Effect of light attenuation on polymerization of ceramic suspensions for stereolithography

Weak bonding strength between interlayers can seriously affect the quality of ceramic parts manufactured by stereolithography. Therefore, the possibility of using chemical bonds to strengthen the adhesion within these parts and the extent to which may be effective are of interest. Thus, a multi-exposure model was built to illustrate the state of this interface. The secondary conversion of a cured layer defined as conversion rate increment caused by decayed ultraviolet (UV) light in a subsequent exposure was selected to represent the extent of a chemical bond. The level of UV light attenuation occurred when travelling through a suspension layer was determined using the Attenuation Law. When decayed light illuminated a cured layer, it underwent further photopolymerization, which was detected by temperature change. The secondary conversion was affected by parameters including the incident energy dose and the propagating length. Optimization of these parameters helped to achieve higher chemical bond ratio.     

Immobilization of tannery industrial sludge in ceramic membrane preparation and hydrophobic surface modification for application in atrazine remediation from water

Chromium laden waste produced from tannery industry was immobilized in ceramic matrix for fabrication of the tubular single channel microfiltration membranes by extrusion. The presence of chromia resulted in substitutional solid solution formation with alumina and catalyzed mullite phase growth, hence increasing the mechanical and chemical stability of the membranes. The structural, morphological and water permeation characteristics of the membranes were studied to analyze their formation mechanism and effect of different parameters, viz. the sintering temperature, amount of waste added, presence of organics and extent of chromium immobilization. The surface of the macroporous membrane was hydrophobically modified, by polydimethylsiloxane (PDMS), producing contact angle of 141°. The process efficiency of the hydrophobic membrane was assessed in terms of the removal of atrazine, a contaminant of emerging concern, following the principle of hydrophobic interaction. Effect of different operating parameters affecting atrazine removal, viz. transmembrane pressure, cross flow velocity and filtration time was studied in cross flow filtration mode. High atrazine removal of >95% was obtained along with the maintenance of high flux during the filtration operation. The prepared cost-effective microfiltration membranes can thus be further modified for efficient water treatment applications.     

The effect of A-site nonstoichiometry on the microstructure,electric properties,and phase stability of NaNbO3 polycrystalline ceramics

The impact of A-site nonstoichiometry on the microstructure, electric properties, and phase stability of sodium niobate ceramics (Na_1+xNbO₃, x = ?2 to 1 mol %) was investigated. All the components maintained an orthorhombic antiferroelectric (AFE) structure. The grain size increased from 3.9 to 14.3 μm with the variation in x from ?2 to 1. The AFE–FE phase transition electric field dramatically increased from 100 kV cm^?1 at x = 0 to 170 kV cm^?1 at x = ?2, confirming the enlarged energy barrier between AFE Pbma and FE Pmc2₁ phase under external field in A-site deficient components. This is attributed to the lattice compressive stress generated by introducing proper A-site vacancies. Combined results of transmission electron microscopy and Raman spectroscopy indicated that the AFE distortion of Pbma phase was significantly enhanced in A-site deficient components, which jointly contributed to the stability of AFE phase in A-site deficient NaNbO₃ material.