Increase In Crystallite Size Research Articles

TiO2 Nanotubes Synthesis with Dominant {001} Exposed Facets for Efficient Photocatalytic and Photoelectrochemical Water Oxidation Applications

The photoreactivity of TiO2 nanotube arrays (TiNT) is mainly related to the light absorption and photogenerated charge carriers separation efficiencies. Recently, engineering of the crystal facets has gained increasing attention because of its exceptional ability to extend the photoresponse toward visible light and to separate photogenerated charges. Here, TiNT with high crystallinity and percentage of exposed {001} facets was synthesized using a two-step anodization process in ethylene glycol based electrolyte containing 2 wt% of water and 0.27 M NH4F. Decreasing the potential of the second anodization (from 50 to 20 V) resulted in an increase in crystallinity, crystallite size, and percentage of exposed {001} facets. Because trap states limit the photoreactivity performance of TiNT by facilitating the recombination of photogenerated electron/hole pairs, correlation between crystallinity, preferential crystalline orientation, gap states characteristics (density and location), and photoreactivity performance was investigated. TiNT with a high percentage of {001} exposed facets, consisting mainly of shallow gap states with low density, significantly improve photoelectrochemical water oxidation and photocatalytic efficiencies.

Modification of structure and optical properties of graphene oxide dots, prepared by laser ablation method

Modification of structure, optical and luminescent properties of graphene oxide (GO) by laser ablation at 532 nm during various times was studied. It was shown that after 30 minutes of laser ablation, the average lateral size of GO sheets decreases from 272±120 nm to 62±29 nm. Studies of structural properties by Raman and FTIR spectroscopy and microscopy indicate the reduction and graphitization of GO at laser irradiation times greater than 20 minutes, which leads to an increase in the average crystallite size of sp2 carbon domains and a decrease in the number of GO layers in the resulting particles. The optical density of the resulting GO solutions and the intensity of their fluorescence are also time dependent. After ablation, the GO fluorescence intensity increased by 10, 25, and 36% for 10, 20 and 30 minutes, respectively. In the long-lived luminescence spectrum of GO, a broad emission band was recorded after ablation, whereas for GO before ablation long-lived luminescence was not exhibited.

Physical Properties of Different Thicknesses ZnO Thin Films Prepared via Sol-gel Spin Coating Technique

This paper presents the investigation of the thickness of the ZnO thin films by varying the number of deposition layers during the spin coating deposition process. ZnO thin films were deposited with a different number of layers (ranging from 1, 3, and 5), and the main purpose of this study is to explore the effect of the thickness on the properties of ZnO thin films. The deposited thin films were characterised using field emission scanning electron microscope, surface profilometer, and X-ray diffraction. From the characterisation results, the morphology of the ZnO thin films changed significantly with the number of layers and their thickness value. As expected, the thickness increased as the number of layers increased. The crystalline quality of the deposited film improved as the thickness increased. A change in crystallographic orientation was also observed in which the thicker, thin films showed crystal growth in the (102) direction, whereas the thinner one was in the (101) direction. A slight increase in crystallite size for dominant orientation also was observed with the increase of film thickness.

Co-relation between mechanical properties and porosity in thick, thin and thinnest sections of stepped casted workpiece using A-356 Aluminum alloy

A-356 aluminum alloy stepped casted workpiece were prepared with step casting technique was investigated for the mechanical properties and porosity defects using various gating elements (ingate/runner) profiles. Similarly, casted workpieces were produced using single and double gating elements with circular (vortex free), square and rectangular runner and ingate profiles. Hardness (HV) and ultimate tensile strength (UTS) of the thick section prepared from single circular runner/ingate system was more in comparison to thin and thinnest sections extracted at respective heights. Similarly, hardness and tensile strengths of thick specimen prepared from double ingate/runner having circular shape was found greater in comparison to thin and thinnest sections accordingly. SEM images depicted increase of porosity levels in thin and thinnest sections prepared from single or double within workpiece manufactured from circular runner & ingate arrangements respectively. In addition, X-ray diffraction results further revealed increase in crystallite size, hardness and tensile strength for specimens manufactured through circular profiled single or double runner/ingate arrangement. The prepared specimens also follow inverse Hall-Petch and D 2/%P statistical fit with p < 0.05 between hardness and crystallite size. Hence, the specimen with lower crystallite size or finer grains depicted attenuated mechanical properties due to higher porosity levels. In other words, D 2/%P index ratio value <1.40 (≥95% data points follows) exhibited reductions in mechanical properties accompanied by decreasing crystallite size and vise-versa. Moreover, double gating runner & ingate combination exhibited comparatively lesser pores relative to single gating design. Hence, this study suggests double runner & ingate arrangement accompanied with circular cross-section are appropriate for large size step castings or complicated geometries production in foundries.

