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The preparation process and the properties of Al2O3-W nanocomposites obtained by gelcasting are reported. The novelty of the synthesis path is the formation of nano-tungsten particles in an in situ reduction of water-soluble precursor during pressureless sintering. The use of water-soluble salt as a tungsten precursor ensured highly homogenous distribution of reinforcing particles and good adhesion between ceramic and metal phases. The maximum content of tungsten in the composites was approximately 0.5 wt%. The size of the reinforcing particles was less than 100 nm. Presence of metallic tungsten and tungsten carbide (W2C) in the composites lead to the improvement of mechanical parameters: an increase of hardness by about 10 % and of fracture toughness by about 20 %, compared to the reference sample of pure aluminum oxide.

0.83 Pb(Zr1/2Ti1/2)O3-0.11Pb(Zn1/3Nb2/3)O3-0.06Pb(Ni1/3Nb2/3)O3 (PZNNT) samples with plate-like PbTiO3 (PT) template were prepared using tape casting technology. The microstructure evolution and reaction mechanism between the matrix and PT template was investigated systematically. The quench heat treatment experiment was designed and the microstructure was evaluated. The results showed that the plate-like PT template has relatively low thermal stability which would decompose to form Pb-rich liquid phase and Ti-rich region at the sintering temperature of 900 °C–1050 °C. Plate-like PT template reacted with the PZNNT matrix materials during the sintering process, which did not contribute to the grain growth orientation for PZNNT matrix. Finally, the mechanism of grain growth for the PZNNT ceramics with plate-like PT template is clarified. This work demonstrated that the thermal stability of plate-like template is one of the key factors for fabricating textured piezoelectric ceramics.

In this work, the preparation of foam-gelcasting was simplified with a copolymer of isobutylene and maleic anhydride (Isobam), avoiding the traditional gelling system including many additives such as monomer, cross-linking agent, initiator and catalyst. Highly porous yttria-stabilized zirconia (YSZ) ceramics with 76.2–84.9% porosity were prepared via foam-gelcasting method using YSZ powder as the raw material, Isobam as the dispersant and gelling agent, triethanolamine lauryl sulfate as the foaming agent and sodium carboxymethyl cellulose as the foam stabilizing agent. The effects of solid loading, the content of foaming agent as well as sintering temperature were investigated. With the increase in solid loading of slurries, lower porosity was obtained, and the compressive strength and thermal conductivity showed a tendency of increase. Porous YSZ ceramics with compressive strength of 0.69–3.66 MPa showed low thermal conductivity in the range of 0.137–0.254 W/(m·K) at room temperature. The as-prepared sample showed good thermal insulating performance at high temperature. The km in GM model was during 0.4–0.7, which indicated the pore structure containing the internal and external porosities. This work provides a facile method for the fabrication of porous YSZ ceramics which can be potentially applied as thermal insulation materials at high temperature.

Herein, we present manifold possibilities of using saccharides and their derivatives in colloidal processing of ceramics. Sugar-based compounds are attractive alternatives for commonly used organic additives, because they are renewable materials, are non-toxic to human skin, and have a positive influence on the rheological behavior and stability of ceramic suspensions which is reflected in the properties of green and sintered bodies. The examined substances include sugar acids (galacturonic and lactobionic acid) as highly effective deflocculants for nanopowders; acryloyl derivatives of monosaccharides and sugar alcohols as organic monomers in gelcasting; polysaccharides as binders; and l-ascorbic acid as an activator of radical polymerization in gelcasting. The multifunctionality of the selected compounds as well as their thermal decomposition during sintering of ceramics is discussed. The study also reviews the related literature focusing on sugar-based compounds in ceramic processing.

A sample of 0.83Pb(Zr0.5Ti0.5)O3-0.11Pb(Zn1/3Nb2/3)O3-0.06Pb(Ni1/3Nb2/3)O3 (PZNNT) to which MnO2 was added, with a high mechanical quality factor (Qm) and a good transduction coefficient (d33×g33), were systematically investigated. Based on the SEM analysis there existed two kinds of “secondary phases”, Rich Ti and Rich Zn phases, which arose due to the B-site substation of PZNNT-based ceramics by manganese ions. One phase was due to the Mn3+ replacing the Ti4+ to create oxygen vacancies and induce the hardening effect. Another phase was due to the Mn2+ replacing the Zn-site to stabilize the perovskite phase. When the addition of MnO2 reached the solubility limit of 1.5 mol% in the PZNNT-based ceramics, the sample showed optimal electrical properties (Qm=357, d33×g33=9859 × 10−15 m2/N, kp=0.56), which suggested its potential application for piezoelectric energy harvesting in larger field excitation environments.

