Mullite ceramics are well known as materials with a high temperature stability, strength and creep resistance. In this research, the effect of a modification with magnesia-stabilized zirconia and yttria-stabilized zirconia, separately, as well as in a mixture with WO₃, in 1:1 and 1:2 ratios on the thermal properties of porous mullite ceramics was investigated. The porous mullite-containing ceramics were prepared by a slip casting of the concentrated slurry of raw materials with the addition of a suspension of Al paste for the pore formation due to the H₂ evolution as a result of the reaction of Al with water. The formed samples were sintered at 1600 °C and the holding time was 1 h. The materials were characterized using X-ray diffractometry, scanning electron microscopy, mercury porosimetry, the laser flash contactless method, thermal shock resistance testing and the non-destructive impulse excitation method for determining the elasticity modulus. The modification of the porous mullite ceramic with a mixture of ZrO₂ and WO₃ oxides had a positive effect by decreasing the thermal conductivity, due to the increased porosity, in comparison to the undoped samples and samples with only ZrO₂. The doubling of the WO₃ amount in the modifying oxide mixtures improved the ceramic thermal shock resistance. The porous mullite ceramics which were modified with magnesia-stabilized zirconia (2.8 mol% MgO) and WO₃ had a lower thermal conductivity and improved thermal shock resistance than the samples with yttria-stabilized zirconia (8 mol% Y₂O₃) and WO₃.

Rigid polyurethane (PUR) foams have outstanding properties, and some of them are successfully used even today as cryogenic insulation. The fourth-generation blowing agent Solstice^® LBA and commercial polyols were used for the production of a low-density cryogenic PUR foam composition. A lab-scale pouring method for PUR foam preparation and up-scaling of the processes using an industrial spraying machine are described in this article. For the determination of the foam properties at cryogenic temperature, original methods, devices, and appliances were used. The properties at room and cryogenic temperatures of the developed PUR foams using a low-toxicity, bismuth-based, and low-emission amine catalyst were compared with a reference foam with a conventional tin-based additive amine catalyst. It was found that the values of important cryogenic characteristics such as adhesion strength after cryoshock and the safety coefficient of the PUR foams formed with new reactive-type amine-based catalysts and with the blowing agent Solstice^® LBA were higher than those of the foam with conventional catalysts.

Mullite and mullite–alumina ceramics materials with dominance of the mullite phase are used in different areas of technology and materials science. Porous mullite ceramics materials can be used simultaneously as refractory heat insulators and also as materials for constructional elements. The purpose of this work was to investigate the WO₃ nanoparticle influence on the evolution of the aluminum tungstate and zircon crystalline phases in mullite ceramics due to stabilization effects caused by different microsize ZrO₂ and WO₃. The use of nano-WO₃ prevented the dissociation of zircon in the ceramic samples with magnesia-stabilized zirconia (MSZ), increased porosity by approximately 60 ± 1%, increased the intensity of the aluminum tungstate phase, decreased bulk density by approximately 1.32 ± 0.01 g/cm³, and increased thermal shock resistance by ensuring a loss of less than 5% of the elastic modulus after 10 cycles of thermal shock.

Ternary system MgO-Al₂O₃-SiO₂ contains many technically valuable crystalline phases such as enstatite, forsterite, spinel and cordierite. For most of these phases coefficient of thermal expansion (CTE) is extremely low (as low as 1.510_-6K_-1) which allows for them to be used in conjunction with other thermally demanding materials like quartz, for example. Also, other important properties like their high mechanical strength and good dielectric permeability is of value for potential use in practical applications. Formation of cordierite from oxide powders takes place above 1350 °C. Rational preparation of such material requires modifications in synthesis rout, i.e., addition of flux forming agents or presence of volatile compounds. In this work the use of Latvian illite clay as partial raw material for preparation of both dense and porous cordierite ceramics was studied. No additional artificial flux and/or volatiles were used. Obtained dense and porous ceramic samples were tested for their phase composition, mechanical strength and porosity. It was determined that the use of illite clay of no less than 1/3 of total mass was enough to form both extremely dense and tough (compressive strength of about 400 MPa) and extremely porous (about 59% apparent porosity) materials by just adjusting thermal treatment regime. The X-Ray diffraction of the samples showed that formation of single-phase crystalline cordierite can also be achieved in relatively lower temperatures, e.g., as low as 1300 °C.

Cordierite ceramics are known for their low CTE and high compressive strength values which affords them place in fields where demanding thermal and mechanical properties are required. Development of such ceramics is greatly dependent on materials used. If raw materials are used formation of additional phases and pore/glass formation is expected. The purpose of this research is to examine the process of cordierite development from mixed compositions formed from precursors of the natural raw materials as illite clay, dolomite and quartz sand and synthetic additives – MgO, γ-Al₂O₃ and their influence on thermal and mechanical properties. It is verified that the addition of 10 wt.% of illite clay and about 20-21 wt.% dolomite in staring compositions at the sintering temperature of 1200 °C results in the development of dense ceramic material with perfect-shaped crystalline cordierite phase and secondary anorthite phase. Sintered cordierite ceramics have been tested, among other properties, for their compressive strength, coefficient of thermal expansion and modulus of elasticity after 20 cycles of thermal shock treatment.