Journal of Progress in Physics of Applied Materials
Volume:3 Issue: 1, Jun 2023

Alkali halides crystals occur in either NaCl structure or CsCl structure and the crystalline alkali halides are important both purely scientific and technological. The importance and applications in several optical, optoelectronic, and electronic devices led to the preparation and characterization of polycrystalline aggregates (with reduced crystallite sizes at or below micro level) of several pure and hybrid (mixed and/or doped) alkali halides in the recent decades. Polycrystalline aggregates of alkali halides can be cut into any shape and polished for their utility in device applications. There are several reports available in the past about two decades on the polycrystalline aggregates of simple and hybrid alkali halides. Presented herewith is an overview of various studies made on the preparation and properties of polycrystalline aggregates of simple and hybrid alkali halides (both single-phased and multi-phased) focusing the results reported by the present author and his co-workers. The reported results have indicated that the optical (particularly absorption and photoluminescence) and electrical (particularly dielectric) properties can be tuned significantly by reducing the crystallite sizes of the polycrystalline aggregates of alkali halides.

In this paper boron doped carbon nanowires have been studied by density functional theory (DFT) with the help of hybrid approximation. The morphology of the studied carbon nanowires with diamond structure, was cylindrical with [100], [110], and [111] growth directions. The carbon atoms on the lateral surfaces were saturated by hydrogen atoms. The results showed that the band gap energy of carbon nanowires has decreased compared to bulk diamond by reducing the quantum dimensions to one dimension. Then the effect of boron atom substitution was studied. The calculation results revealed that changing the growth direction causes interesting behaviors in the study of atomic substitution. Hence, using boron atom dopants are very important in increasing the density of electronic states in [100] and [110] directions. Substitution and change in growth direction caused a change in the position of the Fermi level. Boron substitution in [110] carbon nanowire caused the metallization of the structure, for the nanowire with [111] growth direction it caused a change in semiconductor type, and for the nanowire with [100] growth direction it caused the band gap energy to decrease.

In this paper, the synthesis and structural and optical properties of activated carbon /metal oxide nanocomposites have been studied for energy storage applications. Activated carbon / nickel oxide, activated carbon / iron oxide, and activated carbon / cobalt oxide nanocomposites were synthesized by green synthesis from carbonaceous waste and their structural and optical properties were investigated. The prepared nanocomposites were characterized by X-ray diffraction (XRD), UV-Vis optical absorption spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy techniques. The XRD results of the activated carbon / metal oxide nanocomposites, in addition to the activated carbon background, show a polycrystalline phase corresponding to NiO, Fe3O4, and Co3O4 oxides. According to SEM images, a carbon porous background was observed in nanocomposites, which is filled with metal oxide nanoparticles and these nanoparticles present on its surface non-uniformly. The band gap results of nanocomposites showed the presence of two shoulders clearly indicating the presence of two components in the nanocomposite, i.e., activated carbon (3.62-4.65 eV) and metal oxide (3.0 eV- 4.25 eV). In FTIR analysis, in addition of the carbon-carbon bonds, specific peaks were observed in the range of k=400-700 cm-1, indicating that AC/ metal oxide nanocomposites have been successfully synthesized.

In the fields of science and engineering, photoluminescent fibers have been employed for a variety of purposes, including optical storage, biological labeling, noninvasive imaging, solid-state lasers, light-emitting diodes, spectrum modifiers, and temperature sensors. Here, polyvinyl alcohol (PVA)-based microfibers comprising nanoparticles were fabricated via a simple stretching method as a highly luminescent and flexible material. The structural and optical features of the prepared microfibers were investigated using X-ray Diffraction (XRD), field emission scanning emission microscopy (FESEM) image and ion beam induced luminescence (IBIL) techniques. Utilizing XRD analysis, related tetragonal phase of Bi2WO6   and polymer based PVA peaks were found in the prepared microfibers. Prepared Bi2WO6 microfiber exhibited strong blue-green emission upon excitation of 2.2 MeV proton beam and under a UV lamp at room temperature. Furthermore, microfiber diameter was obtained in the range of 8-33 m. This highly luminescent microfiber is believed to be a good candidate for optical sensor and wearable optoelectronic applications.

