Papers by Keyword: Crystal Structure

Abstract: Dry machining of gears demands advanced coating technologies to withstand high thermal and mechanical stresses. In this study, AlCrN coatings were deposited using the newly developed Focused Magnetron Sputtering (FMS) process and compared with conventional Cathodic Arc Evaporation (CAE)-AlCrN and boroncontaining CAE-AlCrBN coatings. XRD analysis showed that FMS produced a finegrained crystal structure with half the full width at half maximum (FWHM) of CAE-AlCrN. Stressoptimised deposition allowed a 60 % higher coating thickness with improved adhesion. Analogy gear hobbing tests (fly cutting tests) demonstrated that FMS-AlCrN had 52 % lower crater wear than CAE-AlCrN, while CAE-AlCrBN also improved crater wear resistance due to boroninduced grain refinement. However, both finegrained coatings exhibited increased flank wear compared to the coarse-grained CAE-AlCrN coating. The results show that FMS enables the production of dense, fine-grained coatings with superior adhesion and crater wear resistance, highlighting its potential for dry gear hobbing. Further optimisation of hardness and microstructure is required to balance crater and flank wear behaviour.

Abstract: Magnesium alloys are promising for bioabsorbable stents due to their biocompatibility and degradability. Unlike conventional stainless steel stents that remain in the body and may cause complications, magnesium stents gradually degrade, reducing risks like restenosis and thrombosis. However, magnesium has low corrosion resistance, and its corrosion resistance needs to be improved. The crystal structure is one factor affecting the corrosion properties of metallic materials. Several studies have been conducted on the relationship between crystal structure and corrosion properties to improve magnesium's corrosion resistance. It is essential to elucidate the relationship between crystallographic factors and corrosion mechanisms, in the case of stents, plastic deformation during expansion results in the formation of fine crystal grains and twinning deformation. Therefore, the purpose of this study is to investigate the influence of refined grains and twinning on the corrosion properties of magnesium. Hot rolling and compression are used to refine the crystal grains and form twinning in experiments. The crystal structure can be observed by optical microscopy and SEM-EBSD. Following the evaluation of the crystal structure, immersion tests in brine are conducted to measure the mass loss and observe the corrosion behaviour.

Abstract: Inherent magnetic features of engineered nanoparticles are quite important parameters for biomedical application. In this study, trying to process Bengawan Solo iron sand into a material that has potential for cobalt ferrite (CFO-NPs) and silver-cobalt ferrite (AgCFO-NPs) were synthesized by aqueous extract of tumeric. To modify the physical properties, annealing treatment was carried out at non-annealing temperatures and 500°C. The characterized by various instrument, and utilized for biomedical application with antibacterial activity. These are characterized XRD with showing results particle size was calculated by the Scherrer formula, which is around 19 nm to 25 nm. The results of FTIR peak adsorption at 400 and 600 cm^-1 it shows the characteristics of spinel ferrite and the presence of vibrations at tetrahedral and octahedral sites. The coerciveness field (Hc) while those subjected to annealing temperature treatment increased from 46 Oe to 136 Oe. Nanoparticles cobalt ferrite (CFO-NPs) and silver-cobalt ferrite (AgCFO-NPs) can be used as antibacterial application. The AgCFO-NPs material has an antibacterial function as seen in the antibacterial test. AgCFO-NPs showed a good response being able to inhibit the growth of Staphylococcus aureus and Eschericia coli bacteria. By the obtained result it can be claimed that material nanoparticles will be useful model for biomedical applications if they are explored at advance level.

Abstract: A high entropy Ni-Al-Ti-Mn-Co-Fe-Cr alloy (HEA) system was fabricated using spark plasma sintering (SPS). The alloys at different elemental compositions were developed at a sintering temperature of 850 °C, a heating rate of 90 °C/min, a pressure of 50 MPa, and a dwelling time of 5 min. The sintered alloys' mechanical characteristics, microstructure, phase evolution, and density were assessed. The evolved microstructure of the sintered HEAs shows a homogenous dispersion of the alloying metals. The sintered microstructures showed a mixture of simple and complex phases. The phase refinement shows that the sintered HEAs exhibited a lower and the least grain size of 2.28 µm compared to the Ni₅₀Al₅₀ alloy having 8.26 µm. Likewise, a higher micro-strain value of 1.25E-1 was attained by the non-equal atomic HEA, while the unalloyed has 1.87E-3. The microhardness value of the sintered alloys varied from 103.5 HV to 139.2 HV, while their measured density varied from 5.23 g/cm³ to 6.44 g/cm³.

Abstract: In this work, we successfully synthesized a magnetic nanocomposite material (Fe₃O₄@ZnO/TiO₂) with an iron oxide core and a zinc oxide/TiO₂ shell (Fe₃O₄@ZnO/TiO₂). The purpose of this study was to characterize the Crystal Structure, Morphology, and Magnetic Properties of Magnetic Nanocomposites with Iron Oxide Core and Zinc Oxide/Titanium Oxide Shell. The crystal structure of the sample was analyzed using X-ray diffraction, which identified three distinct phases: Fe₃O₄, ZnO, and TiO₂. These phases respectively exhibited cubic spinel, hexagonal wurtzite, and tetragonal crystal structures. Transmission Electron Microscopy (TEM) characterization confirmed that the sample had a magnetic core–shell structure, with superparamagnetic properties and excellent stability owing to its spinel cubic structure, which is the primary magnetic material structure of the sample. The successful formation of the Fe₃O₄@ZnO/TiO₂ nanocomposite represents a significant advancement in the synthesis of materials. This could serve as a basis for further investigations into magnetic materials, opening up possibilities for their application across diverse fields.

