Annual Report July 2012 June 2013  Bangladesh Atomic Energy Commission

4.1 Objective

4.2 Programme

• 
  Development and characterization of elemental, binary, ternary and quaternary semiconducting materials in thin film form.
  
• 
  Development and characterization of diluted magnetic semiconductor (DMS) thin films.
  
• 
  Preparation and characterization of graphene oxide based thin films for optoelectronic applications.
  
• 
  Studies on the fundamental properties of absorber and transparent coating materials of thin film solar cells.
  

Cadmium Telluride (CdTe) is a crystalline compound semiconductor, where Cd is a divalent element and Te is a hexavalent element is called II-VI (two-six) compounds. It is usually sandwiched with Cd sulfide to form a p-n junction photovoltaic solar cell. The objective is to prepare CdTe thin films on glass substrate by Vacuum Evaporation method and investigation of structural, optical and electrical properties by varying film thickness and also varying substrate temperature. The structural studies were carried out by XRD. Each film shows a preferred orientation along [111] plane of cubic phase, in addition two other prominent planes (220) & (311). The grain size of the films was small and was within the range from 32 to 52nm. With the increase of substrate temperature, the micro strain and dislocation density decreased. All the films have high absorption coefficient (~10⁵ cm^-1) above the fundamental absorption edge. The calculated band gap energy (Eg) was found to increase (1.49eV to 1.55eV) with varying thickness and decrease (1.56eV to 1.46eV) with varying substrate temperatures. The high absorption coefficient and nearly optimum band gap energy of this material is favorable for solar photovoltaic application, which are in agreement with others research work.

Infrared (IR) detection is an important subject for military and scientific applications. Graphene oxide (GO) is an attractive candidate for optoelectronic applications due to its fascinating optical and electrical properties. GO absorbs light in the infrared wavelength regime. Therefore, we investigate its infrared photodetecting properties. Solution of GO was prepared by improved synthesis method. Thin films were prepared on clean glass substrate with different concentration. It was found that photo detecting capacity of GO thin film varies with various concentrations. Current increases with concentration and time.

Since Indium Tin Oxide is an expensive material, graphene oxide (GO) can be used alternatively as a window layer in a thin film solar cell. Therefore our objective is to prepare GO thin film on clean substrate and characterize it for cost reduction and large area production. Thin films were prepared on glass with different concentrations. Thin films of concentration 0.5, 0.3, 0.15, 0.075 mg/ml were prepared. Films were annealed from 150C to 200C temperatures. Different optical and electrical parameters were studied. Surface study showed smooth top surface as seen by the scanning electron microscope. The annealed films treated without hydrazine revealed better performance than the hydrazine treated films. Non-reduced film showed insulating behavior.

Polymer is an expensive material in organic thin film solar cell. Therefore GO-based organic thin film solar cell replacing PEDOTT: PSS with chemically converted graphene loxide was characterized. The utilization of graphene oxide thin films as the hole transport and electron blocking layer in organic photovoltaics is demonstrated. Organic GO-based thin film solar cell was characterized. The photo voltage increased with illumination. The cell area was 2×2 mm². The resistance increased from 0.8 KΩ to 2.3 KΩ with the increasing voltage from 0.23 to 0.65 mV.

The objective of the present work is to prepare Co doped ZnO thin films to evaluate cobalt effects on the structural, optical, electrical and magnetic properties of the films. The X-ray diffraction pattern indicated that the Co doped ZnO is a hexagonal wurtzite structure without a second phase. The energy dispersive X-ray spectroscopy revealed that the Co ions were introduced into the ZnO. The calculated values of the lattice constants a and c were found to be 3.24111 Å and 5.19898 Å, respectively. It is observed a little different of lattice constant with Co (cobalt) variation. The XRD results indicate that Co-doped ZnO thin film prepared by spray pyrolysis deposition has good crystallite quality.

A good absorber material is the most important factor of thin film solar cell. The CuInS₂ materials band gap of about 1.5 eV matching almost ideally to the solar spectrum. CuInS₂ thin film has just attracted more attention recently. Very little work on thin thin films by spray pyrolysis has been reported. Therefore, the objective is deposition and characterization of CuInS₂ thin films to make it as an efficient material for solar cell absorber. The ternary compound semiconductor CuInS₂ (CIS) thin films have been successfully synthesized by a simple spray pyrolysis deposition (SPD) method. High values of optical absorption coefficient (10⁵ cm^-1 ) with near optimum band gap 1.45 eV have been obtained. All the films exhibit p-type conduction. The SEM images of the CuInS₂ thin films showed good compound formation. The XRD spectra of the samples showed tetragonal structure and good crystallinity was found in CIS-2 films. The sharp, high intensity and more characteristic peaks showed an improvement of crystallinity at 225C for the four different new concept of Cu:In:S ratio.

