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Glassy Matrix (glassy + matrix)
Selected AbstractsHigh Antibacterial and Antifungal Activity of Silver Monodispersed Nanoparticles Embedded in a Glassy Matrix,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Leticia Esteban-Tejeda Silver doped glass powders have been obtained starting from vitellinate/nAg and montmorillonite/nAg. These powders have shown a high biocide activity against the three different types of microorganisms studied: Escherichia coli (gram-negative bacteria), Micrococcus luteus (gram-positive-bacteria), and Issatchenkia orientalis (yeast). It was found that these glasses keep constant the silver concentration even below the cytotoxic limit. Therefore we interpret that silver doped glasses play the role of dosing devices. [source] Diffusion Kinetics at Liquid-Glassy Polymer InterphasesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2005Luis Arzondo Abstract Summary: We explored the diffusion mechanisms in a series of liquid/glassy polymer interphases. The diffusion experiments were performed in a unique way: the temperature range studied encompassed the glass transition temperature (Tg) of the glassy matrices. We observed that the diffusion behavior of the liquid polymer was remarkably continuous when passing through the matrix Tg, and that the diffusion modes at the liquid/glassy interphases were very similar to those observed in liquid/liquid polymer diffusion. Diffusion profiles of liquid PS in glassy PPO obtained by confocal Raman spectroscopy. The sample was held at 160,°C for the times indicated in the plot. [source] Novel Nanostructure and Deformation Behavior in Rapidly Quenched Cu- (Zr or Hf)-Ti Alloys,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2005J. Saida Novel nanostructure consisting of the metastable nanocrystalline particles embedded in the glassy matrix are reported in the rapidly quenched Cu60(Zr or Hf)30Ti10 alloys. The transformation behavior and mechanical properties in the nanoscale composite alloys are also investigated. The as-cast bulk sample of Cu60Zr30Ti10 alloy exhibits the high fracture strength of approximately 2000 MPa in the compressive test at room temperature. [source] UV-vis-Induced Vitrification of a Molecular Crystal,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2007T. Naito Abstract A charge-transfer complex of 2,5-dimethyl- N,N,-dicyanoquinonediimine (DM) with silver (crystalline Ag(DM)2, defined as ,) is irreversibly transformed by UV-vis illumination. Depending on the illumination conditions, three new types of solids (defined as ,, ,, and ,) with different structural and physical properties are obtained and examined by a variety of analytical techniques, including solid-state, high-resolution, cross-polarization magic angle spinning (CP-MAS) 13C,NMR, elemental analysis (EA), mass spectrometry (MS), X-ray absorption fine structure (XAFS), and powder X-ray diffraction (XRD). The CP-MAS, EA, MS, and XAFS results indicate that compound , is a glass state of Ag(DM)2. The transformation from crystalline (,) to amorphous (,) solid Ag(DM)2 is an irreversible exothermic glass transition (glass-transition temperature 155.2,°C; ,H,=,,126.8,kJ,mol,1), which implies that the glass form is thermodynamically more stable than the crystalline form. Compound , (Ag(DM)1.5) consists of silver nanoparticles (diameter (7,±,2),nm ) dispersed in a glassy matrix of neutral DM molecules. The N,CN,Ag coordination bonds of the , form are not maintained in the , form. Decomposition of , by intense illumination results in a white solid (,), identified as being composed of silver nanoparticles (diameter (60,±,10),nm). Physical and spectroscopic (XAFS) measurements, together with XRD analysis, indicate that the silver nanoparticles in both , and , are crystalline with lattice parameters similar to bulk silver; however, the magnetic susceptibilities differ from bulk silver. [source] Metallic Glasses: Nanoscale Solute Partitioning in Bulk Metallic Glasses (Adv. Mater.ADVANCED MATERIALS, Issue 3 20093/2009) Devitrification of bulk metallic glass leads to novel microstructures with high-density nanoscale crystalline precipitates evenly distributed in a glassy matrix. Xun-Li Wang and co-workers report on p. 305 that significant chemical segregation is revealed in unprecedented detail by atom-probe tomography. This level of detail is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments. [source] Nanoscale Solute Partitioning in Bulk Metallic Glasses,ADVANCED MATERIALS, Issue 3 2009Ling Yang Devitrification of bulk metallic glass leads to a novel microstructure, with high-density nanoscale crystalline precipitates evenly distributed