Microstructure Of Ceramic Samples Research Articles

Evaluation of the Role of the Activating Application Method in the Cold Sintering Process of ZnO Ceramics Using Ammonium Chloride.

The influence of the method of applying the activating additive ammonium chloride and its concentration on the density and microstructure of zinc oxide ceramic obtained by cold sintering at 244 °C was investigated. The activating agent was applied by two methods: impregnation and subsequent autoclave treatment. When the powder was activated by the impregnation method, the crystal sizes remained at the initial level of 0.17-0.19 μm. After the autoclave treatment, the crystal sizes increased to 0.31-0.53 μm. Samples of cold sintering ZnO with relative density up to 0.96 and average grain sizes 0.29-0.86 μm were obtained. ZnO powders and ceramic samples were analyzed using SEM, TGA/DSC, and XRD to reveal the effect of the powder activation method and cold sintering conditions on the material microstructure. The effect of ammonium chloride concentration on grain growth and microstructure of ceramic samples is shown. It was found that the average grain size of ceramic samples with an increase in additive concentration passes through a minimum. In cold sintering of the autoclave activated powder, the effect of reducing the average grain size was observed. The results of this work are discussed on the basis of the idea of the solid-phase mobility of the crystal structure arising when interacting with an aqueous medium.

Effect of particle size distribution on functional properties of Ce0.9Y0.1O2-d ceramics

This paper has investigated the dependence of the mechanical and electrical properties of ceramics Ce0.9Y0.1O2-d (CeY) on changes in the proportion of submicron size particles in a powder with bimodal particle size distribution. The powder was prepared by mixing the products of sol-gel (submicron size fraction with average size of 0.2 μm and specific surface area of 39.52 m2/g) and solid-state synthesis (micron size fraction with average size of 5.68 μm and specific surface area of 4.81 m2/g) in a certain ratio to get different proportion of the fractions. All ceramics samples were formed by isostatic pressing with further annealing under identical conditions. The microstructure of ceramic samples was studied using scanning electron microscopy and static volumetric analysis. The impedance spectroscopy method has determined the temperature dependencies of the grain boundary resistance fraction, which are strongly related to the particle size distribution. The microhardness of samples was determined by the Vickers method. A nonlinear change of mechanical and electrical properties was found for the samples having approximately 20% content of submicron size particles. The dependence of the total electrical conductivity and the dependence of the microhardness on the particle size distribution possess the maxima and minima points for these compositions, respectively. The particle size distribution of powders has a strong impact on the ceramics formation process and allows to control the microstructure and physical properties of materials. We have proposed the ceramics model of “arched structure”, formed by bimodal compositions sintering, which allows to predict the properties of ceramics with other compositions.

Synchrotron micro-XRD applied for the characterization of pottery from the Neolithic to Chalcolithic transitional period: a case study from Tappeh Zaghe, Iran

The production of pottery represented a significant pyro-technological progress in the ancient world. Two types of characteristics pottery from the transitional period (Neolithic to Chalcolithic) found at the Tappeh Zaghe in northern Iran were analyzed in order to investigate newly formed phases produced during the firing stage of pottery. This might have been a sign of technological evaluation through transitional period. Petrographic analysis, coupled with multi-image analysis, X-ray powder diffraction and environmental scanning electron microscope with energy-dispersive X-rays (ESEM-EDX) provided information on the compassion and microstructure of ceramic samples. Synchrotron micro-XRD beamline allowed the spatial mapping of crystalline phases from near surface (at the surface) into the matrix of potteries and the detection of minute, major and minor phases. The mineralogical interaction between various primary phases and decomposition regard carbonate reaction within the potteries fabrication in the as-received. New phases were followed across the wall thickness which were achieved by sintering (partial or total) and show a clear transition from outer side to the core of the pottery.

