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D. Riegert and K. Konopka

Analysis of the Structure of Archeological Objects - Ceramic Pottery

The aim of the present study was to check whether the research methods used in materials engineering could be useful for examining archeological ceramic pottery. The experiments were conducted with the use of stereoscopic microscopy, scanning electron microscopy, and optical profilometry. The examined material included pieces of the archeological clay vessels excavated from various sites and dated at two various historical periods. The first group includes samples from the 5th century B.C. from Biehla (Germany) and Starosiedle (Poland), the second group consists of fragments of vessels of the 10th century A.D. from Starosiedle (Poland) and Rosenhof (Germany). The structure of the matrix and the mineral admixtures distributed throughout it were analyzed on the cross-sections of the archeological material. The examinations were performed using the fractographic method and optical profilometery, which permitted determine the shapes and morphology of the admixtures, examine their embedding in the matrix material (clay), and also revealing possible layers or delaminations within the matrix.

Open access

K. Konopka, L. Litynska-Dobrzynska and J. Dutkiewicz

Methods of enhancing of mechanical properties of ceramic-metal composites, particularly fracture toughness by introducing dispersed metal particles such as W, Mo, Ni, Al, etc to a ceramic matrix are well known. However, the dependence of the microstructures, especially interfaces, on the properties of composites is not well understood yet. Moreover, the ceramic-metal interfaces play a crucial role in tailoring the composite properties.

In this paper we examine the alumina matrix composite with NiAl2O4 spinel phase and present the SEM and TEM studies of spinel distribution, size and crystallographic orientation. The composites were prepared by sintering Al2O3 and Ni powders below the melting point of Ni in argon. During the process of sintering the spinel phase appeared. It was not homogeneously distributed in the alumina matrix. The spinel phase areas were linked together and constituted an almost continuous form. We observed that the distribution and size of spinel influenced the fracture toughness of the composite.

Open access

M. Gizowska, K. Konopka and M. Szafran

Properties of Water-Based Slurries for Fabrication of Ceramic-Metal Composites by Slip Casting Method

The main advantage of ceramic-metal composites is the increase of fracture toughness of the brittle ceramic matrix. The slip casting method gives the possibility to obtain products of complicated shapes without green machining.

In the work results concerning colloidal and rheological aspects of ceramic-metal composite fabrication via the slip casting method are presented. Slurry consisted of ceramic (α-Al2O3) and nickel powder suspended in water with addition of deflocculants composition (citric acid and diammonium citrate), surface-active agents and binder. Ceramic and metallic powders show great differences in electrokinetic behavior, which cause that the heteroflocculation effect in the suspension can take place. In order to investigate the particles interaction characteristics, the zeta potential of each powder was examined. The zeta potential measurements were performed for diluted suspensions as a function of pH. Rheological measurements of the slurries were performed. Although surface of alumina was modified, so that the electrokinetic behavior resembled one of nickel, it turned out that the presence of nickel particles has great influence on the slurry properties. The change of rheological properties for slurries containing nickel particles results probably from strong interaction between alumina and nickel particles.

Open access

K. Konopka, K. Miłkowska-Piszczek, L. Trębacz and J. Falkus

Abstract

The study presents the findings of research concerning the possibilities for application of parallel processing in order to reduce the computing time of numerical simulations of the steel continuous casting process. The computing efficiency for a CCS model covering the mould and a strand fragment was analysed. The calculations were performed with the ProCAST software package using the finite element method. Two computing environments were used: the PL-Grid infrastructure and cloud computing platform.

Open access

K. Miłkowska-Piszczek, M. Rywotycki, J. Falkus and K. Konopka

Abstract

This paper presents the findings of research conducted concerning the determination of thermal boundary conditions for the steel continuous casting process within the primary cooling zone. A cast slab - with dimensions of 1100 mm×220 mm - was analysed, and models described in references were compared with the authors’ model. The presented models were verified on the basis of an industrial database. The research problem was solved with the finite element method using the ProCAST software package.