The objective of R & D and service activities of Health Physics Division are to ensure protection against ionizing radiation by means of: (i) population exposure control by monitoring environmental radiation and measurement of radioactivity in environmental samples, food stuffs, imported and exportable samples;(ii) occupational workers exposure Control by monitoring individual radiation exposure and workplace monitoring throughout the country in order to keep the radiation level below the dose limit as per recommendation of ICRP series 103, 2007 and as per requirement of NSRC Rule 1997; (iii) monitoring and control of radioactive sources of Atomic Energy Centre, Dhaka as per requirement of NSRC Rule-1997; (iv) Training and education on radiation protection; (v) Providing radiation protection service on demand basis.ª

The observed activity concentrations of ²²⁶Ra found in rain water samples varied from 0.15 Bql^-1 to 13.27 Bql^-1 with mean concentrations 4.52 ± 1.26 Bql^-1. The activity of ²³²Th was found in the rain water samples varied from 0.43 Bql^-1 to 22.66 Bql^-1 with mean concentration 4.36 ± 1.37 Bql^-1. The ⁴⁰K activity in these rain water samples was found to be in the ranged from 14.45 Bql^-1 to 182.45 Bql^-1 with average 59.66 ± 3.07 Bql^-1. No artificial radionuclide was detected at any of the sample.

The inter-comparison programme (IAEA-CU-2012-03) was initiated under joint collaboration between BAEC and IAEA. The natural and artificial radionuclides in water, hay and soil such as IAEA-01, IAEA-02, IAEA-03, IAEA-04 and IAEA-05 were determined for worldwide proficiency test in the Health Physics Division. The radioactivities of ⁴⁰K, ²⁰⁸Tl, ^210Pb, ²¹²Pb, ²²⁸Ac, ⁵¹Cr, ⁵⁷Co, ⁶⁰Co, ⁶⁵Zn, ⁸⁵Sr, ^137Cs, ¹³⁴Cs, ¹³⁹Ce, ¹⁵²Eu & ²⁴¹Am were measured in the samples using a low-level gamma counting system, which consists of HPGe detector.

The concentrations of ¹³¹I and ^99mTc in the air samples were to be varied from 0.19-60.67 mBq/m³ and from 0.25-40.27 mBq/m³. The radioactivity of Pb-212, Pb-214, Ac-228, Bi-214, K-40 were to be varied from 0.59±0.001- 295.39±0.004 mBq/m³, 13.55±0.0015-1910.88±0.01mBq/m³, 0.69±0.0085-570.77±0.016 mBq/m³ 7.85±0.007-2192.32±0.028 mBq/m³, 19.69±0.052- 256.07± 0.054 mBq/m³.

For Barendra region soil samples, it is found that the activity concentration of ²³⁸U ranges from 31.9±1.3 to 42.7±1.4 Bq/kg with mean 36.7±1.4 Bq/kg, activity concentration of ²³²Th ranges from 52.9±1.6 to 68.9±1.7 Bq/kg with mean 59.7±1.7 Bq/kg, activity concentration of ⁴⁰K ranges from 232.5±2.3 to 320.6±2.4 Bq/kg with mean 282.5±2.3 Bq/kg. For Mining region soil samples, activity concentration of ²³⁸U ranges from 31.3±1.3 to 48.3±1.5 Bq/kg with mean 37.1±1.4 Bq/kg, activity concentration of ²³²Th ranges from 44.5±1.5 to 81.9±1.9 Bq/kg with mean 56.9±1.7 Bq/kg, activity concentration of ⁴⁰K ranges from 222.0±2.3 to 475.7±2.5 Bq/kg with mean 343.7±2.4 Bq/kg.

Ten vegetable samples have been collected from the location of Tulatuli, Lambari and Moheskhali villages at Teknaf thana under Cox,s Bazar district. Vegetable samples have been counted for the measurement of concentrations of ⁴⁰K, ²²⁶Ra, ²³⁸U and ²³²Th. The average activity concentrations of ²²⁶Ra, ²³⁸U, ²³²Th and ⁴⁰K in papaya samples were 80.95±13.61, 64.77±38.47, 83.53±20.50 and 1691.45±244.98 Bq kg^-1, respectively.

