Papers by Keyword: Crystallinity

Abstract: The production of nitrogen-doped carbon quantum dots (N-CDs) from walnut shell waste is crucially important for green chemistry and sustainable development. Herein we fabricate N-CDs by a bottom-up solvothermal method and use the novel N-CDs to modify the electron transport layer (ETL) in perovskite solar cells (PVSCs). The N-CDs can produce 440 nm fluorescence under the excitation of 350 nm light with a quantum yield of 8.75%. Infrared absorption spectra show that N-CDs contain high proportions of nitrogen-containing and oxygen-containing functional groups. , Through the incorporation of N-CDs into SnO2 ETL, the formation of defects is inhibited, and crystallinity is improved. This is because the N-CDs contains a large number of functional groups such as nitrogen and oxygen and these groups would interact with the ETL and perovskite, which reduce the defect/trap centers in PVSCs. Therefore, the N-CDs modified PVSCs show improved power conversion efficiency. This study provides a novel way to use walnut shell waste to synthesize N-CDs and achieve efficient and stable perovskites solar cells.

Abstract: Silica-calcium phosphate nanocomposite (SCPC) is a porous bioactive resorbable bioactive ceramics. Incorporating apatite bone cement (AC) formulation of tetracalcium phosphate-dicalcium phosphate dihydrate and SCPC has contributed to the higher mechanical strength of a new prototype apatite cement formulation. This in-vitro experiment aims to investigate the bioactivity of AC formulation using simulated body fluid (SBF). The samples consist of two groups of AC formulations (n=4). The first group, AC with 10% SCPC and the second group AC without SCPC, was immersed in the SBF for 14 days. The samples before and after immersion were analyzed by X-Ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscope (SEM). The samples' size and degree of crystallinity were analyzed statistically using Shapiro-Wilk, Levene, and Mann-Whitney test. As a result, there was no significant difference in the crystal size and the degree of the crystallinity of both samples. The surface morphology of all samples were coated with hydroxyapatite after immersing in the SBF solution. Both AC formulations with and without SCPC have bioactivity as the bone substitute materials. Combining AC with SCPC50 is a promising method to improve the bioactivity and mechanical strength of calcium phosphate bone cement.

Abstract: In this study, an experimental investigation of the effect of addition of Alumina (Al₂O₃), Zinc Oxide (ZnO), and Silicon Oxide (SiO₂) particles powders on the mechanical behavior and crystallinity of the PLA films was carried. Granulated of Polylactic acid (PLA) and ceramic powders with different concentrations were prepared to form PLA/ZnO and PLA/ZnO-SiO₂-Al₂O₃ composites films using a solvent casting process. Morphology of PLA and composite films were examined by optical microscopy, chemical and crystal structures of composites are analyzed by (ATR-FTIR) spectroscopy and XRD techniques. Tensile strength and young modulus are determined by traction test. The obtained result by optical microscopy shows the micrograph of PLA samples with different composition are evenly distributed on the film surface. The intensity of the absorption band located at 754 cm^-1 which correspond to the crystalline phase of PLA is verified by the ATR-FTIR characterization. The XRD diffraction shows that the ceramic particles influence on the peaks intensity of PLA films localized at 19.5 ° C and 22.5 ° C, which indicate an augmentation in the crystallinity of the composite films. Mechanical tests show Tensile strength and Elasticity modulus are improved after the addition of Oxide Particles to Polylactic acid films.

Abstract: Bamboo saw dust (BSD) as reducing agent in low-grade manganese ore leaching is used, and therefore the performance of cellulose hydrolysis will affect the percent recovery of Mn ore. This work is studies the effect of sulphuric acid and speed rotation on hydrolysis of BSD. The crytallinity of BSD were investigated. The parameters considered in this work are sulphuric acid concentration and the speed rotation by using 2³ +3 factorial design. The significant factor, main and interaction effect were investigated based on Analysis of Variance obtained from statistical software. It shows that the sulphuric acid concentration is the main factors that affects the percentercent crystallinity compared to rotation speed. It is proved by the DOE analysis and supported by the crystallinity analysis of BSD before and after hydrolysis process. The optimum condition that can be suggested to obtain low percent crystallinity are when the sulphuric acid concentration and speed rotation at 4M and 400 rpm respectively. This indicates that reducing agent can be obtained from BSD in mild condition of hydrolysis due to decrement of cellulose crystallinity

Abstract: Shape memory polyurethane (SMPU) is a very versatile material that has a broad array of applications. The selection of soft segments and hard segments play critical roles in determining the structure-property behaviors of SMPU. This research was conducted to evaluate the role of distinct types of diisocyanate on the final properties of polyurethane (PU). Palm kernel oil polyol (PKO) based PU were produced by using two-step bulk polymerization method with variations of diisocyanates. Isophorone diisocyanate (IPDI), 4,4-methylenebis (cyclohexyl isocyanate) (HMDI) and hexamethylene diisocyanate (HDI) were used in the preparation of PU and the soft segment crystallinity, thermal and shape memory properties of the PU were evaluated. Based on the analyses, it was found that different types of diisocyanate and combination of diisocyanates had huge impact on the properties of the synthesized PU. The Fourier transformation infrared (FTIR) analysis revealed that IPDI based PU achieved the highest hydrogen bonding index value which promoted the phase separation. This is in accordance with differential scanning calorimetric (DSC) and x-ray diffraction (XRD) analysis which showed that IPDI based PU exhibited crystalline soft phase, hence resulted in an excellent shape fixity behavior. On the other hand, HDI and HMDI based polyurethane prepared showed absence of crystalline soft phase based on the DSC thermogram and XRD diffractogram. These results suggest the phase mixing phenomenon between soft and hard segments which contributed to low shape memory behavior of the resulting polyurethane.

