Grain-like Structures Research Articles

Tailoring the opto-electronic properties of SnS thin films by indium doping and fabrication of heterojunction diodes

This study comprehensively investigates the effect of Indium (In) doping on the structural, morphological, and optoelectronic properties of tin mono-sulfide (SnS) thin films deposited using co-evaporation. X-ray diffraction studies identified the orthorhombic phase of SnS. Raman analysis confirmed the formation of SnS by co-evaporation. Morphological analysis revealed uniform coating of the films, a transition from rod-like to regular grain-like structures with increased In doping. A systematic reduction in Sn concentration, with the increase in In is observed in EDS, indicating the substitutional doping of In. The decrease in root mean square roughness with In incorporation suggests smoother film surfaces. The films demonstrated a pronounced improvement in optoelectronic properties, with a notable increase in the absorption coefficient and a bandgap reduction from 2.18 eV to 1.74 eV, resulting from In doping. A significant enhancement in electrical characteristics is observed, including a 140 % increase in conductivity and a systematic rise in carrier concentration with higher In doping levels. Heterojunction devices are fabricated with structure <FTO/Al:ZnO/In:SnS/Ag> having a series resistance of 29.9 Ω having an ideality factor of 2.8.

MODIFICATION OF PINDIGA BENTONITE CLAY WITH DIDODECYLDIMETHYLAMMONIUM BROMIDES SURFACTANT FOR FOUNDRY USE

Bentonite clay from Pindiga, Gombe State, Nigeria, was surface modified with didodecyldimethylammonium bromides (DDAB) by the Base Exchange (cation exchange capacity) method for its possible use in foundries. The surfaces of the unmodified and modified Pindiga bentonite clay were characterised by means of spectroscopic, diffraction, and scanning methods (X-Ray fluorescence spectrometry (XRF)Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM).XRF showed that unmodified sample was rich of montmorillonite (MMt) with ca +2 as exchangeable cation, FTIR analysis revealed that unmodified water absorption causes stretching and bending vibrations for hydroxyl groups, with the most intense bands in the low-frequency region, while DDAB organo-bentonites showed slight changes in wave bands, with a strong methyl band and a weak methyl band indicative of long-chain linear aliphatic structure. The basal spacing of the unmodified bentonite sample was 1.52 nm, and after modification with DDAB, it improved to 2.1 nm as determined from the X-ray diffraction (XRD) analysis. Results of the SEM images revealed rougher surfaces with uniformly dispersed small particles of grain-like structures characteristic of the unmodified, while theorgano-modified bentoniterevealed clusters of different sizes and shapes, larger Fe 3+ ions replacing smaller Al 3+ ions at octahedral sites, discontinuous layers enveloping large grains, polygonal growth foams with octahedral and tetrahedral shapes, mixed layers of calcium bentonite, and particle sizes less than 200nm. The study concluded that modified bentonite with didodecyldimethylammonium bromides gives good microstructure, increases rigidity, and improve thermal stability, to the organoclays. Therefore, it is recommended that DDAB bentonite be used as binder for foundries.

Catalytic Oxidative Desulfurization of 4-Methyldibenzothiophene by Ni/Al Modified Titanium Dioxide and Zinc Oxide

In this study, composite layer double hydroxide-metal oxide catalysts (Ni/Al-TiO2 and Ni/Al-ZnO) were successfully prepared and utilized for the oxidative desulfurization of dibenzothiophene. The catalysts were characterized using XRD, FTIR, and SEM-EDS analysis. The diffraction patterns confirmed the successful synthesis of the composite materials, while the FTIR spectra exhibited absorption bands at specific wavenumbers 3480 cm-1, 1630 cm-1, 1376 cm-1, 830 cm-1, 775 cm-1, and 683 cm-1. The surface morphology of the catalysts showed variations, with Ni/Al-LDH having a smooth particle surface and long particle shape, while Ni/Al-ZnO and Ni/Al-TiO2 formed grain-like or aggregated structures. EDS analysis confirmed the presence of Ni/Al, Ti, and Zn elements in the composites, with Ti and Zn accounting for 29.3% and 10.7% of the composite mass, respectively. The optimized reaction conditions included a reaction time of 40 minutes, catalyst dosage of 0.25 g, temperature of 50°C, and the use of n-hexane as the solvent. The catalysts demonstrated a heterogeneous nature and proved to be reusable, as the conversion of dibenzothiophene remained above 90% even after three catalytic reactions, with Ni/Al-TiO2 and Ni/Al-ZnO composites maintaining conversion rates of 99.36% and 99.32%, respectively.

