Showing papers on "Amorphous solid published in 1997"
TL;DR: A tin-based amorphous composite oxide (TCO) was synthesized in this paper to replace the carbon-based lithium intercalation materials currently in extensive use as the negative electrode (anode) of lithium-ion rechargeable batteries.
Abstract: A high-capacity lithium-storage material in metal-oxide form has been synthesized that can replace the carbon-based lithium intercalation materials currently in extensive use as the negative electrode (anode) of lithium-ion rechargeable batteries. This tin-based amorphous composite oxide (TCO) contains Sn(II)-O as the active center for lithium insertion and other glass-forming elements, which make up an oxide network. The TCO anode yields a specific capacity for reversible lithium adsorption more than 50 percent higher than those of the carbon families that persists after charge-discharge cycling when coupled with a lithium cobalt oxide cathode. Lithium-7 nuclear magnetic resonance measurements evidenced the high ionic state of lithium retained in the charged state, in which TCO accepted 8 moles of lithium ions per unit mole.
2,470 citations
TL;DR: In this article, an electrochemical and in situ x-ray diffraction experiments on a variety of tin oxide based compounds; SnO,,,, and glass, as cathodes opposite lithium metal in a rechargeable Li-ion coin cell were conducted.
Abstract: We report our electrochemical and in situ x‐ray diffraction experiments on a variety of tin oxide based compounds; SnO, , , and glass, as cathodes opposite lithium metal in a rechargeable Li‐ion coin cell. These materials demonstrate discharge capacities on the order of 1000 mAh/(g Sn), which is consistent with the alloying capacity limit of 4.4 Li atoms per Sn atom, or 991 mAh/(g Sn). These materials also demonstrate significant irreversible capacities ranging from 200 mAh/(g active) to 700 mAh/(g active). In situ x‐ray diffraction experiments on these materials show that by introducing lithium, lithium oxide and tin form first, which is then followed by the formation of the various Li‐Sn alloy phases. When lithium is removed the original material does not reform. The ending composition is metallic tin, presumably mixed with amorphous lithium oxide. The oxygen from the tin oxide in the starting material bonds irreversibly with lithium to form an amorphous matrix. The Li‐Sn alloying process is quite reversible; perhaps due to the formation of this lithia "matrix" which helps to keep the electrode particles mechanically connected together.
1,370 citations
TL;DR: The role of implantation defects, the effect of annealing, concentration dependent effects, and optical activation are discussed and compared for different Er-doped thin film photonic materials.
Abstract: Erbium doped materials are of great interest in thin film integrated optoelectronic technology, due to their Er3+ intra-4f emission at 1.54 μm, a standard telecommunication wavelength. Er-doped dielectric thin films can be used to fabricate planar optical amplifiers or lasers that can be integrated with other devices on the same chip. Semiconductors, such as silicon, can also be doped with erbium. In this case the Er may be excited through optically or electrically generated charge carriers. Er-doped Si light-emitting diodes may find applications in Si-based optoelectronic circuits. In this article, the synthesis, characterization, and application of several different Er-doped thin film photonic materials is described. It focuses on oxide glasses (pure SiO2, phosphosilicate, borosilicate, and soda-lime glasses), ceramic thin films (Al2O3, Y2O3, LiNbO3), and amorphous and crystalline silicon, all doped with Er by ion implantation. MeV ion implantation is a technique that is ideally suited to dope these materials with Er as the ion range corresponds to the typical micron dimensions of these optical materials. The role of implantation defects, the effect of annealing, concentration dependent effects, and optical activation are discussed and compared for the various materials.
1,089 citations
TL;DR: A comparison of the carbonyl stretching region of γ indomethacin, known to form carboxylic acid dimers, with that of amorphous indometHacin indicated that the amorphously phase exists predominantly as dimers.
Abstract: Purpose. To study the molecular structure of indomethacin-PVP amorphous solid dispersions and identify any specific interactions between the components using vibrational spectroscopy.