Multilayer Blade‐Coating Fabrication of Methylammonium‐Free Perovskite Photovoltaic Modules with 66 cm2 Active Area

Solar cells based on hybrid organic/inorganic perovskites have shown an astonishing efficiency development in the past years, having peaked in power conversion efficiencies of &gt;25% for small‐area single‐junction devices. To pave the way for future commercialization, however, high power conversion efficiencies also have to be demonstrated on areas multiple orders of magnitude larger. Herein, methylammonium‐free perovskite photovoltaic modules with an active area of 66 cm2 are presented. All functional layers processable from solution are deposited by blade coating without the use of an antisolvent, demonstrating the feasibility of this approach for large‐area module fabrication. The coating process is analyzed in detail and a model based on the Landau–Levich problem is developed for the blade‐coating setup. The perovskite crystallinity can be improved by the addition of lead(II) thiocyanate, which results in increased crystallite size as judged by Williamson–Hall's analysis of X‐ray diffraction data and corresponding scanning electron microscopy images. The homogeneity of the final modules is investigated with dark lock‐in thermography and electroluminescence imaging, indicating only few shunts in the module area. Modules are made up of 15 serially interconnected solar cells and reveal a stabilized efficiency of 12.6% under maximum power point tracking.

Synthesis and Study of Calcination Effect of Zinc Ferrite on the Structure and Morphology of Nanoparticles

Three samples of spinel powdered zinc ferrites were successfully fabricated via microwave-assisted combustion method followed by calcination at temperature of 500oC for three hours. Phase purity and surface morphology that estimated via XRD pattern and field emission-scanning electron microscopy images (FE-SEM) showed that the samples have cubic spinel - structure with average crystallite size is increase from 15.8 nm to 26.53 nm and from (23.03nm to 28.16 nm when glycine–to-nitrate ratio is decreased before and after calcination at 500 oC for three hours. However the calcination results is increase in average crystallite size and average lattice constant. FE-SEM image indicated that the particles Zinc ferrite possesses shape symmetry and uniformity. Fourier transform infrared spectroscopy (FT-IR) were us to study vibration mode in synthesized spinel ferrite. As calcination the absorption band of a specific bonds are shifted to a lower wavenumber.

Synthesis and characterization of manganese ferrite from low grade manganese ore through solid state reaction route

Manganese ferrite spinel has been synthesized by using low grade manganese ore and ferric oxide as sources of manganese oxide and iron oxide through solid state reaction route by taking manganese and iron mole ratio of 1:2 respectively. The impact of sintering temperature on phase composition and particle size is investigated. Similarly, the impact of frequency on dielectric constant, dielectric loss, AC (alternating current) conductivity and tangent losses is also investigated. The results shows the presence of spinel structure manganese ferrite (MnFe2O4) as the major phase for the sample sintered at 1200 °C. It has been established that the crystallite size increase with rise in sintering temperature. The surface morphology of the sample sintered at 1200 °C show pyramidal and triangular shape grains. The dielectric constant (εʹ) and dielectric losses (εʹʹ) were observed to decrease with increasing the sintering temperature and frequency. Furthermore, the AC (alternating current) conductivity was found to rise with rise in applied frequency. On the other hand, the tangent losses falls considerably with rise in applied frequency.