Understanding the formation of surface relief gratings in azopolymers: A combined molecular dynamics and experimental study.

The formation of surface relief gratings in thin azopolymeric films is investigated using atomistic molecular dynamics simulations and compared to experimental results for the specific case of poly-disperse-orange3-methyl-methacrylate. For this purpose, the film is illuminated with a light pattern of alternating bright and dark stripes in both cases. The simulations use a molecular mechanics switching potential to explicitly describe the photoisomerization dynamics between the E and Z isomers of the azo-units and take into account the orientation of the transition dipole moment with respect to the light polarization. Local heating and elevation of the illuminated regions with the subsequent movement of molecules into the neighboring dark regions are observed. This leads to the formation of valleys in the bright areas after re-cooling and is independent of the polarization direction. To verify these observations experimentally, the azopolymer film is illuminated with bright stripes of varying width using a spatial light modulator. Atomic force microscopy images confirm that the elevated areas correspond to the previously dark areas. In the experiment, the polarization of the incident light makes only a small difference since tiny grain-like structures form in the valleys only when the polarization is parallel to the stripes.

Formation of nano and micro scale hierarchical structures in MgO and ZnO quantum dots doped LC media: the role of competitive forces

In this paper, we have studied the effect of doping of ZnO and MgO nanoparticles (NPs) in 4-(trans-4-n-hexylcyclo-hexyl) isothiocyanatobenzoate. A thorough comparison of dielectric properties, optoelectronic properties, and calorimetric phase transition properties has been done for MgO and ZnO NP doped LC. We prepare their homogenous mixture of MgO and ZnO NPs in toluene and transfer into cells made of glass and Indium Tin-Oxide (ITO) coated glass. The observed microstructures in the hybrid system can be classified into three main categories: grain like structures formed by aggregation of smaller size MgO nanoparticles while liquid crystal molecules anchor over the surfaces of nanoparticles, the grtu grain-like structures further integrate to form inorganic polymeric type of honeycomb-like mesostructures in presence of glass surface, and flower-like clusters of MgO nanoparticles on ITO surface. The smaller size nanoparticles can maintain the energy balance by allowing the anchoring of liquid crystal molecules over their surfaces whereas the larger size nanoparticles cannot compromise or maintain the energy balance with the liquid crystal molecules and are separated out to nucleate and form bigger size nanoaggregate or clusters. The energy preference of the substrate and nanoparticle’s surface to liquid crystal molecules plays an important role in the formation of different types of hierarchical nano- and microstructures. We account the reasons for the formation of nano and micro scale hierarchical structures on the basis of the competition between the forces: NP-NP, LC-LC, NP-LC, Glass/ITO-NP, and Glass/ITO-LC interactions. We observed a considerable change in the dielectric properties, transition temperature, bandgap, and other parameters of LC molecules when MgO NPs are doped, but a minor change occurs when ZnO NPs are doped in LC. Optical microscopy, FTIR, Raman, IR, HR-XRD and FESEM-EDX characterization data confirm and validate our guiding conceptions.

Comparative study of surface, elemental, structural and optical morphologies of titanium dioxide-zinc oxide (TiO2-ZnO) and titanium dioxide-zinc oxide/graphene (TiO2-ZnO/Gn)