904 citations
TL;DR: In this article, an exothermic peak at ca. 723 K in the DSC pattern was assigned to the crystallization of amorphous phase to anatase, and its heat was used to evaluate the weight fraction.
Abstract: Titanium(IV) oxide (TiO2) powders of various amorphous−anatase compositions were prepared by heat treatment (573−1073 K) of amorphous TiO2 in air and characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), and BET surface area measurements. An exothermic peak at ca. 723 K in the DSC pattern was assigned to the crystallization of amorphous phase to anatase, and its heat was used to evaluate the weight fraction of amorphous phase. The fraction of anatase crystallites (f(anatase)) was calculated as the remainder after the amorphous phase and contaminated water or organic residue. The XRD data showed that the size of anatase crystallites was slightly decreased but almost constant along with the increase in f(anatase), being consistent with the small change in the BET surface area. These results suggest that each amorphous particle transforms into an anatase crystallite of similar size without sintering or crystal growth. The particles of mixture of amorphous and anatase were ...
782 citations
TL;DR: In this paper, a review is given of anodic alumina film formation on aluminium, with barrier and porous films developed by anodic polarization in an appropriate electrolyte, and means for characterising the developed films are presented as well as applications of the porous, amorphous film material.
733 citations
TL;DR: In this paper, the authors highlight the major research works that deal with the stickiness property of sugar-rich foods and apply various manawm that have been applied to spray dry such products.
Abstract: Stickiness is a major reason that limits the spray drying of various sugar-rich food products.Higher hygrmopicity of amorphous powder, increase in solubility of sugars with temperature, and lower melting point and glass transition temperature, contribute to the aickiness problem. So far, the glass transition temperature has been widely accepted as a ben indicator for stickiness. There are various manawm that have been applied to spray dry such product. Some of them are the addition of drying aids, modilication of drier design and use of mild drying temperature conditions. This review paper highlights the major research works that deal with the stickiness property of sugar-rich foods.
539 citations
TL;DR: In this paper, a two-layer blue electroluminescence device with high color purity, high brightness and low turn-on voltage is presented, which is fabricated by combining a hole transporting spiro-TAD with an electron transport spiro PBD.
499 citations
TL;DR: In this article, a Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy, machined into 7 mm wide, 38 mm thick compact-tension specimens and fatigue precracked following standard procedures, revealed fracture toughnesses in the fully amorphous structure of K(lc)similar to 55 MPa root m, i.e., comparable with that of a high-strength steel or aluminum ahoy.
Abstract: The recent development of metallic alloy systems which can be processed with an amorphous structure over large dimensions, specifically to form metallic glasses at low cooling rates (similar to 10 K/s), has permitted novel measurements of important mechanical properties. These include, for example, fatigue-crack growth and fracture toughness behavior, representing the conditions governing the subcritical and critical propagation of cracks in these structures. In the present study, bulk plates of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy, machined into 7 mm wide, 38 mm thick compact-tension specimens and fatigue precracked following standard procedures, revealed fracture toughnesses in the fully amorphous structure of K(lc)similar to 55 MPa root m, i.e., comparable with that of a high-strength steel or aluminum ahoy. However, partial and full crystallization, e.g., following thermal exposure at 633 K or more, was found to result in a drastic reduction in fracture toughness to similar to 1 MPa root m, i.e., comparable with silica glass. The fully amorphous alloy was also found to be susceptible to fatigue-crack growth under cyclic loading, with growth-rate properties comparable to that of ductile crystalline metallic alloys, such as high-strength steels or aluminum alloys; no such fatigue was seen in the partially or fully crystallized alloys which behaved like very brittle ceramics. Possible micromechanical mechanisms for such behavior are discussed.
423 citations
TL;DR: In this paper, the authors achieved 14.6% initial and 13.0% stable conversion efficiencies using an amorphous silicon-based alloy in a spectrum-splitting, triple-junction structure.
Abstract: We have achieved 14.6% initial and 13.0% stable conversion efficiencies using an amorphous silicon-based alloy in a spectrum-splitting, triple-junction structure. These efficiencies have been confirmed independently by the National Renewable Energy Laboratory. Key factors leading to this major advance include improvements made in the low band-gap amorphous silicon–germanium alloy cell, the pn tunnel junction between the component cells, and the top conducting oxide.