The radioactivity ranges from 0±8.17E-05 – 646.926±9 E-03 mBq/m³ for ²¹⁴Bi which mean value of 323±4.5E-03mBq/m³ whereas the range of radioactivity concentration of ²¹⁴Pb was 0.231±2E-03 – 421±1.34 E-03 mBq/m³ which mean value of 210±1.6E-03 mBq/m³, whereas the range of radioactivity concentration for ²¹²Pb was 1.8±1.4 E-03to 117±3E-03mBq/m³, which mean value of 59.4±2.2E-03 mBq/m³, whereas the range of radioactivity concentration of ²²⁸Ac was 0±1.25 E-03–161 ±2E-03 mBq/m³ for which mean value of 80.5±1.6E-03, whereas the range of radioactivity concentration for ⁴⁰K was 0±5.12E-02–147.07±5.284E-02 mBq/m³ for which mean value of 73.5±5.2E-02 mBq/m³respectively.

In-Situ Environmental gamma-ray dose rate due to ⁴⁰K was measured at 15 locations of Atomic Energy Centre, Dhaka (AECD) using portable HPGe detector (Model No. GEM25P4-83). The dose rate was varied from 0.05851mGy.h^-1 to 0.1222 mGy.h^-1 with an average of 0.09232 ± 0.01663 mGy.h^-1.

The gross alpha and gross beta activity in bottled water of Bangladesh have been measured by using a zinc sulphide scintillation detector. 14 samples were collected from the different market of Dhaka city. The present study may helpful in establishing a regulatory limit on radioactivity in bottled water in Bangladesh.

Air samples have been collected from several locations in Dhaka city by using Hi-Volume Air Sampler (The Staplex Company, Model-IFTA-2, Sl. No.-22407) in air filters (TFA No.-2133). Total twenty air sample have been collected on air filters and the air filters were counted by HPGe detector. The HPGe detector was calibrated by standard source Eu-152 which was mixed with air filter in same geometry.

100 imported food samples were collected from local market viz. Ananda bazar, New Market, New super Market, Kaptan bazar, Moulavi bazar and Tant bazar (Narayanganj). Different Food samples such as Anchor Beans, Dabli, Ginger, Garlic, Onion, Rice, Red Wheat, Lentils, Basmati Rice, Chhola, Palm Oil and Soybean Oil were imported from different countries such as Australia, China, India, Pakistan, Maldives, Malaysia and Nepal. The radioactivity range of ²⁰⁸Tl and ²²⁸Ac of ²³²Th series are found to be (0.50- 4.82) Bqkg^-1 and (4.40 – 28.97) Bqkg^-1, respectively and that of ²¹⁴Pb and ²¹⁴Bi of ²³⁸U series are found to be (3.40- 26.77) Bqkg^-1 and (2.43- 32.03) Bqkg^-1, respectively. The radioactivity range of ⁴⁰K is found to be (93.19 - 418.52) Bqkg^-1. No artificial radionuclide was observed.

The concentrations of ¹³¹I and ^99mTc in the urine samples were measured with High Purity Germanium (HPGe) detector. It showed that the range of the concentrations were to be varied from 6.39 ±0.01 to 575.54±0.52 Bq/l and 12.67±0.02 to 413.12±0.18 Bq/l for ¹³¹I and ^99mTc respectively. The committed effective doses for those were also calculated using the radioactivity concentration and the dose coefficients according to ICRP publication 71. It showed that the range of effective doses were to be from 0.0152×10^-3mSv to 11.3×10^-3 mSv due to inhalation of ¹³¹I, on the other hand due to contamination of ^99mTc the range of effective doses were to be 0.595×10^-3mSv to 19.3×10^-3mSv. The committed effective doses were to be within 2mSv.

The highest gamma radiation exposure was 898.44 µSv. This dose was measured using TLD and it was placed behind the PET-CT scan machine. The radiation exposure due to neutron was 19.63 µSv. Here TLD was placed at the LTF panel in Cyclotron Vault. The radiation exposure due to gamma and for neutron is negligible in the PET-CT and cyclotron compared to other medical imaging modalities.

To measure ECCs, 100 new TLD cards were annealed. Before using as a field card the annealed TLD cards for measuring ECCs were placed on the surface of an ICRU slab phantom made from PMMA, sized 30 cm  30 cm  15 cm at Secondary Standard Dosimetry Laboratory (SSDL), Savar. The phantom was placed at 1 m distance from ¹³⁷Cs gamma emitting source, the dose rate at that distance was 67.600 mSv/h.

To determine energy response, 32 TLD cards were sent to Japan Atomic Energy Agency, Japan. Eight set cards, each having 3 TLD cards, were exposed to 2 mSv dose by using x-ray at eight different energies ranging from 37 to 162 keV. Two set cards were given same exposure by using ²⁴¹Am and ¹³⁷Cs sources having energies 60 and 662 keV, respectively. The irradiated TLDs were measured at Health Physics Laboratory (HPD) of Atomic Energy Centre, Dhaka using TLD reader (Model – 4500 Harshaw, Bicron). The measured doses were normalized relative to the dose of ¹³⁷Cs. The response of 7‐LiF: Mg, Ti TLDs in different energies was found to be within 0.85 – 1.15.