Single crystal of 2-amino-4,6-dimethylpyrimidium 3,5-dinitrobenzoate dihydrate (2APDBD) was grown by solution growth technique. The X-ray diffraction reveals that 2APDBD crystal belongs to a centrosymmetric triclinic crystal system with space group P-1. The UV visible-NIR spectra confirm a peak at 350 nm with lower cut off wavelength shows a wide transmission window in the entire visible region. The electrical characteristics of 2APDBD crystal have a low density of defects and a low value of dielectric loss found from the dielectric studies.  To find out the third order nonlinear susceptibilities (χ(3)) Z-can analysis was used.

Single crystals of KCl(Zn) using different amounts of Zn impurity (0.5 and 1.0 mole percents) with and without rotating crucible were grown by Czochralski method. The speed of rotation and pulling rate of the seed crystal were adjusted at, 10 rpm and 12 mm per hour respectively. The crucible was rotated, in the opposite direction of crystal rotation, with 5 rpm. Crystals, with Zn impurity of 0.5 % grown by both rotating and fixed crucible, were found to be transparent and uniform. Since the KCl crystals with Zn impurity of 1% were not transparent, they were found not suitable for optics. Furthermore, it was observed that the upper and middle parts of the crystals grown with 1 mol% Zn impurity are more transplant but the lower part includes transplant and cloudy layers. The results show that a convenient rotation and pulling rate can improve the stability and uniformity of impurity distribution along the crystals.

In this research, ZnO/ ZnFe2O4 nanocomposites with a weight ratio (1:1) were made using hydrothermal method and annealing temperatures of 600°C and 700°C. Structural, optical, and magnetic properties of the synthesized powders were characterized using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), ultraviolet-visible spectrometer, and vibrating sample magnetometer (VSM). The results obtained from the XRD diffraction patterns confirmed the formation of the mixed phases, hexagonal zinc oxide and cubic spinel phases of pure zinc ferrite. FESEM images showed that with the increase of annealing temperature, the samples have a cohesive and agglomerated structure. The measurement of the absorption spectra of the synthesized samples showed that the absorption in the visible region increases with increase in annealing temperature. The optical band gap value for the ZnO/ZnFe2O4 composites were in the range of 2.1-2.2 eV which is between the band gap values of ZnO (3.37 eV) and zinc ferrite (1.8 eV). The hysteresis loops measured with VSM indicated a soft and weak ferromagnetic magnetic behavior for both samples.

The CSIR- National Physical Laboratory of India (NPLI) constantly prepares and disseminates Indian Reference Materials (Bharatiya Nirdeshak Dravya; BND®) in various areas. Recently, NPLI has prepared the Indian Reference Material (IRM) of α-Alumina to calibrate the Powder X-Ray Diffractometer (PXRD). In this report, the preparation and certification procedure of α-Alumina (BND 2001) has been examined as an Indian Reference Material that can be utilized as the primary standard for powder X-ray diffraction instruments. The developed IRM was utilized to calibrate PXRD for phase purity. The stability of the prepared α-alumina was studied by using powder X-ray diffractometer. The homogeneity and the particle size of the material were characterized by using scanning electron microscopy. The repeatability of the preparation and pertinent characterization were affirmed using different calibrated instruments. The phase purity of the material was verified by performing a round-robin test, and the related uncertainty estimations were reported in the paper.

