Sintered glass-ceramic matrix composites made from Latvian silicate wastes

Powder technology and sintering were used to fabricate glass-ceramic matrix composites from Latvian industrial wastes and alumina platelets reinforcement. The optimization of the sintering behaviour of glass-ceramic compositions containing clay and alumina platelets was carried out. Highly crystalline and dense products (> 90 % theoretical density) were fabricated by sintering at temperatures in the range 1040 to 1060 °C, depending on composition. Addition of waste glass to influence the sintering temperature and sintering interval was also investigated. Composites showed higher fracture strength (up to 97 MPa) and hardness than unreinforced glass-ceramics. The "best" composition in terms of density and mechanical properties contained 20 wt% alumina platelets. The matrix exhibited a microstructure composed mainly of elongated crystals of pyroxene type in a residual glassy matrix. These composites are candidates for applications as building materials, such as floor and wall tiles, and for manufacturing machine elements and parts

Combination of Lidar and Model Data for Studying Deep Gravity Wave Propagation

The paper presents a feasible method to complement ground-based middle atmospheric Rayleigh lidar temperature observations with numerical simulations in the lower stratosphere and troposphere to study gravity waves. Validated mesoscale numerical simulations are utilized to complement the temperature below 30-km altitude. For this purpose, high-temporal-resolution output of the numerical results was interpolated on the position of the lidar in the lee of the Scandinavian mountain range. Two wintertime cases of orographically induced gravity waves are analyzed. Wave parameters are derived using a wavelet analysis of the combined dataset throughout the entire altitude range from the troposphere to the mesosphere. Although similar in the tropospheric forcings, both cases differ in vertical propagation. The combined dataset reveals stratospheric wave breaking for one case, whereas the mountain waves in the other case could propagate up to about 40-km altitude. The lidar observations reveal an interaction of the vertically propagating gravity waves with the stratopause, leading to a stratopause descent in both cases

Cation-Exchange Resins Having Both Methacrylic and Acrylic Acid Groups: Structure and Sorption of Albumin

Porous cation-exchange resins have been synthesized by water-dispersion polymerization of acrylic and methacrylic acids at the ratios 1:3, 1:4, and 1:5 and cross-linking agent triethylene glycol dimethacrylate. The ionization of these resins is characterized by decreased dependence of effective ionization constant from ionization degree α after the achieving of α =0.5. The morphology of resin has been shown by SEM method. BSA sorption study indicates sorption capacity growth with the increase of amount of acrylic acid units in the resins and the complicate character of sorbent structure influence on BSA sorption capacity. The influence of resin ionization, swelling and chain flexibility on sorption been discoursed

3D model of intra-yarn fiber volume fraction gradients of woven fabrics

Accurate predictions of laminate strength is important for engineering. Overestimations of laminate strength can be due to variations in local fiber volume fraction. However, intra-yarn fiber volume fraction gradients within laminated plain woven fabrics (PWF) have not been investigated sufficiently to consider their effect in laminated strength predictions. This study addresses this shortening by a proper determination of in laminated PWFs and proposes a corresponding model (GM). We tested the hypothesis that can be modeled according to analytical models of the laminates meso-level structure. All required parameters were determined from scanning electron microscopy images of laminated PWFs of different fiber volume fraction. The GM was implemented in Matlab and matches the experimental data well. In addition, finite element simulation of interlaced yarns were conducted to understand the origin of . The proposed model is a 3D description of in PWFs. Using this model may lead to a significantly improved prediction of the laminate strength

Facets of Protein Assembly on Nanostructured Titanium Oxide Surfaces

One key for the successful integration of implants into the human body is the control of protein adsorption by adjusting the surface properties at different length scales. This is particularly important for titanium oxide, one of the most common biomedical interfaces. As for titania (TiO2) the interface is largely defined by its crystal surface structure, it is crucial to understand how the surface crystallinity affects the structure, properties and function of protein layers mediating subsequent biological reactions. For rutile TiO2 we demonstrate that the conformation and relative amount of human plasma fibrinogen (HPF) and the structure of adsorbed HPF layers depend on the crystal surface nanostructure by employing thermally etched multi-faceted TiO2 surfaces. Thermal etching of polycrystalline TiO2 facilitates a nanoscale crystal faceting and, thus, the creation of different surface nanostructures on a single specimen surface. Atomic force microscopy shows that HPF arranges into networks and thin globular layers on flat and irregular crystal grain surfaces, respectively. On a third, faceted category we observed an alternating conformation of HPF on neighboring facets. The bulk grain orientation obtained from electron backscatter diffraction and thermodynamic mechanisms of surface reconstruction during thermal etching suggest that the grain and facet surface-specific arrangement and relative amount of adsorbed proteins depend on the associated free crystal surface energy. The implications for potentially favorable TiO2 crystal facets regarding the inflammatory response and hemostasis are discussed with a view to the advanced surface design of future implants