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Today chemistry of materials and as such the ceramic field of research are addressed through more and more complex synthetic methodologies in order to optimize final material performances. The notion of complexity in chemical science is illustrated inhere through the concept of integrative chemistry. Particularly the integration between bi-liquid foams, sol-gel process, organo-silane functionnalization, lanthanides complexation and Pd heterogeneous nucleation is proposed as a non-exhaustive synthetic tool box to reach specific advanced ceramics. The first section is dealing with the synthesis of the first series of Si(HIPE) macrocellular foams where the oil volume fraction of the starting emulsion allows a nice tuning of the foams macroporosity. The second section is dealing with Europium complexation of β−diketone and malonamide hybrid Organo-Si(HIPE) leading to the Eu3+@Organo-Si(HIPE) luminescent foams, while the third part is dedicated to Pd heterogeneous nucleation within host hybrid foams. This last series of macrocellular ceramics are labeled Pd@Organo-Si(HIPE) which demonstrates good turn over number (TON) and turn over frequencies (TOF) when acting as supported catalysts for the Mizoroki-Heck coupling reactions. In the above mentioned foams the HIPE acronym is for High Internal Phase Emulsion.
The hybrid materials consisting of plate-like potassium lithium titanate (K0.81Li0.27Ti1.73O4) micro particles coated with calcia-doped ceria (Ce0.8Ca0.2O1.8) nano particles were prepared by the co-precipitation method and sol-gel method. Broad-spectrum UV-shielding composite materials with good comfort and low oxidation catalytic activity were successfully synthesized. The comfort when applied on skin and UV-shielding ability of the composites prepared by the sol-gel method were superior to those by the co-precipitation method.
Availability of advanced materials has opened up opportunities in meeting several functional requirements through hybridization. Hybrids consisting of ceramics, metals and high performance polymers could benefit many aircraft and space satellite applications. They could meet requirements of low weight, high environmental stability, and high thermal or dimensional stability. In this study, hybrid materials consisting of high performance polymer, porous ceramics (glass microballoons) and other constituents such as Zircornium Tungstate (with negative coefficient of thermal expansion (CTE)) and nanoclay were studied. Specimens were successfully produced with a range of density from 0.4 to 1.1 g/cm3 depending on the degree of fill in the syntactic foams. CTE tailoring was achieved to greatly reduce the residual stress arising from processing and CTE mismatch of dissimilar materials. The evaluations of dimensional stability were examined from thermomechanical analysis. The synergistic effects of resin, ceramic constituents and pores on the hybrid properties will be presented.
The mismatch of the coefficient of the thermal expansion (CTE) is one of the main causes of crack initiation and delamination for carbon fiber-reinforced polymer hybrids and metal/polymer hybrid materials. In this research, a negative CTE ceramic material (zirconium tungstate) was incorporated with a thermoset polymer (bismaleimide) resulting in a ~40% reduction in CTE and a significant improvement in thermal stability. The morphology showed good dispersion of the zirconium tungstate particles within the bismaleimide. Comparisons of the experimental CTE values with the rule-of-mixture and the analytical micromechanical models will be discussed.
Gold nanorods (GNRs) were deposited in ordered mesoporous silica SBA-15 by a liquid-phase synthesis. The X-ray diffraction pattern of GNRs-deposited SBA-15 (GNRs/SBA-15) confirmed that the mesoporous structure of the SBA-15 was maintained even after depositing GNRs in the SBA-15 pores. Laser irradiation and heat treatment for GNRs/SBA-15 were carried out to check the effect on the GNRs morphology alteration. These treatments were found to shorten the length of the GNRs in SBA-15, leading to a blue shift of the surface plasmon resonance wavelength of the GNRs. Especially, heat treatment at high temperatures, e.g. at 500 °C, showed unique result that the inner wall of SBA-15 was collapsed by the overgrowth of gold nanoparticles.
Heterogeneous sol-gel systems (suspensions), synthesized by mixing sols and fillers of various dispersity (oxides, minerals, etc.), are successfully used to prepare glass-ceramic coatings. Sol composition (precursor, catalyst, solvent, dopants), filler dispersity and a homogenization mode for obtained suspensions essentially influence the properties of coatings formed. Here ways of the control of properties of heterogeneous sol-gel systems (by using various dopants, additives of organic low- and high-molecular compounds, as well as ultrasound) to reach set electro-physical and mechanical characteristics of coatings are considered in details. A number of examples of applications of glass-ceramic and hybrid coatings as well as ‘skin’ - layers are resulted.
