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In this work, Ba0.9Sr0.1TiO3, Ba0.7Sr0.3TiO3, Ba0.5Sr0.5TiO3, Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr2+ and Ca2+) on the structural, electrical and optical properties of BaTiO3 ceramics. Sr2+ added samples showed a tetragonal structure which became slightly distorted with increasing Sr2+ concentration and finally achieved a cubic structure for x = 0.50. Ba0.5Ca0.5TiO3 also retained their tetragonality with limited solubility. Presence of second phase, CaTiO3 demonstrated the fact of restricted solubility. The concurrent effect of Sr2+ and Ca2+ didn't alter the tetragonal structure. Sr2+ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba1-xSrxTiO3 was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48 eV to 3.28 eV with increasing Sr2+ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ∼547 for Ba0.5Ca0.25Sr0.25TiO3 ceramics. Both Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr2+ and Ca2+ was a good approach enhancing materials electrical as well as optical property.

In this work, BaTiO3 and Ba(MgxZr0.15Ti0.85-x)O3, (x ​= ​0.005, 0.015, 0.025) ceramics were fabricated by a solid-state sintering route. All of the samples derived a single tetragonal perovskite structure. No significant impurity phases were indicated. A grain growth retardation phenomenon was observed. BaMg0.015Zr0.15Ti0.835O3 ceramics exhibited a maximum dielectric constant of 2010.18 ​at 102 ​Hz, showing a strong dependency on crystallite size (36.79 ​nm). The conductivity of the specimens was mainly due to polaron hopping, while the exponential conductivity factor ranged from 0.96123 to 1.00000. BaMg0.005Zr0.15Ti0.845O3 ceramics showed the lowest electrical resistivity (1.09 ​Ω-m at 102 ​Hz) due to its maximum grain size (873.72 ​nm). Although the complex impedance spectra was a straight line for BaTiO3 ceramics, it became a semicircle for Ba(MgxZr0.15Ti0.85-x)O3 ceramics exhibiting the presence of equal resistance into the grains and grain boundaries. The maximum remnant polarization (44.04 ​μC/cm2 for loop-5) with a coercive field of 1.67 ​kV/cm was observed into BaMg0.015Zr0.15Ti0.835O3 ceramics. The obtained optical band gap energy for BaTiO3 was 3.12 ​eV while the value for BaMg0.005Zr0.15Ti0.845O3, BaMg0.015Zr0.15Ti0.835O3, and BaMg0.025Zr0.15Ti0.825O3 ceramics were 3.10 ​eV, 3.06 ​eV and 3.23 ​eV respectively. Although BaMg0.015Zr0.15Ti0.835O3 ceramics demonstrated the extraordinary electrical and optical properties, the obtained results in BaMg0.005Zr0.15Ti0.845O3 specimens were satisfactory.

Heating water with solar energy is easy and effective in both domestic and industrial areas. The initial implementation cost of a solar-water-heating system is high but long term use of it makes it cost effective. For geographical location, Bangladesh is very suitable for using it. In a solar collector system, collector area is an important design factor. To achieve better thermal performance, 0.81m2 solar collector was used in this study. Commonly used flat plate collector takes more space to be installed. In Bangladesh, space on the roofs of houses and industries are limited and so there is a little scope to use flat plate collector system. Compound parabolic collector can solve this problem. Solar collector with compound parabolic collector needs less space than flat plate collector with reflector. When compound parabolic concentrator was attached with the solar collector, thermal performance improves. Compare with other alternatives that improve thermal efficiency, compound parabolic concentrator shows better thermal performance. Compare thermal efficiency of the consecutive three months. In this system, when water flow rate increase, outlet water temperature decrease but thermal efficiency increases. It is also observed that when solar intensity increases, thermal efficiency also increases likewise when solar intensity decreases, thermal efficiency also decreases. In this research, outputs of different similar researches are compared to show the effectiveness of the compound parabolic concentrator based solar collector. The compound parabolic concentrator reflects more solar radiation, eventually directs it to the collector and increased the difference between the inlet and outlet water temperature.

Thin films of magnesium oxide (MgO) and aluminium (Al) doped MgO were deposited onto glass substrate at 350 °C by spray pyrolysis technique. The microstructure, morphology and optical properties of the MgO films have been investigated and characterized as a function of Al doping concentration (0–2) mol%. X-ray diffraction study confirms the successful fabrication of MgO thin films. The surface morphology of the films reveals that the morphology of the MgO films greatly changes with Al doping concentration. The optical properties like optical transmittance, optical band gap, refractive index, extinction coefficient, real & imaginary part of the dielectric constant, electron energy loss function and optical conductivity have been characterized and discussed. It has been found that the optical properties of MgO films have been changes significantly with Al doping concentration.

