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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.

The paper presents research on ferroelectric ceramic-polymer composites based on barium-strontium titanate and water-thinnable polymeric dispersions, obtained by using tape casting method. Barium strontium titanate with the assumed stoichiometry Ba0,65Sr0,35TiO3 was synthesized by the high temperature solid-state reaction. Water-thinnable polymeric dispersions were synthesized from butyl acrylate, styrene and tert-butyl acrylate containing different amounts of individual monomers. Then, the ceramic-polymer composites were obtained by tape casting. The influence of the chemical structure of synthesized binders on the rheological properties of the slurries and on physicochemical and electrical properties (characterized by using Broadband Dielectric Spectroscopy, BDS) of ceramic-polymer composites were investigated.

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 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.

The thermal transitions of inorganic-organic hybrid polymers composed of linear aluminum tris(diorganophosphate) chains with a general formula of catena-Al[O2P(OR)2]3 (where R = C1-C8 alkyl group or phenyl moiety) have been studied by means of DSC, powder XRD, TGA and TG-QMS, as well as optical spectroscopy. DSC and XRD reveal that most of them undergo reversible structural transformations in the solid state between -100 and 200 °C caused by the changes in conformation of their organic substituents; however, a translational displacement of the rigid polymeric chains occurs only in the case of the derivative bearing long 2-ethylhexyl groups, which becomes liquid at about 140 °C. The thermal decomposition of the studied polymers begins between 200 and 265 °C depending on the type of organic substituent R decorating their aluminophospate core. TGA combined with mass spectrometry of the evolved gaseous products shows that the pyrolytic decomposition of Al[O2P(OR)2]3 proceeds either through β-elimination of olefin (for compounds with C2-C8 aliphatic ligands), or a homolytic cleavage of the P-OR bond (for methyl and phenyl derivatives); both processes are accompanied by condensation of the newly formed POH groups and liberation of water. Powder XRD, FTIR and SEM analyses of the solid residues indicate that thermolysis of Al[O2P(OR)2]3 accompanied by olefin elimination leads to the formation of condensed aluminum phosphates, mainly aluminum cyclohexaphosphate, exhibiting porous morphology. On the other hand, thermal degradation of methyl or phenyl derivatives results in amorphous aluminophosphate residues, and the latter contains conducting carbonaceous phases.

The possibility to fabricate nanoceramic materials by techniques based on colloidal processing requires the use of effectively working deflocculants (dispersing agents) which are able to stabilize and decrease the viscosity of aqueous nanopowders suspensions. Galacturonic and lactobionic acids have been used in the research as deffloculants for nanoalumina; they allowed to obtain ceramic suspensions of high solid loading (50 vol%) and relatively low viscosity (ca. 4 Pa s at a shear rate 10 s−1). High solid loading could be achieved through combining three factors: the application of sugar acids as deflocculants, water leaching of the nanopowders from the surface impurities and precise defoaming of the slurries. Density of sintered bodies equalled 98% TD.

Composite material with a gradient concentration of the metallic phase was prepared by the novel gel-centrifugal casting method. This method combines the consolidation of powders by the centrifugal force with the reaction of radical polymerization of an organic monomer which simultaneously proceeds within the composite slurry. The combination of the centrifugal casting with gel-casting permits production of ceramic–metal composites, including materials with a gradient distribution of metallic particles in a ceramic matrix. Special attention was paid to the thermal analysis of the composite Al2O3–Ni green bodies and the binder used in the fabrication of the material. The experiments were performed on the simultaneous thermal analyzer coupled with the mass spectrometer. The measurements were carried out in air and the inert atmosphere (argon) what allowed to determine the effects characteristic for organic binder decomposition and type of gases released to the atmosphere during thermal treatment. The measurements allowed also to establish the sintering program of the green composite samples and evaluate whether harmful gases are released to the atmosphere. The thermal experiments were complemented with physical and structural measurements, including X-ray diffraction and scanning electron microscopy.

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.

Multilayer dense ceramic materials composed of Al 2 O 3 and Al 2 O 3 -Co 3 O 4 layers have been obtained by gelcasting. The key stage in the process was the optimization of the polymerization idle time in order to ensure strong adhesion between layers without cracks and delamination in a green state and after sintering. The significant advantage of this method is occurence of strong connections between consituent layers due to the slight migration of the slurry to the gelled bottom part of the sample, what is not obseved in techniques based on lamination processes. The multilayer samples were composed of two Al 2 O 3 layers and two Al 2 O 3 -Co 3 O 4 layers arranged alternately. The rheological characterization of the slurries was done. The properties of the sintered multilayer bodies were examined in comparison to the single-layer alumina samples. Observations in SEM and ligth miscroscope were performed. The presence of the transition layer in the sintered bodies was observed.

