Ultrafast synthesis and sintering of materials in a single running experiment approach by using electric fields

Processing of materials in the form of ceramics normally involves several steps including calcination at a relatively low temperature for synthesis of the end-product powder and sintering at a high temperature for densification.The work we have been developing introduces a novel approach enabling synthesis plus sintering of materials in a single running experiment by using electric fields,ending with dense ceramics that display grains noticeably finer than in conventional processing.This new paradigm is fully illustrated with experiments conducted on amorphous CaCu3Ti4O12 precursor powder,shown to experience,on heating,crystallization through intermediate phases,followed by chemical reaction leading to synthesis of the end-product powder,plus densification depending on field adjustment.The processing time and furnace temperature are considerably reduced,demonstrating that enhanced synthesis and sintering rates applied under field input.Similar results found in Bi2/3Cu3Ti4O12are also shown.The different factors that may contribute to this unique scenario,including Joule heating,defect generation,and reduction of free energy for nuclei formation promoted by the applied field,are briefly discussed.Overall,the findings we bring here are exclusive as they show an exploitable way that allows rapid processing of materials with good control over particle and grain coarsening.

NiWO4 powders prepared via polymeric precursor method for application as ceramic luminescent pigments

Ni WO4 was prepared using the polymeric precursor method and studied in terms of physical and chemical properties to verify its stability for industrial applications as pigments.The characterization was accomplished using thermal analyses,X-ray diffraction(XRD),scanning electron microscopy(SEM),photoluminescence(PL)and UV–Vis spectroscopies,colorimetric coordinates,and Raman spectra.Increasing the temperature,successive exothermic reactions were observed and they are related with thermal decomposition of the organic compound.The stability was reached at^700℃.The material is verified to become completely free of second phase at^800℃.The end Ni WO4 powders showed an intense charge transfer(CT)-related tail centered in the ultraviolet region,resulting in a yellow product.In addition,the powders exhibited broad excitation band and broad deep blue–green emission band,which were enhanced with increasing powders’crystallinity.