The aim of this study is to synthesize a highly dense nanosized TiO2-ZnO sample with graphene (TiO2-ZnO/Gn) thin film via solution immersion method and compare its properties with TiO2-ZnO thin film without graphene. To prepare the titanium dioxide solution, the titanium butoxide precursor was added to ethanol, glacial acetic acid and triton-x-100 with a drop of deionized water. Next, to prepare for the ZnO/Gn solution, the zinc nitrate hexahydrate was added to hexamethylenetetramine (HMTA). Then, a specific weight of graphene was added into the solution before left for ageing. The thin films will be characterized in order to consider and enhance the potential of TiO2-ZnO/Gn thin film in treating wastewater. Ultra-Violet Visible spectroscopy (UV–vis), X-ray Diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM) were used to determine the optical, structural and morphological properties of the samples. From the UV–vis absorption spectra, the TiO2-ZnO/Gn shows the better UV–vis performance compared to the TiO2-ZnO sample. While the FESEM images for TiO2-ZnO/Gn confirmed the presence of the Gn deposited on the thin film with specific grain-like structures of TiO2, hexagonal nanorod ZnO and wrinkles shape of Gn. Finally, the XRD analysis confirmed the crystallinity of the samples, and the elements present on the glass substrate. It has shown that there are TiO2, ZnO and Gn peaks present in the XRD patterns. Thus, TiO2-ZnO/Gn is the best candidate to be used as the photocatalyst in treating the wastewater.

Synthesis and Characterization of Barium-Iron Oxide Based Neodymium, Gadolinium and Praseodymium Doped Ceramic Materials

Neodymium, gadolinium, and praseodymium doped barium-iron oxide ceramic materials were synthesized by polymeric precursor method. No carbon contents or the moisture was observed in infrared spectra of the ceramics. Neodymium and gadolinium doped ceramics were crystallized in cubic lattice form, while praseodymium doped ceramic was formed in hexagonal lattice. Same results were observed from SEM images, Neodymium and gadolinium doped ceramics had similar morphological structures, but praseodymium doped ceramics had slightly different morphology. Neodymium and gadolinium doped ceramics consisted of grain-like structure, while praseodymium doped ceramic material consisted of both grain-like and pillar-like crystal structures.

Influence of air addition on surface modification of polyethylene terephthalate treated by an atmospheric pressure argon plasma brush

An atmospheric pressure argon plasma brush with air addition is employed to treat polyethylene terephthalate (PET) surface in order to improve its hydrophilicity. Results indicate that the plasma plume generated by the plasma brush presents periodically pulsed current despite a direct current voltage is applied. Voltage−current curve reveals that there is a transition from a Townsend discharge regime to a glow one during one discharge period. Optical emission spectrum indicates that more oxygen atoms are produced in the plume with increasing air content, which leads to the better hydrophilicity of PET surface after plasma treatment. Besides, an aging behavior is also observed. The hydrophilicity improvement is attributed to the production of oxygen functional groups, which increase in number with increasing air content. Moreover, some grain-like structures are observed on the treated PET surface, and its mean roughness increases with increasing air content. These results are of great importance for the hydrophilicity improvement of PET surface with a large scale.

Facile Synthesis of Fe3O4/ZnO Nanocomposite: Applications to Photocatalytic and Antibacterial Activities

In the current work, we have reported the preparation of Fe3O4/ZnO nanocomposite (NC) via co-precipitation. The prepared Fe3O4/ZnO nanocomposite were characterized by x-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) equipped with energy dispersive x-ray analysis (EDAX), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area analysis, ultraviolet-diffuse reflectance spectroscopy (UV-DRS) and photoluminescence spectroscopy (PL). From the x-ray diffraction pattern, the average crystallite size of Fe3O4/ZnO NC was found to be 13 nm. UV-DRS showed an energy band gap of 2.3 eV for the prepared sample. From the Brunauer–Emmett–Teller (BET) surface area analysis, total pore volume (VP) and mean pore diameter (rp) were found to be 12.647 m2g−1, 0.024125 cm3g−1 and 7.6302 nm. The functional groups and metal to oxygen bonding in Fe3O4/ZnO NC were observed in FT-IR. SEM and TEM micrograph of Fe3O4/ZnO NC show flake- and grain-like structures, and the luminescence spectrum shows blue emission. The photocatalytic activity of Fe3O4/ZnO NC was examined using industrial effluent dyes such as Evans blue (90% in 150 min) and Rhodamine B (RB) (99% in 150 min) under UV light irradiation. Further, Fe3O4/ZnO NC also showed a superior zone of inhibition against pathogenic bacterial strains such as Escherichia coli and Staphylococcus aureus by agar well diffusion compared to Fe3O4 and ZnO nanoparticles.

