Papers by Keyword: Crystallite Size

Abstract: In the research, we show that suboxidic Ti₇O₁₃ and rutile TiO₂ phases formed in addition to the general Ti₃O₅ phase when the sintering temperature was set at constant argon gas flow rate. Suboxidic Ti₇O₁₃ and rutile TiO₂ phases were removed by tuning the flow rate of argon gas at constant sintering temperature. At the 1300°C temperature, the smallest Ti₃O₅ nanocrystals with a size of ~9 nm were produced. Flat shaped particles of Ti₃O₅ crystals were observed in SEM measurements.

Abstract: The annealing temperature dependent on the structural and magnetic properties of hematite (α-Fe₂O₃) powders synthesized via the sol-gel method was studied. The sol-gel method is used to prepare nanoparticles for this experiment. The annealing treatment of 200°C, 400°C, 600°C, and 800°C has been carried out to modify the physical properties. The obtained nanoparticles are characterized by their structural properties using X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Then, magnetic properties were evaluated using Vibrating Sample Magnetometer (VSM). XRD results have shown an increase in crystallite size with an increase in annealing temperature from 35.10 nm to 60.17 nm. The increase in crystallite size can be attributed to the increase in the crystal structure’s internal energy, which promotes atomic diffusion. The FTIR results show an absorption that appears at the peak around ~530 cm^-1. It indicates that the Fe³⁺ cation has successfully formed. The VSM results show an increase in the value of H_c with an increase in the annealing temperature from 117 Oe to 461.5 Oe. It is supported by the increase of anisotropy constant and increasing temperature annealing.

Abstract: This paper studies how the various calcination temperatures affect the structural properties of Barium Titanate (BaTiO₃) and (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9) (BCZT) using solid-state reaction methods. BaTiO₃ and BCZT powders are calcined at various temperatures ranging from 1100°C–1300°C. Using X-ray diffraction, the phase formation, crystal structure and crystallite size of BaTiO₃ and BCZT powders were determined. The cubic crystal structure has been formed for BaTiO₃ and BCZT. At 1200°C, the reaction between BaCO₃ and TiO₂ was complete to produce BaTiO₃ composition. For BCZT composition were not fully react based on the phase structure in XRD due to impurity peak. Next, the crystallite size of BaTiO₃ powder becomes larger with increasing calcination temperature. Meanwhile, BCZT crystallite size becomes smaller when the calcination temperature is increased has discussed at the end of this paper.

Abstract: The paper discusses the change of phosphogypsum surface state produced by Apatit (Cherepovetsky branch, Vologda region) during calcination at 298-1173 K. The authors have determined the average size of its crystallites and studied the atomic composition of raw materials and finished composites that include crushed rock fraction (5-10 mm), oil bitumen, and polyethylene terephthalate additive (1.0-1.2 wt. %). The compounds present in calcined phosphogypsum have been analyzed by X-ray diffraction. The granulate was obtained by pelletizing phosphogypsum with a mixture of the above components. The paper presents the assessment of its physical and chemical properties. The granulated composites based on the specified samples of calcined phosphogypsum, bitumen, and melted polyethylene terephthalate waste show great promise for construction road works in European countries in summer and winter, as well as countries with tropical climates.

Abstract: In this paper, a theoretical model based on multi-gene genetic programming (MGGP) approach has been applied to predict the structural and magnetic properties in nanocrystalline Fe–Ni powders prepared by mechanical alloying (MA) using a planetary ball mill. The MGGP model was used to correlate the input parameters (milling speed, chemical composition, and milling time), to output parameters (crystallite size and coercivity) of nanocrystalline Fe–Ni powders. The model obtained was tested with additional data to demonstrate its performance and prediction ability. The MGGP model is a robust and efficient method to find an accurate mathematical relationship between input and output data. A sensitivity analysis study was applied to determine the most influential milling parameters on the crystallite size and coercivity.

Abstract: The paper is focused on one of the most important component of Portland clinker-on the tricalcium silicate. The study reported in this article is focuses on the changes in crystallite size of synthetic tricalcium silicate obtained using solid state reaction method. Crystallite size changes are monitored during the grinding in three types of laboratory mills in two different conditions. Changing in crystallite size at various grinding time up to 120 minutes are studied with the aid of X-ray diffraction and using the Scherrer equation. It has been found that the most efficient laboratory mill in terms of speed and fineness of the material was the planetary mill.

