Crystallite Size Distribution Research Articles

Preparation of ultrafine grained copper nanoparticles via immersion deposit method

Today, the exploration about synthesis of nanoparticles is much of interest to materials scientists. In this work, copper nanoparticles have been successfully synthesized by immersion deposit method in the absence of any stabilizing and reducing agents. Copper (II) sulfate pentahydrate as precursor salt and distilled water and Ethylene glycol as solvents were used. The copper nanoparticles were deposited on plates of low carbon steel. The effects of copper sulfate concentrations and solvent type were investigated. X-ray diffraction, scanning electron microscopy and UV–Visible spectroscopy were taken to investigate the crystallite size, crystal structure, and morphology and size distribution and the growth process of the nanoparticles of obtained Cu particles. The results indicated that the immersion deposit method is a particularly suitable method for synthesis of semispherical copper nanoparticles with the crystallites size in the range of ~22 to 37 nm. By increasing the molar concentration of copper sulfate in distilled water solvent from 0.04 to 0.2 M, the average particles size is increased from 57 to 81 nm. The better size distribution of Cu nanoparticles was achieved using a lower concentration of copper sulfate. By increasing the molar concentration of copper sulfate in water solvent from 0.04 to 0.2, the location of the SPR peak has shifted from 600 to 630 nm. The finer Cu nanoparticles were formed using ethylene glycol instead water as a solvent. Also, the agglomeration and overlapping of nanoparticles in ethylene glycol were less than that of water solvent.

Structural Arrangement in Close-Packed Cobalt Polytypes

In this paper, we present a comprehensive study on how stacking faults, crystallite size, crystallite size distribution as well as shape and strain dictate the nature of the X-ray powder diffraction patterns of small ( 20 nm) cobalt (Co) nanoparticles. We provide a unique library of simulated diffractograms which can be used for fingerprint analysis. Likewise, the simulated data are used as a basis for structural refinements of experimentally obtained X-ray powder diffractograms. We provide examples of using the library for fingerprint analysis and for full structural analysis of synthesized Co nanoparticles. Structural refinements presented in this study allow to reveal fine structural details that directly correlate to different behavior upon heating in a CO atmosphere relative to a H2 or He atmosphere. All calculations were performed using the Discus package and the Debye scattering equation.

Physical structure variations of bacterial cellulose produced by different Komagataeibacter xylinus strains and carbon sources in static and agitated conditions

The morphology, crystallinity, crystallite size, and production yield of bacterial cellulose (BC) produced with six different carbon sources (glucose, fructose, lactose, maltitol, sucralose, and xylitol) in static and agitated fermentation conditions by five strains of Komagataeibacter xylinus (KX, TISTR 086, 428, 975, and 1011) which are locally available, were studied. In static condition, the BC pellicle was formed as a membrane sheet at the medium surface exposed to air, while in agitated condition, the spherical or asterisk-like shape BC particles were obtained in the culture media. The XRD and FT-IR analyses found no significant differences in the cellulose crystallinity, crystallite size or polymorphic distribution within the carbon sources. However, changes in crystallinity and mass fraction of the Iα allomorph were observed in BC produced from the different bacterial strains and incubation conditions. The BC samples produced by the same bacterial strain with the varying culture conditions showed the alteration of physical properties more clearly than the BC samples prepared by the opposite situation. These findings suggested that the strains of bacteria and fermentation conditions strongly affected on the physical structures of BC.

Elucidation of structural, vibrational and dielectric properties of transition metal (Co2+) doped spinel Mg-Zn chromites

Co2+ doped Mg–Zn spinel chromite compositions Mg0.5Zn0.5-xCoxCr2O4 (0.0 ≤ x ≤ 0.5) have been synthesized by the high-temperature solid state method. Synchrotron and X-ray diffraction (XRD) studies show single-phase crystalline nature. The structural analysis is validated by Rietveld refinement confirms the cubic structure with space group Fd3m. Crystallite size is estimated from Synchrotron XRD which was found to be 30–34 nm. Energy dispersive analysis confirms stoichiometric Mg0.5Zn0.5-xCoxCr2O4 composition. Average crystallite size distribution is estimated from imaging software (Image – J) of SEM is in the range of 100–250 nm. Raman spectroscopy reveals four active phonon modes, and a pronounced red shift is due to enhanced Co2+ concentration. Increased Co2+ concentration in Mg–Zn chromites shows a prominent narrowing of band gap from 3.46 to 2.97 eV. The dielectric response is attributed to the interfacial polarization, and the electrical modulus study supports non-Debye type of dielectric relaxation. Ohmic junctions (minimum potential drop) at electrode interface are active at lower levels of doping (x < 0.2) give rise to a low-frequency semicircle as evidenced from the complex impedance analysis. The low dielectric loss and high ac conductivity of Co2+ doped Mg–Zn spinel chromites are suitable for power transformer applications at high frequencies.