Grain-like structures with minimal and maximal period sequences

Nonlinear feedback shift registers (NFSRs) are important building blocks for stream ciphers. The cascade connection of an n-stage full-length linear feedback shift register (LFSR) into an m-stage NFSR is called a Grain-like structure. In this paper, we focus on Grain-like structures which can generate minimal and maximal possible period sequences. The existence of Grain-like structures which can generate minimal possible period sequences is proved for the cases $$m=n$$ and $$m>n$$ . The number of such Grain-like structures is estimated in both cases. Two necessary conditions are presented for Grain-like structures to generate maximal possible period sequences. Moreover, some interesting properties of such Grain-like structures are discussed.

Chitosan-Hydroxyapatite Composite Layers Generated in Radio Frequency Magnetron Sputtering Discharge: From Plasma to Structural and Morphological Analysis of Layers.

Chitosan–hydroxyapatite composite layers were deposited on Si substrates in radio frequency magnetron sputtering discharges. The plasma parameters calculated from the current–voltage radio frequency-compensated Langmuir probe characteristics indicate a huge difference between the electron temperature in the plasma and at the sample holder. These findings aid in the understanding of the coagulation pattern of hydroxyapatite–chitosan macromolecules on the substrate surface. An increase in the sizes of the spherical-shape grain-like structures formed on the coating surface with the plasma electron number density was observed. The link between the chemical composition of the chitosan–hydroxyapatite composite film and the species sputtered from the target or produced by excitation/ionization mechanisms in the plasma was determined on the basis of X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and residual gas mass spectrometry analysis.

A continuum grain-based model for intact and granulated Wombeyan marble

The discontinuum numerical modeling approaches widely used to simulate brittle rock failure employ the Voronoi tessellation technique to generate polygonal grain-like structures. Using this approach, called the grain-based model (GBM), the progressive micro-cracking leading to macroscopic fracturing and failure of brittle rocks can be realistically simulated. In this paper, a GBM is developed using the continuum numerical program RS2 to reproduce the laboratory behavior of intact and heat-treated (granulated) Wombeyan marble. An iterative calibration procedure is utilized to match the macro-properties of RS2-GBM to those of marble. It is found that RS2-GBM captures some of the most important characteristics of brittle rocks, including the non-linear strength envelope and the change in the failure mode and post-peak response with increasing confinement. It is demonstrated that the peak strength and failure mode of RS2-GBM are comparable to those of previously calibrated discontinuum GBMs. The advantage of the continuum over the discontinuum GBM is its shorter computation time. It is discussed that since the granulated marble serves as an analogue for a highly interlocked jointed rock mass, its calibrated continuum GBM can be used as an alternative tool for stability analyses and design of excavations and mine pillars in jointed rock masses.

Weak Grain-Like Structures

A Grain-like structure is a cascade connection of a primitive LFSR into an NFSR. It is well known that such structures generate sequences with periods multiples of the period of primitive LFSR sequences. In this paper, we study weak Grain-like structures, i.e., Grain-like structures generating at least one sequence with minimum period. Assume the orders of LFSR and NFSR are $n$ and $m$ respectively. We prove that weak Grain-like structures always exist when $m>n$ . For $m=n$ , we give three classes of weak Grain-like structures. Then we extend the method in the second class to prove that weak Grain-like structures exist when $m\ge n-\lg n+4$ . Moreover, our experimental data shows that, the ratio of weak Grain-like structures approximates a value which is a little more than 63% for small $m=n$ , and weak Grain-like structures exist with $m=3$ or 4 when $n\le 18$ .