The paper presents the preparation of porous alumina samples by two techniques. The first one is based on the in situ polymerization of the foamed slurries. The second method is based on the gelcasting of slurries containing polylactide fibers (PLA) and subsequent bun-out of these pore-formers. Foaming has been done in air and nitrogen in order to analyze the influence of the oxygen inhibition on the properties of obtained samples. The prepared slurries were characterized by high concentration of alumina powder (50 and 55 vol %) in order to obtain well densified walls between the pores and as a result high compressive strength of obtained samples. DTA/TG analysis coupled with mass spectrometry allowed to identify the type of gases released to the atmosphere during the thermal decomposition of the PLA fibers and the surfactant Tergitol used in the research. The application of the PLA fibers allows to design the shape of pores; moreover, fibers are well replicated in the ceramic bodies and the burn-out of these pore-formers is not harmful for the environment.

The paper presents the application of 2-carboxyethyl acrylate as a new monomer in gelcasting of alumina. The research showed that the use of 2-carboxyethyl has a positive influence on the properties of green bodies, limiting the negative effect of oxygen inhibition. Oxygen inhibition which hampers polymerization reaction is a well known negative phenomenon in gelcasting but still not fully overcome for samples formed in air atmosphere. As a reference monomer 2-hydroxyethyl acrylate was used in the research. Rheological behavior of alumina suspensions containing both monomers has been studied, as well as the properties of green and sintered bodies obtained by gelcasting have been measured. The differences in the rheological properties and thus ceramic-monomer interactions in the slurries has been analyzed. The high values of densities and mechanical strength, accompanied with the pictures of microstructures of sintered ceramic parts have been presented, as a result of a successfully completed gelcasting process of alumina powder.

This paper focused on the characterization of the composites containing nickel aluminate spinel from Al2O3/NiO and Al2O3/Ni systems. The composites were prepared by die pressing of powders and subsequent sintering of green bodies in air atmosphere. Composites were characterized by XRD, SEM, EDS and DTA/TG/MS analyses. The physical properties of the composites were measured by Archimedes method. Quantitative description of the composites microstructure was made on the basis of SEM images using computer image analysis. The XRD studies and SEM observations of composites confirmed the presence of two phases Al2O3 and NiAl2O4 in the whole volume of samples from both systems. Spinel phase was evenly distributed throughout the volume of the material. Morphology of NiAl2O4 obtained from both systems was characterized by the presence of voids. The DTA/TG/MS measurements showed the characteristics of organic binder decomposition and type of gases released to the atmosphere during thermal treatment. Moreover, the DTA/TG analysis showed the temperature of spinel-phase formation for both systems. It was found that the spinel-phase NiAl2O4 formation retards the process of densification. Therefore, it can be concluded that densification of samples with spinel phase depends mainly on the volume of spinel phase in composite material and does not depend on the substrates used to prepare spinel phase. The values of the selected properties of Al2O3–Ni- and Al2O3–NiO-based materials confirmed that the physical properties depend on the type of substrates used in the fabrication of composites. The type of powder influences the open porosity of samples. For composites produced using NiO powder, open porosity is lower than for samples formed with nickel powder.

Gelcasting is a good method for obtaining ceramic components with a pre-defined shape. From the point of view of the course of the ceramic casting process, a very important issue is the so-called idle time or gelation time whose measurement is usually based on determining changes in ceramic slurry viscosity by means of rheometers. However, searches are being continued to find methods which would have the least impact on the interactions between ceramic powder particles and the forming polymeric structure and would allow more time range to observe changes in gelcasting process compared to classic measurements of viscosity. In the article, based on measurements on Al2O3, ZrO2 and SiC-based gelcasting systems with various water-soluble acrylic monomers, it has been demonstrated that such requirements may be fulfilled by IET (Impulse Excitation Technique).

Polymerization reactions are frequently used in fabrication of a wide range of ceramic components, from 3D elements (gelcasting, UV-curing), through thin tapes (gel-tape casting) to porous samples (mechanical foaming coupled with gelcasting). The analysis of the properties of organic additives used in these techniques as well as factors which influence the polymerization reaction in ceramic suspension are seldom described in the scientific literature. For this reason this paper presents the properties of selected monomers and polymers with influence on the elasticity of zirconia tapes obtained by gel-tape casting. The measured parameters were as follows: glass transition temperature of polymers with and without external plasticizers, wetting angle of ceramic substrates by monomers, and viscoelastic properties of zirconia slurries. The issues of oxygen inhibition, polymerization rate and polymerization shrinkage with influence on unwanted cracking of thin tapes are also discussed. The location of polymeric binder in green bodies was analyzed by SEM.

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.

The fabrication and the characterization of Al2O3/Ni composites with a gradient distribution of the Ni particles are reported. The composites have been obtained by centrifugal-slip casting and subsequent sintering and had the shape of a hollow cylinder. TG/DTA analysis was done for the nickel powder with the addition of the dispersant used in centrifugal-slip casting as well as for the composite green body. The measurements were performed in two atmospheres: argon and the mixture of argon and hydrogen (1:1). Additionally, coupling the thermobalance with the mass spectrometer allowed to determine type of gases released from the samples during thermal treatment. The morphology and chemical composition of the produced composites were analyzed using a scanning electron microscope equipped with an EDS detector. Interface between alumina and nickel was described. Moreover, the X-ray diffraction was made. The stereological analysis confirmed that the nickel particles are distributed in the composite in a gradient way.