To verify the neutron dose measurement conversion factor which was determined (8.06 µSv/nC) previously, eight TL Cards (four elements, Model Harshaw BGN 6776) were annealed. The annealed TLD cards were placed on the surface of a slab phantom made from PMMA, sized 30 cm  30 cm  15 cm at Secondary Standard Dosimetry Laboratory (SSDL), Savar. The phantom was placed at 60 cm distance from ²⁴¹Am-Be neutron source, the dose rate at that distance was 0.344 mSv/h. The total exposure time was 87 minutes and the delivered dose was 0.499 mSv. The exposed TLDs were measured at Health Physics Laboratory (HPD) of Atomic Energy Centre, Dhaka using TLD reader (Model – 4500 Harshaw, Bicron). The average measured charge was 65.11 nC and using the conversion factor (8.06 µSv/nC) the average measured dose was determined 0.525 mSv (delivered dose was 0.499 mSv), which was within 5% variation.

Calibrated 50 TLD chips were packed into polythene sheet in 10 rows and 5 columns have been using for the measurement of effective doses of patients during CT scan such as chest, abdomen etc. Effective doses of eight patients have been measured and further work is under process.

Patients going through CAG have average effective dose of 61.13 mSv within a range of 1.01 mSv to 987.8 mSv, while those who underwent PTCA have average effective dose 109.79 mSv within 1.034 mSv to 923.10 mSv ,who underwent both CAG and PTCA have average effective dose of 151.70 mSv within 1.041 mSv to 886.90 mSv and who underwent PPM have average effective dose 33.02 mSv within 1.623 mSv to 312.30 mSv The average value of DAP found in this study are 6913.44 cGy-cm² for CAG, 4579 cGy-cm² for PPM which are comparable with those published by other authors. However the average value of DAP found for PTCA procedure is 16927.5 cGy-cm² which is significantly larger than those found by other authors.

During the reporting period, 1782 imported milk & milk products samples & other samples and exportable samples were tested in this division. The radioactivity level of ¹³⁷Cs in all the samples was within the limit as per Nuclear Safety and Radiation Control Rule 1997.

This division, the only individual radiation monitoring service provider in Bangladesh, has been providing service all over the country to the occupational workers who have been working in different radiation fields such as medicine, industry, agriculture, education and research. Till June 2013, the total number of organizations and radiation workers came under this service was 2931 and 6476, respectively.

During the reporting period, gross alpha and gross beta activity (04 samples) were tested in this division.

During the reporting period, 250 new TLD badges have been issued to radiation workers of 114 new organizations. Doses of 6987 TLD badges of 2354 old organizations were also measured quarterly.

The radiation level monitoring of five division of AECD viz. Health Physics Div, Non-Destructive Testing Div, Accelerator Facilities Div, Materials Science Div and Chemistry Div is being performed regularly.

Materials Science Division, Atomic Energy Centre, Dhaka is directly involved with the latest materials research and development work. In order to extend the research program on some advanced materials, this division bulk soft and permanent magnet ferrites are prepared by ceramic method, nano-particles of ferrites are synthesized by wet chemical method and the metallic nano-particles are prepared from amorphous ribbon by melt spinning technique. Structural, Magnetic and Electrical properties are studied using X-ray diffraction, scanning electron microscope, energy dispersive x-ray analysis, Mössbauer spectroscopy, vibrating sample magnetometer, B-H loop tracer and impedance analyzer, electrometer and Hall Effect measurement system. To develop academic program this division carries out various research programs through national and international collaboration under which post-graduate research projects such as M.Sc./M.Phil./Ph.D. are supervised. Services are provided to different industries and research organizations through XRD, VSM, SEM systems.

• 
  Development of spinel type soft ferrites using magnetite and commercial grade raw materials and study of their characteristic properties.
  
• 
  Synthesise, characterization and study of the magnetic and structural properties of nanometric scale ferrite/dielectric materials.
  
• 
  Development of ferrite permanent magnets from beach sand mineral magnetite extracted from Cox’s bazar beach sand.
  
• 
  Study of the magnetic and structural properties of amorphous/nanocrystalline materials.
  
• 
  Study of the structural and magnetic properties of perovskites.
  
• 
  Crystallographic characterization and quantitative phase study of inorganic, organic, thin film and unknown materials by XRD method.
  
• 
  In-situ high temperature phase transition study of binary alloys.
  
• 
  Study of the magnetic and electrical properties of microwave ferrite materials.
  
