Gotowa bibliografia na temat „Ceramic Engnieering”

The use of mullite as a ceramic material proliferate from the field of conventional ceramic to the most advanced structural and functional area of ceramic due to its many advantageous properties. The properties of a sintered mullite ceramic are very much dependent on the type of processing route by which powder precursor was prepared. In the present work, the stoichiometric diphasic mullite precursor powder was prepared by reverse addition technique using fume silica and aluminium nitrate nonahydrate as raw material. The effects of solution pH on the properties of the prepared powder have been investigated. The precursor powder made at ph-6, pH-8 and pH-10 were studied by TG-DSC analysis to know about the thermal decomposition behavior. Phase analysis of the precursor powder and calcined powder at different temperatures was done by XRD study. The presence of the different functional group in the precursor powder and calcined powder is confirmed by the FTIR study. The particle morphology, tendency of agglomeration and surface area, was investigated by microstructure analysis, particle size distribution and surface area analysis respectively. It was found that though the desired mullite phase formation is not very much affected by the variation of solution pH but the other properties are pH dependent. The precursor powder formed at pH-8 exhibited better properties compared to the other batches. Therefore, the sintering study of the precursor powder in the presence of the different quantity of TiO2 additive is continued with that powder only. Samples made from different batches were sintered at three different temperatures i.e. 1450 ˚C, 1550 ˚C and 1650 ˚C under ambient atmosphere. The sintered pellets were characterized with respect to shrinkage, percent apparent porosity and bulk density. The phases formed in the sintered pellets were analyzed by X-Ray diffraction study. Morphology and microstructure were evaluated by FESEM.

In the present work the glass of composition 40 % SiO2, 5 % Al2O3, 15 % Na2O, 5 % CaO , 12,5 % NaF , 21 % CaF2 and 1.5 % Sb2O3 (mol%) was prepared to investigate the crystallization of CaF2 in the parent glass matrix. To accelerate the crystallization and to develop the up conversion fluorescence property Er2O3 was doped in 0.5% , 1 % and 1.5 % (mol%). The casted glass was subjected to thermal treatment between 600 – 750oC. To observe the effect of rare earth on crystallization glass samples were examined in DSC. Spectroscopic property of the base glasses were studied using UV-Visible spectrophotometer. Phase authentication was carried out using X-Ray diffraction analysis.

It is now some 70 yrs since ferrites debuted as an important new category of magnetic materials. They were prized for a range of properties that has no equivalents in existing metal magnetic materials, and it was not long before full- fledge research and development efforts were underway. Today ferrites are employed in a truly wide range of applications, and have contributed materially to advance in electronics. Research too, continue apace, and the efforts of many man and women working in this field are yielding many highly intriguing results. New high-performance products are appearing one after another, and it would seem we have only scratched the surface of the hidden possibilities of these fascinating materials.

$CaCu_3Ti_4O1_2$ (CCTO) is a well known nonferroelectric material possessing high and nearly constant (room temperature to 300oC) dielectric constant at 1 kHz. It is being widely used in the electronic industries to manufacture electronic components such as multilayer capacitor (MLCC), DRAMs, microwave devices, electronic devices in automobiles and aircrafts. The properties like high permittivity of CaCu3Ti4O12 depend upon the particle size and powder morphology. The particle size and powder morphology of CaCu3Ti4O12 depend on the different processing parameters that are temperature, heating rate, duration and atmosphere. Several powder synthesis processes have been tried for the synthesis of CaCu3Ti4O12 among which solution combustion process have got enough emphasis now a days. CaCu3Ti4O12 synthesized using combustion synthesis techniques possess high purity and close control of powder morphology, which will result in the desired microstructure and dielectric behavior. Under this context the present study was carried out to evaluate the effect of different processing parameters on the phase purity, particle size, and powder morphology of CaCu3Ti4O12 and to study the effect of microstructure, sintering condition on the dielectric behavior of CaCu3Ti4O12. The study includes the optimization of different process parameters (ammonium nitrate, citric acid, pH) for synthesis of phase pure CCTO powder following solution combustion route. The optimization of process parameters were based on the phase purity, crystallite size and density. The optimized ratio for synthesis of CaCu3Ti4O12 was found to be 1:3:4:1.5:4 for CaCO3,CuO, TiO(NO3)2, citric acid and ammonium nitrate respectively at pH 1.The powder morphology, particle size, densification behavior and dielectric behavior of the sintered samples has been studied. Increasing sintering time found to enhance the density. The dielectric study showed its dependence upon sintering time, grain size and density. Dielectric property increases with increase in sintering time and density. An attempt has also been made to study the effect of lanthanum substitution at A site on the properties of CCTO ceramics.

The study first optimized the different processing parameters e.g. salt systems, heat treatment temperature, holding time. By NaOH-KOH based salt system phase pure powder can be prepared at 175oC. NaCl-KCl based system produced phase pure powder at 700oC. LiCl-KCl based system failed to produce phase pure BaTiO3 powder. Crystallite size of the synthesized powder found to be varying 30-43 nm depending on the processing time and temperature. TEM analysis revealed that particle size in the range of 70-100 nm. It has been observed that NaOH-KOH system synthesized powder can be densified (98%) at a temperature 1225oC. Interestingly ultrafine grain size (200-500 nm) retained in highly dense sintered sample. In case of NaCl-KCl based powder only 91% density achieved, microstructure shows significant amount of porosity. Dielectric constant and loss factor of the sintered samples (εr =1400 and tanδ = 2% at 1 kHz) are on a par with BaTiO3 prepared via conventional sintered sample. NaOH-KOH salt based prepared sample showed almost flatten Curie peak and NaCl-KCl salt system prepared sample showed broad Curie peak with a Curie temperature of 115oC. The peak shift and broadening can be explained qualitatively from temperature dependence of volume fraction between surface cubic layer, bulk tetragonal layer, and gradient-lattice-strain layer (GLSL).

