Volume 61 (2009)
List of Contents
Volume 61, Issue 1
- Stabilized dolomite as a part of new refractory composites
- Strony: 3-6
A new procedure is described for stabilizing sintered dolomite, preventing the material’s tendency to crack as a result of CaO hydration by air humidity. Following high-temperature reactions with alumina having been taken as the main component of the prepared batch, CaO and MgO from the dolomite sinter was converted into calcium dialuminate and Mg-Al spinel, respectively. The very low thermal expansion coefficient is a main advantage of calcium dialuminate. It ensures the significant decrease of thermal expansion of the refractory materials when compared to other non-silicate refractories. Some properties of the composites thus obtained are presented in the article and the effects of various contents of spinel as well as its distribution in the refractory microstructure are discussed and shown graphically. Some technological conclusions are formulated.
- Magnesia refractories containing calcium zirconate in the matrix
- Strony: 7-11
The microstructure and properties of magnesia refractories containing calcium zirconate in the matrix are presented. In experiments, magnesia clinker with a CaO/SiO2 mole ratio of above 2 and dolomite - zirconia clinkers with different contents of secondary oxides were used. The dolomite - zirconia clinkers were produced by sintering of natural dolomites and technical zirconia at the two-degree firing process. The dolomites differed between themselves with small amount of admixture oxides. Mineralogically, the refractory materials consisted of periclase and calcium zirconate and small amounts of silicate phases. Therefore, these materials were characterized by high refractory, high endurance strength, very good chemical corrosion resistance and better thermal shock resistance than magnesia materials. They would be the alternative materials in relation to the magnesia spinel refractories.
- Chemometric methods in identification of cement and clinker sources
- Strony: 12-15
Chemometric methods constitute powerful tools for objective and comprehensive interpretation of multivariate data and for extracting significant information from them. Herein, these procedures were used for identification of cement and clinker sources, i.e. producers. The analysis relies on the assumption that the elemental composition of products made by different producers is not identical due to the use of materials of different geological background, fuels of different types and compositions and due to specificity of production process applied. Magnesium and a group of trace elements: Cr, Zn, Cd, Pb, Co, Ni, Mn, Cu, Sr, Ba, Ti, V were analyzed quantitatively in the studied samples.
As a result of cluster analysis, the whole set of cement samples was divided into some groups, in which objects were similar while features of the objects in individual groups differed. The emerged clusters ideally agreed with the groups of object originating from the selected cement plants. The satisfactory results were also obtained in the case of clinker. The squared Euclidean distance was used in calculation of the distance between objects in multidimensional space. The Ward’s algorithm was applied as the agglomeration procedure. Both determination of the inside structure of the sample set and designation of the minimal number of variables necessary for its description was the goal of principal component analysis. The dimension of the data space was reduced to 3. The calculations were done using the Statgraphics Plus 5.1 program.
- The role of melaphyre as a raw material additive in technology of ceramic building materials
- Strony: 16-20
The influence of quantity and grain size of melaphyre, originated from the Low Silesia region, added to clay raw materials, on properties of ceramic material was investigated.
As a result of the SEM and optical microscopy observations of the fired material, the closed pores being pseudomorphs of the melaphyre grains were noticed. The pores were a result of partial penetration by the liquid phase from melted melaphyre to the surrounding porous matrix being a product of the thermal transformation of the clay raw material. The observed phenomenon led to a decrease of the open porosity.
- Properties of roofing tile ceramic materials
- Strony: 21-26
The properties of ceramic roofing tiles mainly depend on their phase composition i.e. kind, amount and distribution of the crystalline and amorphous components and also on the material porosity. The above mentioned factors are responsible for mechanical strength, water absorbability and frost resistance of the material. The research results concerning the roofing tiles originating from two plants are presented in the paper.
The following properties were studied:
- physical properties: water absorbability, porosity, bending strength, frost resistance,
- microstructure (mercury porosimetry, SEM, EDS),
- phase composition (XRD).
- The influence of composition changes on properties of clay-cement binders
- Strony: 27-30
Clay-cement mixed binders are mainly used in the building constructions and hydro-technical renovations of the buildings. Leakproofness is a principal property of the binder agents, but this feature can be modified, and the material can be used in different kinds of building industry. In this paper, the influences of changes in the clay-cement systems on technological properties eg. mechanical strength, filterability and rheological properties are shown. The flow curves, the values of filterability factor “k”, and the values of squeeze press resistance of the studied binders were compared.
Investigations shows that the flow curves have characteristic inflections depending on the interaction of cement and modificating agents. Increasing the cement content improves mechanical properties of the binder, however, decreases its filterability. Reduction of the filterability factor value can be obtained by the density increase of the clay-cement system.
- Unconventional application of lower Silesian amphibolites
- Strony: 31-35
Up to now, Lower Silesian amphibolites from Wieściszowice and Ogorzelec deposits are applied only as crushed aggregates for the road construction. This paper presents the results of studies of aluminosilicate glasses obtained by melting these raw materials.
The studied amphibolites have rather low melting temperatures (ca. 1230oC – Wieściszowice, 1210oC – Ogorzelec) and their viscosity is advantageous (ca. 2,4 Pa·s at 1400oC). An annealing of glasses at the temperature range of 800 – 1100oC indicates their relatively high crystallization ability. It was found that the crystalline phases are mainly represented by magnetite and hematite as well as by pyroxenes.
The results suggest the application of amphibolite glasses for the production of glass-ceramics wares. The manufacturing of fibrous insulating materials from these glasses is also possible but it requires the modification of their chemical composition.