Transparent KSr2Nb5O15 (KSN) lead-free ferroelectric ceramics have been synthesized via modified pressureless sintering method. A significant photochromic effect was observed for the transparent KSN ceramics prepared without rare-earth dopant modification. The piezoelectric properties depend on the grain orientations were investigated. The optical transmittance of the KSN ceramics is greater than 40% in the wavelength range of 530–800 nm. After NUV irradiation, the absorbance was enhanced by more than 40% in a broad visible range (more than 79%). The absorbance returned to the initial value after a thermal bleaching process. The results of the cycling tests and response experiments showed the stability and saturation of the photochromic effect. In addition, the possible photochromic mechanism of the KSN ceramics is discussed and the photochromic centers are identified. This transparent KSN ceramics exhibits an obvious photochromic effect and is a potential candidate materials for optical data storage and information recording applications.

Gelcasting is a method which allows for the production of high-quality ceramic-metal composites. In this work, the problem of local polymerisation in gelcasting of alumina-tungsten composite and metal influence on activation energy of glycerol monoacrylate was investigated. The broadband dielectric spectroscopy method was used for the first time to study the kinetics of gelation in ceramic processing. Polymerisation reaction rates constant of pure monomer, and monomer with ceramic and the metal filler, within the temperature range from 313 K to 333 K were determined. The obtained results were compared with rheological measurements. The calculated activation energy of polymerisation for monomer with 0.5 vol% of tungsten is 66 kJ/mol in comparison to a pure monomer which is 290 kJ/mol. This indicates the catalytic influence of metal on the polymerisation. Therefore, in the alumina suspension with tungsten polymerisation begins near the surface of the metal particles resulting in polymer structure inhomogeneity and lower mechanical properties of green bodies.

The paper presents the thermal decomposition of the new, highly efficient organic additives used in colloidal shaping of ceramics, that is lactobionic acid (LAc), galacturonic acid (GAc) and diglyceryl acrylate (DGA). The sugar acids are effective deflocculants, especially for nanopowders, while DGA is the new monomer dedicated to gelcasting process. Most organic additives are indispensable in shaping step but must be then eliminated in order to obtain pure ceramic phase. The DTA/TG measurements coupled with mass spectrometry allowed to determine the thermal decomposition of organic compounds and observe type of gasses released to the atmosphere during heating. Additionally, the influence of the analyzed substances on the properties of selected ceramic suspensions and sintered bodies has been discussed. The new compounds have been examined in the preparation of ZTA (zirconia toughened alumina) composites by gelcasting, slip casting and subsequent sintering. The rheological behaviour of Al2O3-ZrO2 suspensions as well as selected properties (Vickers hardness, fracture toughness and microstructure) of sintered ZTA samples are presented.

The regional distribution of fillers can change the distribution of electric field in the ceramic/polymer composites and further affect the dielectric properties. Here, Ba0.6Sr0.4TiO3/PVDF (BST/PVDF) monolayer and its two kinds of sandwich-structural composites, PVDF-BST/PVDF-PVDF (PBP) and BST/PVDF-PVDF-BST/PVDF (BPB), were fabricated using solution casting method combined hot pressing process. The results showed BPB structural composite possesses the best dielectric performances with a relative permittivity of 17.3, an energy density (Ue) of 10.54 J/cm3 which is 2 times of BST/PVDF monolayer composite with the same BST content, as well as a dielectric tunability of 83.33%. Finite element simulation further proves that sandwich structure, especially BPB structure, can reduce the occurrence of electrical breakdown in the composite, and improve the energy storage characteristics and dielectric tunability. This work gives new thinking for the development of energy storage thin-film composites.

