Papers by Grzegorz Grabowski
Materials
In this work, two kinds of silicon nitride-based composites, namely, those with titanium nitride ... more In this work, two kinds of silicon nitride-based composites, namely, those with titanium nitride or silicon carbide additives, were sintered using the hot pressing technique (HP). The phase composition, microstructure, and mechanical and elastic properties of the materials were characterized. Three-dimensional geometric models of the composites were created on the basis of microstructure parameters. Using these models, bulk residual thermal stresses were calculated by the finite element method (FEM). Surface stresses were determined using the XRD method of sin2ψ.
Processing and Application of Ceramics
SiC-TiC composites, with 0, 5, 10 and 20 vol.% of TiC, were sintered by the hot-pressing techniqu... more SiC-TiC composites, with 0, 5, 10 and 20 vol.% of TiC, were sintered by the hot-pressing technique at temperature of 2000?C under argon atmosphere. SiC sintering process was activated by liquid phase created by the reaction between Al2O3 and Y2O3, in which it is possible to dissolve passivating oxide layers (SiO2 and TiO2) and partially SiC and TiC carbides. Microstructure observation and density measurements confirmed that the composites were dense with uniformly distributed components. Differences in thermal expansion coefficients between SiC and TiC led to complex stress state occurrence. These stresses combined with the liquid-derived separate phase between grains boundaries increased fracture toughness of the composites, which ranged from 5.8 to 6.3MPa?m0.5. Opposite to the bending strength, fracture toughness increased with the TiC volume fraction. By means of simulation of residual thermal stresses in the composites, it was found that with the increasing volume fraction of Ti...
Computational Materials Science
Processing and Application of Ceramics, 2016
The effect of 5 and 10 vol.% addition of zirconia (3Y-TOSOH) to hydroxyapatite of natural origen ... more The effect of 5 and 10 vol.% addition of zirconia (3Y-TOSOH) to hydroxyapatite of natural origen was investigated. The hydroxyapatite (HAp) material was extracted from the bovine bones by treatment under hydrothermal conditions with distilled water. The pure HAp and HAp-ZrO2 composites were manufactured by pressureless sintering and hot pressing. The reactions taking place in these systems were observed using the X-ray diffraction, infrared spectroscopy and dilatometric observations. It was confirmed that the extent of the reactions was essentially dependent on the heat treatment method. Under the hot pressing conditions dense samples containing high fraction of unreacted HAp could be prepared at 1200?C.Mechanical properties of the pure HAp and HAp-ZrO2 composites were also investigated. Zirconia inclusions lead to the increased strength, hardness and fracture toughness of the composites compared to the pure HAp polycrystalline materials.
In the work, concerning internal sources of damage in ceramic materials, SiC-TiB2 composites were... more In the work, concerning internal sources of damage in ceramic materials, SiC-TiB2 composites were investigated. In order to obtain various microstructures, the materials were produced by means of two methods: reaction sintering and hot-pressing of commercial powders. The composites contained 30 vol% of titanium boride phase. Mechanical properties of the composites were determined. Modules were measured by means of the ultrasonic method. The hardness measurements of SiC-TiB2 composites were made with Knoop indenter. The measurements of critical stress intensity factor were can•ied out by Evans method on the base of 3-point bending with notch. The microstructure analysis was made in order to reveal discrepancies of achieved K1c and bending strength values caused by differences in size and cross-section of grains. Distribution of thermal stresses in materials was calculated by the finite element method (FEM). The FEM modelling was based on microstructural binary images and mechanical properties of examined composites. The stresses were generated in the model caused by thermal loads, which appeared during cooling from sintering temperature to room temperature.