- Miscibility of ceramic pigments in the cie l*a*b* colour system
- Strony: 36-40
The colour of every ceramic pigment consists of basic colours. It is possible to determine derivative colours by giving a proportion of basic component ones. Correction of the colour consists in the change of basic colour share in the mixture.
In the case of ceramic pigments, the change of colour doesn’t concern one basic colour only. All three basic colours are inserted together with pigment and additionally black one in the CMYK (Cyan, Magenta, Yellow, blacK).
In this paper, the relationships resulting from a passage from the CMYK colour system into the CIE L*a*b* colour system, applied in practice of ceramic works, were presented.
Getting to know these relationships enables prediction of the colours, obtained as a result of ceramic pigments mixing. It also enables optimization of the pigment selection, determination of the pigment basis and a number of colours obtained on its basis in the applied carriers (glazes, fluxes, mass and the like).
- Applications of red perovskite pigments in gres porcellanato masses
- Strony: 41-45
The results of research on preparation of ceramic pigments with the perovskite structure, coloured by chromium ions are discussed in the paper. The Y(Al1-xCrx)O3 pigments were obtained via the solid state reaction using different mineralizers. The effect of synthesis conditions on the phase composition as well as unit cell volumes, particle size distributions and the morphology of the pigments was connected with their colour.
The thermal and chemical stability of the pigments was established in industrial gres porcellanato bodies.
- Texture and microstructure of porous and sintered ceramic tiles
- Strony: 46-50
The texture and microstructure of porous and sintered tiles after their formation and thermal treatment were studied. The following texture and microstructure parameters were determined: grain sizes and shape, sizes and compactness of aggregates as well as sizes, volume and shapes of pores. Contents of liquid phase formed in the porous and fired materials were evaluated, based on the phase diagrams. It has been found that the texture of fired materials is influenced by chemical composition of raw materials, heat treatment temperature and the amount of liquid phase formed, whereas the microstructure of the materials, obtained after firing, depended on the texture parameters.
- Effect of alkaline additives on the sintering process of siliceous fly ashes
- Strony: 51-54
Fly ashes are captured in the standard dedusting systems in three sections of the electrofilter located in series behind the combustion chamber. Fly ashes captured by the last, third section of the elecrofilter can be used as a raw material in the production of ceramic materials with sintered body such as stoneware and clinker bricks. The grain size distribution and phase composition of fly ashes captured by the third section of the electrofilter intensify sintering processes and accelerate the appearance of liquid phase. The purpose of this research was to modify the physical and chemical properties of those fly ashes in order to further intensify the sintering processes in ceramic mixtures doped with them. The studied fly ashes were modified by means of milling or by incorporation of alkaline or alkaline earths carbonates. The milling increased slightly densification ability of the ashes and therefore the properties of the sintered materials. The chemically modified ashes enriched with Na2O, K2O or CaO did not show the improved densification ability when compared to the unmodified ones.
- Natural radioactivity of selected building aggregates
- Strony: 55-58
In the paper, the research results concerning natural radioactivity of building aggregates, carried out in Building Research Institute and Department of Building Processes at the Silesian University of Technology, were presented and discussed. The tests included both natural building aggregates of the magmatic origin and artificial building aggregates formed in the burning process of granulated and dried clayey raw materials or/and mineral industrial waste materials.
- Application of adsorptive stripping voltammetry to determination of uranium content in the raw materials and ceramic products
- Strony: 59-61
Differential pulse adsorptive stripping voltammetry (DP AdSV) is applied for the determination of uranium(VI) in the raw materials and ceramic products. The friendly environmental cyclic silver mercury film electrode (Hg(Ag)FE) was applied as a working electrode. The calibration graph was linear from 0.4 nM (95 ng·L−1) to 250 nM (60 μg·L−1) for an accumulation time of tacc = 20 s, with the correlation coefficient of 0.9996. The repeatability of the method, expressed as R.S.D. was 2.5% (n=7). The proposed method was successfully applied to the uranium determination in dolomite, kaolin, ash, cement, concrete and cavity brick.
- FTIR spectroscopy application to study degradation of ceramic materials in historical objects
- Strony: 62-65
The aim of the work was to characterize degradation of historical materials, particularly the building ceramics, by means of Fourier transform infrared spectroscopy (FTIR). Patina formed on historical limestone and sandstone tombs was subjected to the analysis. The effects of deformation of the historical stained-glass windows were also studied. Corrosion of the ceramic materials was also simulated in the laboratory conditions. The FTIR measurements were performed in the 400-4000 cm-1 range. The FTIR results have been confirmed by scanning electron microscopy (SEM) combined with X-ray microanalysis (EDX).
- Talc of dae hung deposit as raw material for the production of ceramic tiles
- Strony: 66-71
North Korean talc is recently introduced on the Polish market of raw materials. It is exploited together with chlorite rock and zeolites as the raw material accompanying magnesites in Dae Hung mine. These raw materials are supplied to overseas customers in untreated form (talc, chlorite) as well as after thermal treatment (magnesite clinker).
The talc sample studied showed distinctly white colour due to very low Fe2O3 content (below 0.10 wt. %). Mineralogical investigations indicated that talc, as dominant phase, is accompanied only by subordinate or trace amounts of magnesite and chlorite. After firing at the temperatures above 1050oC, enstatite Mg2[Si2O6] was the dominant or only crystalline phase.