One of the important aspects in the preparation of composite materials is the possibility of reaction between used components. In the case of composite of ZrO2–Ti system, it could be the reaction between zirconia and titanium particles during sintering process. In this work ZrO2/Ti interface at 3Y-ZrO2–10 vol.% Ti composites was analyzed. The composites were prepared by slip casting method. Sintering process was carried out at 1450°C in the inert atmosphere of argon. The sinters were prepared for SEM and STEM microscope observations by polishing and ion milling. The chemical analysis was conducted by EDS. The bonding between Ti particle and ZrO2 matrix was continuous. XRD analysis, microscopic observations and chemical analysis showed the limited diffusion between components. The creation of new phases at ZrO2/Ti interface was not revealed.

The centrifugal-slip casting method was used for producing the Al2O3-Ni composites with a gradient distribution of the Ni phase. The final products had the shape of hollow cylinders. The casting slurries were water-based and contained alumina and nickel powders with two different particle sizes. The cast samples were then subjected to sintering at a temperature of 1400 °C in an N2/H2 reducing atmosphere with heating and cooling rates of 1 °C/min, and the dwell time - 4 h. The rheological properties of the water-based slurries were examined. It appeared that the presence of the Ni particles strongly affected the slurry properties which was probably associated with the strong interactions between the Ni and α-Al2O3 particles. The Al2O3-Ni composites with a gradient distribution of the Ni particles were examined using the X-ray diffraction method. No new phases such as the nickel aluminate spinel were identified in the sintered composites. The microstructure of the samples was analyzed using Scanning Electron Microscopy (SEM). The observations revealed that the samples were composed of three zones with different distributions of the Ni particles on their cross-section. Finally, the Ni particle distribution in the functionally graded materials was described quantitatively.

This paper reviews recent developments and challenges of (Ba,Sr)TiO3/polymer functional composites. The microstructure of barium-strontium titanate (Ba,Sr)TiO3(BST)/polymer composites with different polymer matrices and the nature of the interface between the BST and polymer matrix is critical in the final dielectric properties. The effects of concentration, particle size and BST filler shape on the dielectric properties of BST/polymer composites are discussed. A theoretical model for the dielectric constants of ceramic/polymer composites and the fabrication of BST/polymer composites are described briefly. The development of a dielectric tunability for the BST/polymer composites is summarized. A dielectric tunability theoretical model is proposed based on our previous research results and the effects of several factors on the dielectric tunability of the composites are discussed, which contributes to a prediction of the dielectric tunability of the composites and provides important theoretical and research significance for future work.

The paper presents the analysis of thermal stability and decomposition of Al2O3 and (Ba,Sr)TiO3 green bodies as well as commercially available organic additives which are used in shaping of ceramics by colloidal processing. The first analyzed ceramic material was Al2O3 green body obtained by gelcasting. The second examined material was elastic ceramic–polymer composite based on ferroelectric powder Ba0.8Sr0.2TiO3 with NiO obtained by tape casting method. This flexible and durable material is characterized by high value of dielectric constant and finds the application in devices operating at very high frequencies up to sub-THz. Most organic additives are indispensable just in forming step but must be then eliminated in order to obtain pure ceramic phase, additionally some of them have to be stable in a wide temperature range. The analyzed organic substances were as follows: 2-carboxyethyl acrylate, SYNTRAN 8250, DURAMAX D-3005, DURAMAX B-1000. The DTA/TG measurements coupled with mass spectrometry allowed to gain new knowledge concerning degradation of selected organic additives, thermal stability of ceramic–polymer composite and type of gases released from samples during thermal treatment.

Ceramic – metal composites are widely used materials in a whole world. There were invented many fabrication methods for those kind of materials, but still exists some problems which need to be fixed. Stability of high density metal particles (e.g. W, Mo, Nb) in ceramic-metal composite suspensions is one of crucial issues to be solved in order to obtain homogenous composite material with desired properties such as high fracture toughness, mechanical strength, hardness, wear resistance.In this paper, results of two different methods of stabilizing W particles in Al2O3– W – H2O system were compared. The zeta potential by laser doppler electrophoresis, stability by static multiple light scattering and rheological behavior of prepared suspensions were analyzed. As a result application of hetero-flocculation effect was consider as a good way to obtain homogeneous dispersion of metal particles with a high density.