Abstract: In this study, the use of the Fourier synthesis and the so-called Maximum Entropy Method (MEM) are evaluated in order to reveal the crystalline defect of the T’-type structure of one of 214 cuprate system, namely Pr_2-xCe_xCuO₄ (PCCO) powders. In the low-level density, the MEM calculations give a clear picture of the scattering and can eliminate the secondary scattering which may bother the main electron distribution of the specific atomic site. The covalent-bond is even clearer to be seen rather than the one obtained by the Fourier synthesis. This brings a further suggestion to use the MEM calculations in case of describing the scattering density of electron. Moreover, by means the used of the MEM calculations, the defect induced magnetism including the role of the tetravalent ionic doping and the annealing reduction effect is briefly discussed in this report.

Abstract: FeCoNiAlSi and FeCoNiAlBSi high entropy alloys (HEAs) were synthesized by mechanical alloying. Phase evolution, crystallite size, lattice strain, microstructure and morphology for the two alloys were investigated. It was found that two simple structures which are face-centred cubic (FCC) and body-centered cubic (BCC/B2) solid solution appear in FeCoNiAlSi HEA after 50 h of milling. Formation of Fe₂B peak was observed in the XRD pattern when a small amount of boron was added to the base alloys. The particle size of the alloy was increased after 20 h of milling time. The structural analysis shows that the average crystallite size decreases while lattice grain size increases with the increasing milling time. The morphology structure of the milled powders shows the particles size becomes rounded, flat and rough as the milling time prolongs. The newly developed HEA synthesized by mechanical alloying is expected to provide prominent efficiency in degradation of azo dyes (Methyl Orange). Although the HEAs have been reported to provide larger surface area and excellent capacity, only a few studies have been reported on degradation of azo dye by using HEAs as catalyst. Therefore, the method derived from the results of this study will contribute in treating azo dyes for wastewater treatment. Keywords: azo dye; high entropy alloys; mechanical alloying; crystal structure; morphology

Abstract: In this study, the synthesis and analysis of the crystal structure of silver nanowires (AgNWs) have been performed using the polyol method. In this research, materials used as the main raw material were silver nitrate (AgNO₃). Polyvinyl pyrrolidone (PVP) was used as a capping agent and stabilizer, and Iron (III) Chloride (FeCl₃) for controlling the shape and size of AgNWs. AgNWs were synthesized using two different solvents i.e., ethylene glycol (EG) and propylene glycol (PG). The crystal structure of AgNWs was analyzed using X-ray diffraction (XRD) with a scanning 2θ in the range of 20° to 90°. Furthermore, the structure and electron diffraction patterns were analyzed using transmission electron microscopy (TEM). The XRD pattern of the AgNW sample also has five diffraction peaks, these five diffraction peaks were identified at 38.24°, 44.42°, 64.54°, 77.52°, and 81.68° representing lattice constants (111), (200), (220), (311), and (222), respectively. Based on the results of the calculation of lattice constant values of AgNWs-EG and AgNWs-PG were 4.084 Å. The TEM images of AgNWs-EG have a diameter of 84 to 133 nm, corresponding to the SEM calculation data having a diameter of 109 ± 22 nm. AgNWs-PG has a diameter of 84 to 264 nm. The study results revealed that the results of the characterization performed are interconnected. The XRD characterization results revealed that both samples were crystal-indexed. AgNWs-PG has a larger crystal size than AgNWs-EG.

Abstract: Calculations of the structural and energy parameters, band structure and density of electronic states of new structural varieties of graphyne have been performed by the density functional theory method. The initial structure of the nine polymorphs was theoretically constructed on the basis of the 5-7a graphene layer. As a result of the calculations, the structure of only five graphyne layers was found to be stable: α-L_5-7a, β1-L_5-7a, β2-L_5-7a, β3-L_5-7a and β4-L_5-7a. The structure of layers γ1-L_5-7a, γ2-L_5-7a, and γ3-L_5-7a is transformed into the structure of graphene layers by geometric optimization, and the graphyne layer γ4-L_5-7a is transformed sp+sp² layer L_3-6-13. The sublimation energy of the stable graphyne polymorphs varies from 6.66 to 6.78 eV/atom. The density of electronic states at the Fermi energy level for all α-L_5-7a and β-L_5-7a layers of graphyne is different from zero, so the new graphyne polymorphs should have metallic properties.

Abstract: A series of luminescence phosphors M_0.955Al_{2 –x}Ga_xSi₂O₈∶Eu²⁺ (M=Ca, Sr, Ba, x = 0~1.0) were prepared via solid-state reaction in weak reductive atmosphere. The lattice positions were discussed. It was found that when Ga³⁺ entered MAl₂Si₂O₈ lattice and substituted Al³⁺, complete solid solutions formed. The lattice parameters (a, b, c) and unit cell volume of phosphors M _0.955Al_{2 –x}Ga_xSi₂O₈: Eu²⁺ (M=Ca, Sr, Ba, x = 0~1.0) increased linearly, the lattice parameters (α, β,γ) of Ca_0.955Al_2–xGa_xSi₂O₈∶Eu²⁺(CAS) decreased linearly and the lattice parameter β of Sr_0.955Al_2–xGa_xSi₂O₈∶Eu²⁺(SAS) and Ba_0.955Al_2–xGa_xSi₂O₈∶Eu²⁺(BAS) increased linearly as Ga³⁺ content increased.