Both Barium titanate and Nickel ferrite were synthesized by Conventional ceramic processing method. Mixed oxide of BaCO3 and TiO2 for BaTiO3 and NiO and Fe2O3 for NiFe2O4 were calcined at 1000 oC for four hour and 900 oC for four hour respectively. Phases of particular compounds have been confirmed by XRD. For preparing multi ferroic composites the two separate powders are proved to be suitable. Composite (Four batches were prepared with composition 50:50, 60:40,70:30 and 80:20 ).

The aim of this study was to prepare four different composition of Alumina/Lanthanum Hexaaluminate powder. Four different compositions ranging from 10 to 80 vol % of Lanthanum Hexaaluminate were prepared. To prepare the Alumina-Lanthanum Hexaaluminate ceramic composite, stable aqueous Alumina slurry was needed to prepare. Thus, selection of electrolyte was made after comparing Darvan and tri-ammonium Cytrate. Darvan was chosen as an electrolyte to prepare stable aqueous Alumina slurry. The effect of pH on zeta potential was also studied. After preparation of Alumina-Lanthanum Hexaaluminate ceramic composite powder, pellets of approximately 0.7gram for each composition were made by applying 4 Ton pressure for 120 seconds. The pellets were then sintered at 16500C in chamber furnace. The soaking time was kept for 4 hours. Then the bulk density, aparent porosity and strength were compared after calculation of dry weight, soked weight, suspended weight. The results revealed that bulk density increased with increasing vol % of LHA content and aparent porosity decreased with increasing vol% of LHA content. The strength also increased with increasing vol% of Lanthanum Hexaaluminate.

The present project dealt with the preparation of a multiferroic composite (Na0.5K0.5)NbO3-(Ni0.6Zn0.4)Fe2O4 in which the constituent materials (Na0.5K0.5)NbO3 [NKN] and (Ni0.6Zn0.4)Fe2O4 [NZFO] were prepared by coating method and combustion method respectively. These were mixed in required proportion and densified by conventional sintering process to form composite. Four compositions were prepared to form composite (1-x)(Na0.5K0.5)NbO3-x(Ni0.6Zn0.4)Fe2O4 [NKN-NZFO] ceramics, where x=0.01, 0.10, 0.15 and 0.20. XRD of the sintered and ground sample showed no reaction between individual phases and no secondary phase formation in the final product. SEM image shows that addition of NZFO significantly modifies the microstructure of the sintered sample. Grain size found to be 10-15 µm for 1% NZFO addition. The grain size reduced to 2-5 µm for higher NZFO addition. The dielectric constant and dissipation factor were studied as a function of frequency for ceramic composites

Barium Zirconate (BaZrO3) is a promising candidate for structural to electronic application. Different industry demands nano scale powder for the technology enhancement and hence, the preparation of BaZrO3 nano-powders and their sintering study through microstructure synchronization are the prime interest of this research. A typical combined wet chemical and calcination technique was employed to synthesis of 100nm BaZrO3 nano-powders. Elongated Barium carbonate (BaCO3) nano rod was prepared through wet chemical method, whereas, near spherical yttria stabilized zirconia nanoparticle was used to prepare this BaZrO3. Transmission electron microscope analysis (TEM), XRD and BET surface area confirmed the purity and morphology of developed nanoparticles. Prior to sintering, dilatometric study was conducted to understand the sintering behaviour this class of nanoparticles. A wide horizon of sintering profile optimized the sintering condition with consideration of relative density and microstructure. The nano powder was near to 98% dense at 1650oC for 2h. Field Emission Scanning Electron (FESEM) microscope study reveals the grain size is around 250nm. The developed perovskite BaZrO3 nano powders could be successfully used for different sectors.

The present work deals with the processing and sintering of phase pure Mag–Al spinel by auto-combustion process. Magnesium and aluminum nitrates have been used as the oxidizers and glycine as the fuel. Addition of glycine to the mixture of magnesium and aluminium nitrates results in a series of redox reactions to form a complex which subsequently crystallizes to form spinel at a lower temperature. Mag-Al spinel has been synthesized by varying metal to glycine ratio as 1:0.5, 1:1 and 1:2 and its effect on the spinel formation was studied. Variation of calcination temperature was done from 5000 C to 10000C for 1 hour and 2 hours and their XRD analysis were performed to identify the exact starting temperature for obtaining phase pure spinel. The phase pure Mag-Al spinel was formed at 700 °C, when using metal to glycine ratio as 1:2. However, the phase pure Mag-Al spinel formation took place at higher temperature in case of other metal to glycine ratios. Bulk density was achieved in the range 3.135 – 3.34. Apparent porosity in the range of (0 – 6.64) % was achieved.