The aim of the current paper is to present the development of the method used for fabricating highly textured α -alumina elements. The experimental procedure described is based on a combination of two techniques: gelcasting is used in tandem with high magnetic field exposure. In the element shaping process, a new, low-toxic and environmentally friendly gelating system was implemented that is based on in situ polymerisation of an acryloyl derivative of galactose. Here, care was taken to achieve a highly textured structure of elements gelcast from the ceramic slurries of high solid contents (45–50 vol%), which have not been processed successfully for magnetic field alignment before. A secondary aim of the study was to investigate the combined effect of magnetic field exposure duration and the idle time of polymerisation on the effectiveness of the alignment. In the course of the experiment, high degrees of crystalline orientation of the gelcast samples were obtained ranging from 0.92 to 0.96, developed after the subsequent sintering at 1600 °C (the parameters were calculated on the basis of XRD pattern of the surface perpendicular to the magnetic field direction). The microstructures of the obtained elements are described in detail at the end of the paper, in a stereological analysis.

Plate-like Ba0.6Sr0.4TiO3/Poly (vinylidene fluoride - trifluoroethylene -chlorotrifluoroethylene) (P-BST)/P(VDF-TrFE-CTFE) functional composite films were prepared via a tape casting method. All samples have textured microstructure, and the orientation degree of the composites is above 50%. Though pure terpolymer has a low dielectric permittivity (20.4) and a high loss (0.52), the introduction of ceramic particles can effectively enhance its permittivity as well as decrease the loss. The composite filled with 40 vol% ceramic fillers showed a high permittivity of 88.3 as well as a low loss of 0.056 accompanying with a high dielectric tunability about 30%. Additionally, the dielectric tunable theoretical model of the composite was investigated. The functional relationship between phenomenological coefficient ratio β1/β2 and the ceramic content was obtained. The final results indicate that the value of β1/β2 is inversely proportional to the ceramic phase content, as opposed to the composites matrix's dielectric constant which cannot be tuned by the electric field.

The controlled development of texture in ceramics allows to improve some electrical, piezoelectric and mechanical properties of advanced ceramics materials by tailoring the microstructure. A highly textured microstructure of undoped dense alumina was attained by applying a novel combination of gelcasting techniques with magnetic alignment followed by sintering. A newly synthesized low-toxic acrylic monomer based on galactose was introduced to the gelcasting procedure. Thermal analysis of the gelcast has been performed to examine decomposition process of the new binder and match appropriate sintering rate. The effectiveness of the proposed procedure has been related to rheological properties of the suspension by clarifying the influence of the powder and the dispersant content. It has been also related to the idle time of polymerization by clarifying the influence of the initiator content. The new method is compared to slip casting in high magnetic field that has been used widely so far.

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.

The aim of the work was to study a use of an acryloyl derivative of glycerol (glycerol monoacrylate), as a low-toxic, water soluble monomer in shaping of ZrO2 by using the in situ polymerization. The derivative was synthesized by the authors in a one-step synthesis. The work presents an interdisciplinary research in polymer chemistry and ceramic technology showing, how the properties of the system monomer/polymer influence the properties of zirconia green bodies. The wetting angle, glass transition temperature and polymeric shrinkage of the synthesized compound were measured at first. Then the zeta potential and rheological properties were measured to characterize the zirconia slurries. Ceramic green bodies were obtained by gelcasting through in situ polymerization of glycerol monoacrylate. The density, porosity and tensile and bending strengths were then measured, and thermal analysis and microstructure observations were performed for zirconia samples. The results have confirmed that glycerol monoacrylate provides a good homogeneity and high mechanical strength of ZrO2 samples both before and after sintering (749 MPa). The density of the sintered samples was around 99% of TD. The polymer is characterized by a very low glass transition temperature (−61 °C). It means that it is elastic at room temperatures, what positively affects the tensile strength of green bodies. The research has shown that the acryloyl derivative of glycerol is a good alternative for commercially available acrylic monomers used in shaping of zirconia by gelcasting.

The paper reports the development of a new system applicable in shaping techniques using in situ polymerization. The system is based on saccharides derivatives and allows to eliminate harmful processing agents from ceramic slurry. Instead of commonly applied 2-hydroxyethyl acrylate or acrylamide (monomers) and N,N,N′,N′-tetramethylethylenediamine (activator) the compounds based on glucose were used. As a monomer 3-O-acryloyl- d -glucose was applied. As a new activator l -ascorbic acid (also known as vitamin C) was used. Research was carried out for YSZ. As initiators ammonium persulfate and hydrogen peroxide were used. The new system was studied in terms of zeta potential, pH and rheological measurements. Ceramic samples were prepared by gelcasting and gel-tape casting methods. The experiments showed that l -ascorbic acid used as the activator has positive influence on rheological properties of suspensions with YSZ and together with ammonium persulfate allows to form defect free ceramic bodies with a homogenous composition.