• 
  Mineralogical study of soil, rock, clay, terracotta and silt materials by XRD method.
  

Structural, magnetic and electrical properties of CoZn_xFe_2-xO₄ (x=0.0, 0.1, 0.2, 0.3 and 0.4) prepared by conventional solid state reaction method were studied. The decrease of lattice constant for pure cobalt ferrite than the reported value is also observed due to the presence of Co³⁺ ions. The sharp fall of the permeability with temperature indicates the homogeneity and the single phase of the studied samples, which have also been confirmed by XRD experiment. Permeability as a function of frequency decreases with Zn content up to x=0.3 and increases for x=0.4. The dielectric constant decreases with increasing frequency, which confirms the dielectric behaviour of the ferrite materials. DC electrical resistivity initially decreases for x=0.1 and then increases up to x= 0.4. The decrease of resistivity may be related to higher porosity, lower density of the sample.

Influence on the electromagnetic and transport properties of Fe-deficient Ni-Cu-Zn ferrites was studied. Ni_0.28Cu_0.10Zn_0.62O)(Fe₂O₃)_1-x where x= 0.00, 0.02, 0.04, 0.06 and 0.08 were prepared using the solid state reaction technique. The phase identification was carried out by x-ray diffraction. A slight increase of Curie temperature (T_c), saturation magnetization (M_s) and initial permeability (µ) have been found with increasing Fe-deficient. From the B-H loops, the romance (B_r) and coercive force (H_c) were determined. Saturation induction (B_s) and B_r/B_s are measured from low field B-H loops is found to increase with increasing Fe-deficient up to x = 0.04 thereafter decrease.

Hexagonal ferrite is a class of ceramic magnet having large technological applications such as permanent magnet, microwave device and magnetic recording media. In order to get permanent magnet four different compositions were prepared having formula SrFe₁₂O₁₈, BaSr₂(Fe₂O₃)6, SrCr(Fe₂O₃)₆ and SrSn(Fe₂O₃)₆. Further activities will be taken by melting all of the samples using an Induction Furnace for get a fine alloy composition.

The powder of diluted magnetic semiconductor Zn_0.9Ni_0.10O was prepared using standard solid state reaction technique. XRD patterns confirmed formation of single phase hexagonal Wurtzite structure of ZnO with a small signature of NiO. The lattice parameters ‘a’ and ‘c’ were calculated and they were found to be very close to the reported values for ZnO based DMS. Scanning electron microscopy (SEM) was used to study the surface morphology and grain size measurement. VSM and impedance analyzer measurements indicated dominant paramagnetic ordering along with a slight ferromagnetism in fabricated compositions.

Substitution of Ca in Mn_xZn_0.4Ca_0.6-2xFe_2+xO₄ ferrites, where x=0.30, 0.25, 0.20, 0.15and 0.10 sintered at 1300°C have been studied. The XRD patterns confirmed the single phase cubic spinel structure of samples without having any other intermediate phases. Curie temperature of the samples was determined and the values were found to be decreased from 365 to 335°C with increasing the Ca-content for the x values from 0.30 to 0.10, respectively. Real part of permeability decreases with increasing Ca-content for both the temperature and frequency dependent cases.

Structural, electrical, magnetic and dielectric properties of Ni-substituted Li_xMg_0.5Ni_0.5-2xFe_2+xO₄ ferrites, where x= 0.25, 0.20, 0.15, 0.10 and 0.00 sintered at 1300°C were studied. The bulk density of the samples decreased in the range from 4.47 to 4.21 gm/cc with increasing the Ni-content for the x values from 0.25 to 0.00, respectively. The XRD patterns confirmed the single phase cubic spinel structure without any impurity phases. Curie temperature of the samples was determined and the values were found to be decreased from 542 to 530°C with increasing the Ni-content. The temperature and frequency dependent permeability, loss tangent and Q-factor have been determined in the temperature range from 0 to 550°C and the frequency range from 1 to 500 kHz. Dielectric Constant and resistivity have been measured as a function of frequency and the values were found to be decreased with increasing frequency and decreasing Ni-content.

The effect of annealing condition on FINEMET type of alloy with nominal composition Fe₇₄Cu_1.5Nb_2.5Si₁₂B₁₀ prepared by rapid solidification method has been investigated on the structural and magnetic properties of the alloy. XRD results indicate that the sample form nano-structured Fe₃Si phase at 475°C. In the as-cast condition and for annealing temperature of 475⁰C, the Curie temperature of the sample was measured to be 425⁰C and 419⁰C, respectively and the Curie temperature of the residual amorphous phase decreases with increasing annealing temperature. Superior soft magnetic properties of the alloy were obtained at 550⁰C for 15 minutes of annealing time.