85ZnO–15TiO2, 75ZnO–25TiO2, and 65ZnO–35TiO2 nanocomposites were prepared by the sol-gel method. The structural, morphological, antibacterial, optical and photocatalytic performances were analyzed. Three phases, i.e., hexagonal wurtzite, anatase, and hexagonal ZnTiO3 were detected for each of the specimens. The crystallite size reduced as the TiO2 content increased, whereas the corresponding values for 65ZnO–35TiO2 were 39.02 nm (ZnO), 20.40 nm (anatase) and 34.89 nm (ZnTiO3). A particle size reduction phenomenon was observed as approaching from 85ZnO–15TiO2 (66 nm) to 65ZnO–35TiO2 (47 nm). The antibacterial activity was measured through the inhibition of the growth of Escherichia coli bacteria by ZnO–TiO2. The maximum inhibition zone for bacterial growth was achieved for 65ZnO–35TiO2 (19.7 mm). Two types of absorption bands were obtained within the UV–Visible region. However, the blue shifting of these bands resulted in the enhanced band gap. Moreover, 65ZnO–35TiO2 demonstrated the highest photodegradation efficiency of methylene blue dye backing the reason for the lowest particle size (47 nm). The photodegradation efficiency values of 85ZnO–15TiO2, 75ZnO–25TiO2 and 65ZnO–35TiO2 at 100 min were 72.9%, 80.2%, 90.7% respectively.

In this study we examine the solar radiation conversion into thermal energy and energy storage into phase change material (PCM) in the photovoltaic thermal (PVT) collector system. In order to get better solar radiation satisfactory compound parabolic concentrator (CPC) has been mounted on PVT collector. In this study outdoor experiments were carried out to compare performance study between clear day and semi-cloudy day in winter season. PVT solar collector with CPC that act as a solar collector, a PCM tank and CPC was integrated into one piece because of simplicity structure for PCM storage in same unit. No connection pipe i , e small area needed for installation and continuous tracking was not needed for better concentration ratio. Total heat loss, total useful energy, thermal efficiency and overall efficiency of the collector by varying different parameters were evaluated using modified equations derived for the energy storage system from the basic derivation of Hottel–Bliss–Whillier. The results show that thermal efficiency of solar collector varies from 40% to 50% for clear day and around 40% for semi-cloudy day. The overall efficiency of the PVT collector between 55% and 63% for clear-day and around 46–55% for semi-cloudy day whereas corresponding top loss value around 3 W/m 2 K for clear day and around 2.5 W/m 2 K for semi-cloudy day. Up to around 3 m from entrance, the plate temperature was increased and then it became nearly steady. But in case of applying same system without PCM temperature was increased sharply.

Ceramic industries in Bangladesh are using raw materials imported from abroad. For this reason, manufacturing costs of the ceramic products are quite high. Now a day, the demand of the ceramic products in Bangladesh is very high. To reduce the cost of these ceramic products, different types of local clays can be used as raw materials with quartz and feldspar to manufacture ceramic ware, tile, and sanitary ware. In this research, locally available clay of nine different areas had been used to prepare the sample. Their physical and mechanical properties were tested and studied to evaluate the quality of the products. Khagrachari (canal) and Padma (north) clay have shown better physical and mechanical properties. This clay is suitable for the production of ceramic ware and Khagrachari (Hill) and Padma (South) clay for quality tiles. The compositions of locally available clays were determined using X-Ray Fluorescence (XRF). XRF analysis showed the presence of excess SiO 2 content in the form of Silicate, Fe 2 O 3, and TiO 2 but the amount of Al 2 O 3 in most of the compositions was also not up to the minimum level. Observing the physical and mechanical properties, it is found that the local clay materials are suitable to use in ceramic industries by replacing the imported/traditional clay to reduce cost and make a perfect use of our natural resources.

Characterization of both uncalcined and calcined eggshells was done in this work. Raw eggshells turned out as a good source of calcite phase. Calcined eggshells had a mixture of lime and portlandite phase. A significant impact of calcination temperature on the percentage of generated phases was observed. Qualitative as well as semi-quantitative phase analysis, morphological characterization and physical property estimation was done for the produced powder. The influence of synthesized raw material on soil stabilization and biomaterial formation was further assessed. The eggshell turned out as a potential source of raw material for various sectors. Resumo A caracterização de cascas de ovo não calcinada e calcinada foi feita neste trabalho. A casca de ovo mostrou-se uma boa fonte de fase de calcita. As cascas de ovo calcinadas apresentaram mistura de cal e fase portlandita. Observou-se impacto significativo da temperatura de calcinação na porcentagem das fases geradas. Foram realizadas análises de fase qualitativa e semiquantitativa, caracterização morfológica e determinação da propriedade física para o pó produzido. Foi avaliada a influência da matéria-prima sintetizada na estabilização do solo e na formação de biomaterial. A casca de ovo mostrou ser uma fonte potencial de matéria-prima para vários setores.

An experimental investigation was conducted to examine the fretting fatigue behavior of physical vapor deposition-coated CrN film deposited on Ti - 6Al - 4V specimens contacted on both sides with pads of the same material. Behavior against the CrN -coated specimens was characterized through the determination of fretting fatigue strength up to 107 cycles. Fretting damage of specimen surface was characterized by SEM and surface profilometer. The experimental results from the S – N tests indicate that the CrN coating is effective to improve the fretting fatigue strength until about 106 cycles, but over 106 cycles, the strength is lower than that of uncoated specimens. The enhanced fretting fatigue resistance can be attributed to the improved hardness of the CrN film due to change of bias voltage during the film deposition. It has also been concluded that below and about 106 cycles, there is smaller influence of bias voltage on fatigue strength, whereas, over 106 cycles, fatigue strength is clearly changed by bias voltage as well as contact pressure.