Aluminum nitride was found to be of great significance in advanced ceramics. A widely applicable semiconductor, AlN is also commonly known for its considerable heat conductivity, as high as 320 W/(m·K). The idea behind the studies was to use AlN dispersions as a heat transferring liquid in closed systems. Such a liquid heat-carrier should give a proper rheological response when under variable shear-temperature conditions. Contrary to other systems reported in literature, i.e. nanofluids [1–20], the systems presented consisted of AlN micropowder and some novel base liquids: poly(propylene glycols) with an average molecular weight of 425 and 2000. The optimal result was to produce dispersions which display Newtonian-like flow at increased temperature and shear rate, as well as a suitable AlN concentration with sustained time-stability. This compilation of research assumptions should result in intensified heat exchange capabilities of liquid transferring media made on the basis of aluminum nitride.

Recently, great effort has been devoted to obtain porous materials with customized pore size distribution, high surface area and submicrometer sized microstructures or nanostructures. In this work, the viability of colloidal processing routes to obtain porous bulk ceramics using alumina nanopowders and d -fructose as a dispersant and a porosity former has been explored. The rheological behaviour of nanosuspensions was studied in order to assure their stability and to analyse the influence of different parameters (solids loading, fructose content, pH, sonication time). Mesoporous green bodies were obtained by slip casting with d -fructose in concentrations ranging from 5 to 50 wt%. The drying and burning-out conditions were determined by DTA-TG measurements and the sintering cycles were selected from the dynamic sintering curve. Sintered alumina materials with high porosity (>60%), open microstructures, submicrometer sized porosity (dp = 140–210 nm) and grain size lower than 500 nm, were obtained for pieces sintered at temperatures of 1300 and 1400 °C. The influence of different processing parameters on the porosity and the microstructure of the sintered materials is discussed.

Synthesis of a new low-toxic monomer obtained from glucose is reported and its application in gelcasting process is presented. The new monomer named 3-O-acrylic- d -glucose is an interesting alternative for the commercially available acrylic monomers. The presence of many hydroxyl groups in the monomer molecule allows to create hydrogen bonds in the polymer network. The resulting network does not need any external cross-linking agent to obtain a rigid ceramic part. The present paper describes the properties of ceramic slurries, green and sintered elements obtained from two alumina powders of different grain size (0.21 μm and 0.70 μm) with the use of the new monomer 3-O-acrylic- d -glucose and commercially available 2-hydroxyethyl acrylate.

A new type of composites, i.e. polymer-in-ceramic (as opposed to the “classical” ceramic-in-polymer approach) was introduced into the field of composite polymeric electrolytes. In this work the preparation of porous ceramic samples based on alumina is designed and their properties are characterised by XRD, porosimetry and SEM. Special setup was developed for the preparation of electrolytes in vacuum/controlled atmosphere conditions and it was used for preparing the composites. The studied systems exhibited excellent mechanical properties, high conductivities and good stability vs. Li metal electrodes under prolonged storage.

Gelcasting has been extensively studied and applied as a nearnet- shaping technique for preparing complex ceramic parts. However, the use of acrylamide as a main component is an important drawback of this method as it is a hazardous, neurotoxic compound. In this context, a new low-toxicity monomer, glycerol monoacrylate, has been synthesized and successfully used for the gelcasting of ceramic suspensions. The presence of two hydroxyl groups in a monomer molecule allows the formation of a polymer network by the monomer polymerization and cooperative hydrogen bonding without any external crosslinking agent. The stability and rheological behavior of alumina gelcasting suspensions containing the new monomer has been studied by oscillatory measurements under the controlled deformation mode. The results were compared with those obtained for commercially available monomers, 2-hydroxyethyl acrylate and diethylene glycol diacrylate used as a crosslinking agent, in which case the effect of an initiator and activator was studied. The gelcasting performance for both the commercial and the newly synthesized monomers was studied and compared, showing that the former allows a faster gelation, whereas the latter leads to more uniform microstructures and higher sintered densities of up to 99% of TD.