408 citations
TL;DR: In this article, the authors developed models on the effective thermal conductivity of periodic thin-film structures in the parallel direction based on the Boltzmann transport equation for different interface conditions including specular, diffuse, and partially specular and partially diffuse interfaces.
Abstract: Superlattices consisting of alternating layers of extremely thin films often demonstrate strong quantum size effects that have been utilized to improve conventional devices and develop new ones. The interfaces in these structures also affect their thermophysical properties through reflection and transmission of heat carriers. This work develops models on the effective thermal conductivity of periodic thin-film structures in the parallel direction based on the Boltzmann transport equation. Different interface conditions including specular, diffuse, and partially specular and partially diffuse interfaces, are considered. Results obtained from the partially specular and partially diffuse interface scattering model are in good agreement with experimental data on GaAs/AlAs superlattices. The study shows that the atomic scale interface roughness is the major cause for the measured reduction in the superlattice thermal conductivity. This work also suggests that by controlling interface roughness, the effective thermal conductivity of superlattices made of bulk materials with high thermal conductivities can be reduced to a level comparable to those of amorphous materials, while maintaining high electrical conductivities. This suggestion opens new possibilities in the search of high efficiency thermoelectric materials.
TL;DR: In this paper, the growth of in-plane textured (100) MgO on amorphous Si3N4 substrates by ion beam assisted deposition (IBAD) was reported.
Abstract: We report the growth of in-plane textured (100) MgO on amorphous Si3N4 substrates by ion beam assisted deposition (IBAD). The textured MgO can be used as a structural template for subsequent epitaxial thin film deposition. The results are compared with IBAD of (100) and (111) yttria-stabilized-zirconia (YSZ). Based on transmission electron microscopy (TEM) and in situ reflection high energy-electron diffraction (RHEED), we find that MgO texturing is a nucleation-controlled process and the alignment is a function of nuclei size and density. This differs greatly from the evolutionary-type texturing process observed for IBAD (100) YSZ. Consequently, we are able to make 100 A thick MgO films with 7° in-plane alignment, whereas IBAD (100) YSZ films need to be thicker than 5000 A to achieve in-plane alignment better than 13°. This has important implications for the economical application of IBAD induced alignment in real manufacturing processes, including high Tc superconductor (i.e., YBCO) coated tapes, photov...
TL;DR: In this article, the fiber morphology of the dragline silk of Nephila clavipes has been investigated by the detailed analysis of wide-angle X-ray diffraction (WAXD) patterns, giving the crystal lattice dimensions, the orientation distribution, the crystalline fraction, and an estimate of the crystal size.
Abstract: The fiber morphology of the dragline silk of Nephila clavipes has been investigated by the detailed analysis of wide-angle X-ray diffraction (WAXD) patterns. WAXD gives the crystal lattice dimensions, the orientation distribution, the crystalline fraction, and an estimate of the crystal size. It is found that the crystals are very small and well oriented. The mean (minimum) crystal dimensions are 2 × 5 × 7 nm, and the angle, φ, between the molecular chains in the crystals and the fiber axis has a full width at half-maximum (fwhm) of 15.7° and an orientation function f = 0.981. The X-ray crystallinity is in the range 10−15%, and the amorphous diffraction is divided 60:40 between an isotropic ring and an oriented halo with fwhm 30°. This means one-third of the material is in the oriented amorphous state, with a chain orientation of fwhm 43° and f = 0.87. When the fiber is extended up to 10%, the orientation of the crystals increases as predicted for affine deformation at constant volume. There is no observa...
TL;DR: The glass-forming ability of a Pd 4 Cu 30 Ni 10 P 20 alloy was found to increase significantly by B 2 O 3 flux treatment, as is evidenced by the decrease in the critical cooling rate from 1.57 K/s in the non-fluxed state to 0.100 K/m in the fluxed state as mentioned in this paper.