Abstract: In this article four samples of HgBa₂Ca₂Cu_2.4Ag_0.6O_8+δ were prepared and irradiated with different doses of gamma radiation 6, 8 and 10 Mrad. The effects of gamma irradiation on structure of HgBa₂Ca₂Cu_2.4Ag_0.6O_8+δ samples were characterized using X-ray diffraction. It was concluded that there effect on structure by gamma irradiation. Scherrer, crystallization, and Williamson equations were applied based on the X-ray diffraction diagram and for all gamma doses, to calculate crystal size, strain, and degree of crystallinity. It is observed through the results that gamma irradiation causes a change in the atomic density, crystal size, strain, degree of crystallinity and thus a change in the diffraction angle and intensity peaks. It was found that the highest crystal size was 69.3269 nm at 4MRad dose, crystallization is 69.3269 at 4MRad and the strain is 0.0068 when sample without radiation.

Abstract: In this manuscript, the effect of substituting strontium with barium on the structural properties of Tl_0.8Ni_0.2Sr_2-xBr_xCa₂Cu₃O_9-δ compound with x= 0, 0.2, 0.4, have been studied. Samples were prepared using solid state reaction technique, suitable oxides alternatives of Pb₂O₃, CaO, BaO and CuO with 99.99% purity as raw materials and then mixed. They were prepared in the form of discs with a diameter of 1.5 cm and a thickness of (0.2-0.3) cm under pressures 7 tons / cm², and the samples were sintered at a constant temperature of 860 ° C. The structural properties were studied using X-ray diffraction for all samples, and the results showed that the samples have tetragonal structure and the change of the parameters structure with the change of the barium concentration. Full Width Half Maximum (FWHM) was calculated by Orange Pro using X-RAY data. The crystal size was calculated using Scherrer and Willeamson-Heall methods, where the results showed that the crystal size, compliance and degree of crystallinity changed with the change of barium concentration, and the highest average for the crystal size was 70.0271nm at x=0, and crystallization at 61.46% at x=0.6, and the strain decreased to 0.0037 when barium concentration equals 0.4.

Abstract: The purpose of this study was to evaluate the effect of weak magnetic fields on the structure and physical properties of chitosan (Ch) membranes. The membranes were prepared by a casting method using chitosan and a solvent of acetic acid. The magnetic field of 1.5 mT is applied during the membrane-forming reaction with administration times of 2, 4, 8, and 12 hours. The membranes formed were named M-2h, M-4h, M-8h, and M-12h, respectively. The chitosan membrane without magnetic fields is used as a control, namely M-0. The structure and physical properties of the membranes were examined using Fourier Transform Infra-Red (FTIR) spectrophotometer, water uptake test, dynamic mechanical analysis (DMA), and X-ray diffraction (XRD). The result showed that the membranes with magnetic fields are thicker compared to the control membrane. FTIR analysis revealed that some peaks of the membranes with magnetic fields shifted to the higher or lower wavenumber with increased or decreased absorption intensity. The membranes become stronger and more flexible; their degree of crystallinity increases as increasing the time of the magnetic fields' application, and their hydrophilicity improved. The membranes' crystal structure becomes more regular, and their degree of crystallinity increases as increasing the time of the application of the magnetic fields; and their mechanical properties such as ultimate tensile strength, tensile modulus, and elongation at break were improved. Those results explain that the structure and physical properties of chitosan membranes were significantly affected by the membrane-forming reaction's magnetic fields.

Abstract: The quality of the carbon material for application of electrodes in the battery is indicated by its ability to intercalate ions, atoms or molecules. Graphite is a carbon material with good intercalation capability. In this research, a carbon material in the form of activated charcoal produced from biomass of water hyacinth has been prepared, which is carbonized at various temperatures of 400, 500, and 600 °C with three different activators of ZnCl₂, KOH and H₃PO₄. The activated charcoal will be used as a cathode composite in lithium sulfur batteries. To determine the quality of the activated charcoal, the structure properties of activated charcoal were characterized using X-ray diffraction (XRD). Several parameters that are determined from XRD data included the degree of crystallinity, and the degree of graphitization (Y). The degree of crystallinity was found in the ranges between 5.56 and 12.6%, where activated charcoal was dominated by amorphous structures. The value of the degree of graphitization was about 36%.

Abstract: Multilayered laminate structures obtained by coating of ultrafine-grained metallic materials with bioactive and multifunctional composite coatings are considered for biomedical applications. Laser-assisted densification of multiple materials using laser cladding and selective laser melting is an alternative route to reduce the risk of early implant failure allowing for faster and cheaper fabrication. To understand the cooperative relationships between different factors that cam influence the manufacture of such bioactive laminates reflecting in their bioactivity and mechanical properties, the multi scale numerical modelling is applied. This work presents resent advances on development of integrated numerical models including generation, melting and solidification of the powder bed, considering surface flow, wettability, surface tension and other physical phenomena, specific mechanical and thermo-mechanical aspects and microstructure evolution.