The design of ceramic–metal composites with a gradient concentration of the metal particles fabricated by the slip casting method is presented. The gradient concentration of the metal particles was achieved through their sedimentation under the action of the gravitational force and a magnetic field. The paper describes the method of calculating the distance between the ceramic particles and indicates the correlation between this distance and the size of the metal particles. Preliminary experimental results of fabricated Al2O3–Fe composites confirmed the calculations. The metal particles, whose density is higher than that of ceramic particles, can undergo gravity-induced sedimentation only when the distance between the ceramic particles is greater than the diameter of these metal particles. With a slip casting containing 50 vol.% of solid phase, no concentration gradient of metal particles occurred. The Fe gradient concentration was achieved when the sedimentation was aided by a magnetic field.

The present paper is focused on Al2O3–Al composites obtained via infiltration of porous ceramics by liquid Al. Infiltration of porous ceramics by liquid metal leads to produce microstructure with percolation of metal phase in ceramic matrix. However, the process of Al released caused by pressing is observed. This effect should be taken into consideration in designing of composites (in calculation of the amount of Al which is needed for full infiltration). To improve wettability between Al2O3 and Al the ceramic preforms were coated by the Ni–P. Ni–P deposited in form of a thin, tight film encapsulated ceramic grains and as a consequence, the liquid Al contacts first with Ni and then penetrates inside porous preform. The size of metal phase in this case depends on the size of pores. The size of pores influences also the kinetics and extent of infiltration. This method is useful for fabrication composites with metal phase size in the range of micrometers. During the process of infiltration, the new phases appeared. Among them there are spinel phase and aluminides. These phases are an evidence of diffusion reaction between liquid aluminium and alumina. As a consequence, they can influence the fracture toughness of the composites. Filling up pores by the metal provide a microstructure with interpenetrating network. Such composites are design for their strength and toughness. Moreover, such a microstructure can be an important in applications in which electrical properties of material are relevant.

This paper describes the technology and microstructure of Al2O3-Fe functionally graded composites, FGM, obtained by slip-casting under magnetic field. Alumina a-Al2O3, provided by Alcoa (symbol A16SG), with average grain size of 0.5 µm, and iron powder, (symbol Distaloy AB) from Hoganas, with average grain size of 35 µm, were used to produce a series of specimens which differed in contents of Fe particles in Al2O3. As a source of magnetic force a permanent magnet was used. Preforms were sintered in a vacuum at temp. 1470oC. The microstructures of the specimens were quantitatively described via stereological methods. Sections, parallel to the magnetic field lines were analyzed using special image analysis software. Stereological methods presented in this work have been used to determine gradient in the volume fraction of the Fe particles and variation in their size and dispersion. These parameters are essential for controlling the technological process of interest and to design microstructure for needed properties (fracture toughness).

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.

The results of studies on the effect of the chemical structure of acrylic-styrene copolymers on the properties of ceramic tapes from Al2O3 obtained by the tape-casting method are presented. The properties of the emulsions that serve as ceramic binders have been modified by insertion of selected amphiphilic macromonomers and acrylic acid into the polymer molecules. These amphiphilic macromonomers, because of the proper ratio of the hydrophilic to hydrophobic fragments, serve as internal plasticizers and modifiers of the adhesion of such binders to the ceramic powder particles. The presence of carboxylic groups as polymer pendant groups in an optimal amount has an additional effect on the ceramic tape density, uniformity, and mechanical properties, before and after the sintering process.

The present paper describes technology and properties of novel ceramic–polymer construction and functional composites obtained via infiltration of porous SiO2 by polynitrile–urea–urethane elastomer (PNUU). The obtained results show that infiltration method can be used to fabricate composites with percolation of ceramic and polymeric phases. These composites exhibit a high compression strength together with ability to sustain large deformations. During the cycling loading, the elastomer behaves as strengthened by the ceramic. On the other hand, the presence of elastomeric phase prevents the composite from rapid failure. Scanning electron microscopy (SEM) technique was used to describe the composite microstructure and stereological methods for its quantitative description. The elastic modulus and density of composites were measured and discussed in terms of the rule of mixture.

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.

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.