The effect of ball to powder ratio on the processing of a novel Mo-Cu-Al2O3 composite

In the present article a 45Mo-45Cu-10Al2O3 (wt%) nano-composite was produced by mechanical alloying, shaped by cold pressing then by hot pressing at 950 °C. Our aim was to investigate the effect of different ball to powder ratio (BPR) on the particle size and shape, as well as on the material composition. Investigations were done with XRD, SEM and for hot pressed specimens Brinell hardness measurement. Lower BPR resulted in nano-sized crystallites in the powder, a homogenous phase distribution and higher BPR resulted in even smaller crystallite sizes, but with ZrO2 contamination from the milling equipment. The milling resulted in two separate fractions in the metallic phases separated by crystallite size, strain and lattice parameter. After hot pressing, the lower BPR powders developed a homogeneous, evenly distributed microstructure. Cu recrystallized during hot pressing, but still remained nanocrystalline, the crystallite size of Mo and α-Al2O3 decreased even more due to crystallite deformation and in the case of Mo, the lattice strain values indicates that recovery had also happened. The heating eliminated the crystal defects at highly strained areas and the subsequent cooling evened out the stresses in the respective metallic phases. The inner grain structure was revealed by etching, showing that α-Al2O3 particles congregated only at the Mo grain boundaries, but penetrated the Cu grains. The lattice strain values combined with the BSE images reveal that the Cu is the main matrix of the α-Al2O3 particles. The results indicate that the α-Al2O3 particles induced Particle Stimulated Nucleation (PSN) in the Cu explaining its moderate crystallite size increase. The hot pressed samples of higher BPR had higher ceramic (ZrO2 and α-Al2O3) content, resulting in higher hardness, but lower relative density (92.4%), compared to the samples of lower BPR, which reached 97.2% relative density and hardness still significantly higher than MoCu alloys.

Structure, ionic transport properties and ion dynamics of Ce0.8Y0.2O1.9 oxygen ion conductor: Understanding the impact of sintering temperature

This study investigates the effect of sintering temperature on structure, ionic conductivity, and dielectric properties of Ce0.8Y0.2O1.9. The lattice parameter, crystallite size, and relative density increase with the sintering temperature. The conductivity and activation energy also has been observed to vary with sintering temperature and show the highest and lowest value respectively at a sintering temperature of 800 ​°C. Grain boundary thickness exhibits an enlarged value at both low and high sintering temperatures. The samples sintered at high–temperature exhibit lower conductivity and higher activation energy due to the formation of stable defect associates. Sintering temperature affects the dielectric constant of the system. Havriliak–Negami (HN) formalism is used to investigate the effect of sintering temperature on different parameters of dielectric and modulus spectra. Scaling spectra confirms that the conduction, relaxation and reorientation mechanism are sintering temperature independent.

The Effect of 3-(Glycidoloxy Propyl) Trimethoxy Silane Concentration on Surface Modification of SiO2 Nanoparticles

SiO2 is widely used in nanocomposites as reinforcement nanoparticle to enhance mechanical properties especially wear resistivity. Prior to use, surface modification with proper and sufficient coupling agent should be performed on it. Coupling agent concentration plays a key role in modification process. In this study, the influence of 3-(glycidoloxy propyl) trimethoxy silane (GPTMS) concentration on surface modification of SiO2 nanoparticles, is experimentally investigated. The surface modification of nano-silica were performed by 30, 50, 80 and 110 wt.% of GPTMS in order to introduce the optimal GPTMS concentration to complete the process. Fourier Transformation Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Thermo Gravimetric Analysis (TGA) and X-Ray Diffraction (XRD) characterized the pure and surface modified samples; then, the results were compared to each other to achieve the aim of the research. FTIR results confirmed the silanization proceed due to the silane absorption peak disappearing and shifting of the hydroxyl group bonds in to the amide bonds. This test showed that 30 wt.% GPTMS has not been sufficient for full functionalization of the NPs. According to FESEM images, it seems that the NPs were better modified by 80 wt.% GPTMS due to the least NPs aggregation and lack of coupling agent deposition on the NPs. Also, TGA illustrates that this sample has higher thermal stability because of lower weight loss (11.2%) in coupling agent decomposition temperature range: 130–380 °C. Furthermore, X-Ray Diffraction confirmed the FESEM and TGA results about the mentioned sample due to its highest crystallite size (increase 26.64% in crystallite size in comparison with the pure sample). So, the 80 wt.% of GPTMS introduced as the optimal concentration for surface modification of SiO2 nanoparticles.

Characterization of structural changes in modern and archaeological burnt bone: Implications for differential preservation bias.