Abstract: The glass-forming ability of a Pd 4 Cu 30 Ni 10 P 20 alloy was found to increase significantly by B 2 O 3 flux treatment, as is evidenced by the decrease in the critical cooling rate from 1.57 K/s in the non-fluxed state to 0.100 K/s in the fluxed state. The flux treatment also causes the extension of the supercooled liquid region by the increase in the onset temperature of crystallization (T x ). The effect of the flux treatment is presumably due to the increase in the thermal stability of the supercooled liquid by the suppression of heterogeneous nucleation. The critical cooling rates in the non-fluxed and fluxed states for a Pd 40 Ni 40 P 20 alloy are measured to be 128 and 0.167 K/s, respectively, both of which are larger than those for the Pd-Cu-Ni-P alloy. The use of the molten Pd-Cu-Ni-P alloy subjected to the flux treatment enabled the production of bulk amorphous alloys in cylindrical forms of 50 to 72 mm in diameter and 52 to 75 mm in length. The glass transition temperature (T g ) and T x values of the bulk amorphous alloys are the same as those for the melt-spun amorphous ribbon prepared from the fluxed molten alloy. The success of synthesizing an amorphous alloy of 72 mm in diameter is encouraging both for the future development of basic science of bulk amorphous alloys and for their engineering application.
TL;DR: In this paper, phase transitions between adhesive metal, load supporting carbide, and wear-resistant diamond-like carbon (DLC) surfaces were investigated on the Ti-C system prepared by a hybrid of magnetron sputtering and pulsed laser deposition.
TL;DR: In this article, a process for making thick, stress-free, amorphous-tetrahedrally bonded carbon (a-tC) films with hardness and stiffness near that of diamond was developed.
Abstract: We have developed a process for making thick, stress-free, amorphous-tetrahedrally bonded carbon (a-tC) films with hardness and stiffness near that of diamond. Using pulsed-laser deposition, thin a-tC films (0.1–0.2 μm) were deposited at room temperature. The intrinsic stress in these films (6–8 GPa) was relieved by a short (2 min) anneal at 600 °C. Raman and electron energy-loss spectra from single-layer annealed specimens show only subtle changes from as-grown films. Subsequent deposition and annealing steps were used to build up thick layers. Films up to 1.2 μm thick have been grown that are adherent to the substrate and have low residual compressive stress (<0.2 GPa). The values of hardness and modulus determined directly from an Oliver–Pharr analysis of nanoindentation experimental data were 80.2 and 552 GPa, respectively. We used finite-element modeling of the experimental nanoindentation curves to separate the “intrinsic” film response from the measured substrate/film response. We found a hardness ...
TL;DR: In this paper, the thickness and composition of several kinds of titanium oxide films formed on a titanium substrate were determined by surface analysis techniques: X-ray photoelectron spectroscopy, Rutherford back scattering, Xray diffraction and atomic force microscopy.
Abstract: The thickness and composition of several kinds of titanium oxide films formed on a titanium substrate were determined by surface analysis techniques: X-ray photoelectron spectroscopy, Rutherford back scattering, X-ray diffraction and atomic force microscopy. Most titanium oxide samples were prepared by anodisation, using a galvanostatic procedure. The films were shown to be composed of an amorphous TiO2 outer layer (10–20 nm thick) and an intermediate TiOx layer, in contact with the TiO2 layer and the metallic substrate. The outer layer is sensitive to the environment: its thickness usually decreases with ageing in a corrosive solution. A stabilisation procedure was proposed in order to improve its ability to withstand corrosion.
TL;DR: In this article, the dependence of optical characteristics on the structure of atomic layer-deposited titania (TiO 2 ) thin films has been studied and the formation of preferentially oriented crystal (anatase) structure contributes to this increase of refractive index most significantly.
TL;DR: The low-energy cluster beam deposition technique (LECBD) is applied to produce cluster assembled films with hitherto unknown nanostructured morphologies and properties as discussed by the authors, which can be applied to various fields of applications such as optical and optoelectronic nano-structures, magnetic and magneto-optic nanostructure and quantum devices.