The results of experiments on application of NaH2PO4 as a binding agent for ceramic kaolin samples were presented. The experiments were carried out at temperatures of 973, 1073 and 1173 K and NiO and CoO additives were used as tempering agents. The parameters of the obtained samples with NaH2PO4 were compared with the samples compressed with water only. The materials of 3-4 times higher bending strength, lower water absorption as well decreased open porosity were prepared during these experiments. The binding function of the NaH2PO4 additive relies on creation of some compounds in reaction between the products of its condensation and products of kaolin decomposition. Finally a ceramic material of prospective properties was created.

Direct Coagulation Casting (DCC) method was applied for an alumina powder molding. In the paper the results of studies on the application of the reaction of acetic acid generation from glycerol triacetate catalyzed by lipase PPL for the flocculation of ceramic slips are presented. The ceramic samples obtained according this method were homogenous of a low content of organic binder (below 0.5 mass%), high tensile strength in the green state (>1 MPa) and high uniformity of thickening and a uniform structure.

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).

Preliminary results are reported on the synthesis and use of new water-soluble polymer binders for making ceramic films from Al2O3 by casting. The binders produce cast materials having high contents of the solid phase and with rheological properties that provide for good flow of the cast mass and for easy separation of the film from the substrate. The emulsions wet Al2O3 well, so one can make ceramic films with appropriate densities, elasticities, and mechanical strength in the raw state, and these can be fired to make planeparallel specimens free from cracks and having high density, good mechanical strength, and low roughness.

The paper presents the recent research in ferroelectric ceramic-polymer composites for sub-THz tunable devices. Developed composites are very promising group of materials due to the possibility of fabrication of materials with desired electrical and mechanical properties. Appropriate selection of components for ceramic slurry enables to obtain composites with low losses and high tunability. Using tape-casting technology and water-dispersible polymers environmentally friendly thin and flexible ferroelectric tapes can be realized. Particular emphasis is made on measurement methods of electrical properties in sub-THz range. In addition, various composites, process of fabrication and characterization of developed ferroelectric ceramic-polymer composites are discussed.

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.

In this paper the two new low toxic water-soluble monomers: glycerol monoacrylate and 3-O-acrylic-D-glucose are introduced and their application in gelcasting of alumina powder is reported, in comparison with 2-hydroxyethyl acrylate, the commercial monomer. Both synthesized substances do not need an addition of cross-linking agent to the ceramic slurry, because hydrogen bonds can be formed in the polymer network, owing to the presence of two or more hydroxyl groups in their molecules, unlike in the case of 2-hydroxyethyl acrylate. Rheological behavior of alumina gelcasting suspensions containing these monomers has been studied, as well as the characteristics of raw and sintered elements formed from these slurries by initializing an in situ polymerization.

The results of studies on the application of new water-dispersible binders such as poly(acrylic-styrene), poly(acrylic-allyl ether) for die and isostatic pressing and tape casting of Al2O3 ceramics are presented. The properties of these acrylic polymers were modified by insertion of selected amphiphilic macromonomers into the polymer chains. These amphiphilic macromonomers, due to the proper ratio of the hydrophilic to hydrophobic fragments, play the role of not only an internal plasticizer, but they also modify the adhesion of such binders to the ceramic powder particles. The influence of chemical structure of these copolymers on the properties of alumina ceramics is discussed. The investigations on properties of alumina ceramics obtained by gelcasting method using new water soluble acrylic monomers containing hydroxyl groups in their chemical structure as well as by direct coagulation casting method using polymeric flocculants are also presented and discussed.

In this paper, an impulse method for the measurement of ceramic-polymeric materials has been presented. Investigations of composite ceramic-polymeric layers comprising modified ceramic ferroelectric powder Ba/sub 0.65/Sr/sub 0.35/TiO/sub 3/ type and a suitable polymer in which the grains of this powder have been discretely distributed, have also been carried out. Obtained results (e.g. tuning ability coefficient of the effective permittivity) show that ceramic-polymer substrates can be utilized in designing new type of antennas and microwave devices.

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.

From the phenomenological point of view classic press molding of ceramic bodies from loose ceramic powders is a process of dense packing of fine grains in rigid form. The non-uniformity in the thickening of the samples pressed along the direction of the pressure applied is the greatest shortcoming of the classic die pressing. It results from the non-uniform distribution of the pressing forces in the sample, which is the effect of friction forces between the ceramic powder particles, and also between the ceramic powder particles and walls of the matrix.

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 NO x gases are released to the atmosphere.

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.