Properties Of Ceramic Samples Research Articles

ВЛИЯНИЕ МОРФОЛОГИИ, ФАЗОВОГО СОСТАВА И СОДЕРЖАНИЯ ЧАСТИЦ ОКСИДА АЛЮМИНИЯ НА РЕОЛОГИЧЕСКИЕ СВОЙСТВА ВОДНЫХ СУСПЕНЗИЙ НА ИХ ОСНОВЕ

This work investigated the chemical and phase composition of aluminum oxide powders obtained by various methods (alkoxide, codeposition, thermal and plasma-chemical). The physicomechanical, thermophysical and thermal properties of ceramic samples based on them have been determined. The effect of the nature of the aluminum oxide powder and the production process parameters on the sedimentation stability of aqueous suspensions based on them has been determined. The influence of the content of particles of aluminum oxide, buffer solution and rheological additives on the viscosity, sedimentation and aggregate stability of aqueous suspensions has been determined.

The research of the effect of oxidizing agents on the burning process of the carbon-containing component of ceramic masses and their firing properties

The efficiency of using different oxidizing agents to intensify the burnout of the organic component of ceramic masses is investigated. The ceramic masses contained coal flotation wastes with a high carbon content as a fuel-mineral additive. Various inorganic salts, which are oxygen donors during the firing of ceramic masses and form oxidizing agents O2, NO2, N2O during their thermal decomposition, are considered. A new calculation method for determining the content of an oxidizing salt in a ceramic mixture is proposed. This method takes as a basis the amount of «effective oxygen» that released during the thermal decomposition of the oxidizing agent, but not its mass, as it was before. The method allows calculating the rational content of an oxidizing agent necessary for efficient combustion of the carbon component of fuel-mineral additives. When calculating, it is necessary to take into the composition of the organic part of the additive, its content in the ceramic mass and the degree of carbon oxidation. Calculation of the rational content of the oxidizing agent according to this method allows avoiding its excessive and economically unreasonable use. The effect of oxidizing agents and their combinations on the burnout of the carbon component and the firing properties of the masses for wall ceramics is studied. The masses contained 15 % of coal flotation waste with a carbon content of 29 %. It was found that the use of oxidizing agents accelerates the burnout of the organic part of the masses, improves the appearance and mechanical properties of ceramic samples. The use of combined oxidizing agents with different decomposition temperatures makes it possible to create an oxidizing medium in a wider temperature range. This positively effects on the mechanical properties of ceramics. The optimal combinations of oxidizing agents NH4NO3+Ca(NO3)2 і NH4NO3+NaNO3, which made it possible to obtain ceramic samples with a compressive strength 10 МПа, were determined. This mechanical strength meets the requirements of the State Standard of Ukraine B M.2.7-61: 2008 in part of ordinary brick of the M100 brand.

Corrosion Experiments on Ceramic Samples Within Molten Salts

The molten salts can provide many possibilities for their use, e.g., an electrolyte in fuel cells or as a heat transfer medium and an oxygen transporter for flameless oxidation in molten salt oxidation (MSO) technology. The environment of molten salts is very corrosive; therefore, it is crucial to find such ceramic materials, which could be used as reactor filling for MSO technology. The aim of this work was to research physical properties of ceramic samples after the exposure within the eutectic mixture of Na2CO3, K2CO3, Li2CO3 and temperature of 700 °C.

Synthesis of Mg(Fe0.8Ga0.2)2O4 by Gel Combustion Using Glycine and Starch

A powdery material Mg(Fe0.8Ga0.2)2O4 has been prepared by combusting a gel containing magnesium(II), iron(III), and gallium(III) nitrates and a glycine–starch mixture. The gel produced during the synthesis has been studied by thermal analysis (TGA/DSC) and IR spectroscopy. This mixture has been shown to be efficient to produce a homogeneous nanosized powderlike material Mg(Fe0.8Ga0.2)2O4. The morphology and properties of ceramic samples are characterized by scanning electron microscopy, X-ray powder diffraction, neutron diffraction, and vibrational magnetometry.