The small addition (in the amount of 1-2 wt. %) of the studied talc to ceramic body for the production of gres porcellanato lowers the water absorption after firing in the temperature range of 1080-1200oC.The additive of talc in the amount of 3 and 6 wt. % to ceramic glaze improves its smootherness and stain resistance. Moreover, engobes containing talc from the Dae Hung deposit shows higher whiteness compared to those without this raw material, whereby the addition of 3 wt. % should be considered as optimal.
List of Contents
Volume 61, Issue 2
- Preparation and properties of the biferroic PFN ceramics
- Strony: 75-79
The PbFe1/2Nb1/2O3 (PFN) ceramics shows multi-ferric properties with two well ordered subsystems: (i) ferro-electric and (ii) anti-ferro-magnetic with the phase transition at about 112°C and -130°C, respectively [1-2]. Those properties cause that it becomes an interesting material for the production of multi-functional intelligent elements, namely those, which strongly react to different types of external influences e.g.: magnetic, electric, mechanical or thermal). The PFN material can be used as a dielectric and magnetic medium for the multilayer ceramic capacitors (MLCC) and inductors, multilayer microwave resonators and memory devices [3-5].
The PFN ceramics and the PFN ceramics doped with bismuth were obtained by the one and two stage method and examined in the work. Densification was carried out by natural sintering. The specimens were subjected to microstructure and dielectric examinations and to the tests of direct current conductivity. The tests showed that a powder synthesis by the two stage columbite method involving calcination creates favorable conditions for obtaining the PbFe1/2Nb1/2O3 ceramics with the optimum application parameters. Admixtures of bismuth to the PFN ceramics increased a maximum of electric permittivity, increasing simultaneously dielectric losses and electric conduction.
- Sintering polycrystalline boron nitride in the presence of amorphous liquid and glass-crystalline silicate phases
- Strony: 80-86
Experimental investigations aimed to determine the effects of phenomena proceeding in an interface during the process of sintering the microcrystalline cBN with two types of binders i.e. fusible amorphous and glass-crystalline silicate materials were carried out.
Strength of these materials is mainly bounded up with properties of the cBN–molten silicates interfaces and the final structure of a bonding phase. The chemical composition of the interface corresponding to the characteristic temperature of composite treatment was tested.
It was found that a low wetting angle in the cBN–molten silicates system and high work of adhesion had not the explicit connection with a high value of Young’s modulus of the abrasive composites.
- Microstructure and properties of the Al2O3-Si3N4 composites produced by a sol-gel method with hetero-crystallization
- Strony: 87-91
Mixtures of the Al2O3-Si3N4 nano-powders were prepared via hetero-crystallization by using a sol-gel method with the contribution of chemical reactions that proceeded between the alkoxyaluminum compounds and water. In order to achieve the best possible homogeneity of the Si3N4 particles in the Al2O3 matrix, pH of the solution was controlled during the process. The mixture containing 20 wt.% of Si3N4 was calcined for 20 h at a temperature of 800°C in air, then added to a commercial-grade Al2O3 powder so as to obtain Al2O3+xSi3N4 mixtures (where x = 1.25, 2.5 and 5 wt.%), which were finally sintered for 1 h at a temperature of 1350 or 1450°C under a pressure of 30 MPa.
The paper describes the microstructure, density, water absorption, porosity and mechanical properties, such as Young modulus, hardness and fracture toughness, of the sinters obtained.
The sintered composites had the relative density exceeding 95%, and the distribution of component phases was uniform. It has been found that the presence of Si3N4 considerably improved mechanical properties of the Al2O3 matrix. The hardness and fracture toughness of the Al2O3+xSi3N4 composites were higher than those of the sinter produced from the Al2O3 nanopowder delivered by the Taimei Company. The highest toughness was measured for the composite with 2.5 wt.% Si3N4.
- Selected physico-chemical properties of Sm1-xSrxCo0.2Fe0.8O3-δ perovskites
- Strony: 92-96
In this paper, the results of structural, transport and thermal expansion coefficient measurements of the perovskite type Sm1-xSrxCo0,2Fe0,8O3-δ materials are presented. These compounds are considered as possible cathode materials for the Solid Oxide Fuel Cells. Substitution of Sm3+ ions by Sr2+ is beneficial to the transport properties of these materials, leading to higher electrical conductivity, an appearance of oxygen vacancies at high temperatures, which makes ionic transport possible. It is also advantageous in terms of structural properties. A decrease of distortion of the crystal lattice allows 3d metals and oxygen orbitals to overlap more effectively. Simultaneously, higher values of the thermal expansion coefficient are observed, especially at the high temperatures. This effect, which may be associated with the higher deviation from oxygen stoichiometry, is disadvantageous in terms of a possible application of these materials. For the compound with a large degree of substitution (x = 0,8), deterioration of the transport properties is observed.
- Production of ceramics films using gel suspensions
- Strony: 97-101
In this paper, the preparation procedure of ceramic foils from the Al2O3 and ZrO2 powders by the gelcasting method is shown. This method consists of the use of a special set of gelling agents, based on water soluble monomers i.e. acryloamide (AAm), metacryloamide (MAm), and 2-hydroxyethylometacrylane (HEMA). Special processing of the monomers allows ceramic foils to obtain a thickness of ~0,2 mm and good flexibility after polymerization. Moreover, the foils show the exceptionally high mechanical strength, both in the dried and fired state, and very smooth surfaces.
