Micro and Nanosystems - Volume 12, Issue 2, 2020

Background: Lithium Niobate (LiNbO3) is a ferroelectric material suitable for a variety of applications. Its versatilityis made possible by the excellent electro-optic, nonlinear, and piezoelectric properties of the intrinsic material. Objective: Study of structural, microstructural and electrical propertiesare to understand the structure and topography of the composites. Methods: The sample of LiNbO3 was prepared by solid state reaction method at high temperature using high purity ingredients. Results: The analysis of the X-ray diffraction at room temperature confirmed the trigonal structure. The grains are more or less homogeneously distributed throughout the surface. The dielectric constant and dielectric loss are decreases with increase in frequency. The material has high dielectric constant and low dielectric loss at room temperature. The magnitude of real impedance decreases with rise in temperature which shows negative temperature coefficient of resistance behavior.The nature of the conductivity in solids is analyzed which obeyed Jonscher’s power law. The temperature-dependence of dc conductivity indicates that the electrical conduction in the material is a thermally activated process. Conclusion: The compound exhibits a dielectric anomaly at high temperature suggesting ferroelectric–paraelectric phase transition. The activation energy of the material is found to be 0.00184 eV in the high temperature region of Arrhenius plot for electrical conductivity. The nature of temperature dependence of the dc conductivity exhibited the NTCR behaviour of the material.

Background: Mg2TiO4 – based ceramics have proven their potentiality in the field of wireless communication systems. In the past, Mg2TiO4 ceramics was considered a quite optical response material in thin film form. Moreover, there is very few studies have been done whatever the proposed work in the present study. Objective: To prepare Mg2TiO4 nano-powders with the help of High Energy Ball Mill (HEBM) and intend to investigate its effect on crystal structure, microstructure and on thermodynamic behavior of MgO-TiO2 system. Methods: Mg2TiO4 ceramics were synthesized using Mechanical alloying method from high- purity oxides MgO and TiO2 (99.99%) of Sigma Aldrich (St. Louis, MO). Results: From the experimental studies it is observed that the powder’s particle size decreases with an increase of milling time. XRD analysis is carried out for phase confirmation of the mixed Mg2TiO4 powder. Further, the result also showed that there is structural changes occurred in the sample by high energy ball milling process, milled at different times. The nanocrystalline nature Mg2TiO4 powder was confirmed from microstructure taken by Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). Further, differential thermal gravimetric analysis has been carried out to investigate the thermal behavior of milled Mg2TiO4 -powder (35 hours). Conclusion: In work, the effect of mechanical alloying on structural, microstructural and thermal properties of nanocrystalline Mg2TiO4 powders has been investigated systematically. The effect of milling time on particle size, crystal structure and the microstructure was studied using XRD, FE-SEM, TEM and DSC/TGA analysis. The microstructural analysis (FE-SEM and TEM) reveals the nanocrystallinity nature of MTO ceramics prepared by mechanical alloying method. The thermal decomposition behavior of the milled powders was examined by a Thermo-Gravimetric Analyzer (TGA) in argon atmosphere.

Objective: The aim of the present study was to prepare highly luminescent additive composite polymer with hyamine 1622 and Thioglycolic Acid (TGA) coated CdTe Quantum Dots (QDs). Methods: The additive nano-composite was synthesized by the colloid synthesis method for the first time. The properties like particle size, fluorescence efficiency, fluorescence imaging, self-assembling, quantum dots, encapsulation, etc. were characterized by the employing of instrumental techniques such as 1H and 13C NMR, Fourier Transform Infrared spectroscopy (FT-IR), BAB image analysis system spectroscopy, Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Results: CdTe quantum dots were stabilized successfully in the solid phase by hydrophobic conversion with hyamine 1622 as the cationic surfactant. The experimental results show that the prepared composite is ideal for various applications, easily synthesized, safe, and maintain good fluorescence properties. Conclusion: The newly prepared additive nanocomposite having sharp and narrow excitation/ emission properties is expected to be applicable in biomedical/analytical systems.