Basics of recreation of ancient ceramics production technology

The paper investigates possibility of ancient ceramics technology recreation based on materials of archaeological excavations and experimental simulation and describes results of the research. The structure and properties of ceramic samples found during archaeological excavations of the neolithic age and clay raw materials from different deposits were studied. The fragments under study were shown to consist mainly of light-melting clays, possessing polimineral composition with additives of fire clay, sand, loose sedimentary rock, and in some cases wool and vegetation. Clays under study are characterized by variability of chemical and mineral composition, by their combining it is possible to obtain optimal moulding compositions to produce ceramic products of artistic and architectural-structural purpose. Overview of scientific and technical information in archaeology and the obtained experimental results enable to reveal compositions and peculiarities of ancient technology of ceramics production and technical decoration application. Peculiar features of experimental simulation of the ancient ceramics technology considering chemical and mineral composition of clay raw materials are described.

Elastic and anelastic relaxation behaviour of perovskite multiferroics II: PbZr0.53Ti0.47O3 (PZT)\u2013PbFe0.5Ta0.5O3 (PFT)

Elastic and anelastic properties of ceramic samples of multiferroic perovskites with nominal compositions across the binary join PbZr0.53Ti0.47O3–PbFe0.5Ta0.5O3 (PZT–PFT) have been assembled to create a binary phase diagram and to address the role of strain relaxation associated with their phase transitions. Structural relationships are similar to those observed previously for PbZr0.53Ti0.47O3–PbFe0.5Nb0.5O3 (PZT–PFN), but the magnitude of the tetragonal shear strain associated with the ferroelectric order parameter appears to be much smaller. This leads to relaxor character for the development of ferroelectric properties in the end member PbFe0.5Ta0.5O3. As for PZT–PFN, there appear to be two discrete instabilities rather than simply a reorientation of the electric dipole in the transition sequence cubic–tetragonal–monoclinic, and the second transition has characteristics typical of an improper ferroelastic. At intermediate compositions, the ferroelastic microstructure has strain heterogeneities on a mesoscopic length scale and, probably, also on a microscopic scale. This results in a wide anelastic freezing interval for strain-related defects rather than the freezing of discrete twin walls that would occur in a conventional ferroelastic material. In PFT, however, the acoustic loss behaviour more nearly resembles that due to freezing of conventional ferroelastic twin walls. Precursor softening of the shear modulus in both PFT and PFN does not fit with a Vogel–Fulcher description, but in PFT there is a temperature interval where the softening conforms to a power law suggestive of the role of fluctuations of the order parameter with dispersion along one branch of the Brillouin zone. Magnetic ordering appears to be coupled only weakly with a volume strain and not with shear strain but, as with multiferroic PZT–PFN perovskites, takes place within crystals which have significant strain heterogeneities on different length scales.

Improvement Insulating Properties of Ceramic Materials by Incorporating Additives

AbstractThe objective of this study is to improve the thermal performance of masonry bricks produced by the factory Briqueteries du Nord. This industrial plant is located in the north of France. The use of additives in the raw material admixture presents a promising approach for improving the thermal performance of building materials, and consequently to respond of requirements of the thermal regulation. Therefore, three additives are selected as part of an approach supporting sustainable development and waste valorization: flax shives, maize starch, and polystyrene beads. This experimental study is focused on the effect of these additives on the physical, mechanical, and thermal properties of ceramic samples. Different characterization tests were conducted at the laboratory scale. The results indicated that mixtures containing 2.5% flax shives or 7.5% starch ensured an optimal thermal performance, taking into account the mechanical strength of these products.

Phase equilibria and electrical properties of barium-containing relaxor-based solid solutions

We have studied the effect of modification with Ba on the phase composition, structure, and electrical properties of ceramic samples of Pb(1−x)Bax(Mg1/3Nb2/3)m(Zn1/3Nb2/3)y(Ni1/3Nb2/3)nTizO3 (0 ≤ x ≤ 0.15) solid solutions and investigated phase equilibria in this system in the range 0 ≤ x ≤ 0.15. The results indicate that a tetragonal and a low-symmetry phase coexist in the composition range 0 ≤ x ≤ 0.05, a pseudocubic phase exists in the range 0.05 γ, Ba2+ substitutes for Pb2+ on the cuboctahedral site. The sintering temperature is shown to influence the phase composition of the modified ceramics. We demonstrate, that varying the Ba content of the solid solutions, one can obtain a series of materials with a wide range of electrical parameters (ɛ/ɛ0 = 2880–11000, Kp = 0.07–0.43, and Qm = 48–8300) and potential applications in hydroacoustics, piezoelectric motors, and capacitor technology.