Abstract: The low-energy cluster beam deposition technique (LECBD) is applied to produce cluster assembled films with hitherto unknown nanostructured morphologies and properties. Neutral clusters having the very low energy gained in the supersonic expansion at the exit of the inert gas condensation-type source are deposited without fragmentation upon impact on the substrate. Depending on the deposition conditions (nature, size and flux of incident clusters, nature and temperature of the substrate, vacuum conditions), granular nanostructures resulting from the diffusion and coalescence of supported clusters are obtained with materials of any type (covalent or metallic). A critical size for coalescence limits the supported grain size and, finally, highly porous thick films growing by random stacking of nanoparticles are obtained. A recent model developed by combining several dynamical processes simultaneously occurring on the substrate (deposition - diffusion - aggregation, DDA) is used to simulate the cluster assembled film morphology in good agreement with the experimental observations. Examples of novel materials obtained by LECBD are presented to illustrate the interesting potentialities of the technique. In the case of covalent materials such as carbon and silicon, 'amorphon'-type disordered structures, different from the conventional amorphous structures (a-C and a-Si), are obtained with some unique properties. With transition metal (Fe, Co and Ni) cluster assembled films, a specific magnetic behaviour, resulting from the competition between the intrinsic properties of the grains (magnetocrystalline anisotropy) and the interactions between grains, is observed. Also, films of clusters embedded in various co-deposited matrices are produced in order to control the interactions between grains via the matrix materials (insulating, conducting ...). Interesting optical properties (from metallic clusters in ) or giant magnetoresistance effects (from Co clusters in silver) are reported for such systems, emphasizing the future role of LECBD in various fields of applications such as optical and optoelectronic nanostructures, magnetic and magneto-optic nanostructures and quantum devices.
TL;DR: A sonochemical decomposition of solutions of volatile organic precursors, Fe(CO)5 and Ni(CO4), in decalin at 273 K, under an oxygen pressure of 100−150 kPa was reported in this article.
Abstract: Nanosized amorphous NiFe2O4 powder was prepared by sonochemical decomposition of solutions of volatile organic precursors, Fe(CO)5 and Ni(CO)4, in decalin at 273 K, under an oxygen pressure of 100−150 kPa. The amorphous nature of these particles was confirmed by various techniques, such as SEM, TEM, electron microdiffraction, and X-ray diffractograms. Magnetic measurements, Mossbauer, and EPR spectral studies indicated that the as-prepared NiFe2O4 ferrite particles were superparamagnetic. The Mossbauer spectrum of the crystallized sample showed a clear sextet pattern, with hyperfine field values of 500 and 508 kOe for A (tetrahedral) and B (octahedral) sublattices, respectively, of the inverse spinel NiFe2O4. Saturation magnetization of the annealed sample (25 emu/g) was significantly lower than that for the reported multidomain bulk prticles (55 emu/g), reflecting the ultrafine nature of the sample. Thermogravimetric measurements with a permanent magnet gave Curie temperatures of 440 °C for amorphous and...
TL;DR: In this paper, the influence of post-deposition annealing between 300 and 1100 °C on the structural and optical properties and surface morphology of titanium oxide has been investigated.
TL;DR: The water sorption isotherm and the crystallization rates for amorphous indomethacin were determined at 30 degrees C as a function of relative humidity (RH), along with the effects of water content on the glass transition temperature (T(g).
TL;DR: Amorphous and single-crystal α-SiC were exposed to various oxygen sources at room temperature and X-ray photoelectron spectroscopy was used to follow changes in the surface composition and to determine the local bonding environment of the Si atoms as discussed by the authors.
Abstract: Amorphous and single-crystal α-SiC were exposed to various oxygen sources at room temperature. The oxygen sources included the residual gas in an ultrahigh vacuum environment, ambient air, ozone, and oxygen plasma. X-ray photoelectron spectroscopy (XPS) was used to follow changes in the surface composition and to determine the local bonding environment of the Si atoms. It was found that silicon oxycarbide species are formed when these SiC materials are initially exposed to oxygen. With extended exposure to ambient air, a SiO2 layer is subsequently formed over the silicon oxycarbide. However, the native oxide on the single-crystal SiC consists mainly of silicon oxycarbide species. The thicknesses of these native oxides were calculated using the XPS data.