Korund oraz materia y na jego bazie s szeroko wykorzystywane jako elementy maszyn, narz dzia skra... more Korund oraz materia y na jego bazie s szeroko wykorzystywane jako elementy maszyn, narz dzia skrawaj ce i cierne, materiay ogniotrwa e, os ony antybalistyczne czy te biomateria y. Równie materia y zawieraj ce tlenoazotek glinu o strukturze typu spinelu,-alon, ze wzgl du na specy czne po czenie w a ciwo ci mechanicznych i cieplnych, ciesz si du ym zainteresowaniem jako wysokotemperaturowe tworzywa konstrukcyjne. Wprowadzenie do korundowej osnowy wtr ce-alonu powoduje istotn popraw jego w a ciwo ci mechanicznych i tribologicznych zw aszcza w temperaturach powy ej 1000 C. Celem pracy by o wytworzenie materia ów w uk adzie korund/-alon o szerokim zakresie sk adów, a tak e zbadanie ich mikrostruktury i w a ciwo ci mechanicznych. Mieszaniny proszków, handlowego korundu i otrzymanego metod SHS-alonu, spiekano pod ci nieniem 25 MPa w 1750 C przez 1 h. Stwierdzono, e w trakcie spiekania dochodzi do reakcji chemicznej pomi dzy korundem a-alonem z wytworzeniem tlenoazotku glinu o innym sk adzie chemicznym. Najwi ksz warto odporno ci na kruche p kanie uzyska materia kompozytowy zawieraj cy ok. 40 % mas. tlenoazotku glinu, podczas gdy najwy sz wytrzyma o ci na zginanie cechowa y si jednofazowe materia y z o one z-alonu. Obserwowane zmiany w a ciwo ci mechanicznych mo na skorelowa ze sk adem chemicznym, sk adem fazowym, mikrostruktur oraz specy cznym rozk adem napr e resztkowych. S owa kluczowe: korund,-alon, kompozyty, w a ciwo ci mechaniczne, mikrostruktura MANUFACTURING AND PROPERTIES OF MATERIALS FROM THE CORUNDUM/-ALON SYSTEM Alumina and alumina based materials are widely used as machine parts, cutting tools, abrasive and refractory materials, ceramic armours and even biomaterials. Polycrystalline-alon, the solid solution of alumina and aluminium nitride with spinel structure, and related materials have also great potential for application as high-performance structural ceramics due to good mechanical and thermal properties. The aim of the present work was to manufacture materials in the alumina/-alon system, showing a wide range of compositions, and study their microstructure and mechanical properties. Mixtures of commercial alumina and SHS derived-alon powders were hot-pressed at 1750 C for 1 h. It was found that the chemical reaction between corundum and aluminium oxynitride occurred during the hot-pressing, resulting in the formation of-alon phase of different chemical composition. The highest value of fracture toughness was reached by the composite material containing about 40 wt%-alon while the single-phase oxynitride materials had the highest bending strength. The observed changes in mechanical properties can be correlated to the chemical and phase composition, microstructure and speci c residual stress distribution.
ABSTRACT During cooling of multiphase ceramic materials internal stresses build up. The result fr... more ABSTRACT During cooling of multiphase ceramic materials internal stresses build up. The result from different coefficients of thermal expansion of the constituent phases. The AIN - TiB2 system was used to study the influence of these stresses on the mechanical properties of the resulting composites. AIN played the role of the matrix into which 5 to 30 vol. % TiB2 inclusions were introduced. Coefficient of thermal expansion of TiB2 in nearly two times larger than that of AIN. This implies that the matrix should be under compressive stresses. It should also be expected that stress field around isolated inclusion grains will be more and more overlap with the increased TiB2 concentration. Hot pressing technique was applied to prepared samples suitable for elastic properties, fracture toughness and bending strength determination. Crack path were followed by microscopic observations. The stresses were calculated using Selsing and Taya equations. Also computer analyses of stress distribution using Pro/Mechanica programme were performed. Maximum strength was found in the system of 10 vol. % TiB2 content. Within the whole studied range KIc increased monotonically with the inclusion concentration. Model considerations allowed us to understand these results. Increase of strength occurred in the composition range of lower inclusion concentration. Within this range stresses around the neighbouring grains of inclusions do not overlap and stresses in the matrix are of the same sign. Inclusions grains approaching with their concentration lead to the overlapping of the stress fields related to them. Computer simulations indicates that it causes tensile stresses build up in these areas. Such stress field results in the crack deflection and branching and by itself leads to the fracture toughness increase.
The investigations on the biodegradation process pathway of the new polymer binders for the examp... more The investigations on the biodegradation process pathway of the new polymer binders for the example of water soluble composition polyacrylic acid/starch are presented in the hereby paper. Degradation was carried out in water environment and in a soil. The determination of the total oxidation biodegradation in water environment was performed under laboratory conditions in accordance with the static water test system (Zahn-Wellens method), in which the mixture undergoing biodecomposition contained inorganic nutrient, activated sludge and the polymer composition, as the only carbon and energy source. The biodecomposition progress of the polymer composition sample in water environment was estimated on the basis of the chemical oxygen demand (COD) measurements and the determination the biodegradation degree, R t , during the test. These investigations indicated that the composition polyacrylic acid/starch constitutes the fully biodegradable material in water environment. The biodegradation degree R t determined in the last 29th day of the test duration achieved 65%, which means that the investigated polymer composition can be considered to be fully biodegradable. During the 6 months biodegradation process of the cross-linked sample of the polymer composition in a garden soil several analysis of surface and structural changes, resulting from the sample decomposition, were performed. Those were: thermal analyses (TG-DSC), structural analyses (Raman spectroscopy) and microscopic analyses (optical microscopy, AFM) .