Special attention has been paid to the preparation of suspensions, selection of monomer compositions, and rheological behaviour. Selection of the suitable composition of the suspension assures its good fluidity and obtainment of the thin homogenous layers with the uniform structure. A drying process was elaborated, preventing the foil deformation.
- Selection of agents facilitating densification of Si3N4 powders
- Strony: 102-106
In this paper, the influence of glycol and liquid paraffin on improvement of density of the silicon nitride green bodies, formed by uniaxial pressing, was analysed. The different amounts of additives were applied which resulted in a considerable increase of both density and durability of the compacts. As a consequence, it was possible to obtain dense Si3N4 materials of up to 98 wt/% by means of pressureless sintering.
- Application of the carbon laminates for reinforcing concrete-based building units
- Strony: 107-112
The paper presents the results of a study on compressive strength improvement in case of the cylindrical concrete specimens reinforced with different types of carbon laminates. The cylindrical specimens made of C25/30 class concrete, having a diameter of 47 mm and a height of 112,5 mm, were wound with the K 63712 carbon fibers forming a various number (0-5) of composite layers. The concrete specimens were also wound with carbon fibers in a form of 1D mat and 2D cloth. The compressive strength of the cylindrical concrete specimens reinforced with five K63712 carbon fiber layers increased more than 3 times. The most effective reinforcement was found in case of the concrete specimens wound with two layers of 1D carbon fiber mat (300 g/cm2). The strength increased 3.1 times in comparison to the non-reinforced specimens that had the compressive strength of 54.6±3.2 MPa and 178.5±19.0 MPa before and after reinforcing with the 1D carbon fiber mat, respectively.
- Metal-like carbides. Part I. Sinterablity investigations
- Strony: 113-118
Metals belonging to groups 4-6 of periodic table of elements form with carbon compounds named metal-like carbides (TiC1-x, NbC, TaC, WC, CryCz). It was established that it is possible to manufacture dense sintered bodies of this carbides at temperatures close to 2000°C using only carbon powder as an additive. Its role consists in reduction of oxide impurities.
- metal-like carbides. part iI. Investigations on mechanical and chemical properties
- Strony: 119-124
Metals belonging to Groups 4 to 6 of the periodic table of the elements form with carbon compounds called metal-like carbides. The results of investigations on sintering of the TiC1-x, NbC, TaC, WC, CryCz powders show that it is possible to produce dense sintered carbides at temperatures close to 2000°C by using only carbon powder as an additive . Its role consists in reduction of oxide impurities.
The presented paper summarizes the results of studies on mechanical and chemical properties of the WC, TiC1-x, NbC, TaC and CryCz bodies consolidated with the carbon additive. The dense materials were characterized mechanically with respect to their hardness, bending strength and fracture toughness. A special care was taken to a description of effects of the microstructure and the way of cracking on fracture toughness expressed by the critical stress intensity factor (KIc). It was stated that both the cracking manner and fracture toughness depend on a type of the carbide microstructure.
- Manufacturing of dense carbides and nitrides sinters for the comtemporary analytics
- Strony: 125-129
In relation to the eventful development of nanotechnology and instrumental electroanalytical methods the continuous requirement exists of investigation of new electrode materials, which are responsible for sensitivity and reliability of the performed analysis. Moreover, because of toxicity of many substances in human environments e.g. lead or cadmium, searching on non complicated methods of their detection on a trace level is obligatory. The electrode ceramic material applied in an electrode construction have to be nonporous in order to facilitate removal all the electrolyte and regeneration of the working electrode surface.
The application of ceramic materials such as carbides and nitrides in contemporary analytics is an innovative way of application of the chemically stable and corrosive resistant materials of high purity. In this publication, a complete procedure of silicon carbide, titanium carbide and titanium nitride electrode manufacturing is described. All the technological stages are discussed, first of all a powder synthesis using the elements, grinding, forming, sintering, mechanical treatment and embedding the electrode material in the resin matrix. Two methods of sintering were applied. The first one was carried out as a pressureless sintering, and the second one was done by using hot pressing. An influence of the manufacturing method on the microstructure of the studied materials was studied in a context of their possible application in electrodes for electroanalytics.
- Isothermal sintering of metal-like carbides originated from group 4-6 of the periodic table of the elements
- Strony: 130-135
In this work, sintering kinetics of some pure metal-like carbides such as TiC08, NbC, WC was studied. Measurements were made by means of a high temperature dilatometer. Sintering shrinkage as a function of time was recorded under isothermal conditions. An analysis of the sintering kinetics was based on sintering models worked out by Kuczynski and Frenkel. Kinetic equations describing a sintering process of each carbide were formulated according to the Kuczynski’s model. Comparison of kinetic equations and densification behaviour was fundamental to determine similarities and differences in the sintering process of the studied carbides. The second sintering model was used to determine sintering parameters i.e. α, β, α−1, β−1 and ηo as a function of temperature. The presented results allowed a full sintering characteristics of the studied metal-like carbides to be obtained.
- Phase evolution of hot- pressed quarternary materials in the Ti-Al-C-N system
- Strony: 136-139
Ternary and quaternary materials in the Ti-Al-C-N system belong to a group of heterodesmic materials also called as the 312 and H or MAX phases. These compounds are characterized by the layered structure with metallic and covalent bounds. Due to their properties, they can be located between metals and ceramics, which opens new possibilities of applications as structural materials (so called plastic ceramics). Ti3AlC2, Ti2AlC and Ti2AlN are described in literature, but there is no data about quaternary compounds.
