Mikolaj Szafran

Ceramic–metal composites with an interpenetrating network

Abstract Preliminary results of studies of ceramic–metal composites Al2O3–Fe obtained via infiltration of a porous ceramic matrix are reported. Composites with a thin FeAl2O4 spinel layer, as observed in the present work, on the ceramic/metal interface, will give an opportunity to develop an interpenetrating network with a strong ceramic–metal bonding.

Thermal decomposition of monosaccharides derivatives applied in ceramic gelcasting process investigated by the coupled DTA/TG/MS analysis

The paper reports the decomposition of saccharides derivatives in comparison to commercial substances during the process of binder removal from ceramic samples. The saccharides derivatives are polymers synthesized from glucose and fructose with acryloyl group in the sugar molecule. The synthesized compounds played the role of binder in the shaping of ceramic powders by gelcasting method. The method belongs to colloidal processes and allows to produce ceramic elements of complicated geometry. As ceramic powder Al2O3 was used. The thermal analysis have been done on apparatus coupled with mass spectrometer. MS analysis showed what types of gasses are released to the atmosphere during the thermal decomposition of polymers. The obtained results showed important differences in decomposition of polymers obtained from commercial acrylamide, 2-hydroxyethyl acrylate and N,N′-methylenebisacrylamide in comparison to synthesized glucose and fructose derivatives. The measurements allowed to establish the sintering program of the green ceramic samples and evaluate whether harmful NOx gases are released to the atmosphere.

Effect of the bonding ceramic material on the size of pores in porous ceramic materials

Abstract The results of studies on the effect of the grain size and amount of ceramic bonding materials (ceramic binder) on the size of pores in porous ceramic materials are presented. Electrocorundum and silicon carbide of various grain sizes were used as the grain material. Borosilicate glass was used as a ceramic binder for electrocorundum, whereas a mixture of kaolin with feldspars was used as that for silicon carbide. The sintering conditions were chosen so as the borosilicate glass was in a melted form, and the ceramic binder for silicon carbide only sintered during the sintering process. The studies showed that the mean pore size of the porous ceramic material decreases with an increase in the amount of the sintering ceramic binder and increases with that of the melting ceramic binder during the sintering process.

Si3N4–Al2O3–TiC–Y2O3 composites intended for the edges of cutting tools

Abstract This paper is concerned with the synthesis of composites in the Si 3 N 4 –Al 2 O 3 –TiC–Y 2 O 3 system. The materials obtained have a high density and a good fracture toughness (K IC =9.3 MPa√m). Machining tests show that the service life of the tool blades made of these composites may even be tenfold longer than that of commercial blades made of Si 3 N 4 with an additon of Al 2 O 3 , MgO and Y 2 O 3 .

EFFECT OF GLASS TRANSITION TEMPERATURE OF POLYMERIC BINDERS ON PROPERTIES CERAMIC MATERIALS

In the paper are presented the studies of the effect of glass transition temperature of new water-thinnable polymeric binders on the properties of ceramic materials obtained by die pressing. The parameters of ceramic samples comprising polymeric binders have been compared with those of samples comprising poly(vinyl alcohol) (PVA) — water-soluble binder. When using poly(acrylic-styrene) (AS), poly(acrylic-allyl) (AA) and poly(vinyl-allyl) (VA) water-thinnable binders, materials of greater density and mechanical strength were obtained in the green state as well as after sintering than those in the case of using PVA. The dependence of the chemical structure of the binders applied on the properties of samples such as the glass transition temperature and hydrophobic-hydrophilic balance of the copolymers has been discussed.

Al2O3-Fe Functionally Graded Materials Fabricated under Magnetic Field

This paper describes technology, which can be used to obtain ceramic-metal composites with a gradient of metal particles concentration. Graded composites, have been obtained by slip casting. The gradient of iron concentration was induced by magnetic field. Microstructures of the specimens have been investigated using a light and scanning electron microscopy. Quantitative analysis of microstructures has been carried out with the help of image analyzer. The obtained results prove the possibility to produce Al2O3-Fe functionally graded materials under the magnetic field.

Monoacryloyl esters of carbohydrates: Synthesis, polymerization and application in ceramic technology

The article presents the interdisciplinary research among organic synthesis, chemistry of polymers and ceramic technology. It presents the synthesis of monoacryloyl esters of fructose and glucose that is 1-O-acryloyl-D-fructose and 3-O-acryloyl-D-glucose, conditions of their polymerization and application in shaping of advanced ceramic powders by the so called gelcasting method. The paper presents the influence of carbohydrate esters on the viscosity of Al2O3 suspensions and microstructure of final ceramic samples. The results showed that synthesized esters of saccharides can play the role of organic monomers able to polymerize in situ and self-cross-linking compounds in gelcasting. The paper presents the proposed structure of polymeric network which is formed from acryloyl ester of glucose during gelcasting process. The paper describes rheological behaviour of slurries composed of synthesized substances and A2O3 powders, wetting angles of alumina substrate by synthesized compounds, differences in glass transition temperatures of polymers and the microstructure of obtained final ceramic samples.

Saccharides Derivatives in Shaping of Ceramic Powders – New Monomers and Dispersants

Saccharides, particularly monosaccharides, as well as their derivatives, were found to be a group of effectively working processing agents in case of alumina which has been used as a solid phase of highly loaded suspensions. The synthesis of new low-toxic monomers obtained from saccharides is reported and their application in gelcasting process is presented. The synthesized monomer named 3-O-acrylic-D-glucose is an interesting alternative for the commercially available acrylic monomers. The present paper describes the properties of ceramic slurries obtained from two alumina powders of different grain size (47nm and 0.70mm) with the use of the new monomer 3-O-acrylic-D-glucose. The rheological measurements showed that new monomer can be applied not only as monomer able to polymerize in situ but also as dispersing agent for nanoalumina powders.

VINYL ACETATE COPOLYMERS IN DIE PRESSING OF ALUMINA

The studies on the application of the emulsions of poly(vinyl acetate-co-allyl ether)s containing nonionic hydrophilic poly(oxyethylene) fragments as binders in the die pressing of alumina is presented. It was found that introduction of hydrophilic fragments into molecules of a typical water dispersible polymer led to better polymer affinity to the ceramic powders. It was also shown that low molecular mass of such copolymers should be relatively low ca 1500 g mol–1 to increase the density and thickening uniformity of the samples before and after sintering. The resultant sinters indicated exceptionally high mechanical strength (bending strength ca 500 MPa).

Ceramic-polymer ferroelectric materials for antenna applications

Ceramic-polymer composites with modified ferroelectric powder Ba/sub 0.65/Sr/sub 0.35/TiO/sub 3/ and an appropriate polymer have been synthesized and investigated. A time-domain method for microwave measurements of the ceramic-polymer material parameters has been also developed. As an example of a possible use of the ceramic-polymer ferroelectric material, a new microstrip electrically controllable traveling-wave antenna is presented. The feasibility of dielectric scanning (changing the direction of the beam by varying the relative permittivity of the electronically controlled ceramic-polymer composite) is investigated. It shows that the beam angle changes more than 30/spl deg/ when a DC bias field of 200 V is applied.