TL;DR: In this paper, the authors describe the numerical procedure for calculating three-dimensional profiles of temperature in a multilayer stack illuminated by a laser beam, and model the crystallization and amorphization kinetics for phase-change rewritable media.
Abstract: We describe the numerical procedure for calculating three-dimensional profiles of temperature in a multilayer stack illuminated by a laser beam, and model the crystallization and amorphization kinetics for phase-change rewritable media. Experimental methods have been used to determine indirectly the probabilities of nucleation and growth for Ge2Sb2Te5 alloy. Some of the fundamental behaviors of phase-change erasable media, such as the crystallization of as-deposited amorphous phase, amorphization of supercooled liquid, and recrystallization of quenched amorphous phase, have been illustrated based on our three-dimensional temperature calculations and the model kinetics. The calculated transient reflectance behavior of as-deposited Ge2Sb2Te5 amorphous films in a single layer and in a quadrilayer stack, as well as the erasure behavior of Ge2Sb2Te5 alloy in a quadrilayer disk are in good agreement with experimental observations.
TL;DR: In this article, the microstructural properties of amorphous silicon (a-Si) alloy solar cells were investigated using high-resolution transmission electron microscopy (TEM) and Raman spectroscopy.
Abstract: We investigate why high levels of hydrogen dilution of the process gas lead to enhanced light soaking stability of amorphous silicon (a-Si) alloy solar cells by studying the microstructural properties of the material using high-resolution transmission electron microscopy (TEM) and Raman spectroscopy. The TEM results show that a-Si alloy (with or without hydrogen dilution) is a heterogeneous mixture of amorphous network and linear-like objects that show evidence of order along their length. The volume fraction of these ordered regions increases with increasing hydrogen dilution.
TL;DR: In this article, the properties of starch plastic sheets were investigated by stress-strain measurements in relation with starch crystallinity, and the changes are related to changes in water content and glass transition temperature.
Abstract: The properties of starch plastic sheets were investigated by stress—strain measurements in relation with starch crystallinity. Granular potato starch was plasticized with different amounts of glycerol and water by extrusion. The materials were amorphous directly after processing. During aging above the glass transition temperature at various humidities single helical (V and E-type) and double helical (B-type) crystallinity was formed. The rate of crystallization is a function of water and glycerol content. The amorphous rubbery materials were soft and weak with high elongations. During aging the materials became less flexible with higher elastic modulus and tensile stress. The changes are related to changes in water content and glass transition temperature and to changes in B-type crystallinity. The changes in stress—strain properties are explained by the formation of helical structures and crystals, which results in a reinforcement of the starch network by physical crosslinking. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1411–1422, 1997
TL;DR: In this paper, a model for the atomic arrangements in the gallium oxide layer and its interface with the underlying liquid was proposed based on comparisons with known crystal structures. But the results showed that the oxide layer provides rigidity to the liquid surface and is likely a solid.
Abstract: and roughness of the liquid/oxide and oxide/vapor interfaces do not change with oxygen dosage up to 1600 L nor with temperature up to 573 K. This is in contrast to what is observed for the bare liquid-Ga surface, which is roughened significantly by thermally excited capillary waves with temperatures up to only 443 K. This is a good indication that the oxide layer provides rigidity to the liquid surface and is likely a solid; grazingincidence measurements suggest that the film is amorphous or poorly crystallized. Based on comparisons with known crystal structures, models are suggested for the atomic arrangements in the gallium oxide layer and its interface with the underlying liquid. @S0163-1829~97!03815-0#
15 Jun 1997-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a review of the recent findings of bulk amorphous alloys with soft or hard magnetism at room temperature is presented, where the authors show that soft magnetic properties combined with large glass-forming ability (GFA) were obtained in Fe 72 Al 5 Ga 2 P 11 C 6 B 4 and Fe 72 al 5 Ga 6 B4 Si 1 amorphized alloys.