The unique properties of magnetic nanoparticles have made them useful and important particles for use in various fields, especially in heat-based applications. This research presents a hopeful facet of magnetic hyperthermia by superparamagnetic Fe3O4/Alumina nanoparticles. We synthesized Fe3O4/Alumina nanoparticles of different sizes by sonochemical method and evaluated their ability to generate heat. We found by characterizations with Field emission scanning electron microscopy (FE-SEM), X-ray diffraction technique (XRD), and Transmission electron microscopy (TEM) the samples to be of spherical shapes and spinel structure whose diameter could be controlled in the range from 15 to 25 nm. The magnetic behavior of the samples determined using a vibration sample magnetometer (VSM) showed hysteresis loops with a coercivity (HC) close to zero, suggesting superparamagnetic behavior at room temperature. The saturation magnetization (MS) for sample 3 after synthesis is 23 emu/g. We also investigated the potential of the samples for magnetic hyperthermia using alternating magnetic fields at various frequencies. Samples 1, 2, and 3 achieved heat production rates of 0.22 °C/min, 0.41 °C/min, and 0.62 °C/min respectively under an alternating magnetic field with an amplitude of 120 Oe and a frequency of 250 kHz.

Graphyne is of great interest to researchers due to its unique electronic and mechanical properties, which make it a potentially valuable material for a wide range of applications. The importance of graphyne lies in its potential to enable new technologies and applications in a variety of fields, from electronics to materials science. In this paper, the density functional theory (DFT) calculation was used to investigate CO2 and N2 adsorption on pristine and oxidized γ-graphyne in both two horizontal and vertical directions at hollow and bridge sites. Based on the results, the highest stability was observed when the CO2 and N2 molecules approached the γ-graphyne sheet in a hollow space. Oxygenation of γ-graphyne led to increased CO2 adsorption capacity compared to pristine γ-graphyne. This can be attributed to the interaction between the Pπ electrons of the carbon in graphyne and carbonyl groups with the unbonded electron pair of the oxygen in CO2, leading to a more significant interaction of CO2 with the γ-graphyne surface. Furthermore, no significant N2 absorption was observed for oxygenated γ-graphyne.

In this work, an eco-friendly “green” nanocomposite of chitosan containing graphite and maghemite (g-Fe2O3) nanoparticles were prepared by solution casting method. The effect of g-Fe2O3 nanoparticles on structural, electric and dielectric properties of Chitosan-graphite (Cs-graphite) composites was investigated. The dielectric constant of Cs-graphite composites increased with incorporation of g-Fe2O3 nanoparticles. Among the composites Cs-20% graphite - 20% g-Fe2O3 has dielectric constant of ~16.5 at 1 MHz at room temperature. With increase in temperature the dielectric constant varied significantly. The conductivity of Cs-graphite is enhanced by one order of magnitude with addition of g-Fe2O3 nanoparticles, and the value is found to be 5.7x10-6 S/cm. Various parameters such as dielectric constant, dielectric loss, electric modulus, conductivity, activation energy were analyzed. Magnetic measurement of g-Fe2O3 nanoparticles and the PNCs showed superparamagnetic behaviour. A model is proposed to explain the observed dielectric behavior of polymer nanocomposites (PNCs). The formation of microcapacitors by incorporation of maghemite nanoparticles between graphite is proposed.

Additives as surfactant can affect the structural, morphological, and optical properties of WO3 nanostructures. However, it is important to find optimum amount of additive for obtaining the best nanostructure of WO3. Therefore, the effect of oxalic acid (C2H2O4) and potassium sulfate (K2SO4) concentration as organic and inorganic additives were studied in this work. Also, the effect of pH adjustment stage (before/after oxalic acid addition) in the synthesis process was investigated for the first time. The WO3 nanostructures were characterized by X-ray powder diffraction (XRD), Raman scattering, field emission scanning electron microscopy (FESEM) and diffuse reflection spectroscopy (DRS). In addition, the photocatalysis activities of the samples with suitable properties were studied. The results proved that the WO3 properties can be affected by additive concentration and pH value of the solution. The creation of uniform nanorods (the length to diameter ratio of 9.4) was showed by FESEM analysis due to the addition of K2SO4. The smallest crystallite size (about 24.10 nm) was obtained for the sample synthesized at low concentration of potassium sulfate with the band gap of 2.64 eV (the ratio of Na2WO42H2O:K2SO4 1:3). Furthermore, the 10 mg of synthesized nanorod displayed the meritorious degradation of methylene blue (10 ppm) under UV light and visible light with the degradation efficiency of 88% and 77% in 90 min, respectively.