In this paper authors attempted to prepare the Ti3Al(C,N)2 powder by the SHS method and then to hot-press it to obtain dense body. The powder was synthesized in a three-stage process by using intermetallic materials as precursors, and Ti3AlC2. Powder was hot-pressed in various sintering conditions. The phase composition of dense products was examined by the XRD method.
- Microstructure evolution of composite materials based on transition metal carbides
- Strony: 140-145
The structural changes, which take place in sinters composed of a matrix based on transition metal carbides and the modifying phase in a form of low-melting chromium carbide Cr23C6, are presented in the work. The investigations were run on three systems of materials: TiC0,85–Cr23C6, NbC0,95–Cr23C6 and WC–Cr23C6. The modifier content changed in a range of 1.5 – 30 vol.%. The method of synthesis and preparation of the composite components and the sinters for purposes of microstructural examinations was discussed. The results of microstructure evolution of the investigated materials were shown. The results of the determination of element distribution (EDS), phase changes (XRD) and structural changes (Rietveld), made on the samples of investigated systems, were used in order to discuss the microstructure of sinters.
- Preparation of ceria based pigments and their application in ceramic decoration
- Strony: 146-150
Solid solutions of some chromphoric cations in ceria are often used as pigments in the gres porcellanato ceramic bodies due to their high resistance against chemical environment and thermal stability. The present paper shows preparation of the (PrxCe1-x)O2 powders by co-precipitation-calcination method as an alternative for traditional synthesis based on solid state reaction. The structural and colour parameters of the prepared pigments were investigated. It was stated that both the praseodymium molar fraction in the solid solutions and calcination temperature influence the colour of the powders. The pigments prepared by co-precipitation-calcination at the highest temperatures method were intensive chocolate-brown. The examples of application of the pigments in the industry glazes and ceramic bodies were also showed.
- Wear of composite materials with alumina and zirconia matrices in different environments of work
- Strony: 151-155
The paper presents the results of investigations on abrasive wear of a group of sintered composite materials basing on zirconia or alumina matrix containing oxide or carbide inclusions. Investigations were performed for the composites with dispersed inclusions (particulate composites). They were also made for materials with continuous phases with comparable content. In such systems the word “matrix” loose its meaning. The composites with continuous phases were investigated in two- and three-phase case.
The abrasive wear was performed using coarse SiC grains in both, dry and wet environments. The composite microstructures were described. Microstructural parameters were compared to the results of wear and prophilographic tests.
List of Contents
Volume 61, Issue 3
- Electrochemical hydrogen pumps and membranes
- Strony: 159-172
In this work different methods of hydrogen purification were presented and discussed. Special emphasis was given to electrochemical hydrogen pumps and membranes. The general principle of operation of such devices was presented, the basic criteria for materials selection were formulated. The experimental part shows the results of structural, microstructural and chemical stability against CO2 investigations done on BaCeO3 samples, modified by yttrium dopant or by the change of Ba/Ce cationic ratio. Two methods were used for the powders preparation: standard procedure, where solid-state reagents were used and “sol-gel” wet method (Pechini process). The example results, concerning the pumping efficiency, were also presented, demonstrating the possibility of application of high-temperature protonic conductors for the construction of pump or membrane for hydrogen purification.
- Moulding ceramic materials with slip casting
- Strony: 173-178
In the paper, basic principles of slip casting are presented. Slip casting is a forming method in ceramic technology, in which ceramic slurry poured into a porous mould replicates its negative. This method is well known and widely used in ceramic technology, in the manufacture of sanitaryware and tableware. However, the slip casting method may find application in production of advanced ceramic materials where research is carried out concerning the use of this forming method in obtaining nanomaterials and ceramic-metal composites.
In order to obtain slurry of the most beneficial properties, leading to obtaining ceramic bodies without defects, some additives are introduced into it. Generally additives are as follows: deflocculants, binders and surface active agents. In the paper, the role of each ingredient is described. Mechanisms of deflocculation of ceramic powder in liquid medium are described.
- Electrical properties of titanium nitride TiNx (x = 1 & x = 0.9)
- Strony: 179-182
Electrical resistivity of TiN and TiN0.9 ceramics has been studied in the temperature range of 300-673 K. It was found, that materials exhibit stable metallic electrical properties. Resistivity changes with temperature according to the Bloch-Gruneisen’s charge carrier scattering theory. Effect of the nitrogen departure from nonstoichiometry remains in agreement with the Matthienssen’s rule.
- Effect of oxidation on electrical properties of TiNx (x = 0.9 & x = 1.0)
- Strony: 182-185
The van der Pauw method has been applied to determine electrical resistivity of TiN and TiN0.9 ceramics in the temperature range of 300-1000K. It was found, that depending on chemical composition materials show either metallic or semiconducting properties. Transitions metal → semiconductor (for TiN) and semiconductor → metal (case TiN0,9) accompany to the oxidation process.
- Effect of milling on properties of powders applied as fillers of the polymer micronanocomposites
- Strony: 186-191
High energy milling is a valuable technique for grinding micropowders in order to obtain them in a nanometric fraction. It applies in manufacturing the polymeric micronanocomposites (bimodal composites) with sensor properties, particularly for electrotribology. This publication presents an impact of grinding time on comminution and surface area of the selected micropowders applied for manufacturing the polymeric micronanocomposites.