Modification of Ashaka and Tango Bentonites with Tetraphenyl Phosphonium and Hexadecyl Pyridinium Bromides for Possible Use in Polymer-Clay Nanocomposite Preparation

Bentonites from Ashaka (GA) and Tango (GT) of Gombe State, Nigeria were surface modified with Tetraphenyl phosphonium (TPP) and Hexadecyl pyridinium bromides (HDP) by cation exchange method for their possible use in Clay/polymer nanocomposite preparation. The surfaces of the modified products were characterized by means of spectroscopic, diffraction and scanning methods [Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM)]. The basal spacing of the unmodified bentonite samples was 1.52nm and 1.29nm and after modification with TPP + and HDP + it increased to 1.86nm, 1.74nm and 2.15nm, 2.11nm respectively as determined from the X-ray diffraction (XRD) analysis. Results of the SEM images revealed rougher surfaces with uniformly dispersed small particles of grain-like structures characteristic of the organomodified bentonites. Bentonites from Ashaka (GA) and Tango (GT) of Gombe State, Nigeria were surface modifiedwith Tetraphenyl phosphonium (TPP) and Hexadecyl pyridinium bromides (HDP) by cationexchange method for their possible use in clay/polymer nanocomposite preparation. Thesurfaces of the modified products were characterized by means of spectroscopic, diffractionand scanning methods (Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction(XRD) and scanning electron microscopy (SEM)). The basal spacing of the unmodifiedbentonite samples was 1.52 and 1.29 nm and after modification with TPP+ and HDP+ itincreased to 1.86 and 1.74 nm; and 2.15 and 2.11 nm respectively as determined from the Xraydiffraction (XRD) analysis. Results of the SEM images revealed rougher surfaces withuniformly dispersed small particles of grain-like structures characteristic of theorganomodified bentonites.

Spectroscopic studies on the temperature-dependent molecular arrangements in hybrid chitosan/1,3-β-D-glucan polymeric matrices

Chitosan/1,3-β-D-glucan matrices have been recently used in various biomedical applications. Within this study, the structural changes in hybrid polysaccharide chitosan/1,3-β-D-glucan matrices cross-linked at 70 °C and 80 °C were detected with Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR FT-IR) and Raman spectroscopy enabled thorough insights into molecular structure of studied biomaterials, whereas X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) provided their surface characteristics with confirmation of their effective and non-destructive properties. There are temperature-dependent differences in the chemical interactions between 1,3-β-D-glucan units and N-glucosamine in chitosan, resulting in surface polarity changes. The second order derivatives and deconvolution revealed the alterations in the secondary structure of studied matrices, along with different sized grain-like structures revealed by AFM. Since surface physicochemical properties of biomaterials have great impact on cell behavior, abovementioned techniques may allow to optimize and modify the preparation of polymeric matrices with desired features.

Oxygen-deficient lanthanum doped cerium oxide nanoparticles for potential applications in spintronics and photocatalysis

In this report, we have investigated oxygen-deficient lanthanum (La) doped cerium oxide (CeO2) nanoparticles for their potential applications in spintronics and photocatalysis. XRD measurements indicate lattice expansion with an increase in La content in the host matrix. TEM images show that morphology of cerium oxide nanoparticles transformed into grain-like structures with La3+ ion concentration. The increase in defects with La content was confirmed by spectroscopic techniques viz. Raman and X-ray photoelectron spectroscopy (XPS). XPS revealed the introduction of new networks La3+-O-Ce3+ and La3+-O-Ce4+ that enhanced the vacancy defects. The defects in the form of oxygen vacancies played a vital role in increasing the net magnetization that can be explained by F-center exchange mechanism. Further, the formation of vacancy defects were responsible for the reduction in band gap up to La 8% (Eg = 3.08 eV) as compared to non-substituted CeO2 (Eg = 3.21 eV). Henceforth, it can be concluded that defects in the form of oxygen vacancies are key component for the enhancement in magnetic properties and photocatalytic efficiency towards the degradation of Rose Bengal dye.

Keratinocyte infection by Actinomadura madurae triggers an inflammatory response.