Structural and thermodynamic factors which may influence burnt bone survivorship in archaeological contexts have not been fully described. A highly controlled experimental reference collection of fresh, modern bone burned in temperature increments 100-1200˚C is presented here to document the changes to bone tissue relevant to preservation using Fourier transform infrared spectroscopy and X-ray diffraction. Specific parameters investigated here include the rate of organic loss, amount of bone mineral recrystallization, and average growth in bone mineral crystallite size. An archaeological faunal assemblage ca. 30,000 years ago from Tolbor-17 (Mongolia) is additionally considered to confirm visibility of changes seen in the modern reference sample and to relate structural changes to commonly used zooarchaeological scales of burning intensity. The timing of our results indicates that the loss of organic components in both modern and archaeological bone burnt to temperatures up to 700˚C are not accompanied by growth changes in the average crystallite size of bone mineral bioapatite, leaving the small and reactive bioapatite crystals of charred and carbonized bone exposed to diagenetic agents in depositional contexts. For bones burnt to temperatures of 700˚C and above, two major increases in average crystallite size are noted which effectively decrease the available surface area of bone mineral crystals, decreasing reactivity and offering greater thermodynamic stability despite the mechanical fragility of calcined bone. We discuss the archaeological implications of these observations within the context of Tolbor-17 and the challenges of identifying anthropogenic fire.

Effect of magnesium ferrite doping with lanthanide ions on dark-, visible- and UV-driven methylene blue degradation on heterogeneous Fenton-like catalysts

The catalytic behavior of magnesium ferrites doped with lanthanide ions (La3+, Ce3+, Sm3+, Gd3+, and Dy3+) on Methylene Blue (MB) degradation using Fenton process was studied. A slow increase in cubic Fd3m crystalline structure parameters and increase in crystallite size of doped samples magnesium ferrites were observed. A dramatic decrease in catalytic activity of catalysts obtained at 600 °C as compared to catalysts obtained at 300 °C was explicitly observed and this was grossly attributed to the elimination of surface hydroxyl groups as ascertained by FT-IR analysis. The initial magnesium ferrite demonstrated the highest catalytic activity under dark- (kˈ 0.0555 min−1) and visible-light (kˈ 0.1029 min−1) conditions. Catalytic efficiency of the lanthanides doped catalysts under UV-irradiation in accordance with the maximum appearance rate constant kˈ decreased in the following order Ce3+ > Dy3+ > La3+ ≈ MgFe2O4 > Sm3+ > Gd3+. The most active ferrites provided up to 99% of MB degradation in 60 and 20 min for visible- and UV-driven Fenton processes. Findings obtained from this study were observed to be competitive with other heterogeneous Fenton catalysts.

Fabrication of carbon and silver nanomaterials incorporated hydroxyapatite nanocomposites: Enhanced biological and mechanical performances for biomedical applications

Hydroxyapatite is widely utilized for different biomedical applications because of its outstanding biocompatibility and bioactivity. Cuttlefish bones, which are available aplenty, are both inexpensive and eco-friendly sources for calcium carbonate. In the present study, cuttlefish bones-derived HAp nanorods have been utilized to fabricate HAp nanocomposites incorporating 1, 3 and 5 wt% each of GO, MWCNTs, GONRs and Ag NPs. Characterization using such techniques as XRD, FTIR, HRSEM and EDS was performed to analyze the physicochemical properties of nanocomposites, and MTT assay, hemolysis, bioactivity and drug release to evaluate the biological properties. The XRD and HRSEM results reveal that crystallite and particle size increase with increasing wt% of carbon nanomaterials and Ag NPs. However, the addition of nanomaterials did not modify the shape of HAp. The MTT assay and hemolysis results suggest GONRs possess better biocompatibility than GO and CNTs due to their smooth edge structure. While adding carbon materials up to 3 wt% caused an increase in the hardness, adding up to 5 wt% of them caused a decrease in the hardness due to the agglomeration of the particles. Biocompatibility and Vicker's hardness studies show that adding carbon nanomaterials up to 3 wt% caused significant improvement in biocompatibility and mechanical properties. Antibacterial activity test was performed to analyze the ability to preclude the formation of biofilms. The results showed better activity for silver-incorporated nanocomposites in the presence of E. coli and S. aureus bacteria. Drug release studies were performed using lidocaine drug and the results showed nearly similar drug release profile for all the samples except HAg3. Finally, nanocomposite HRA3 could be a suitable candidate for biomedical applications since it shows better biological and mechanical properties than GO and MWCNTs nanocomposites.