- Gradient microstructure of PCD composites assigned for cutting tools
- Strony: 192-196
In this paper, a manufacturing method of the graded Ti3SiC2-diamond composite is presented. The material contained a gradients of phase concentration distribution, formed by a centrifugal densification process. The FGM material was obtained due to a difference in sedimentation velocity of the particles which differ in size. Hardness measurements were carried out from a top to bottom surface of the sample. Phase distribution was modelled and compared with the results of hardness measurement. The materials with the continuous change of phases distribution allowed to the delamination, which appeared frequently in commercial two-layer PCD composites, to be reduced.
- Characteristics of the Ti3AlC2 containing material reactively sintered under pressure
- Strony: 197-200
A trial of manufacture of material in the Ti-Al-C-N system was made by using reactive sintering under pressure. For that purpose, Ti3Al was synthesised in the first step. Then it was homogenized with carbon in the weight ratio corresponding to the stoichiometry of Ti3AlC2. The mixture was exposed to reactive sintering under pressure. The microstructural observation of chemically etched surfaces of the sintered material was made. The EDS element distribution and X-ray diffraction measurements were carried out. Further, the sinter was tested for hardness, bending strength, elastic properties and fracture toughness. Cracks were generated by the Vickers indenter on the surface of the sinter to observe a propagation path.
- Application of wastes from foundry processes for manufacturing ceramic building materials – part I
- Strony: 201-207
This study summarises the properties of ceramic materials containing waste moulding sands, obtained from processing spent moulding and core mixes. The sand preparation involved crushing processes and separation of metallic parts. Thus prepared substance acted as a substitute for natural quartz sand, which is widely used as a leaning agent in ceramic plastic masses to be formed into ceramic-based construction materials. The issues addressed include the basic functional parameters, selected structural aspects and microstructure of ceramic materials made from plastic mixtures varying in the qualitative proportion of moulding sand contents. Other aspects include the potential threats associated with manufacturing and utilisation of these type of materials. Potential hazards include atmospheric emissions of hazardous gaseous substances, particularly in the form of polycyclic aromatic hydrocarbons (PAHs) as derivatives of organic binders used in manufacturing moulding and core mixes. These substances can originate from the process of burning of ceramic products or might be produced when heavy metals are released from the ceramic matrix. This process might occur throughout the whole service life of ceramic products in the given conditions. Applicability of waste sands in this utilisation scheme is well proved by good parameters of thus obtained ceramic materials and positive results evidencing the absence of atmospheric emissions of hazardous substances and low-level leaching of heavy metals.
- Rare earths as dyes of glass – an effect of Pr3+
- Strony: 208-211
Rare earth elements are widely used as active optical dopants to luminescent and photonic materials. Energy transition between f-f orbitals of rare-earth elements gives effects in the visible region of spectrum. It induces the change of colour of the glass. The effect of a glassy matrix (SiO2, P2O5, B2O3, PbO) on the colouration properties of Pr3+ has been studied. It was stated that the matrix does not influence the position of absorption bands. However, it affects the intensity of bands at 470 nm and 483 nm, which are connected with electron transfers to the 3P1 and 3P0 states, respectively. Basing on the L*a*b CIE system, it was shown that the colouration ability of Pr3+ depends on the type of glass..
- An aspect of mechanical comminution of ZrO2/TiB2/TiC/Zr(C,B) composite powders obtained by high temperature solid state synthesis
- Strony: 212-216
Presented paper describes an infl uence of preparation conditions and chemical composition of precursors of the ZrO2/TiB2/TiC/Zr(C,B) composite powders on their grinding abilities during 12 hours grinding with a rotary-vibratory mill. Abrasive action between 3Y-TZP grinding balls and the powders was also investigated as a function of the above mentioned technological parameters. Orthoboric acid and amorphous boron were used as the boron precursors to manufacture the composite powders by means of high temperature solid state synthesis at 1100-1600°C. Research was ground on the specific surface area measurements conducted for the non-grinded and grinded composite powders by using the BET nitrogen adsorption method. Abrasive wear of the 3Y-TZP grinding media was determined by the gravimetric method. An influence of the phase composition and the TiB2 crystallite size on abrasive action of the powders on the grinding balls was discussed. Phase composition of the powders was measured qualitatively and quantitatively by means of the XRD method and Rietveld refinements of the diffraction patterns. The crystallite size was obtained from X-ray line broadening, applying the Scherrer’s formula. It has been stated that the composite powders derived from the amorphous boron had stronger abrasiveness than the powders of H3BO3 origin. Abrasiveness of both types of the composite powders increased with the temperature of synthesis as a result of both the increased amount of hard inclusions and their sizes.
- Strony: 218-221
List of Contents
Volume 61, Issue 4
- Magnesium aluminate spinel raw materials for high performance refractories for steel ladles
- Strony: 223-227
High quality steel production requires extended treatment of the steel in the steel ladle. This has a remarkable impact on the steel ladle refractories, e.g. the need for high performance functional refractories like purging plugs. Operational changes such as increasing tapping temperatures, longer hold times and more aggressive secondary metallurgy are countered by the need for thinner refractory linings and longer refractories life. These combined factors have led to a resurgence in interest in magnesium aluminate spinel raw materials. Magnesium aluminate spinels have been used in steel-making refractories for many years, in a variety of different forms. This paper reviews the production, properties and performance of spinels. Recent developments in the applications of spinels will also be discussed.