Barium hexaferrite with the general formula BaO.6(Fe₂O₃) has been prepared by double sintered method at sintering temperature of 1100ºC, 1200ºC and 1300ºC. Structural characterization of BaO.6(Fe₂O₃) by XRD is under process. Strontuim hexaferrite with the general formula SrO.6(Fe₂O₃) is under preparation.

Structural and magnetic properties of Fe_75.5Si_13.5Cu₁Nb₁B₉ soft magnetic alloys, obtained by rapid quenching method and subsequently annealed at various annealing temperature from 475°C to 650°C for different annealing time from 5 to 30 minutes, have been studied by X-ray diffractometer (XRD), Vibrating Sample Magnetometer (VSM) and Impedance. After getting the nanocrystalline phase, the Curie temperature of the residual amorphous phase gradually decrease with the increase of annealing temperature. The temperature dependence of initial permeability of amorphous and devitrified toroid shaped samples has been measured.

Nanocrystalline structure offers a new opportunity for tailoring soft magnetic materials. Nanocrystalline alloy in the form of ribbon with the composition of (Fe_0.95Co_0.05)_73.5 Cu₁Nb₃Si_13.5B₉ prepared by rapid quenching method has been studied for structural, crystallization behavior and nanocrystalline phase formation by Differential Thermal Analysis (DTA) and X-ray Diffraction (XRD) measurements. Nanocrystalline alloy with this composition shows excellent soft magnetic properties when they are heat treated above the crystallization temperature of the amorphous state and produce homogeneous ultrafine grain of α-Fe(Si) with bcc structure having average grain size D_g ≈ 18 – 24 nm. The results of evolution of magnetization of the amorphous samples are well correlated with results of crystallization behavior manifested by DTA measurement of samples previously annealed under identical temperature.

The paper reports the synthesis of NiFe₂O₄ nanoparticle by sonochemical method followed by sintering at temperatures ranging from 200-1400C for 3 hrs. We have successfully obtained ultrafine particles of 2-50 nm size in the heat treatment range of 200-1200C. This can be compared with the particle size in the range of 6-110 nm that was obtained by chemical co-precipitation of NiFe₂O₄ in our previous study in the similar range of heat treatment. Abrupt change of B-H loops manifested in coercivity, H_c and maximum induction, B_max due to the change of sintering temperature from 1200C to 1100C indicates transition from ferrimagnetic towards superparamagnetic state. NMR studies of the particles less than 5 nm (sintered at 200ºC) coated with biocompatible chitosan yielded T₁ and T₂ relaxivities as 0.001 and 0.045 sec^-1 ppm^-1 respectively. Higher value of T₂ relaxivity by an order of magnitude than T₁ indicates that this is suitable as T₂ contrast agent for magnetic resonance imaging.

Ultra-fine particles of Mn_1-xZn_xFe₂O₄ series (0x1) were synthesized through wet chemical co-precipitation method followed by calcination at 200C for 4 hours. Grain size determined by using the Scherrer’s formula has been obtained in the range of 2 nm for MnFe₂O₄ up to 6.8 nm for ZnFe₂O₄. Formation of ferrites has also been confirmed by selected area diffraction (SAD) patterns of TEM and Fourier Transform Infra-red Spectroscopy (FTIR). The particles of different compositions in the series have been coated with biocompatible chitosan in order to study their application as contrast agent for magnetic resonance imaging (MRI). Coating with chitosan has been examined by FTIR, where a strong bonding of chitosan molecules to the surface of ferrites is observed. Spin-spin, T₂ relaxivities of nuclear spins of hydrogen protons of the solutions for different ferrites were measured from concentration dependence of relaxation time by nuclear magnetic resonance (NMR).

We have prepared Co₈₂Zr₁₈ and Co₇₄Fe₈Zr₁₈ two-phase magnetic alloy in order to study their structural and magnetic properties by arc melting followed by suction casting. In order to study the disposition of different phases of binary two-phase alloy of Co₈₂Zr₁₈, the constituent phases of Co₁₁Zr₂ (or Co_5.1Zr) and Co₂₃Zr₆ have also been prepared under similar condition. X-ray diffraction and electron diffraction studies of Co₈₂Zr₁₈ and Co₇₄Fe₈Zr₁₈ reveal two-phase character of the alloy systems. Vicker’s hardness of both Co₈₂Zr₁₈ and Co₇₄Fe₈Zr₁₈ are considerably high. However, mechanical properties improved with the addition of 8 at.% Fe since this led to an enhancement of % deformation from ~4% to about 11%. Magnetic properties of these systems are governed by strong magnetic anisotropy of Co₁₁Zr₂ phase and antiferromagnetic behavior of Zr.