Enhanced energy storage density and high efficiency of lead-free Ca1-xSrxTi1-yZryO3 linear dielectric ceramics

Ca1-xSrxTi1-yZryO3 (0.40 ≤ x ≤ 0.60, 0.1 ≤ y ≤ 0.4) ceramic samples were fabricated by conventional solid state method. The microstructure of ceramic samples were studied by XRD and SEM, and the influence of Zr4+ doping on the electric properties and energy storage performances were systematically studied. The results showed that the introduction of Zr4+ results in an inhibition of interfacial polarization and enhancement of grain boundary barrier effect. Ca0.5Sr0.5Ti1-yZryO3 ceramic samples exhibit excellent energy storage properties, with breakdown strength being on the order of 390 kV/cm versus 280 kV/cm for the counterpart Ca0.5Sr0.5TiO3 ceramic samples, together with energy efficiency above 95%. Meanwhile, a maximum breakdown strength of 390 kV/cm, a high energy storage density of 2.05 J/cm3 and an ultrahigh energy efficiency of 85% at high temperature of 125 ℃ were obtained in the sample with y = 0.1 as well, indicating it as a good candidate for linear energy storage fileds.

Phase transitions of (Cu,Ni)3TeO6 solid solutions

(Cu,Ni)3TeO6 solid solutions with the bixbyite (pseudocorundum) and ilmenite structures have been prepared by solid-state reactions and characterized by a variety of techniques. We have studied the effect of nickel substitution for copper on the phase composition of the materials, examined the microstructure of ceramic samples, and measured their magnetic susceptibility, heat capacity, permittivity, and loss tangent as functions of temperature. This allowed us to reveal dielectric anomalies related to structural phase transitions and to determine the antiferromagnetic ordering temperatures of the (Cu,Ni)3TeO6 ceramics.

Characterisation of mullite – ZrO2 ceramics prepared by various methods

Mullite – ZrO2 ceramics was sintered from variously prepared powder mixtures -different time milled and hydrothermal synthesized. As sintering aid 8 wt. % illite clay for one part of starting mixtures was added. Two sintering routes was applied for consolidation of powder – spark plasma sintering (SPS) technique and conventional sintering reactions in air. It is shown that the structure of sintered samples for SPS was completed at 1250°C and by conventional - at 1300°C. The developed microstructure both conventional and SPS can be characterized by mullite matrix with evenly distributed ZrO2 grains. For conventionally prepared and sintered samples corundum and ZrO2 tetragonal grains are observed, but for SPS dominates ZrO2 cubic. The microstructure of ceramic samples from hydrothermal synthesized powders and consolidated by SPS is amorphous like, with xenomorfic crystals of mullite and inclusions of ZrO2 cubic grains. It is stated that additive of illite clay promotes the densification. At conventional sintering clay prevents the transformation of ZrO2 tetragonal to ZrO2 monoclinic by cooling of samples, but for SPS promotes formation of ZrO2 cubic. SPS sintered samples processed from conventionally milled powder mixture are characterized by pressure strength.

Preparation, characterization and dielectric properties of Ba3−xSrxLiM3Ti5O21[M=Nb and Ta, x = 0 to 3] ceramics

The ceramic compositions Ba3−xSrxLiM3Ti5O21[M=Nb and Ta, x = 0 to 3] were prepared through conventional solid state ceramic route. A detailed study has been carried out to correlate the structure of Ba3−xSrxLiM3Ti5O21[M=Nb and Ta, x = 0 to 3] with respect to their dielectric properties. The structure and microstructure of ceramic samples were studied using powder X-ray diffractometer and Scanning Electron Microscopic techniques. The dielectric properties of the sintered ceramic compacts have been studied. The Ba-rich compositions were identified as promising candidates for high frequency applications whereas the Sr-rich compositions were excellent ionic conductors and can be commercially exploited for applications in solid-state batteries.

Preparation of Sb3Nb3O13 powders using molten salt method

The powders of pure cubic phase of Sb3Nb3O13 were obtained using molten salt method at 1,100 °C with incubation time of 3 h. The formation of a kind of compound with hydroxyl restrains the volatilization and oxygenation of antimony oxides. The powder of cubic Sb3Nb3O13 shows octahedral shape and its size lies between 1 μm and 20 μm. Densified ceramic was obtained using the Sb3Nb3O13 powders. The microstructure of ceramic samples was studied by XRD and SEM analysis. And the dielectric properties as a function of frequency and temperature were measured between 25 °C and 550 °C and 100 Hz∼1 MHz.