- SECAR 41 – nowy cement glinowy do betonów zwykłych i izolacyjnych
- Strony: 228-232
Regular and insulating castables for application temperatures of 1000°C to 1500°C are often formulated with calcium aluminate
cements containing either 40% Al2O3, for example Ciment Fondu® (CF), or 50% Al2O3 as Secar®51 (S51). While CF is frequently used in insulating concretes together with vermiculite or perlite, S51 is often the preferred choice for dense regular castables with good fluidity and high abrasion resistance. It exhibits also excellent dry-gunning properties. S51 has a low water demand and gives high strength due to its mineralogical composition. It allows application of temperatures up to 1500°C when aggregates with an adequate temperature resistance are used. CF focuses more on the lower temperature application and offers a very good usage value for very cement rich mixes like insulating castables based on vermiculite, perlite and lightweight fireclay.
This paper will discuss the introduction of Secar®41 (S41) into the family of Secar® calcium aluminates in Europe. Secar®41, a fused calcium aluminate cement with 46% Al2O3, already successfully used in the American refractory industry for many years, combines the low water demand of Secar®51 with a superior refractoriness compared to CF. It allows improving the rheology and temperature resistance compared to CF-based lightweight and dense castables. Where S51 was chosen for its superior flow property and abrasion resistance compared to CF, S41 offers an excellent alternative with an adapted cost/performance-ratio. Compared to CF, S41 gives for example a 30-40°C higher application temperature when combined with fireclay. This brings more furnace security in case that overheating occurs unexpectedly. Due to the optimised mineralogy of S41, it exhibits a higher hydraulic potential than CF. Secar®41 has the potential to improve insulating castables either by increased strength at constant density or by better insulating properties through density reduction without compromising the strength level. These unique properties of Secar®41 make it an all-round hydraulic binder for dense and insulating castables with application temperature of 1350°C, which shall be installed either by vibro-casting, dry-gunning or traditional rodding methods.
- Practical application of EN 1402 for quality valuation of refractory castables
- Strony: 233-237
The European Standard EN 1402 specifies whole issues related to the terms, classification, sampling and determination of the properties of unshaped refractory materials. In the presented work, a discussion and practical application of the standard for determination of the properties of refractory castables were shown, including an experience gained during putting it into the laboratory practice in ZBL Ferrocarbo.
- Microporous refractory material based on ZrO2 powder
- Strony: 238-243
Development of manufacturing conception of microporous refractory materials made from powders is based on the progress in area of effective preliminary densification of ceramic powders. Vacuum granulation is a production technology, which allows us to obtain high level of preliminary densifi cation. In this paper, the efficiency of vacuum granulation technology is shown and the influence of grain size distribution of the powder on granules densification is determined. The research results are presented for manufacturing the microporous refractory material based on a ZrO2 powder. In the research, the cheap, low chemical purity and coarse ZrO2 powder, partially stabilized with CaO was used. The aim of this research was to obtain the material of microporous structure and with high densification level. A vacuum granulation technology was used for the powder preparation in order to reduce shrinkage to minimum during sintering. This technology allows us to obtain green compacts with an apparent density of 78% TD and the very advantageous unimodal pore size distribution with an average diameter of 0,36 μm. During sintering process, a very advantageous microstructure of the material was obtained with high densification level at surface areas and small closed pores. This microstructure guarantees high resistance against infiltration by liquid metals and slag.
- A method of repairing the heating wall head of coke oven battery by using „zero” expansion modules
- Strony: 244-249
Lifetime extension of coke oven batteries is the invariably large challenge for the creators of repair techniques. Despite of many work done, until now there is no one universal method designed and all new attempts to solve this problem must arouse understandable interest of users of the coke oven batteries. The main topic of the presented study was to utilize possibility of minimization of the factors, determining the time of repair work through the substitution of low-dimension silica bricks for large-dimension block of “zero” expansion, containing fused silica. Substantial reductions in quantity of the refractory repair pieces, shortening of the repair time, improving quality of the repair work and limitation of the production hearth were achieved.
- Corrosion resistant sialon–based refractories for applications in the aluminium industry
- Strony: 250-252
This papers describes manufacturing the sialon–based ceramics for the modern application in aluminium industry. Sialon based ceramics is characterized by excellent mechanical properties in high temperatures, good corrosion and thermal shock resistance, and low wettability, thus, the sialon material is an ideal candidate for a long term liquid aluminium contact. In the presented method, the relatively cheap and commonly available components, i.e. fi ne Si and Al2O3 powders, were used to obtain reaction bonded materials. The specimens were examined for the phase composition and dimension stability after heating in fl owing nitrogen. The corrosion resistance test in liquid aluminium and the test of wettability after sintering were performed. The microstructure of contact surface was examined by the SEM/EDS method. The application of the studied refractories in a horizontal continuous aluminium casting line is planned.
- Chemical corrosion of magnesia-zirconia refractories by the cement kiln charge
- Strony: 253-259
The paper describes formation of the phases in magnesia-zirconia refractories due to a reaction with the cement furnace charge in a form of pre-calcined meal or portland clinker, containing sulphur and chlorine in a different content, at a temperature of 1300°C and 1450°C. The studies were carried out by using the coating test. The microstructure changes in the contact zone between the coating and the brick were studied by scanning electron microscopy, SEM, coupled with EDS. The temperature dependence of reactivity of the precalcined meal and the portland in relation to the magnesia-zirconia bricks has been documented and discussed.
- Prefabricated vaults in the electrical arc furnances
- Strony: 260-262
In the paper, preparation of the uncooled vault lining for the arc electrical furnace is described, in which prefabricated blocks made of refractory castable containing bauxite were used. Except of the vault lining composed of the prefabricated blocks only, the variant of uncooled vault was shown, which used a combination of the blocks and silica bricks. Suitability of a concept of the usage of prefabricated blocks instead of the fired silica bricks for fabrication of the uncooled vault linings was confirmed.
