			Home About us Contact

Internal Walls (internal + wall)

Distribution by Scientific Domains

Polymers and Materials Science	60%
Chemistry	40%

Selected Abstracts

Fabrication of multilayer ceramic membranes

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009
V.V. Zyryanov
Abstract The development of multilayer mixed conducting oxide membranes on macroporous dead-end tubular composite glass/ceramic substrates is presented. Sol modification of glass/ceramic substrate enhances the performance of catalytic membrane reactor (CMR) with reduced thickness of ceramic layers. The shrinkage misfit between support and ceramic layers can be regulated by different processing steps including sol modification of substrate and preliminary annealing of ceramic powders. Nanopowders of compatible complex perovskites as membrane materials were obtained by mechanochemical synthesis. Porous and dense ceramic layers were supported onto the internal wall of substrate by slip casting of slurries comprised of the narrow fractions of agglomerated powders dispersed in organic media with addition of surfactants. For SrFeO3 -based dense perovskite ceramics, both dynamics of oxygen loss at high temperatures and mechanical properties were found to be affected by the presence of SrSO4 surface inclusions formed due to sulfur admixture in starting reactants. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Lightweight Porcelain Stoneware by Engineered CeO2 Addition,

ADVANCED ENGINEERING MATERIALS, Issue 1-2 2010
Enrico Bernardo
The use of porcelain stoneware in innovative applications such as the covering of internal walls or the manufacturing of ventilated facades may be limited by its relatively high density. In this paper, we discuss the achievement of a reduction in density of about 30%, coupled to a limited water absorption (about 2%), by the addition of CeO2 to the raw materials. This additive provides some porosity due to the evolution of oxygen, in turn caused by the high temperature reduction to Ce2O3. This gas formation depends both on sintering temperature, holding time, and is obviously affected by the concentration of additive. Two different processing strategies were found to match the density and water absorption requirements for the application of stoneware tiles. One involved the the control of the CeO2 content together with processing at high temperature for a limited holding time; the other one corresponded to the fabrication of a graded material, comprising a highly porous core (produced using a high content of CeO2) sandwiched between two external compact surface layers. [source]

Synthesis of Porous Silicon Nitride with Unidirectionally Aligned Channels Using Freeze-Drying Process

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002
Takayuki Fukasawa
Porous silicon nitride with macroscopically aligned channels was synthesized using a freeze-drying process. Freezing of a water-based slurry of silicon nitride was done while unidirectionally controlling the growth direction of the ice. Pores were generated subsequently by sublimation of the columnar ice during freeze-drying. By sintering this green body, a porous silicon nitride with high porosity (over 50%) was obtained and its porosity was controllable by the slurry concentration. The porous Si3N4 had a unique microstructure, where macroscopically aligned open pores contained fibrous grains protruding from the internal walls of the Si3N4 matrix. It is hypothesized that vapor/solid phase reactions were important to the formation mechanism of the fibrous grains. [source]

Preparation of oily core polyamide microcapsules via interfacial polycondensation,

POLYMER INTERNATIONAL, Issue 4 2003
L Soto-Portas
Abstract Microcapsules obtained by interfacial polycondensation from an original system based on the polyaddition of specific di- or polyamines and more classical acyl chloride molecules were studied. The originality of the system lies in the fact that the encapsulated agent is the internal phase allowing its incorporation without an organic solvent, which is an advantage from the point of view of environmental protection. Once the optimal parameters of the emulsion were determined, the membrane formation was studied by optimizing the emulsification and reaction times in relation to simultaneous acyl chloride hydrolysis. The microcapsules were obtained by interfacial polycondensation between an excess of amine functions (diamine and diethylenetriamine) and acyl chloride (sebacoyl chloride and 1,3,5-benzene tricarbonyl trichloride) from an oil-in-water emulsion in the presence of 88% hydrolyzed poly(vinyl alcohol) as a surfactant. Various formulations in terms of COCl concentration, crosslinking agent concentration, excess of amine functions, emulsification and reaction times were prepared. The hydrolysis of acyl halide functions is the main parameter which influences the growth of the membrane. The increase in acyl chloride function concentration allows compensation for that lost by hydrolysis, and increases the encapsulation yield to about 90%. The degree of crosslinking of the membrane was controlled in order to minimize the subsequent release of oil by the addition of trifunctional monomers. An optimal formulation was developed offering high encapsulation yield and optimal elastic behaviour. Almost spherical capsules, with a membrane thickness of approximately 500,nm, relatively smooth internal walls and crumpled external walls, were observed by scanning electron microscopy. © 2003 Society of Chemical Industry [source]

Hollow Boron Nitride (BN) Nanocages and BN-Nanocage-Encapsulated Nanocrystals

CHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004
Ying-Chun Zhu Dr.
Abstract Hollow boron nitride (BN) nanocages (nanospheres, image on the left) and BN-nanocage-encapsulated GaN nanocrystals (right) have been synthesized by using a homemade BNO precursors. The as-prepared BN hollow nanocages have typically spherical morphologies with diameters ranging from 30 to 200 nm. The nanocages have crystalline structures. Peanutlike nanocages with double walls have also been observed; their internal space is divided into seperated compartments by the internal walls. The method is extended to sheathe nanocrystals with BN nanocages; BN-shell/GaN-core nanostructures have been successfully fabriacted. The method may be generally applicable to the fabrication BN-sheathed nanocrystals. [source]