Background: The alternative of oil is highly essential in the present context due to the acute shortage of oil as well as increasing demand for it from different public and private sectors. Since 1980, attention has been focused on coal-water slurry as an alternative fuel for the power generation industry and a suitable substitute for oil in several industrial applications. One of the exciting areas in Coal Water Slurry (CWS) is coal–water-alcohol slurry in which different alcohol compound can act as a dispersant for the stabilisation of coal–water slurry. Objective: The objective of this paper is to prepare a high concentration coal–water-alcohol slurry using glycerol, glycol and ethanol as an additive, and different particle size distribution of coal. This will increase the surface activity of the coal thereby, decreasing the viscosity of the slurry. Method: Two bimodal samples are prepared in which coarse particles are (212 μm - 300 μm), (150 μm – 212 μm) and fine particle below 75 μm. Three types of alcohol additive namely glycerol, glycol and ethanol are used as a dispersant. Malvern Particle size analyzer is used to measure the particle size distribution of the coal samples. Rheological study of CWAS was conducted using HAAKE RHEO STRESS 1. Result: From the experiment, it has been concluded that the optimum addition of glycerol in water is taken as 90:10 of water and glycerol ratio because after that, there is no further decrease in the value of viscosity. An optimum value of glycol and ethanol mixed in water was determined and found as in the ratio of 86:14 and 82:18, respectively. Conclusion: From different parameter studies like coal concentration, pH, temperature, apparent viscosity and stability, it has been concluded that coal-water-glycerol slurry is better than other coal water- alcohol slurry. This is because of the presence of more OH- groups in glycerol. The static stability of this coal-water-alcohol slurry exists for the maximum period of 31 days.

Background: Research on harvesting solar energy through an artificial photosynthetic device is gaining momentum in the present era. The device is a promising solution to the energy crisis by overcoming the crunch in fossil fuel and low efficiency of heat engine. Reports are available on design of isolated parts of the photosynthetic device, for example, only sensitizer or only redox unit containing metallo-peptides. Objective: An attempt has been made to design an in silico photoreaction center in a single chain protein matrix containing all the three basic units: sensitizer, electron donor, and acceptor mimicking the photosynthetic reaction center II. Methods: A single chain of a protein containing a closely packed transmembrane four-helix bundle (PDB ID 2bl2 A) is selected for the purpose. The protein is suitably mutated in silico to accommodate the basic elements of a reaction center: Mn-Ca binding site as water oxidizing moiety, Fe-binding site as quinine reducing moiety, and MgDPP as photosensitizer to achieve the desired function of photoredox reaction. Results: A photoelectron transport protein has been designed, which may incorporate into the bilayer membrane system. It has the potential to photo-oxidize water to oxygen on one side and reduce quinone on the other side of the membrane. The stability and transmembrane orientation of the molecular device in an artificial membrane system has been validated theoretically by molecular dynamics study. Conclusion: An attempt to incorporate in silico all the elements essential for a photoelectron transport device into a single chain transmembrane protein model is the first of its kind. Donor and acceptor moieties are separated on the inner and outer side of a membrane bilayer. These features make the model unique and novel. The design of the model is the first step towards the study of experimental viability of the model, which remains to be validated in future.

Background: Industries such as thermal power plants use coal as a source of energy and release the combustion products into the environment. The generation of these wastes is inevitable and thus needed to be reused. In India, coals with high ash content usually between 25 to 45% are used. The refractory bricks that were used earlier in steel industries were mainly based on silica, magnesia, chrome, graphite. In modern days, several other materials were introduced for the manufacturing of refractory bricks such as mullite, chrome-magnesite, zircon, fused cast, and corundum. The materials selection for refractory brick manufacturing depends on various factors such as the type of furnace and working conditions. Objectives: The current work aims to focus on the fly-ash subjected to spark plasma sintering process with a maximum temperature of 1500 °C and pressure 60 MPa for 15 minutes and to characterize to observe the properties with respect to their microstructure. Methods: Fly-ash collected from Rourkela Steel Plant was sintered using spark plasma sintering machine at the Indian Institute of Technology, Kharagpur. The powder placed in a die was subjected to a heating rate of 600-630 K/min, up to a maximum temperature of 1500 °C. The process took 15 minutes to complete. During the process, the pressure applied was ranging between 50 to 60 Mpa. 5-10 Volts DC supply was given to the machine with a pulse frequency of 30-40 KHz. The sintered product was then hammered out of the die and the small pieces of the sintered product were polished for better characterization. The bricks collected from Hindalco Industries were also hammered into pieces and polished for characterization and comparison. Results: The particles of fly-ash as observed in SEM analysis were spherical in shape with few irregularly shaped particles. The sintered fly-ash sample revealed grey and white coloured patches distributed around a black background. These were identified to be the intermetallic compounds that were formed due to the dissociation of compounds present in fly-ash. High- temperature microscopy analysis of the sintered sample revealed the initial deformation temperature (IDT) of the fly-ash brick and the refractory brick which were found to be 1298 °C and 1543 °C, respectively. The maximum hardness value observed for the sintered fly-ash sample was 450 Hv (4.413 GPa) which is due to the formation of nano-grains as given in the microstructure. The reason behind such poor hardness value might be the absence of any binder. For the refractory brick, the maximum hardness observed was 3400 Hv (33.34 GPa). Wear depth for the sintered fly-ash was found to be 451 μm whereas for the refractory brick sample it was 18 μm. Conclusion: The fly-ash powder subjected to spark plasma sintering resulted in the breaking up of cenospheres present in the fly ash due to the formation of intermetallic compounds, such as Cristobalite, syn (SiO2), Aluminium Titanium (Al2Ti), Magnesium Silicon (Mg2Si), Maghemite (Fe2O3), Chromium Titanium (Cr2Ti) and Magnesium Titanium (Mg2Ti), which were responsible for the hardness achieved in the sample. A large difference in the maximum hardness values of sintered fly-ash and refractory brick was observed due to the hard nitride phases present in the refractory brick.