in a glassy matrix. Significant chemical segregation is revealed at unprecedented detail by atom-probe tomography. This level of detail is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments, an unsolved mistery for over a decade. [source] Australasian microtektites and associated impact ejecta in the South China Sea and the Middle Pleistocene supereruption of TobaMETEORITICS & PLANETARY SCIENCE, Issue 2 2006Billy P. Glass Unmelted ejecta were found associated with the microtektites at this site and with Australasian microtektites in Core SO95,17957,2 and ODP Hole 1144A from the central and northern part of the South China Sea, respectively. A few opaque, irregular, rounded, partly melted particles containing highly fractured mineral inclusions (generally quartz and some K feldspar) and some partially melted mineral grains, in a glassy matrix were also found in the microtektite layer. The unmelted ejecta at all three sites include abundant white, opaque grains consisting of mixtures of quartz, coesite, and stishovite, and abundant rock fragments which also contain coesite and, rarely, stishovite. This is the first time that shock-metamorphosed rock fragments have been found in the Australasian microtektite layer. The rock fragments have major and trace element contents similar to the Australasian microtektites and tektites, except for higher volatile element contents. Assuming that the Australasian tektites and microtektites were formed from the same target material as the rock fragments, the parent material for the Australasian tektites and microtektites appears to have been a fine-grained sedimentary deposit. Hole 1144A has the highest abundance of microtektites (number/cm2) of any known Australasian microtektite-bearing site and may be closer to the source crater than any previously identified Australasian microtektite-bearing site. A source crater in the vicinity of 22° N and 104° E seems to explain geographic variations in abundance of both the microtektites and the unmelted ejecta the best; however, a region extending NW into southern China and SE into the Gulf of Tonkin explains the geographic variation in abundance of microtektites and unmelted ejecta almost as well. The size of the source crater is estimated to be 43 ± 9 km based on estimated thickness of the ejecta layer at each site and distance from the proposed source. A volcanic ash layer occurs just above the Australasian microtektite layer, which some authors suggest is from a supereruption of the Toba caldera complex. We estimate that deposition of the ash occurred ,800 ka ago and that it is spread over an area of at least 3.7 times 107 km2. [source] Effect of Sucrose and Maltodextrin on the Physical Properties and Survival of Air-Dried Lactobacillus bulgaricus: An in Situ Fourier Transform Infrared Spectroscopy StudyBIOTECHNOLOGY PROGRESS, Issue 3 2005Harriėtte Oldenhof The effect of sucrose, maltodextrin and skim milk on survival of L. bulgaricus after drying was studied. Survival could be improved from 0.01% for cells that were dried in the absence of protectants to 7.8% for cells dried in a mixture of sucrose and maltodextrin. Fourier transform infrared spectroscopy (FTIR) was used to study the effect of the protectants on the overall protein secondary structure and thermophysical properties of the dried cells. Sucrose, maltodextrin and skim milk were found to have minor effects on the membrane phase behavior and the overall protein secondary structure of the dried cells. FTIR was also used to show that the air-dried cell/protectant solutions formed a glassy state at ambient temperature. 1-Palmitoyl 2-oleoyl phosphatidyl choline (POPC) was used in order to determine if sucrose and maltodextrin have the ability to interact with phospholipids during drying. In addition, the glass transition temperature and strength of hydrogen bonds in the glassy state were studied using this model system. Studies using poly- l -lysine were done in order to determine if sucrose and maltodextrin are able to stabilize protein structure during drying. As expected, sucrose depressed the membrane phase transition temperature (Tm) of POPC in the dried state and prevented conformational changes of poly- l -lysine during drying. Maltodextrin, however, did not depress the Tm of dried POPC and was less effective in preventing conformational changes of poly- l -lysine during drying. We suggest that when cells are dried in the presence of sucrose and maltodextrin, sucrose functions by directly interacting with biomolecules, whereas maltodextrin functions as an osmotically inactive bulking compound causing spacing of the cells and strengthening of the glassy matrix. [source] | ||||||||||