Homogeneous precipitation synthesis and thermoelectric properties of Ca2Co2O5 ceramics

Homogeneous precipitation method was applied to synthesise Ca2Co2O5 powders using calcium nitrate, cobalt nitrate and urea as raw materials. Uniform plate-like Ca2Co2O5 powders with an average grain size of 1 μm can be obtained by calcining the precursor for 8 h at 1073 K in the air. The Ca2Co2O5 ceramics were gained after sintering for 4 h at 1083 K using uniaxial pressure moulding and then sintering technique. The thermoelectric properties of ceramic samples were measured from 303 to 973 K, and the result shows that the electrical conductivity, Seebeck coefficient, thermal conductivity and figure of merit of the sample are 2236·85 S m−1, 175·95 μV K−1, 1·01 W m−1 K−1 and 0·69 at 973 K respectively.

Influence of the granule size on the magnetocaloric properties of manganite La0.5Ca0.5MnO3

The influence of the granule size on the magnetic and magnetocaloric properties of ceramic sample of manganite La0.5Ca0.5MnO3 has been investigated. Anomalies indicating the coexistence of the ferromagnetic metallic and antiferromagnetic charge-ordered phases below TC have been found in the temperature dependence of the magnetocaloric effect. It has been shown that a decrease in the granule size to 90 nm leads to the complete suppression of the antiferromagnetic charge-ordered phase.

Ferroelectric phases and relaxor states in the novel lead-free (1 − x) Bi1/2K1/2TiO3 − x BiScO3 system (0 ≤ x ≤ 0.3)

The novel lead-free Bi-based ferroelectric system with perovskite structure (1 − x) Bi1/2K1/2TiO3 − x BiScO3, chemically designed to show a ferroelectric morphotropic phase boundary (MPB) and high piezoelectric response, was synthesized by the conventional solid-state reaction method for compositions with 0 ≤ x ≤ 0.3. X-ray diffraction analysis shows that the samples possess perovskite-type structure for x < 0.3 and reveals a phase evolution in the symmetry from tetragonal for x < 0.1 to pseudocubic for 0.1 ≤ x ≤ 0.3. Electrical and piezoelectric properties of ceramic samples were systematically investigated, and results indicate that a ferroelectric MPB is not formed, but instead a transition from conventional ferroelectric to relaxor ferroelectric behavior occurs when increasing the (Bi, Sc) content between 5 and 10%. The origin of this unexpected effect, and its implications in the design of novel lead-free piezoelectric materials are discussed.

Light-tone ceramic facing brick manufacture using ferrous-metallurgy by-products

The principal variational regularities of the properties of ceramic samples obtained from compositions based on combinations of loam, semi-fireclays, and metallurgical slag are examined. The phase composition of and structure formation processes in wall ceramic have been investigated using high-precision modern equipment. The composition of ceramic mix making it possible to produce high-quality ceramic facing brick based on clay raw materials and ferrous-metallurgy by-products is presented.

Microstructure and Young’s modulus of high-pressure Li x Na1 − x TayNb1 − y O3 ceramics

The microstructure and elastic properties of ceramic samples of high-pressure LixNa1 − xTayNb1 − yO3 perovskite solid solutions have been studied for the first time in relation to their composition and the synthesis temperature. The results demonstrate that, with increasing sintering temperature, the Young’s modulus of the Li0.17Na0.83TayNb1 − yO3 solid solutions decreases, which can be understood in terms of the recrystallization behavior of the disordered solid solutions under high-pressure synthesis conditions.

