in situ by the reduction of Se powder in b-sitosterol. Good control on the growth rate and the shape of the crystallites is obtained by varying the reaction time and temperature, and the concentration of Se. The crystallites are ferromagnetic at room temperature and under optimal synthesis conditions exhibit a low temperature magnetic moment of about 2.3 m B per Cr, which is close to reported value for the bulk. r

The crystallography of the silicon phase in unmodified Al-Si eutectic alloys has been studied by conventional and high-resolution electron microscopy. Examination of the flake morphology eutectic silicon, at two mutually perpendicular <110) zone axes, revealed internal twin traces at only one (110) zone axis, parallel to the flake surface. Internal twins in the silicon phase appear to develop as a result of purely two-dimensional crystal growth on pre-existing silicon nuclei containing a group of parallel twins. The twins grow along coplanar (112) directions by the twin plane re-entrant edge (TPRE) mechanism. Stacking faults and twins present in the high-resolution images of eutectic silicon are consistent with TPRE growth originating at the silicon nuclei containing parallel twins. 0022-0248/91/$03.50 © 1991 -Elsevier Science Publishers B.V. (North-Holland)

Electron diffraction studies of silicon fibres in strontium-modified and chill-modified Al-14%Si alloy show a significant difference in behaviour. In the strontium-modified alloy the silicon fibres exhibit a very high twin density and at least two (111) twin systems operate in each fibre. In the chill-modified alloy only a single (111) twinning system was observed in each fibre, as in unmodified eutectic, and twin density was much lower. It seems probable that strontium modification causes refinement by intensification of the TPRE growth mechanism, but that a different mechanism operates in chill modification.

The crystallography of eutectic silicon in an unmodified Al-12.7 wt% Si alloy has been studied by transmission electron microscopy and diffraction of thin films cut from bulk samples. Twinning mechanisms are described by which the silicon changes direction or adjusts interflake spacing at the solid-liquid interface. The branching mechanism observed by previous workers is confirmed but found to be infrequent at moderate freezing rates. A side-branching mechanism is described which is considered to be the primary mechanism for branching in the wheatsheaf configuration. Orientation relationships between the eutectic silicon and aluminium phases are described. These differ from those previously observed in thin films drawn from the melt. It is proposed that orientation relationships vary with freezing rate. Evidence is presented that the eutectic aluminium re-nucleates repeatedly during growth of a single eutectic grain.

Electron diffraction studies of the silicon phase in chill-modified Al-Si eutectic have revealed a twin density higher than in unmodified flake eutectic silicon. The growth crystallography of the chill-modified silicon is closely similar to that of unmodified eutectic silicon but different from that in strontium-modified eutectic. It is concluded that the chill-modified eutectic is a refinement of the flake-silicon eutectic due to large undercooling whereas impurity-modified eutectic has been shown to have a different growth mechanism.

... of Fe-Co-Ni alloys containing a limited amount of impurities and their structural, magnetic, and electrical ... The magnetic properties of Fe-Co-Ni alloys are determined to a large extent by ... JJ Krebs, BT Jonker, and GA Prinz, “Magnetic properties of single-crystal Fe films grown on ...

Co 80 Pt 20 thin films (0:125 -1:0 mm) were galvanostatically (10 -50 mA=cm 2 ) electrodeposited onto Cu(1 1 1) oriented seed layers. Coercivity (3 -6:1 kOe), saturation magnetization (778-832 emu=cm 3 ) and uniaxial magnetic anisotropy ð0:82 Â 10 7 -1:02 Â 10 7 erg=cm 3 ) in the perpendicular direction increase both with current density and film thickness due to a combined effect of decrease in the porosity and increase in the crystallinity of the films. r

The ilmenite–hematite (1 − x) FeTiO3 � xFe2O3 solid solution system is considered to be a novel material for spin-electronics, microelectronics, high-temperature electronics, and radhard electronics. This paper focuses on thin films of composition x = 0.33 grown on (100) MgO single-crystal substrates using pulsed-laser deposition (PLD) under different argon–oxygen mixtures. The surface of the MgO was found to possess MgO2 crystals, yielding an orientation relationship,

A technique to reduce the micropipe density in SiC substrates by first filling in the defects and then growing an LPE layer on the filled material has been developed by TDI. LPE growth in SiC is known to result in poor surface morphology, namely step-bunching due to the off-axis substrate orientation. Chemical vapor deposition (CVD) growth experiments on SiC substrates

Bulk platinum has been knownt ob ec hemically inert, but shows remarkably high activity as ac atalyst when finely dispersed as nano particles (10 nm) in ceramic substrates. In order to understand this mechanism, we have studied the effect of ar educing environmento nt he structure, morphology, and distribution of these Pt nano particles as well as of oxide support in gadolinium-doped ceria catalysts by transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy( XPS) methods. In fresh catalysts prepared by calcinations, the Pt nano particles weref ound to be crystalline with many of them twinned and distributed randomly in the microstructure of crystalline ceria support. The size of the Pt nano particles ranged between 20 and 50 nm. Aspecial featurefound in these catalysts is that no constituting Pt particlei sp artially or fully embedded in the ceria grain.U pon reduction with hydrogen gas at high temperatures, both Pt and ceria crystals showed evidence of crystalline defects. The Pt nano particles in reduced catalysts appeared similar in sizea nd shape to those observed in the fresh catalysts,a nd they resided on the surfaceo ft he ceria crystal. Ther esults ared iscussed in relation to their expectedcatalytic activity in autothermal reforming of iso-octane.