Open access

M. Knap, J. Falkus, A. Rozman, K. Konopka and J. Lamut

Abstract

The objective of the research that has been presented was to model the effect of differences in chemical composition within one steel grade on hardenability, with a very broad and heterogeneous database used for studying hardness predictions. This article presents the second part of research conducted with neural networks. In the previous article [1] the most influential parameters were defined along with their weights and on the basis of these results, an improved model for predicting hardenability was developed.

These developed neural networks were applied to model predictions of hardenability for three steel grades VCNMO150, CT270 and 42CrMoS4.

The results proved that the correlation between the chemical composition differences within a chosen steel grade and the hardness changes can be modeled. If the database is big enough, predictions would be accurate and of high quality. But for a less comprehensive database, the differences in hardness predictions for various chemical compositions of the steel grade concernedwere observable.

Open access

P. Łada, A. Miazga, P. Bazarnik and K. Konopka

Abstract

In this work the microstructure analysis of composite from ZrO2 – Ti system were presented. For the preparation of the composite samples nanometric ZrO2 powder stabilized by 3 mol% of Y2O3 and micrometric titanium powder were used. The composites with 10 vol.% addition of titanium particles were prepared by slip casting method. The sintering process was conducted at 1450°C with 2 hours’ dwell time, in the inert atmosphere of argon. The microstructure observations were carried out with the use of SEM and STEM microscopes. The quantitative analysis and stereological characterization were performed. The SEM and STEM observations allowed characterizing the microstructure of composite samples. Especially, the interface between titanium particles and zirconia matrix was described. The growth of the zirconia grains around the Ti rich areas was observed. The increase of the zirconia grains size results from the reaction on the interface between titanium particle and zirconia matrix during the sintering process.

Open access

J. Zygmuntowicz, A. Miazga and K. Konopka

Abstract

The presented work focuses on the quantitative description of the spinel phase (NiAl2O4) located into Al2O3 matrix. Three series of samples were prepared. Series I, II and III containing following amount of nickel powder: 0.21% vol, 0.43% vol and 1.3% vol respectively. In order to obtain nickel aluminate spinel sintering was carried out in an oxidizing atmosphere (air). Based on the SEM observation and XRD analysis the presence of spinel phase was confirmed in all samples. Difference in volume fraction of the Ni in the compacts before sintering, resulted in the different content of the spinel phase in the final material. All tested composites were characterized by homogeneous distribution of NiAl2O4 in the whole volume of the material. The purpose of the study was also the use the stereological analysis to determine the shape parameters of new phase.

Open access

P. Łada, P. Falkowski, A. Miazga, K. Konopka and M. Szafran

Abstract

Slip casting is one of the most popular shaping method in ceramic technology which allows producing a large number of elements in small period of time. This shaping technique gives a possibility to fabricate ceramic or composite materials such as ZrO2-Ti. Ti with its properties (low density, high melting point, high-temperature strength, good corrosion resistance and others) combine with ZrO2 (high flexure strength, high compression resistance and very high KIC) can be considered for different applications as constructional and functional materials. For the preparation of such composite nanometric zirconium oxide powder stabilized by 3 mol% Y2O3 and micrometric titanium powder were used. Water-based slurries with 35, 40, 45 and 50 vol.% solid phase content were prepared with 3, 10 and 15 vol.% addition of titanium powder. Zeta potential and pH of prepared slurries were considered. The pH changes were tested as a function of Ti content. The viscosity of the prepared slurries was measured. The sedimentation tests for selected slurries were performed. The casting rate for slurry of 35% solid phase with 10 vol.% Ti was examined. These measurements showed good stability of slurries. With the increasing of the solid phase concentration the density of the green bodies increased. However, the increase of the content of Ti powder reduced the density of green body samples. For selected samples the SEM observations was carried out. Composites produced by slip casting were characterized by a homogenous distribution of Ti particles in the ZrO2 matrix.