Smart processing for ceramics structure tectonics is new strategy of science and engineering to create novel functional materials with special patterns and morphologies. In this lecture, various investigations to develop the functionally structured materials by using smart processes of stereo- lithography will be introduced. For example, photonic crystals with periodic arrangements in dielectric constants are strong candidates of artificial functional materials to control electromagnetic wave energies effectively. Special modifications of dielectric micro patterns to harmonize electromagnetic waves in terahertz frequency ranges with molecule vibrations of various biochemical solutions will be introduced as investigative results of artificial photosynthesis.
A simple, inexpensive, and environmentally-friendly process for converting mixtures of clays and polymers has been developed. Polymer and clay are combined in water, and the mixtures are freeze dried to produce materials which have bulk densities typically in the range of 0.03 – 0.15 g/cm3. These low density polymer/clay aerogel materials possess good mechanical properties similar to those of traditional polymer foams, can be reinforced with fibers, modified with nanoparticles, biomineralized, or converted into porous ceramics.
Among the porous media, hydroxyapatite (HA) possesses good biocompatibility and bioactivity properties with respect to bone cells and tissues, due to its similarity with the hard tissues of the body. In this study, mesoporous HA was synthesized using a soft-templating technique via a selfassembly between HA and cationic surfactant ecyltrimethylammonium bromide (C10TAB), which is analogous to the synthesis of mesoporous silica MCM-41. This co-precipitation method involved formation of hexagonal-phase micelle template by the surfactant and the precipitation of HA surrounding the micelle. After ageing, calcination was carried out to remove the templates, revealing the pores as well as to produce more crystalline and more stable HA structure. This study showed that instead of hexadecyltrimethylammonium bromide (C16TAB) which was conventionally used, C10TAB could also be used to synthesize single-phase mesoporous HA with pore size ca. 3 nm. Ageing temperature of 120 °C, for 24 hours was found sufficient for the formation of mesoporous HA. The adsorption properties of mesoporous HA was able to be improved by increasing the water content of C10TAB-phosphate solution and by constant pH adjustment during the mixing of solutions.
The improvement of ceramic synthesis and processing methodology based on digital image processing and analysis of ceramic samples is in its initial stage. The main reason is that the models are based on poorly obtained data from sample’s digital image processing. The lack of a solid statistical analysis and digital-imaging setup standardization make the method less useful that it should be if set in a sound basis. Therefore the importance of setting a new methodology in digital image processing for data acquisition on ceramic morphology analysis is essential for setting new models for customized ceramic synthesis and processing. The present paper shows results based on Scanning Electron Microscopy (SEM) from Al2O3 ceramics obtained by starch consolidation method. Observation of different sample’s regions allowed a more accurate description of ceramic morphology. Plots of resistance to flexion versus porosity and its correlation with the grain size and shape allowed one to choose the best model for representing ceramic’s morphology. Correlation of starch percentage with sample’s porosity and mechanical resistance allowed the best experimental conditions for customized ceramic’s performance.
Porous ceramic materials are used in medicine as well as in industry. They can be prepared in the form of filter components, thermal insulators, or composite components. Preforms of this type can only be applied if they meet the respective structural requirements. In the present study, such a porous ceramic material was produced by the polymeric sponge method using a polyurethane sponge and a-Al2O3 Almatis. The aqueous suspension was prepared with binders of the two types: polyvinyl alcohol and a dispersion based on methacrylic acid esters and styrene. The aim of this study was to find the relationship between the composition of the weight slips, sintering conditions, and the structure of the porous ceramic obtained. The paper presents the results of studies on the rheological properties of the ceramic slurries and the results of strength tests of the ceramic material.
High performance porous structural ceramics have been widely studied. Silicon nitride is an interesting material for this application because bodies with high mechanical strength, achieved as a result of “in situ” anisotropic grain grown, can be obtained. In this study, Si3N4 bodies with different porosity related aspects (percentage, morphology, etc.) are made using the sacrificing template method, by changing the percentage (vol%) and the drying method of the mixture as well as the sintering time. The porosity, apparent density (Archimedes method), microstructure (SEM) and the mechanical strength (in compression) of these bodies were determined. It was thus possible to relate the type and amount of starch with the porosity and mechanical properties of the bodies.
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