ABSTRACT The microstructure and composition of a nanoparticle Ni catalyst supported on gadolinium-doped ceria (Ce1−xGdxO(4−x)/2) were studied using transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The support of the fresh catalyst exhibits a homogenous aggregation of crystalline grains, with sizes ranging between 20 nm and 50 nm. The crystalline structure of the fresh catalyst support is of the CeO2 phase, in which gadolinium atoms exist in a solid solution of CeO2. Nickel in the fresh catalyst is highly dispersed and forms granular crystals that are 5–30 nm in size on the surface of the ceria support. The support of the used catalyst exhibits a bimodal distribution of grains in which smaller grains have similar structure and morphology as those in the fresh catalyst, while the larger sized grains appear dull and exhibit nonfaceted crystal morphology resulting either from the sintering of a number of CeO2 grains or by the occupation of highly defective crystals of Ce2O3 and CeO phases. A thin amorphous layer of carbon also covers most of the larger grains in the used catalyst. The Ni particles could not be imaged by TEM in the used catalyst, but energy dispersive x-ray spectroscopy (EDX) detected their presence. The XPS analysis of the catalyst samples suggests the participation of lattice O atoms from the ceria support in the catalytic reaction. The XPS data also show the presence of carbonate species and a higher hydrocarbon concentration in the used catalyst.

Co-rich, Co-Pt alloy films containing $20 at% Pt and small amounts of P, with thickness from 125 to 1000 nm have been galvanostatically (constant current) grown by electroplating onto Cu seed layers with strong (1 1 1) orientation. The influence of deposition current density (cd ¼ 10-50 mA/cm 2 ) and film thickness on their growth morphology, structural and magnetic properties have been investigated. When electrodeposited on Cu(1 1 1), Co-Pt(P) films develop a microstructure consisting of a disordered hexagonal-closed-packed (hcp) matrix with {0 0 0 1} preferential orientation. At low cd, a small amount of simple cubic L1 2 phase was detected, which disappears altogether by increasing cd to 50 mA/cm 2 . The plated films show saturation magnetization in the range 775-832 kA/m (778-832 emu/cm 3 ), large perpendicular magnetic anisotropy up to 1.02 MJ/m 3 (1.02 Â 10 7 erg/cm 3 ), and coercivity up to 486 kA/m (6.1 kOe) in the out-of-plane direction. The perpendicular anisotropy was found to originate predominantly from the high magnetocrystalline anisotropy of the hcp phase of Co-Pt(P) with c-axis perpendicular to the substrate. r

X-ray diffraction and transmission electron microscopic studies were undertaken to characterize various magnetic phases observed prior to and during in-situ annealing of FeN films deposited on glass substrates by reactive rf-biased sputtering techniques. The concentration of nitrogen in the films was controlled by altering the nitrogen flow rate (R) during reactive sputtering. Experiments were carried out on three films prepared with R = 2, 5 and 8 standard cubic centimeters per minute (sccm). The films contain an α-Fe phase saturated with nitrogen atoms and a martensite phase supersaturated with nnitrogen atoms in the as-deposited state. The increase in the value of R in film deposition results in a very small change in the lattice parameter of the α-Fe phase, but allows the martensite phase to progressively increase supersaturation with nitrogen atoms. The sample prepared at R = 2 sccm, upon annealing at temperatures ranging between room temperature (RT) and 500°C, showed no structural changes. Annealing of the samples prepared at R = 5 and 8 sccm also exhibited no structural changes between RT and 400°C, but showed some new phases when heated to 500°C. The sample for R = 5 sccm contained a Fe16N2 phase, while the sample for R = 8 sccm contained Fe16N2 and Fe4N phase. During annealing, the grain size for the samples increased from 10–30 nm at RT to 60–90 nm at 500°C. The phases formed at 500°C in all samples were stable and remained unchanged when the specimens were cooled to room temperature.

This paper presents a geometrical description of aperiodic grain boundaries within the framework of a quasiperiodic lattice. Experimental evidence is given in support of a structural unit model of quasiperiodic [100]45° twist and [100]45° twist plus tilt grain boundaries in aluminum.