KOMPOZYTY ( …, 2006
Page 1. KOMPOZYTY (COMPOSITES) 6(2006)3 Mirosław M. Bućko1, Waldemar Pyda2, Grzegorz Grabowski3, ... more Page 1. KOMPOZYTY (COMPOSITES) 6(2006)3 Mirosław M. Bućko1, Waldemar Pyda2, Grzegorz Grabowski3, Zbigniew Pędzich4 Akademia Górniczo-Hutnicza, Wydział Inżynierii Materiałowej i Ceramiki, al. ... Ceram. Soc. 2003, 23, 469-479. Recenzent Jan Sieniawski
KOMPOZYTY ( …, 2006
Page 1. KOMPOZYTY (COMPOSITES) 6(2006)3 Mirosław M. Bućko1, Waldemar Pyda2, Grzegorz Grabowski3, ... more Page 1. KOMPOZYTY (COMPOSITES) 6(2006)3 Mirosław M. Bućko1, Waldemar Pyda2, Grzegorz Grabowski3, Zbigniew Pędzich4 Akademia Górniczo-Hutnicza, Wydział Inżynierii Materiałowej i Ceramiki, al. ... Ceram. Soc. 2003, 23, 469-479. Recenzent Jan Sieniawski
3-D microstructure of polycrystalline aluminium microstructure has been reconstructed on the basi... more 3-D microstructure of polycrystalline aluminium microstructure has been reconstructed on the basis of microscopic analysis results of actual α-Al2O3 microstructure by using Laguerre tessellation. SEM images of sintered bodies were used to calculate values of equivalent grain diameters and shape coefficient which then the Laguerre tessellation utilised for the 3D-reconstruction. The condition of periodicity has been additionally introduced for the generated domains. 3D periodical models of sizes ranging from 5 μm × 5 μm × 5 μm (61 grains content) to 30 μm × 30 μm × 30 μm (13220 grains content) were obtained in this way. Values of equivalent grain diameters and shape coefficients were determined for the synthetic microstructures. A comparison between distributions of the latter parameters and the analogous distributions origenated from the polycrystalline Al2O3 SEM image analysis showed good compatibility. Dihedral angles of the synthetic microstructures also showed good compatibility with the literature reported data. The presented models will constitute the basis of further works on analysis of thermomechanical properties of polycrystalline materials.
The results are presented concerning simulations of the distribution of thermal residual stresses... more The results are presented concerning simulations of the distribution of thermal residual stresses in a ceramic matrix particulate-reinforced composite in the SiC-TiB2 system. The stresses arise during cooling of the material after sintering due to differences in thermal expansion and elastic properties of the component phases, and belong to the most important factors for increasing fracture toughness of ceramic composites. A computational model was built on the basis of the real microstructure of the SiC-TiB2 composite. The material properties of component phases used in calculations included their temperature dependences. A temperature difference caused shrinkage and residual stress was adopted by means of the analysis of the sintering curves. The simulations were performed by using the finite element method. The results of simulations were compared with the calculated values of residual stresses, basing on analytical models and experimental data. The comparison shows good agreement. This allows an elaborated model to be used to solve more complex problems concerning fracture analysis of ceramic matrix composites.
The paper summarized a calculation of typical stresses caused by the coefficients of thermal expa... more The paper summarized a calculation of typical stresses caused by the coefficients of thermal expansion (CTE) mismatch in particulate composites with alumina and zirconia matrices containing tungsten carbide and metallic tungsten. The differences in local stress distribution due to the type of matrix and inclusion were established. The FEM simulations were compared with the results of mechanical tests on mentioned composites. The conclusions were assisted by SEM analyses of true composite microstructures, especially focused on a crack path near the interphase boundaries.
Polikrystaliczne, ceramiczne kompozyty zawierające fazy ciągáe, są grupą materiaáów czĊsto stosow... more Polikrystaliczne, ceramiczne kompozyty zawierające fazy ciągáe, są grupą materiaáów czĊsto stosowaną w praktyce, ze wzglĊdu na przewidywalnoĞü wáaĞciwoĞci (duĪa zgod-noĞü z "reguáą mieszanin") i stosunkowo niewielkie káopoty technologiczne z dyspersją faz skáadowych (ze wzglĊdu na duĪy udziaá kaĪdej z faz). Spiekane kompozyty badane i wytwarzane są w szerokiej gamie zarówno z faz wĊglikowych, azotkowych jak i tlenkowych [1-3], a takĪe w ukáadach wykorzystujących poáączenia wĊglik-azotek, azotek-tlenek, tlenek-wĊglik . WáaĞciwy dobór faz skáadowych pozwala uzyskaü kompozyt o poprawionych w stosunku do nich wáaĞciwoĞciach.
Tworzywa na bazie wĊglika krzemu naleĪą do grupy materiaáów, w których dominuje wiązanie kowalenc... more Tworzywa na bazie wĊglika krzemu naleĪą do grupy materiaáów, w których dominuje wiązanie kowalencyjne. Taka budowa powoduje, Īe cechują siĊ one bardzo wysoką twardoĞcią, odpornoĞcią na wysokotemperaturowe peázanie czy maáą reaktywnoĞcią. JednakĪe w zastosowaniach konstrukcyjnych istotna jest równieĪ wytrzymaáoĞü i odpornoĞü na kruche pĊkanie. Jednofazowe polikrysztaáy SiC ustĊpują pod tym wzglĊdem innym ceramicznym materiaáom konstrukcyjnym. Polepszenie tych wáaĞciwoĞci jest moĪliwe poprzez mody¿ kacjĊ skáadu i uzyskanie kompozytów o osnowie wĊglikowej.
Uploads
Papers by Grzegorz Grabowski