بررسي ساختاري و ريزساختاري نانو ذرات دي الكتريك تيتانات كلسيم– مس توليد شده به روش مكانوشيميايي

Structural and Microstructural Investigation of Nano-sized Calcium-Copper-Titanate Dielectric Prepared by Mechanochemical Route

در اين پژوهش، نانوذرات دي الكتريك تيتانات كلسيم- مس (CCTO) به روش مكانو شيميايي توليد شده است. تركيب شيميايي پودر آسيا شده با استفاده از آناليز فلورسانس اشعه X (XRF) و آناليز ساختاري كمي وكيفي فازها با پراش اشعه X (XRD) و با استفاده از روش رتويلد صورت گرفت. افزون بر اين، بررسي اندازه ذرات با استفاده از ميكروسكوپ الكتروني عبوري (TEM) انجام شد. نتايج آناليز XRF نشان داد كه ميزان آلودگي وارد شده در حين فرآيند سنتز مكانيكي به سيستم، بسيار اندك بوده است. نتايج XRD نشان داد كه در مراحل گوناگون آسياكاري، به ترتيب كاهش اندازه ذرات، تشكيل ساختار نانو و به ميزان زيادي آمورف شدن رخ مي دهد و هم چنين، مشخص گرديد كه سرعت آمورف شدن در مورد فازهاي گوناگون، متفاوت است. با تبديل تمامي فازهاي بلورين به فاز آمورف و با نزديك شدن تركيب اين فاز به تركيب استوكيومتري فاز CCTO، اين فاز از زمينه ي فاز آمورف، جوانه زني و رشد مي كند. تصوير TEM نشان داد كه اندازه ي ذرات فاز CCTO پس از 256 ساعت آسياكاري در محدوده ي 10 الي 35 نانومتر است.

In this study, the formation of calcium-cupper-titanate (CCTO) perovskite powder by mechanical alloying of the constituent oxides under air atmosphere at ambient temperature was investigated. By applying a relatively low-energy ball milling, the reaction sequence was identified. The chemical composition of the as-milled powders was evaluated by X-ray florescence analysis. The qualitative and quantitative structural analysis was performed by X-ray method using the Rietveld refinement. Moreover, the particle size evolution was studied by transmission electron microscopy. The mechano-synthesis of CaO, CuO, and TiO2 led to the formation of perovskite CCTO, where negligible contamination due to milling was detected. In the early stages of milling, the particle size reduction, the nanostructure formation, and a high degree of amorphization were observed. It was also found that the rate of amorphization is different in the constituent oxides. In the middle stage of milling a fully amorphous structure was formed and since the amorphous composition reached the CCTO composition, the CCTO phase was nucleated from the amorphous phase in the final stage of milling. The TEM micrograph shows the CCTO particle size is in range of 10-35nm. influences of different dispersing agents (sodium dodecyl sulfate, SDS) as a benchmark for future dispersion experiments and excitation wavelength are discussed and the results are compared to the commonly used UV-Visible spectroscopic analysis. The results indicated that synthesis of hydroxyapatite particles in the presence of the carbon nanotubes had the best result in homogenization of the carbon nanotube dispersion and faster crystallization of hydroxyapatite, and usage of SDS for dispersion carbon nanotubes at hydroxyapatite matrix, the render formation hydroxyapatite coating on CNTs surface. The average crystallite size of heat-treated (at 600°C) samples, estimated by Scherrer,s equation was found to be ~50-60 nm that confirmed by TEM.