E. Sinha

Effect of Plasma Treatment on Structure, Wettability of Jute Fiber and Flexural Strength of its Composite

The aim of this article is to study the influence of physical treatment on morphology, wettability, fine structure of fibers and its impact on the interfacial adhesion of natural fiber-reinforced thermosets. For that purpose, jute fibers were treated with argon cold plasma for 5, 10, and 15 min and processed for composite with unsaturated polyester resin. Scanning electron microscopy (SEM) micrograph had shown the rough surface morphology and degradation of fiber due to etching mechanism causes by plasma. Surface properties of fibers before and after treatment were determined by mean of contact angle determination and fine structural details by Fourier transform infrared-spectroscopy (FT-IR). Plasma treatment resulted in the development of hydrophobicity in fibers, that is contact angle were found increasing with water. This could be due to the decrease in phenolic and secondary alcoholic groups or oxidation of basic structural component, lignin and hemicelluloses after plasma treatment as studied by FTIR. Rough surface morphology and development of hydrophobicity of fiber after plasma treatment resulted in the better fiber/matrix adhesion as revealed from SEM micrograph of plasma treated fiber composite. However, among all treated fiber composite, flexural strength of composite prepared with 10 min plasma treated fiber only had shown improve mechanical strength of ~14% in compare to raw fiber composite.

Diffuse phase transition of BaTi0.6Zr0.4O3 relaxor ferroelectric ceramics

BaTi0.6Zr0.4O3 ceramic was prepared through solid state reaction route. X-ray diffraction showed that the composition has cubic perovskite structure with space group Pm-3m at room temperature. Temperature dependency dielectric study of the ceramic has been investigated. Bulk density was determined using Archimedes principle and found to be ∼97% of X-ray density. The average grain size in the pallet is measured by an optical microscope and found to be 22.23 µm. The dielectric measurement revealed diffuse phase transition of second-order, where dielectric peak temperature (T m) is dependent of frequency showing relaxor-type behaviour. A clear deviation from Curie–Weiss law is observed in the paraelectric region. The dielectric relaxation rate follows the Vogel–Fulcher relation with E a = 0.1020 eV, T f = 106 K, ν0 = 8.5 × 1011 Hz.

Ferroelectric phase transition of Ba1− x Sr x Ti0.6Zr0.4O3 ceramics

Perovskite type Ba1− x Sr x Ti0.6Zr0.4O3 (with x = 0.0, 0.1, 0.2, 0.4 and 0.5) ceramics have been synthesized through solid oxide reaction route. The room temperature XRD study suggests the compositions have single phase cubic symmetry. Microstructural studies have shown a step decrease in grain size. The dielectric study reveals that the materials are of relaxor type and undergo a diffuse type ferroelectric phase transition. The diffusivity increases with increase in Sr contents in the studied composition range. The transition temperature decreases with increase in Sr contents due to the decrease in grain size.