We report the possibility of the use of biocompatible chitosan coated ferrite nanoparticles for possible contrast agent in nuclear magnetic resonance applications. The single phase ferrite particles are synthesized by chemical co-precipitation (CoFe₂O₄ and Fe₃O₄) and by the route applying ultrasonic vibration (CoFe₂O₄ and Co_0.8Zn_0.2Fe₂O₄). Although magnetic anisotropy of CoFe₂O₄ nanoparticle leads to finite coercivity even for nanoensembles, superparamagnetic cobalt ferrite has been obtained by applying ultrasonic vibration in this study with almost zero coercivity and remanence. Substitution of Co by Zn in CoFe₂O₄ increases the magnetization with a small increase in coercivity and remanence. T₂ relaxivity of particles is much higher synthesized by the application of ultrasonic vibration than chemical coprecipitation. We report that the T₂ relaxivity of nuclear magnetic resonance of these particles are two orders of magnitude higher than corresponding T₁ relaxivity. Thus these particles are evidently suitable as contrast agent for T₂ weighted MR images.

We report the mechanical and magnetic properties of the binary eutectic alloys Co_90.5Zr_9.5 and Fe_90.2Zr_9.8, and the pseudo-binary alloys Co_82.4Fe₈Zr_9.6, Co₇₈Fe_12.4Zr_9.6 and Co_49.2Fe_49.2Zr_9.6 prepared by arc-melting followed by suction casting. Suction-cast Co_49.2Fe_49.2Zr_9.6 gave the highest VHN of 713 as well as the highest magnetic moment of 1.92 (at 5K) and 1.82 _B (at 300K) per formula unit. The magnetization vs. applied field data at 5 K show a directional anisotropy, which has been explained in terms of collinear and non-collinear magnetization due to exchange frustration and transverse spin freezing due to the presence of antiferromagnetic Zr.

In the present study, ZnFe₂O₄ nanoparticles were synthesized by the chemical co-precipitation followed by calcinations at 473 and 673 K for 4 hrs. Particle sizes obtained were 4 and 6 nm for the calcination temperatures of 473 and 673 K respectively. To study the origin of system’s low temperature spin dynamic behaviour, temperature dependence of susceptibility  was investigated as a function of particle size and frequency. Temperature dependence of  at different frequencies also resulted in peak shift. Relaxation time dependence of peak temperature obeys a power law, which provides the fitting parameters within the range of super paramagnetic nature of the particles. Further, dependence of relaxation time and peak temperature obeys Vogel-Fulcher law rather than Néel-Brown equation demonstrating that the particles follow the behaviour of superparamagnetism of slightly interacting system.

Total 329 samples of ZnO, BaTiO₃, Cu, Dolomite, NA-MMT, DDA-MMT, Ribbons, Ferrites, Sand, Ash, Films and Compounds from different Universities and Industries have been studied by XRD.

Total 124 samples of Fe-Ni, Al alloy, SnCu, PVC, CuInSe, Al-Zr oxide, Ba and Li-Mg Ferrites, Archeological Sample, ZnO, Ribbons, Ferrites, Films and Compounds from different Universities and Industries have been studied by SEM & EDX.

To improve the research quality, Materials Science Division is involved with a collaboration work titled on Magnetic and structural properties of Ferrites, Nanocomposites and Perovskite Materials with International Program for Physical Sciences (IPPS) under International Science Program of Uppsala University, Sweden.

On the other hand, to help in the development of manpower, this division is involved with the preparation of question paper, evaluation of examination paper, evaluation of thesis paper in the level of M.S. /M.Phil./Ph.D. at different public Universities in the country. This division is also involved with the collaboration research work with different public and private Universities in the country.

7. NON-DESTRUCTIVE TESTING DIVISION, AECD

7.1 Objective

Non-Destructive Testing (NDT) Division has been working as an excellent centre for R & D, acquisition & dissemination of knowledge and technology on NDT in the country. Since its inception, NDT Division has been working with right earnest to develop and promote the science and practice on NDT and its application in industries throughout Bangladesh having the objective of reducing foreign dependency and to make Bangladesh self-reliant on NDT technology for facilitating its socio-economic development.