Study of controlled tetracycline release from porous calcium phosphate/polyhydroxybutyrate composites

AbstractPorous calcium phosphate ceramics were prepared by sintering of mixtures of nanocrystalline apatitic calcium phosphate and fibrous natural cotton cellulose after pressing at temperatures of 1150 °C and 1250 °C. Micro-and macropores were present in microstructures of ceramic samples. The microstructures of porous ceramics were similar to those observed in bone tissues and fiber-like randomly oriented texture was observed in ceramics. Polyhydroxybutyrate (PHB) biopolymer layers are distributed homogeneously in the samples after evaporation of the diluent (chloroform) from the PHB vacuum impregnated porous samples. The tetracycline (TTC) release rate decreases with the content of polyhydroxybutyrate in the ceramic samples, which corresponds to the rise in amount of biopolymer displaced in the pores of ceramics. The concentration of TTC in the phosphate buffer saline solution varies almost linearly with time after the first seven hours from the start of the release of the calcium phosphate ceramic samples with 2.4 mass % of polyhydroxybutyrate. The initial burst effect was significantly depressed by the preparation method used.

Synthesis and Characterization of Sr 2 [Sr n−1 Ti n O 3n+1 ] Series by Mechanochemical Activation

A new synthesis method, based on high-energy milling, has been applied to obtain the n=1 to 3 members of Sr 2 [Sr n m 1 Ti n O 3n+1 ] Ruddlesden-Popper series, producing a very important decrease in the temperature and time reactions as compared with the traditional ceramic method. The mechanosynthesis of SrTiO 3 was observed during ball milling processes. Similar results were obtained with vibrating and planetarium milling systems, although the time scales involved are shorter when last one was used. The milled samples were annealed at different temperatures up to the formation of the layered perovskites in one single step. Final products as well as milled powders were studied by thermal analysis, infrared absorption spectroscopy and X-ray diffraction. The microstructure of ceramic samples with Sr 2 TiO 4 and Sr 3 Ti 2 O 7 compositions was investigated.

Synthesis and Characterization of Sr 2 [Sr n−1 Ti n O 3n+1 ] Series by Mechanochemical Activation

A new synthesis method, based on high-energy milling, has been applied to obtain the n=1 to 3 members of Sr 2 [Sr n m 1 Ti n O 3n+1 ] Ruddlesden-Popper series, producing a very important decrease in the temperature and time reactions as compared with the traditional ceramic method. The mechanosynthesis of SrTiO 3 was observed during ball milling processes. Similar results were obtained with vibrating and planetarium milling systems, although the time scales involved are shorter when last one was used. The milled samples were annealed at different temperatures up to the formation of the layered perovskites in one single step. Final products as well as milled powders were studied by thermal analysis, infrared absorption spectroscopy and X-ray diffraction. The microstructure of ceramic samples with Sr 2 TiO 4 and Sr 3 Ti 2 O 7 compositions was investigated.

AEM study of perovskite Pb(Zn1/3Nb2/3)O3 ferroelectric relaxor

Lead zinc niobate (Pb(Zn1/3Nb2/3)O3 : PZN) is a ferroelectric relaxor with perovskite-related stmcture exhibiting a diffuse phase transition at ˜140°C. Single crystals of PZN have shown excellent dielectric, electro-optic and electrostrictive properties. However, attempts to achieve these properties in polycrystalline ceramic PZN samples have failed. Using conventional powder processing it has not been possible to synthesize a monophase perovskite stmcture, due to the pervasion of lead niobate pyrochlore phases. It is thought that the pyrochlore phases are the detrimental factor of most importance. However, lack of information on pyrochlore structures and on the PZN perovskite phase prevents full characterization of the microstructures of ceramic samples. To understand more completely the composition and stmcture of the various phases present in PZN ceramics, an AEM study of polycrystalline samples has been undertaken. Furthermore a clarification of the microchemical ordering situation in PZN has been achieved.