Titanium alloy has an attractive strength-to-weight ratio and good fatigue properties. However, the titanium alloy has very poor wear resistance, therefore, surface treatments must be considered in order to make the contact parts. Hard thin film deposited by PVD technique is well-known to improve the wear resistance. In this study, chromium nitride ( CrN ) film was applied to titanium alloy and its effect on the fatigue behavior was investigated. Ti -6 Al -4 V alloy was used as a substrate material. The CrN film was deposited by arc ion plating (AIP) method at two different negative bias voltages because the film hardness, crystal orientation and surface morphology were strongly depended on the bias voltage during the deposition. Tension-tension fatigue test and tensile test were carried out to investigate the fatigue properties. As the result, the fatigue strength was influenced by the deposition of the CrN film, especially, the fatigue strength was remarkable decreased by the deposition of the CrN film at high negative bias voltage compared to the uncoated specimen and the deposition of the CrN at low negative bias voltage. The difference of the fatigue strength was also investigated on the basis of crack initiating behavior during fatigue test and tensile test.

The work was done to understand the effects of naturally occurred bone and teeth ash on the physical as well as mechanical properties of bone china products. Both bone and teeth ash was prepared following conventional thermal decomposition method. Locally found cattle bones and tooth was utilized for this purpose. Three different routes of powder or ash preparation i.e. boiling-wood firing, excavating-calcination and boiling-calcination were followed. The calcination temperature was fixed at 950°C-2 hours. After that, density and phase identification of ash was carried out. Finally, bone china product was manufactured using powder compaction and slip casting route. Firing was done at a constant temperature (1150°C-2 hours). Further characterizations (density, percent firing shrinkage, percent water absorption and modulus of rupture measurement) of the sintered samples were evaluated. Boiling-calcination route was found to be the most superlative route. However, enhanced properties of bone china were obtained by the addition of teeth ash.

PVD technique incorporating CrN coating was applied to the titanium alloy (Ti-6Al-4V) and its effects on the fatigue life and fatigue strength were studied in this paper to explore the fatigue behavior of Ti-6Al-4V specimens. A CrN film deposited by arc ion plating (AIP) improved the mechanical properties; specially hardness and fatigue life of Ti-6Al-4V specimens. The properties were studied using XRD, hardness and fatigue testers. The fatigue life of CrN-coated Ti-6Al-4V specimens was improved significantly compared to those of uncoated specimens. The enhanced fatigue life can be attributed to the improved hardness of CrN film due to change of bias voltage during the film deposition. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the substrate surface. It has been determined that the fatigue fracture of the substrate-coating composite is dominated by the fracture of the CrN film since fatigue cracks have been observed to form first at the surface of the film and subsequently to propagate towards the substrate. It has also been concluded that the increase in fatigue properties of the coated substrate is associated mainly with the changing of bias voltage during the coating observed in most of the maximum alternating stress range explored in this work.

Titanium alloy offers several material properties including strength-to-weight ratio and good fatigue properties. Wear resistance of Titanium alloy is comparatively lower. To improve its wear resistant properties surface treatment must be considered. Hard thin film deposited by PVD technique is well-known to improve the wear resistance. In this study, ceramic film (CrN) was applied to titanium alloy and its effect on the fatigue behavior was investigated. Substrate material for this work was Ti-6Al-4V. As the film hardness, crystal orientation and surface morphology were strongly depended on the bias voltage during the deposition, the ceramic film was deposited by arc ion plating (AIP) method at two different negative bias voltages. Tension-tension fatigue test and tensile test were carried out to investigate the fatigue properties. As the result, the fatigue strength was influenced by the deposition of the ceramic film, especially; the fatigue strength was remarkably decreased by the deposition of the ceramic film at high negative bias voltage compared to the uncoated specimen and the deposition of the ceramic at low negative bias voltage. On the basis of crack initiating behavior during fatigue test and tensile test the difference of the fatigue strength was also investigated.

A fracture behavior of PVD coated ceramic film deposited on Ti-6Al-4V specimens was evaluated for a fretting fatigue geometry in which specimens were contacted on both sides with pads of the similar material. Behavior against the ceramic film coated specimens was characterized through the determination of fretting fatigue strength up to 107 cycles. Fretting damage of specimen surface was characterized by SEM and surface profilometer. Ceramic film coating has a great effect to improve the fretting fatigue strength. From the experimental results of S-N tests it is clear that until about 106 cycles ceramic coating is effective to improve the fretting fatigue strength. But over 106 cycles the strength is lower than that of uncoated specimens. The enhanced fretting fatigue resistance can be attributed to the improved hardness of ceramic film due to change of bias voltage during the film deposition. It has also been concluded that there is smaller influence of bias voltage on fatigue strength below and about 106 cycles; whereas, over 106 cycles, fatigue strength is clearly changed by bias voltage as well as the contact pressure.