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Amorphous Matrix (amorphous + matrix)
Selected AbstractsFracture Properties of Wood and Wood CompositesADVANCED ENGINEERING MATERIALS, Issue 7 2009Stefanie E. Stanzl-Tschegg Wood has a complex hierarchical structure and is a kind of polymeric composite with elongated cells in an amorphous matrix. Therefore, fracturing is a complicated process that is influenced by loading mode and direction, humidity, etc. Standard linear-elastic fracture mechanics methods mostly cannot sufficiently quantify fracturing, and combining fracture mechanical with structural investigations at different levels of magnification (centimeter to nanometer levels) helps obtaining insight into the fracture mechanisms. [source] Novel ZrInZnO Thin-film Transistor with Excellent StabilityADVANCED MATERIALS, Issue 3 2009Jin-Seong Park Novel ZrInZnO semiconductor materials to resolve transistor instability for active-matrix organic light-emitting diodes are proposed. The ZrInZnO film is preprared using a cosputtering method, and presents a nanocrystal structure embedded in an amorphous matrix. The thin-film transistors fabricated have good electrical performances as well as excellent stability under long-term bias stresses. [source] Comparative aspects of the inner root sheath in adult and developing hairs of mammals in relation to the evolution of hairsJOURNAL OF ANATOMY, Issue 3 2004Lorenzo AlibardiArticle first published online: 17 SEP 200 Abstract The inner root sheath (IRS) allows the exit of hairs through the epidermal surface. The fine structure of monotreme and marsupial IRS and trichohyalin is not known. Using electron microscopy and immunocytochemistry, the localization of trichohyalin and transglutaminase have been studied in monotreme and marsupial hairs, and compared with trichohyalin localization in placental hairs. Trichohyalin in all mammalian species studied here is recognized by a polyclonal antibody against sheep trichohyalin. This generalized immunoreactivity suggests that common epitopes are present in trichohyalin across mammals. In differentiating IRS cells, trichohyalin granules of variable dimensions are composed of an immunolabelled amorphous matrix associated with a network of 10,12-nm-thick keratin filaments. Transglutaminase labelling is present among keratin bundles and trichohyalin granules, and in condensed nuclei of terminally differentiating cells of the inner root sheath. The IRS in monotreme hairs is multistratified but lacks a distinguishable Henle layer. Cornification of IRS determines the sculpturing of the fibre cuticle and later shedding from the follicle for the exit of the hair fibre on the epidermal surface. It is hypothesized that the stratification of IRS in Henle, Huxley and IRS cuticle layers is derived from a simpler organization, like that present in the IRS of monotremes. The IRS is regarded as a localized shedding/sloughing layer needed for the exit of hairs without injury to the epidermis. The formation of the IRS during the evolution of mammalian epidermis allowed the physiological exit of hairs produced inside the skin. The peculiar morphogenesis of hairs in possible primitive skins, such as those of the monotremes (mammals with some reptilian characteristics) or the tails of some rodents (a scaled skin), may elucidate the evolution of hairs. In monotreme and rodent tail skin, the dermal papilla remains localized on the proximal side of the hair peg and forms a hair placode with bilateral symmetry. The papilla is progressively surrounded by the down-growing hair peg until a dermal papilla with radial symmetry is formed. It is speculated that the progressive reduction of the extended dermal papilla of reptilian scales into small and deep papillae of therapsid reptiles produced hairs in mammals. [source] Crystal structure of defect-containing semiconductor nanocrystals , an X-ray diffraction studyJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2009Maja Buljan Defects of crystal structure in semiconductor nanocrystals embedded in an amorphous matrix are studied by X-ray diffraction and a full-profile analysis of the diffraction curves based on the Debye formula. A new theoretical model is proposed, describing the diffraction from randomly distributed intrinsic and extrinsic stacking faults and twin blocks in the nanocrystals. The application of the model to full-profile analysis of experimental diffraction curves enables the determination of the