Considering the present industrial needs NDT Division has taken up the following programs:

• 
  Research & Development on NDT techniques those are useful to our industries
  
• 
  Render valuable NDT services and consultancy to the local industries
  
• 
  Training and Certification to develop expertise and proficiency of local NDT practitioners to meet international standard
  

To control & maintain the quality of industrial products & to assure reliability to the users, it is required to use NDT applications in all stages of processes for the uninterrupted operation of the industrial components. Considering the demands of the industries & to make these industries benefit & productive, NDT Division is continuing it’s application based R&D programs. For this purpose the details technical working procedures of both conventional & advanced NDT methods like Radiographic, Ultrasonic, Magnetic Particle, Liquid Penetrant & Eddy Current Testing have been developed to solve various technical problems exists in industries. Depending on the geometry, dimension, orientation of the components, service condition, anticipated defect nature in the component and applicable codes & standards, the working procedures were developed for the inspection of different equipment used in various industrial sectors viz. Power Generating Equipment, High Rise Building Structures, Ship Buildings, Fertilizer Factories, Pharmaceutical Industry, Cement Factory, Amusement Park etc.

The scope of this work is to evaluate the corroded zones and to measure wall thickness of insulated pipes by tangential radiography in order to make a correlation in assessing the remaining life time of power plants, petroleum, petrochemical industries etc. without removing specially insulations from the metal part so that the cause of accident due to fire & leaks, low production or unpredictable shutdown of plants can be minimized. For this purpose radiographs of few small diameter pipes have been taken using X-Ray and by evaluating the film the thickness of pipe has been assessed primarily & attempt has been taken to perform the above mentioned program applying modern technology Digital Industrial Radiography.

Eddy Current Testing Method has been using as a quality control tool for the inspection of numerous engineering components particularly the ferro-magnetic and non-ferromagnetic Heat Exchanger Tubes, Feed Water Heater Tubes, Condenser Tubes, Air Conditioner Tubes etc. of Petrochemical Industries. A program on the above topic has been taken whose objective is to interpret the signals arising from different known defects and finding the better response of a defect at a particular frequency by utilizing Multi Frequency Eddy Current Testing Equipment - MS 5800 with Multiview 6.0R software. Few experiments have been performed with the equipment having options to use 4 frequencies simultaneously. For this purpose artificial defect of ASTM standard tube of Stainless Steel material has been analyzed experimentally.

The scope of this work is to make the digital image of an object onto the imaging plate by the ionizing radiation and processing the image with the aid of appropriate computer facility in order to enhance their contrast & spatial resolution and to sharpen and smoothen their edge definitions for analysis of object structures. Digital image of few welding joints have been analyzed to assess the wall thicknesses by adjusting different parameters of Pentameter Window available in the I See! Software and thus enhanced digital image quality was achieved upon applying this function.

NDT Training and Certification program has been taken up in BAEC since 1986 under the framework of IAEA/RCA plan to build a strong and effective infrastructure at international standards & to attain self reliance in this field. Under this program, NDT Division has organized 61 National Training Courses on various NDT methods from which about 950 people have been trained. A large number of the above trained people have been working abroad with good reputation.

During this tenure, NDT Division of AECD in active collaboration with NDT Personnel Certification Committee organized the following two National training courses as per ISO 9712.

This 62^nd National NDT training course was attended by 15 participants from 03 Govt. and 03 private organizations like Gas Transmission Co. Ltd., Titas Gas Transmission & Distribution Co. Ltd. Bangladesh Air Force, Bangladesh Industrial X-ray, Castle Construction Ltd., Star Bangla Technical Training Institute and 02 self Participants.

This 63^rd National NDT training course was attended by 15 participants from 08 Govt. and 02 private organizations like Ashuganj Power Station Company Ltd., Bangladesh Inland Water Transport Corporation, Bangladesh Air Force, Gas Transmission Co. Ltd., Natural Gas Fertilizer Factory Ltd., Training Institute for Chemical Industries, Jamuna Fertilizer Co. Ltd., Bangladesh Army, Solutions NDT & Inspection Services, Lucky Group of Companies and 02 self Participants.

i) A training course entitled “Radiographic Film Interpretation for A-Star NDT Training and Service Centre (BD) Pvt. Ltd.” was organized at NDT Division AECD during 03-07 February 2013 where 05 participants of A-Star NDT Training and Service Centre (BD) Pvt. Ltd. attended.

ii) A training course entitled “Radiographic Testing Method for BAF Personnel” was organized at AECD during 17 Feb – 07 Mar 2013 where 10 officials of different grades of Bangladesh Air Force took part.

iii) A national workshop entitled “AECD-BSNDT-SAJ National Workshop on Advanced NDT & Plant Condition Monitoring”, was arranged jointly by Bangladesh Society for Non-Destructive Testing (BSNDT), Saj Engineering & Trading Company and Atomic Energy Centre, Dhaka (AECD) held at AECD from 25-26 January 2013. A total no. of 92 delegates from 40 different Government/Private organizations & Universities took part in this workshop. Local Experts along with 05 foreign experts delivered theoretical talks & practical demonstrations in the technical sessions of the workshop.