- Determination of abrasive wear of ceramic materials
- Strony: 263-268
Wear in the friction process (tribological wear) belongs to the most frequent mechanisms of destruction of the mating surfaces. The work presents theoretical aspects of wear with particular emphasis on the mechanisms, which cause abrasive and erosive wear of ceramics. The effect of different parameters on the durability of materials working in the conditions requiring high abrasive resistance has been discussed. Selected methods for determination of the tribological wear have been presented.
The experimental part contains a description of selected methods for increasing the abrasive resistance of ceramics, which involve incorporation of abrasion-resistant additives or applying special protective coatings. The work proves the universal character and usability of the described methods of tribological wear determination and shows prospects of its further development.
- A method of aluminium dross management in the production of insulating-exothermic materials for metallurgical industry
- Strony: 269-272
In the conducted investigations, aluminium dross, i.e. solid waste formed in the production and recycling of aluminium, was used as one of the basic raw material to obtain a material characterised by insulating- and exothermic properties, applied to heat riser heads in the process of iron or steel casting. The product was obtained by filtrating the slurry. In the raw mix, aluminium dross played the role of a refractory filler and a source of metallic aluminium, taking part in exothermic reactions.
The trials conducted in semi-technical conditions, using prototype riser sleeves, proved their good quality and effectiveness in the metallurgical process, comparable to the currently applied imported sleeves.
- The effect of selected additives on hydration of magnesium oxide
- Strony: 273-277
The importance of hydration in technology and in selected application areas of basic materials was shown. The thermodynamic and kinetic data of the reaction were presented. Methods of counteracting the hydration of free magnesium oxide in basic materials and the most frequently applied methods of quantitative evaluation of the effects of MgO hydration were discussed.
Basing on the investigations, the chemical inertness of MgAl2O4 and MgCr2O4 spinels in the non-pressure hydration conditions was proved. The effect of four glycols on MgO hydration was analysed and it has been proved, that intensity of the reaction decreased in sequence from mono-ethylene to propylene glycol. The effect of disodium salt of EDTA on MgO hydration was described.
The literature reports were experimentally verified with a negative result, regarding the limitation of MgO hydration by the introduction of silicon. The chemical inertness of free MgO in the MgO-SnO2 coclinker has been proved, contrary to the well known magnesite-chromite materials. The effect of pH of the electrolyte water solutions on MgO hydration was explored and the results seemed to be in a good accordance with theoretical expectations.
It was concluded, that the solution pH change seems to be an effective way for increasing the hydration degree, while the opposite effect should be sought through adsorption of selected organic substances, taking into consideration a specific character of the given technology.
- Structural masses for electric-arc furnace bottoms
- Strony: 278-282
Major factors, influencing the wear of steelmaking furnace bottoms, include slag corrosion, erosion caused by metal movement, metal infiltration in the fissures formed due to mass shrinkage as a result of sintering, and mechanical damage caused by scrap charge. Methods of limiting the effects of the above mentioned destructive factors have been presented. The phenomenon of slag corrosion was limited chiefly through the appropriate selection of chemical composition, so that the products of mass and slag reaction were compounds with melting temperatures higher than the process temperatures. The phenomenon of erosion and mass shrinkage during sintering can be limited mainly through optimal selection of the grain size composition, which ensured high degree of consolidation at the stage of bottom refractory lining installation. The selected chemical composition and grain composition allow the working surface of the mass to be sintered at relatively low temperatures, so the bottom damage due to scrap charge is reduced. Materials, fulfilling the above conditions, have been used to line the bottoms of electric-arc steelmaking furnaces having the capacity of 90 t, 25 t, 30 t and 140 t in Poland and abroad. The obtained durability results come up to the expectations of the producer and users.
- Refractory materials industry in the Czech Republic, Slovakia and Poland – differences and similarities
- Strony: 283-287
Changes have been characterized in the market of refractory materials in the Czech Republic, Slovakia and Poland during the last two decades. Strong influence of the domestic raw materials on the structure of production in the Czech Republic and Slovakia was emphasized. The structure of refractory consumption and the balance of foreign trade were described. The problems appearing before refractory materials producers in the analyzed countries are mainly connected with a recession and rules introduced by the European Commission, concerning the CO2 emission and REACH.
- Effect of mineral admixtures on the selected properties of andalusite
- Strony: 288-294
Commercially available concentrates of andalusite taken from two separate deposits were investigated. The aim of investigations was to determine the relationship between type of mineral inclusions found in the andalusite raw material and physicochemical properties, related to raw material quality requirements, as well as the mullitization ability. To identify the mineral inclusions, the microscopic microstructural analysis (OM and SEM/EDS), X-ray qualitative and quantitative phase analysis (XRD), and thermal analysis (DTA, TG, DTG) were used.
Apart from the presence of andalusite, quartz and muscovite, the investigations revealed differences in the mineral composition concerning a mica group (biotite, paragonite and micas rich in Ca) clayey minerals (kaolinite, illite), chlorites (clinochlore) and ore minerals (ilmenite, rutile, and smithsonite).
Thermal expansion at 1000°C turn out to be largely dependent on the sample preparation manner and the heating rate. It was shown that the differences in mineral composition of the investigated raw materials markedly influenced thermal expansion and the amount of mullite being formed during heating.
- List of Content for Volume 61
- Strony: 299-300
- Spis treści tomu 61