Objective and Method: In this present research, a simple hydrothermal implantation technique for synthesizing N,S co-doped reduced graphene oxide (NS-r-GO) has been presented in which thiourea was used as a single-source precursor of N and S atoms. Results: Maximum N and S atoms, with an atomic percentage of 3.50 and 7.50 (at.%), were achieved in the GO matrix at the reaction temperature of 250°C. Introduction of N and S atoms into the GO lattice was confirmed by X-ray photoelectron spectroscopy (XPS). Different chemical bonds such as –C– S–C, C=O, N–O, and C–N–C have been suggested from the corresponding C1s, N1s, O1s, and S2p high-resolution XPS spectral analyses. Conclusion: FT-IR measurement also confirmed the presence of different functional groups as well as the formation of different bonds such as –OH, –N–H, –C=O, –C–OH, and C-S. XRD and Raman spectroscopy analyses confirmed the defects structures that arose from the penetration of N and S atoms into the GO lattice.

Background: Polymer matrix-based composites are the workhorse of the composite industries. Besides, the idea of modifying the polymer matrix by various inorganic fillers has greatly drawn the attention of materials engineers due to their diversified applications and advanced properties. Objective: The objective of this work was to prepare and characterize Titania (TiO2) and Silica (SiO2) nanoparticles and develop 1wt%, 3wt%, 5wt% and 10wt% TiO2 and SiO2 incorporated epoxy-based nanocomposites. Here, we used TiO2 incorporated epoxy composites as a model to compare the effectiveness and contribution of locally available nano SiO2 in the epoxy matrix. Method: The TiO2 nanoparticles were prepared by most famous and conventional sol-gel method and SiO2 nanoparticles were extracted from Padma river (silica) sand obtained from Rajshahi city, Bangladesh from a very easy and inexpensive route. Both TiO2/epoxy and SiO2/epoxy nanocomposites (approximately 1.3-1.5 mm thick) were prepared via a solution casting method incorporating the TiO2 and SiO2 nanofillers in the epoxy matrix. Results: The XRD patterns and SEM image ensure the formation of TiO2 and SiO2 nanoparticles. A number of tests reveal that mechanical properties especially hardness and young’s modulus of the nanocomposites have increased while decreasing the tensile and flexural strength than neat epoxy due to the incorporation of nanofiller. It is visible that, TiO2/epoxy nanocomposites have shown better performance than the virgin epoxy but surprisingly in most cases, nano SiO2 exhibited comparable and even better contribution than TiO2/epoxy nanocomposites. This indicates that the use of TiO2 in epoxy might be replaced by inexpensive nano SiO2 to be used in various structural sectors. Conclusion: The TiO2 and SiO2 nanoparticles were synthesized successfully. The preliminary experiments predict that the addition of nanoparticles (TiO2, SiO2) converts the composite from being ductile into a brittle material where SiO2/epoxy shows comparable performance with TiO2/epoxy nanocomposites.