concentrations of individual defect types in the nanocrystals. The method has been applied for the investigation of self-organized Ge nanocrystals in an SiO2 matrix, and the dependence of the structure quality of the nanocrystals on their deposition and annealing parameters was obtained. [source] Microstructure of ball milled and compacted Co,Ni,Al alloys from the , rangeJOURNAL OF MICROSCOPY, Issue 2 2009W. MAZIARZ Summary Two powder alloys from the , phase region of compositions Co28.5Ni36.5Al35 and Co35Ni30Al35 were ball milled for 80 h in a high energy ball mill. The formation of amorphous structure was observed after 40 h of milling and further milling did not change their structure. The analytical and high-resolution transmission electron microscopy (TEM, HREM) examination of powder structure showed that nanoparticles of L10 phase of size of about 5 nm were present within the amorphous matrix. The vacuum hot pressing of the milled powders under pressure of 400 MPa at 700°C for 12 min resulted in the formation of compacts with density of about 70% of the theoretical one. The additional heat treatment at 1300°C for 6 h followed by water quenching, led to significant improvement of density and induced the martensitic transformation manifested by a broad heat effect. The characteristic temperatures of the transformation were determined using DSC measurements, which revealed only small differences within the examined alloys compositions. TEM structure studies of heat-treated alloys allowed to identify the structure of an ordered , (B2) phase and L10 martrensite. [source] Role of thermodynamic, molecular, and kinetic factors in crystallization from the amorphous stateJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2008Chandan Bhugra Abstract Though there is an advantage in using the higher solubility amorphous state in cases where low solubility limits absorption, physical instability poses a significant barrier limiting its use in solid oral dosage forms. Unlike chemical instability, where useful accelerated stability testing protocols are common, no methodology has been established to predict physical instability. Therefore, an understanding of the factors affecting crystallization from the amorphous state is not only important from a scientific perspective but also has practical applications. Crystallization from the amorphous matrix has been linked to the molecular mobility in the amorphous matrix and recent research has focused on developing the link between these two fundamental properties of glass forming materials. Although researchers have been actively working in this area for some time, there is no current review describing the present state of understanding of crystallization from the amorphous state. The purpose of this review therefore is to examine the roles of different factors such as molecular mobility, thermodynamic factors, and the implication of different processing condition, in crystallization from the amorphous state. We believe an increased understanding of the relative contributions of molecular mobility and processing conditions are vital to increased usage of the amorphous state in solid oral dosage forms. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1329,1349, 2008 [source] Low-wavenumber Raman scattering spectroscopy in studies of new gallium-doped silica glass-based transparent vitroceramic mediumJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2001R. Ceccato Optically transparent, silica glass-based vitroceramic material doped with gallium oxide was obtained by standard glass fusion and appropriate thermal treatments. Low-wavenumber Raman scattering spectroscopy allowed the determination of the microstructure and in particular the size distribution of nanoparticles embedded in the amorphous matrix. The nanocrystal growth was accurately controlled by heat treatment conditions. Transmission electron microscopy and X-ray diffraction measurements revealed the presence of a single crystalline phase, spherical-shaped nanoaggregates, homogeneously distributed in the transparent composite medium. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of Nanotube Array Composed of an Amorphous Matrix Embedded with NaCl-Type SiC Crystallites by Chemical Vapor Infiltration TechniquesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2010Wen Yang Highly dense oriented arrays of nanotubes were synthesized via a chemical vapor infiltration process using anodic alumina membrane as a template. The nanotubes have a unique granular structure, which is composed of SiC nanocrystals embedded in an amorphous matrix. X-ray diffraction and high-resolution transmission electron microscopy examinations both indicate an NaCl-type crystalline structure of the SiC nanocrystals in the nanotubes. The process described here can be extended to the preparation of other nanomaterials that are suitable to be obtained via a vapor,solid approach. [source] Preparation of NiAl2O4/SiO2 and Co2+ -Doped NiAl2O4/SiO2 Nanocomposites by the Sol,Gel RouteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2006I. Prakash NiAl2O4/SiO2 and Co2+ -doped NiAl2O4/SiO2 nanocomposite materials of compositions 5% NiO , 6% Al2O3, 89% SiO2 and 0.2% CoO , 4.8% NiO , 6% Al2O3, 89% SiO2, respectively, were prepared by a sol,gel process. NiAl2O4 and cobalt-doped NiAl2O4 nanocrystals were grown in a SiO2 amorphous matrix at around 1073 K by heating the dried gels from 333 to 1173 K at the rate of 1 K/min. The formations of NiAl2O4 and cobalt-doped NiAl2O4 nanocrystals in SiO2 amorphous matrix were confirmed through X-ray powder diffraction, Fourier transform infrared spectroscopy, differential scanning calorimeter, transmission electron microscopy (TEM), and optical absorption spectroscopy techniques. The TEM images revealed the uniform distribution of NiAl2O4 and cobalt-doped NiAl2O4 nanocrystals in the amorphous SiO2 matrix and the size was found to be ,5,8 nm. [source] Compatibilization of Polyamide-6/Polyarylate Blends by Means of an IonomerMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2005Aritz Retolaza Abstract Summary: Polyamide-6 (PA6)/polyarylate of bisphenol A (PAr) blends rich in PA6 and modified with an additional 15% poly[ethylene- co -(methacrylic acid)] partially neutralized with zinc (PEMA-Zn) as a compatibilizer were obtained by melt mixing. Their phase structure, morphology, and mechanical performance were compared with those of the corresponding binary blends. The ternary blends were composed of a PA6 amorphous matrix and a dispersed PAr-rich phase in which reacted PA6 and PEMA-Zn were present. Additionally, minor amounts of a crystalline PA6 phase, and a PEMA-Zn phase were also present. The chemical reactions observed led to a clear decrease in the dispersed particle size when PEMA-Zn was added, indicating compatibilization. Consequently, the mechanical behavior of the blends with PEMA-Zn improved, leading, mainly in the case of the blend with 10% PAr, to significant increases in both ductility and impact strength with respect to those of the binary blends. These increases were more remarkable than the slight decrease in stiffness as a consequence of the rubbery nature of the compatibilizer. Cryogenically fractured surface of the PA6/PAr-PEMA-Zn 70/30-15 ternary blend. [source] The influence of substrate on the magnetic properties of MnZn ferrite thin film fabricated by alternate sputteringPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2008Lanxi Wang Abstract Mn0.5Zn0.5Fe2O4 film which has the highest saturation magnetization among Mn1,xZnx Fe2O4 thin films was prepared by the alternate rf sputtering method from two targets with compositions of MnFe2O4 and ZnFe2O4, respectively. The films were deposited on single-crystal Si(100), MgO(100) and SiO2/Si(100) substrates. The as-deposited films were amorphous, and after annealing in a vacuum furnace at 550 °C, polycrystalline MnZn ferrite films with residual amorphous matrix were obtained. The coercivity of all films is low, and the film on the MgO(100) substrate shows a coercivity as low as 27 Oe. The grain size of all films is about 20 nm and is less than the ferromagnetic exchange length (160 nm), so magnetic anisotropies are averaged to lower effective values. Furthermore, the negative magnetostriction constant of crystalline MnZn ferrite and the positive magnetostriction constant of amorphous Fe-based matrix will cancel out and may lead to a low or vanishing saturation magnetostriction constant. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of Nb substituted for Fe on the microstructure and magnetic properties of Fe-based nanocomposite alloyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007N. Q. Hoa Abstract The influence of Nb substituted for Fe on the microstructure and magnetic properties including the magnetoimpedance effect of a Fe-based have been investigated. The nanocomposite structure composed of ultra-fine Fe(Si) grains embedded in an amorphous matrix was obtained by annealing the Fe-based amorphous alloy prepared by rapidly-quenched method. The measurements of thermomagnetic curves indicated that the Curie temperature of the amorphous phase of the samples decreases with increasing Nb content. The optimal heat treatment was performed at Ta = 480 °C for 30 min and showed that the ultrasoft magnetic properties of nanocomposite materials were obtained. The magnetoimpedance (MI) of these samples has been studied in range frequency from 1MHz to 5 MHz and varying a dc magnetic field within 300 Oe. The correlation between the MI effect and the soft magnetic properties is discussed. The incremental permeability ratio (PR) showed the drastic changes of soft magnetic properties as a function of annealing temperatures. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic study of Hitperm alloys (Fe0.5Co0.5)1,x ,y ,zMxByCuz (M = Hf, Zr, Nb)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006Abstract A family of the Hitperm alloys (Fe0.5Co0.5)1,x ,y ,zMxByCuz (M = Hf, Zr, Nb) produced in an argon atmosphere as amorphous ribbons with 0.025 mm thickness are investigated up to 1200 K. The partial replacement of Fe by Co with optimal Fe0.5Co0.5 ratio increases the Curie temperature of the amorphous phase and the magnetic moment per formula unit. The early stages of crystallization can be observed by magnetization measurements. Alloys subjected to the first controlled crystallization stage are built of bcc-(Fe,Co) nanocrystals that are homegeneously embedded in the amorphous matrix. Mean grain sizes are about 11 nm. These two-phase alloys exhibit good soft magnetic properties with the relatively low coercive fields up to 50 A/m. Hafnium and hafnium/zirconium mixture are found to be the best inhibitors of the nanograin growth resulting in the best soft magnetic parameters. Alloys with niobium exhibit lower thermal stability and higher coercive fields. The correlation between the structure evolution and the magnetic properties is analysed and discussed. Conditions for optimum heat treatment are also determined. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nanocrystalline alloys studied by positron annihilation lifetime spectroscopyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007Martin Petriska Abstract Nanocrystalline alloys present a new class of materials that exhibit interesting magnetic properties. These stem primarily from the presence of crystalline grains with the size of several tens of nanometers embedded in a residual amorphous matrix. In this paper, we employ positron annihilation spectrometry to investigate the relation between positron lifetime and microstructure of the NANOPERM-type metallic Fe76Mo8Cu1B15 alloy. The behaviour of positron lifetime with respect to the annealing temperature is discussed for samples, which were prepared by one hour thermal treatment in a vacuum at temperatures ranging from 330 up to 700 °C. Samples in amorphous (as-quenched) state were analysed, too. The results of this work confirm that the optimum annealing temperature of 550 °C correlates with the minimum of free volume and coincide with the temperature at which superior magnetic properties are observed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Necrotizing infundibular crystalline folliculitisBRITISH JOURNAL OF DERMATOLOGY, Issue 1 2001S. Kossard We describe a 22-year-old woman with a background of acne who developed multiple folliculocentric facial papules associated with sharply demarcated waxy, keratotic plugs. Multiple skin biopsies showed umbilicated craters that were filled with dispersed bundles of eosinophilic filaments embedded in a pale amorphous matrix forming a plug. The plugs bulged into the upper dermis. Serial sections showed vacuolar and filamentous destruction of the infundibular and adjacent perifollicular epithelium and a close relationship of the crystalline necrosis to follicles. Electron microscopy revealed that the filamentous bundles were tonofilaments. No fresh material was available for polarization and the paraffin sections failed to polarize. The clinical and pathological findings of the lesions in our patient were identical to those reported as a new perforating disorder with urate-like crystals. Our case indicates that the process may represent crystalline folliculocentric necrosis rather than a primary perforating disorder. The nature and basis of the crystals that have a urate-like appearance remain to be determined. [source] | |||||||||||||||||||