Dielectric properties of PbBO3 perovskites with mixed-valence substitution in the B position

This paper reports on the synthesis of PbBO3 perovskites with mixed-valence substitution in the B position in which the number of ions n in different valence states occupying oxygen octahedra varies from 2 to 6. The dielectric properties of ceramic samples have been studied at frequencies in the range from 12 Hz to 100 kHz and in the temperature interval 77–450 K. The new compounds have been shown to possess relaxor properties.

Structure and Transport Properties of Sr0.75-xCaxY0.25Co0.25Mn0.75O3-δ (0 ≤ x ≤ 0.6)

AbstractNew complex oxide Sr0.75-xCaxY0.25Co0.25Mn0.75O3-δ with a perovskite-like structure has been synthesized and characterized. DC and AC transport properties of ceramic samples have been studied in the temperature range 4.2K – 1173K. DC conductivity data at T &gt; 300K are discussed in terms of the small polaron hopping model. Dependence of the polaron activation energy on the calcium content is found to correlate with the change of structural distortion parameters. Both the temperature dependence of DC conductivity and the frequency dependence of the real part of the admittance reveal hopping transport at low temperatures.

Phase transitions in solid solutions (1 − x)BaTiO3-xBaMg1/3 B 2/3O3 (B = Nb, Ta)

The dielectric properties of ceramic samples of (1 − x)BaTiO3-xBaMg1/3Nb2/3O3 and (1 − x)BaTio3-xBaMg1/3Ta2/3O3 solid solutions (x = 0–0.25) are investigated in the frequency range from 10 Hz to 100 kHz at temperatures of 77–450 K. It is shown that the (x−T) phase diagrams of these solid solutions at x = 0.05 have a multiphase point at which the lines of all three phase transitions of BaTiO3 converge.

Peculiarities of Large-Grained Lead Zirconate-Titanate Solid Solutions in the Vicinity of Morphotropic Phase Region

(Pb0.9Ba0.05Sr0.05)(Zr1−xTix)O3 solid solutions series in which the width of the morphotropic region (MR) (determined by X-ray structure analysis) does not exceed 0.5%, are obtained using a modified ceramic technique. The grain size of the ceramics is 20–25 μm. As established by the performed investigations, piezoelectric and dielectric properties of ceramic samples and diffusion of PE phase transition depends on the position of the given solid solution in the phase diagram. The maximum diffusion is observed in the middle of MR. There exists a temperature range ΔTcf of the order of several decades of degrees above the Curie point, where piezoelectric resonance can be observed. ΔTcf value reduces considerably when moving from MR.

Ceramics and Thin Films of Some New Pb(B 3+ ,Nb)TiO 3 -PbTiO 3 Systems

The structure, dielectric, and electromechanical properties of (1 m x )Pb(B 3+ ,Nb)TiO 3 - x PbTiO 3 binary systems (B = Lu, Er, Tb, Ho) are reported. The crystallographic features at the morphotropic phase boundary (MPB) between tetragonal P4mm and pseudo-monoclinic M phases are discussed with respect to electro-mechanical properties. Doping effect (with La 3+ ) on the properties of ceramic samples of pseudobinary Pb(Lu 1/2 Nb 1/2 )O 3 -PbTiO 3 (PLuNT) system has been investigated. Pb(Mg 1/3 Nb 2/3 )-PbTiO 3 (PT) solid solutions were studied under different processing conditions for obtaining ceramics of 100% perovskite structure with sufficient high j T EC ∼ 1 K near room temperature. The PLuNT with composition near the MPB formed by in situ pulsed laser deposition onto LSCO/(100)MgO as well as PluN thin films exhibit ferroelectric behaviour at room temperature (in contrast to typical antiferroelectric features of PLuN ceramic).

Polar state in a SrTiO3-KTaO3 solid solution

Dielectric properties of ceramic samples of a 0.85SrTiO3-0.15KTaO3 solid solution have been studied. The temperature dependence of the dielectric permittivity exhibits maxima with a strong frequency dispersion, which is described by the Vogel-Fulcher law with a characteristic temperature Tg=26 K. These features are apparently connected with transition to a polar glasslike state.