Kazi Hanium Maria

Structural phase transformation and hysteresis behavior of Cu-Zn ferrites

A series of Cu1-xZnxFe2O4 ferrite (with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) compositions were synthesized using the standard solid-state reaction technique. X-ray diffraction was used to study the structure of the above investigated samples. The theoretical and experimental lattice parameters (ath and aexp) were calculated for each composition. A significant decrease in density and subsequent increase in porosity were observed with increasing Zn content. Curie temperature, TC, has been determined from the temperature dependence of permeability and found to decrease with increasing Zn content. The anomaly observed in the temperature dependence of permeability was attributed to the existence of two structural phases: cubic phase and tetragonal phase. Low-field hysteresis measurements have been performed using a B-H loop trace from which hysteresis parameters have been determined. Coercivity and hysteresis loss were estimated with different Zn contents.

Production and Properties of Carbon Nanotube/Cellulose Composite Paper

Multiwalled carbon nanotube/cellulose composite papers have been prepared by mixing the cellulose with MWNT/gelatin solution and drying at room temperature. The CNTs form an interconnected network on the cellulose paper and as a result CNT paper sheet exhibits enhanced electrical properties and thermal stabilities. It is found that both sides of CNT paper sheet have the uniform electrical conductivities. The sheet exhibits strong microwave absorption in the microwave range of 10.5źGHz. The CNT/cellulose paper is as flexible and mechanically tough as the pure cellulose paper. This work provides a novel and simple pathway to make CNT/cellulose sheet as multifunctional biomaterials for electronic, magnetic, semiconducting, and biotechnological applications.

Influence of Annealing Conditions on Nanocrystalline and Ultra-Soft Magnetic Properties of Fe75.5Cu1Nb1Si13.5B9 Alloy

The magnetic and structural properties of FINEMET alloy with a composition of Fe 75.5 Cu 1 Nb 1 Si 13.5 B 9 were investigated after primary and secondary crystallization of amorphous ribbon sample. The crystallization behavior and the nanocrystal formation of the samples were performed by differential thermal analysis (DTA) which in turn was supported by X-ray diffraction (XRD) study. Temperature dependence of initial permeability of amorphous and devitrified toroid shaped samples has been measured. Enhancement of Curie temperature of the amorphous alloy has been observed due to the irreversible structural relaxation. With the appearance of nanocrystalline phase the Curie temperature of the residual amorphous phase gradually decrease with the increase of annealing temperature. Their temperature dependence reflects the characteristic annealing temperature evolution of the basic magnetic parameters in these nanocrystalline systems. Saturation magnetization, M s , increases with annealing temperature T a for the samples and finally decreases during annealing at a temperature much higher than peak crystallization temperature.

Effect of gelatin on the water dispersion and centrifugal purification of single-walled carbon nanotubes

We report a convenient and effective procedure for the water dispersion and purification of single-walled carbon nanotubes (SWNTs). The purification procedure involves a combination of dispersion and centrifugation, in which gelatin; an environmentally friendly material is used as a dispersing agent. It has been found that an aqueous solution of gelatin effectively disperses SWNTs for more than a month. Another advantage of using gelatin as a dispersing agent is that it can be easily removed by washing with water and filtration. The centrifugation procedure employs a centrifugal force of about 2500 times the gravitational force to separate the particles. Although carbonaceous and metallic impurities usually have higher density than SWNTs in arc-produced carbon soot, the centrifugation can easily remove impurities leaving undamaged SWNTs in solution when appropriate centrifugal force and a centrifugation time are used. Centrifugation is carried out for three times to sufficiently remove impurities. Finally, the SWNTs are separated from the gelatin by heating in water and filtering.