Actinomycetoma is a syndrome of the skin characterized by chronic inflammation and lesions with nodular grain-like structures. The most common aetiological agents are Nocardia brasiliensis and Actinomadura madurae. In response to infection with these organisms the body produces an inflammatory immune response in the skin. The aim of the present study was to determine the production of chemokines, pro-inflammatory cytokines, antimicrobial peptides and the expression of Toll-like receptors (TLRs) in keratinocytes infected by A. madurae. A cell line of HaCaT keratinocytes was infected with A. madurae at a multiplicity of infection of 20:1 for 2 h and the samples were collected from 2 to 72 h post-infection. Intracellular replication of the bacterium was evaluated by counting of colony-forming units, the TLR expression and antimicrobial peptide production were assayed by confocal microscopy and chemokine and pro-inflammatory cytokine levels were determined by enzyme-linked immunosorbent assay. Early in the infection, A. madurae was able to achieve intracellular replication in keratinocytes, however, the cells eventually controlled the infection. In response to the infection, keratinocytes overexpressed TLR2 and TLR6, produced high concentrations of cytokines monocyte chemoattractant protein-1, interleukin 8, human β-defensin-1, human β-defensin-2 and LL37 and low levels of tumour necrosis factor α. The human keratinocytes contribute to the inflammatory process in response to A. madurae infection by overexpressing TLRs and producing chemokines, pro-inflammatory cytokines and antimicrobial peptides.

Growth and properties of one-dimensional β-Ga2O3 nanostructures on c-plane sapphire substrates

One-dimensional β-Ga2O3 nanostructures were grown at different temperatures on c-plane sapphire substrates by MOCVD using Au as catalyst. The structural, morphological and photoluminescence properties of β-Ga2O3 nanostructures grown at different temperatures were characterized and compared in detail. As the growth temperature was increased, β-Ga2O3 nanostructures exhibited improved crystalline quality and possessed a typical β-Ga2O3 structure with high purity. The β-Ga2O3 nanostructures grown at 750°C showed intense ultraviolet-blue emission at room temperature. Different morphologies including islands-like, nanowires, nanorods, grain-like structures were obtained depending on the growth temperature. The correlation between the nanostructures shapes and the growth processes was also discussed.

Folding in metal polycrystals: Microstructural origins and mechanics

Surface folding in large-strain deformation of metal polycrystals, mediated by unsteady sinuous plastic flow, was recently uncovered by direct observations. Here, we examine microstructural origins and mechanics of the folding process in polycrystalline aggregates, using computational methods and in situ, high-speed imaging experiments. Our model loading system is an indenter contact that imposes large strain deformation typical of metal forming, sliding and cutting.Folding arises primarily from intrinsic, grain-level flow stress variation in the polycrystalline ensemble. This flow stress heterogeneity is incorporated, spatially, in a continuum Lagrangian finite element framework, by partitioning the metal surface into grain-like structures. This pseudograin model captures all key aspects of the folding as observed by direct imaging, from fold nucleation via microstructure heterogeneity through various stages of fold development on the surface; surface strain fields; and deformation parameter effects such as indenter geometry and friction. The folding phenomenon is quite general, and provides a direct route for formation of surface defects and delamination wear particles. The microstructure-based simulation capability, thus validated, can be used as a virtual tool for analyzing large-strain plastic flow at surfaces and its consequences. Besides demonstrating the importance of folding in surface plasticity, the study points to a critical need to consider microstructure effects on local plasticity for sliding wear and deformation processing.

Effect of VI/II gas ratio on the properties of MOCVD grown ZnO nanostructures

In the present work, various nanostructures of zinc oxide were grown on quartz substrates using metal organic chemical vapor deposition technique. The growth was carried out at 450 °C and at atmospheric pressure using diethyl zinc and tert-butanol as zinc (group II) and oxygen (group VI) sources, respectively. The VI/II gas ratio was varied by varying the diethyl zinc flow rates from 20 to 35 sccm, and keeping the flow rate of t-butanol fixed at 60 sccm. Effects of this VI/II gas ratio on the structural, micro structural and optical properties of the zinc oxide nanostructures were discussed and a possible growth mechanism explaining the micro structural transition was proposed. At low diethyl zinc flow rate the grains were oriented along the c-axis, while higher flow rate of diethyl zinc promoted three dimensional growths resulting in sheet-like structures. The significant effects of variation of VI/II gas ratio on the micro structure of zinc oxide could be understood from the formation of various nanostructures including grain-like and sheet-like structures.