The effect of vacuum and air annealing on the structural, optical and photoluminescence properties of ZnS films

The deposition temperature and post-deposition heat treatment can be effectively used to fine tune the structure and composition of the films to obtain desired performance. In this paper, we have investigated the effect of elevated substrate temperature and post-deposition annealing (in air and vacuum) on the properties of ZnS films. Both the tools were found to produce considerable changes in the crystal structure of the films. The major impact was found to be an increase in crystallite size which effectively reduced the defects. Although a small amount of tensile stress was produced as a side-effect of heat treatment, the films remained structurally intact. The vacuum annealing was found to be far more productive than annealing in air. It produced nearly the same amount of improvement in the crystallite size, but with considerably less tensile stress. Furthermore, the bandgap of the films remained unaffected by vacuum annealing.

Investigation of Cu2ZnSnS4 thin film with preannealing process and ZnS buffer layer prepared by magnetron sputtering deposition

Unlike traditional methods for fabricating a CdS buffer layer through chemical bath deposition in thin-film solar cells, this study fabricated a ZnS thin film by sulfurizing the Zn film that was deposited using a magnetron sputtering system at varied temperatures from 500° to 560 °C in a sulfurization furnace. The ZnS thin film have been used as a buffer layer on the Cu2ZnSnS4 absorption layer. In this study, the Cu2ZnSnS4 absorber layer was prepared by first depositing a copper–zinc–tin (CZT) precursor film with a metal stack order of Zn–Sn–Cu–Zn through magnetron sputtering, followed by a preannealing process on the CZT precursor, to promote the interdiffusion of elements for the transfer of the metal phase into the alloy phase. Experimental results revealed the increased crystallite size in the SEM observation, an enhanced Raman intensity at 336 cm−1, and a reduced FWHM value in the XRD study for the Cu2ZnSnS4 thin film fabricated at a sulfurization temperature of 510 °C for 20 min with a preannealing treatment of the CZT precursor at a temperature of 420 °C for 30 min. In addition, the improved optical transmittance to 81.3% and an increased optical band gap value to 3.28 eV due to the reduced grain boundaries was obtained for the ZnS film with improved crystallinity quality fabricated at a sulfurization temperature of 560 °C.

Effect of synthesis temperature on catalytic activity and coke resistance of Ni/bio-char during CO2 reforming of tar

Understanding how the synthesis parameters affect nickel particle distribution is critical to the synthesis of Ni/bio-char with excellent catalytic performance. In this work, the influence of synthesis temperature on catalytic activity and coke resistance of Ni/bio-char during CO2 reforming of tar was explored. With the increase of synthesis temperature from 200 °C to 250 °C, the dispersion of nickel precursor into bio-char was promoted, resulting in an increase in crystallite size of metallic nickel particle from 51.98 nm to 62.45 nm. Besides, parts of the metallic nickel particles were oxidized to nickel oxides, providing more lattice oxygen to oxidize the coke deposited on the catalyst. However, further increasing the synthesis temperature to 300 °C would aggravate the oxidation of active nickel particles. The increase in crystallite size of nickel oxide particle from 23.25 nm to 43.38 nm could block the pore structure and hinder the access of reactants, resulting in a drop in the tar conversion rate from 40-51% to 13–27%.

The state of BEA zeolite supported nickel catalysts in CO2 methanation reaction

Two model nickel catalysts for CO2 methanation reaction were prepared by the impregnation method using unmodified and dealuminated BEA-type zeolite supports, denoted NiHAlBEA and NiSiBEA. Transmission electron microscopy (TEM) and X-ray diffraction studies evidenced formation of metallic nickel crystallites of different size, partially located on the external surface of zeolite grains in of NiHAlBEA catalyst and small nickel nanoparticles uniformly distributed within the zeolite grains in the NiSiBEA catalyst. Higher CO2 conversion and selectivity towards methane at low reaction temperatures were observed for NiSiBEA catalyst. This catalyst showed an improved resistance towards sintering at high reaction temperatures. The decrease of CO2 conversion with the time on stream, accompanied by the drop in methane selectivity in NiHAlBEA catalyst was attributed to the increase in Ni crystallite size, resulted from the migration of small crystallites from the inner to external surface of the zeolite grains and subsequent agglomeration. Diffuse reflectance infrared Fourier transform, and quasi in-situ X-ray photoelectron spectroscopy studies evidenced the presence of metallic nickel crystallites in the catalysts and their partial reoxidation under CO2 methanation reaction conditions. High nickel dispersion and sintering resistance of NiSiBEA led to the retardation of the deactivation of catalyst by H2S.

