Shamima Choudhury

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.

Effect of Cerium doping on microstructure and dielectric properties of BaTiO3 Ceramics

A solid state reaction method was used to synthesize barium titanate (BT) and barium cerium titanate (BCT) ceramics at sintering temperature of 1473 K for 4 h. The effect of cerium (Ce) on the structure, microstructure and dielectric properties of BCT was investigated. The scanning electron microscopy (SEM) investigations revealed that the grain size increases with increasing Ce content. The X-ray diffraction (XRD) patterns showed mostly the BT phase, where the lattice parameter decreased with the addition of Ce. The temperature dependence of dielectric constant showed decrease in the phase transition temperature with higher Ce content. The dielectric constant decreased slightly with increasing frequency. The direct current (dc) density-voltage characteristics of the ceramics showed ohmic behavior for both the BT and BCT. As the temperature increased, the dc resistivity of the ceramics decreased. The activation energy increased with increasing Ce content.

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 synthesis methods and a comparative study of structural and magnetic properties of zinc ferrite

Zinc ferrite samples were prepared by two different routes which are chemical co-precipitation and standard solid state double sintering method. Structural properties of ZnFe2O4 were determined, and initial particle size was found as 5 nm in the samples prepared by chemical co-precipitation technique. The XRD patterns showed the single phase of ZnFe2O4 spinel structure and confirmed by the lattice parameter and the unmixed hkl values for both the synthesis techniques. M-H curves at room temperature showed superparamagnetic nature of the samples sintered from 200°C to 600°C, synthesized by chemical co-precipitation technique. The Mossbauer analysis at room temperature showed a doublet which is the signature of superparamagnetic nature, and it is in agreement with the acquired M-H curves. The magnetization of ZnFe2O4 synthesized by chemical co-precipitation method was found higher than the magnetization of ZnFe2O4 synthesized by the solid-state double sintering method in the sintering temperature from 1100°...

Problems and Prospects of Science Education in Bangladesh

Scientific and technological know‐how, not the amount of natural resources, determines the development of a country. Bangladesh, with insignificant natural resources and a huge population on a small piece of land, can be developed through scientific and technological means. Whereas it was once the most sought‐after subject at secondary and postsecondary levels, science is losing its appeal in an alarming shift of choice. Problems in science education and possible solutions for Bangladesh, which has limited resources for encouraging science education, are presented.

Ultra-soft magnetic properties and correlated phase analysis by 57Fe Mössbauer spectroscopy of Fe74Cu0.8Nb2.7Si15.5B7 alloy

A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe74Cu0.8Nb2.7Si15.5B7 was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mossbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark field (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. K...

Investigation of various magnetic features of spinel type cobalt ferrite (CoFe2O4) nanoparticles tuned by annealing temperature

Cobalt ferrite (CoFe2O4) nanoparticles synthesized by chemical co-precipitation method were studied to see the effect of annealing temperatures on the structural parameters and magnetic properties of the sample. X-ray powder diffraction (XRD), transmission electron microscope (TEM) and SAD pattern demonstrated that single face (fcc) spinel structure of CoFe2O4 has been formed showing particles in completely crystalline state which was further confirmed by the lattice parameter and the unmixed hkl values. The particle size is in the range of about 5-10 nm depending on the annealing temperature from 200°C to 400°C. The grain growth occurred monotonically with the increase of annealing temperature. The magnetic properties demonstrated a strong dependence on particle size. The saturation magnetization Ms, remanent ratio Mr/Ms and coercivity Hc increased with the increase of particle size. The hysteresis curves for samples of different grain size showed the ferrimagnetic behavior which is completely analogous to the slow relaxation sextet peaks of Mossbauer spectroscopy. Other parameters such as chemical shift, quadruple splitting and hyperfine field and site occupancy of Fe3+ were determined by Mossbauer spectroscopy. Ferrimagnetic to superparamagnetic transition temperature known as blocking temperature TB was determined from the temperature dependent magnetization curves. With the increase of grain size, Blocking temperature also increases. Maximum entropy changes due to magnetic phase transition were also observed for mentioned annealing temperatures in the context of Magnetocaloric effect.

915 STRATIFICATION OF RISK FACTORS FOR NEPHROPATHY IN HYPERTENSIVE DIABETICS

Objectives: Significant proportion of diabetics develop nephropathy in time and hypertension is considered as an adverse influencing factor.The aim was to identify risk factors related to possible deterioration in renal function among Bangladeshi type 2 diabetic hypertensive (DH) subjects. Method: Diabetic subjects with normal renal function (estimated GFR ≥60 ml/min and urinary albumin <30 mg/day) were included in this cross sectional study. Hypertension was taken as BP ≥140/90mmHg when untreated or taking ≥2 antihypertensives. Results: In DH group 342 and another 496 normotensive diabetic (DM) as control group were included. The comparisons between 2 groups respectively showed systolic BP 130 ± 14 vs. 118 ± 11 and diastolic BP 80 ± 7 vs. 76 ± 6, mmHg; (p < 0.001). The diabetes duration was 8 ± 5 vs. 8 ± 4 yrs, HbA1c 8.1 ± 1.8 vs. 7.1 ± 1.3, %; Serum creatinine (SCr) 0.9 ± 0.1 vs. 0.9 ± 0.2, mg/dl and LDL 103 ± 35 vs. 99 ± 37, mg/dl; (P =NS) were similar. The differences in 2 groups, though mostly clinically less significant, were for age 55 ± 8 vs. 53 ± 8 yrs, (p < 0.001); BMI 25 ± 4 vs. 24 ± 2 kg/m2, (p < 0.03); 24hr urinary albumin (Uralb) 10.9 ± 6.4 vs. 9.6 ± 6.4 mg/day (p < 0.01) and estimated GFR 80 ± 20 vs. 84 ± 21 ml/ming/1.73m2, (p < 0.004). Bivariate correlations showed only age had a negative association with SCr, Uralb and eGFR. Further stratification showed around 65% from both DH and DM groups was in the lower range of eGFR (60-90 ml/min).When DH group was compared for eGFR above and below 90 ml/min (33 vs. 67%), no difference was seen for most of the clinical or laboratory parameters (systolic 129 ± 12 vs. 130 ± 14 & diastolic BP 80 ± 7 vs. 79 ± 7, mmHg; and SCr 0.7 ± 0.1 vs. 0.9 ± 0.1, mg/dl; p = NS) Conclusion: It is found that majority of type 2 diabetics with hypertension had lower normal renal function which could only be identified by estimating GFR. Both groups of high and low renal function had similar traditional clinical and laboratory parameters. Additional tools are needed to stratify which of the hypertensives are more at risk for developing nephropathy.