Abstract: In this study, doped ytterbium oxide (Yb₂O₃) nanoparticles (NPs) with different dopant type (Eu and / or Tb) and undoped were synthesized by wet chemical method using nitrate salt as a starting source. Afterwards, they were calcined at 900 °C for 4 h. The crystal structure phase, size, and morphology of undoped and doped Yb₂O₃ nanoparticles (NPs) were characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Undoped and doped NPs were exhibited cubic bixbyite-type crystal structure (Ia-3 space group). Lattice parameter changes caused by dopant element in NPs were examined using X-ray peak profile analysis. In order to investigate the occuring changes in the crystal structure, average crystallite size (CS) and lattice parameter (LP) values were computed with Williamson–Hall (W–H) and Cohen-Wagner (C–W) methods, respectively. It was observed that the crystal structure of the doped NPs expanded compared to the undoped Yb₂O₃ NPs, which explains the increase in the LP and CS values. The LP values of all the NPs were ranged from 10.444 Å (R² = 94.9) to 10.453 Å (R² = 81.8) while the CS of them were between 19 nm (R² = 95.9) and 24 nm (R² = 88.8). All the NPs exhibited nearly spherical and agglomerate structure and there were also few pores between the agglomerate particles in the structure. Besides, continuous agglomerate morphology formation was observed in particles containing Tb. The average nanoparticle size values were varied between 46 and 115 nm depending on the dopant element.

Abstract: Nanoparticles of La₂CuO₄ (LCO) with different particles and crystallite size have been synthesized by the sol-gel method. The samples have been sintered at 600, 650, and 700°C. The sintering process have been performed in atmospheric pressure and vacuum pressure. The structural and morphological properties of the samples have been investigated by the X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The XRD patterns of the samples have shown that all samples crystallize in orthorhombic structure with Bmab space group. Additionally, Rietveld refinement process have shown that higher sintering temperature, as well sintering process under vacuum pressure, can improve both phase purity and the crystallinity of the samples. SEM and TEM results have also shown that higher sintering temperature results in a sample with larger particle size.

Abstract: Hematite is one of the most stable oxide phases and has been used as a rock-art pigment material in the prehistoric era. Hematite in the form of ochre has been widely used in rock art, burial rites, cosmetics, and decorations on pottery surfaces. Hematite has several hues, ranging from red to black. The variety of hues might arise due to the differences in physicochemical properties of hematite such as crystallinity, crystallite size, morphology, and electronic structure. The differences in physicochemical properties in hematite pigments might be originated from the differences in the pretreatment technique used before application. Herein, we have conducted a thorough study to investigate the evolution of the crystal structure of hematite under various temperatures. We aim to determine the temperature needed to change the hematite color and uncover the transformation of crystallographic properties as a function of sintering temperature. The hematite was synthesized using the precipitation method with Fe (NO₃)₃.6H₂O as a precursor and ammonia (NH₄OH) solution as a precipitating agent. The study of the hematite structural evolution was carried out by varying the sintering temperatures from 600 to 900 °C and analyzing the products after sintered using X-ray diffraction technique. The results showed that hematite hue was gradually darkened as the sintering temperature increased as a consequence of higher crystallinity and larger crystallite size of hematite crystal. This study confirms that the origin of color changes in hematite is due to the heating treatment of hematite material.

Abstract: Pure and copper doped tin oxide nanoparticles were synthesized by co-precipitation method and are characterized by XRD, SEM, EDAX, UV-Visible, photoluminescence, and FT-IR analysis techniques. Tetragonal rutile structure is confirmed from XRD and the crystallite size is found to be between 3.8nm and 4.8nm. The optical band gap is observed from UV-Vis spectrum and is found to be 3.99eV and 3.93eV for tin oxide and copper doped tin oxide respectively. The optical band gap of pure and Copper doped tin oxide were blue shifted due to quantum confinement. Photoluminescence spectrum shows UV, blue and green emission peaks.