High magnetic coercive field in Ca‐Al‐Cr substituted strontium hexaferrite

The structural and magnetic properties of Sr0.67Ca0.33Fe9Al3−xCrxO19 submicrometric powders with substitution levels ranging from x = 0 up to x = 3, prepared by sol-gel synthesis method, have been investigated. The powders were characterized by high resolution synchrotron X-ray diffraction, scanning electron microscopy, powder neutron diffraction and MPMS-SQUID magnetometer. The structural analysis shows that upon Ca-substitution of SrFe12O19 at the Sr site and Al–Cr at the Fe sites, the magnetoplumbite structure is preserved, even for large levels of substitutions. The X-ray powder diffraction peak broadening and Williamson-Hall plots analyses indicate an increase of crystallites size and relaxation of the microstrain with increasing amounts of Chromium. The magnetic hysteresis loops reveal high coercivity fields at room temperature, with the highest value of HC = 1125 kA/m (1.41 T) obtained for Sr0.67Ca0.33Fe9Al2.5Cr0.5O19 powder interesting to develop free-Rare Earth high coercivity magnets. The saturation magnetization and remanence values increase monotonically with increasing Cr content while the switching field decreases. The structural Rietveld refinement of combined X-ray/neutron diffraction data shows the affinity of Al3+ and Cr3+ cations to migrate mainly towards (2a) Fe-Oh2 and (12k) Fe-Oh3 sites and only minor amounts is found on the (4f1) Fe-Oh1 octahedral sites. The structural observations corroborate the magnetic properties, demonstrating a correlation between the structure and magnetic properties in Ca–Al–Cr substituted strontium hexaferrite. The role of the particle size to maximize the coercivity properties is discussed.

Synthesis and characterization of Sn-doped TiO2 film for antibacterial applications

Simple sol–gel method has been exploited to deposit Sn-doped TiO2 thin films on glass substrates. The resultant coatings were characterized by X-ray diffraction (XRD), UV–visible techniques (UV–Vis), Fourier transform infrared spectroscopy (FTIR), and photoluminescence analysis (PL). The XRD pattern reveals an increase in crystallite size of the prepared samples with the increasing doping concentration. A decrease in doping concentrating resulted in the decrease in bandgap values. The different chemical bonds on these films were identified from their FTIR spectra. The photoluminescence analysis shows an increase in the emission peak intensity with increasing dopant concentration, and this can be attributed to the effect created due to surface states. The prepared samples were tested as antibacterial agent toward both Gram-positive and Gram-negative bacteria like S.aureus (Staphylococcus aureus) and E.coli (Escherichia coli), respectively. The size of the inhibition zones indicates that the sample shows maximum inhibitory property toward E.coli when compared to S.aureus.

The microstructural parameters analysis of SnSe0.2S0.8 thin film

Sn(S0.8Se0.2) thin films were successfully grown by evaporation technique with the distance variation between substrate and source (10, 15, and 25 cm) to investigate their microstructural parameters and morphology. The X-ray diffraction patterns showed that Sn(S0.8Se0.2) thin film had a single phase with the orthorhombic crystal structure. The crystallite size and the lattice strain were evaluated using the Williamson-Hall (W-H) analysis with Uniform Deformation Model (UDM). The increase of the spacer (d = 10, 15, and 25 cm) causes the increase of the value of strain and crystallite size. One of the factors that affect the increase of crystallite size in the SnSe0.2S0.8 thin films with the spacer is the lattice strain value of the crystals. The scanning electron microscopy (SEM) confirmed the high homogeneity of grains. SnSe0.2S0.8 thin films contain Stannum (Sn) at 21.88 %, Selenium (Se) at 2.31 %, and Sulfur (S) elements at 14.24 % in the majority.