Abstract: This paper reviews our recent findings of bulk amorphous alloys with soft or hard magnetism at room temperature. Soft magnetic characteristics combined with large glass-forming ability (GFA) were obtained in Fe 72 Al 5 Ga 2 P 11 C 6 B 4 and Fe 72 Al 5 Ga 2 P 10 C 6 B 4 Si 1 amorphous alloys. The maximum thickness for glass formation by copper mold casting was about 3 mm. These bulk amorphous alloys have a Curie temperature (T c ) of 600–606 K in an annealed state and their soft magnetic properties are about 1.1 T for saturation magnetization (B s ) and 2–6 A m −1 for coercive force (H c ). The thick amorphous sheets up to 180 gmm in thickness exhibit high permeability of 7000–12 000 at 1 kHz. On the other hand, the hard magnetic properties were obtained for amorphous Ln 60 Fe 30 Al 10 (Ln = Nd or Pr) cylinders with diameters below 15 mm. The large GFA is due to the high T x /T m of 0.85–0.90 and the small temperature intervals of 85–140 K between T m and T x . The T c is around 600 K and typical magnetic properties are 0.13 T for remanence, 0.15 T for B s , 280 k A m −1 for H c and 19 kJ m −3 for (JH) max . The hard magnetic properties disappear in the crystallized state. The first success of synthesizing the ferromagnetic bulk amorphous alloys is important for future progress of basic science and applications.
TL;DR: In this article, the authors designed a thin wave absorber composed of the present material by introducing a low-permittivity area such as a free space into the present metal-containing material.
Abstract: Soft magnetic material has been produced in which flaky thin amorphous metal particles, about 2 /spl mu/m thick, are aligned in polymer in the direction perpendicular to electromagnetic wave propagation. This material yields a permeability two to three times higher than the spinel-type ferrite system in the quasi-microwave band. We have designed a thin wave absorber composed of the present material by introducing a low-permittivity area such as a free space into the present metal-containing material. This decreases the average permittivity, striking a balance between complex permeability and permittivity values, and thus reducing the reflection coefficient of the absorber. A thin (about 3-mm thick) wave absorber with a reflection loss of over 30 dB in the quasi-microwave band was successfully obtained when the free space region was 5% of the total volume.
TL;DR: Amorphous alumina (Al2O3) was produced by a sol-gel technique in order to make available its optical constants for possible astrophysical applications as discussed by the authors, and Mie calculations show that amorphous alumine exhibits a wide Al-O vibrational band, peaking at 11.5-11.8 μm and having a steep blue and an extended red wing.
Abstract: Amorphous alumina (Al2O3) was produced by a sol-gel technique in order to make available its optical constants for possible astrophysical applications. Gradual annealing showed that the X-ray amorphousness of alumina ended somewhere between 723 and 873 K. Above this transition point, the structure changes into disordered γ-Al2O3. At T > 1273 K, crystalline α-Al2O3 (corundum) is formed. Mie calculations show that amorphous alumina exhibits a wide Al-O vibrational band, peaking at 11.5-11.8 μm and having a steep blue and an extended red wing. It may be an important contributor to the continuous opacity between the silicate bands in oxygen-rich circumstellar envelopes, whereas it is ruled out for the explanation of the 13 μm band. An average 13 μm band profile was derived from 51 IRAS low-resolution spectra of bright Mira stars and semiregular variables. Its shape, which is satisfactorily represented by a Lorentz profile, can be reproduced by Mie calculations with the data of α-Al2O3, but not with those of γ-Al2O3. The calculations show that the 13 μm band profile of α-Al2O3 is sensitive to grain shape. If α-Al2O3 is the absorber, a second band should be present at 21 μm. A close correlation was found between the strengths of the 13 μm band and the 10 μm silicate band. It suggests that the 13 μm band carrier could also be somehow connected with silicate dust. Experimental arguments supporting this attribution are presented.