Monte Carlo Simulation of Crystalline Morphology Under Temperature Gradient: A Case Study of Syndiotactic Polypropylene

In this work, a mathematical model for describing the crystallization kinetics and morphological development of syndiotactic polypropylene (s‐PP) during crystallization under temperature gradient is developed based on Monte Carlo simulation. The effect of temperature range is also investigated. The results shows that temperature range significantly affected the relative crystallinity, average crystallite size, and crystallite size distribution. The average Avrami rate constant is found to be adequate for describing the overall crystallization rate at the early state of crystallization.

X-ray powder diffraction line broadening analysis of the nanocrystalline tin dioxide by the classical Warren-Averbach approach

In the present study, the X-ray diffraction line profile analysis technique has been applied to investigating the microstructure of nanocrystaline materials in terms of average crystallite sizes, size distributions and micro strains. We have calculated the size and strain Fourier coefficients by using classical Warren-Averbach method for the two (110) and (220) reflections. Assuming that the grain size distribution in the nanocrystaline SnO2 can be approximated by a log normal function, the area- and volume-weighted average grain size value were estimated as $ 16.14 \pm 0.23$ and $ 19.67 \pm 0.23$ nm, respectively. To validate the results obtained from Warren-Averbach analysis, the obtained size was compared by the SEM results reported in our previous work and the results are in good agreement. The behavior of strain indicates the extent of the inhomogeneous strain distribution which causes the broadening of X-ray line profile in the crystalline lattice of tin dioxide nanoparticles.

Fabrication of bioactive porous bredigite (Ca7MgSi4O16) scaffold via space holder method

AbstractBredigite has been recently evaluated as a biodegradable ceramic with high mechanical strength, biocompatibility, bioactivity and excellent cell behavior. The objective of this research was to fabricate a nanostructured bredigite scaffold for bone repair and restoration via the space holder technique. The crystallite size, phase composition, particle size, pore morphology and pore size distribution of the scaffold were characterized using X-ray diffraction, as well as transmission and scanning electron microscopy. The results showed the fabrication of a highly interconnected porous scaffold, with a total porosity of about 86%, a pore size of about 400–600 μm, and the compressive strength of about 1.1 MPa. The prepared scaffold with nanosized structure and high porosity level leading to a high specific surface area could be used as an ideal scaffold for bone regeneration in bone tissue engineering applications.

Nanostructured CeO2:Eu3+ luminophore obtained by low temperature benzenetricarboxylate method

Nanostructured CeO2:Eu3+ was synthesized by low temperature thermolysis (500 °C, 1 h) of RE3+-benzenetricarboxylate precursors (RE: Rare Earth). This preparation method is shown to produce easily dispersible highly crystalline nanoparticles with sharp crystallite size distribution, presenting large advantage over widespread available processes. The resulting nanomaterial (Ø 7–48 nm obtained from TEM and PXRD analysis) presents exclusively CeIV oxidation state according to XANES measurements. The doping process provides a solid solution with Eu3+ occupying the octahedral CeIV site, indicated by the photoluminescent characterization of the nanoparticles. The use of aqueous solvent, simple experimental apparatus, low energy input and easily accessible precursors make the benzenetricarboxylate method attractive for low cost nanoparticle synthesis.

Structural and Magnetic Рroperties of Copper Substituted Mg-Ferrites

Polycrystalline ferrite powders of Mg1-xCuxFe2O4 (x = 0.2, 0.4, 0.6, 0.8, 1) system synthesized by ceramic technology have been investigated. Samples showed the non-monotonic dependency of heat generation effect in AC magnetic field with increasing concentration of copper. To reveal peculiarities of the structural and magnetic state of the samples and their influence on the heat generation ability we performed a complex study, including X-ray diffractometry, Mössbauer spectroscopy, Scanning electron microscopy, measurements of temperature dependencies of susceptibility and saturation magnetization, hysteresis parameters and FORC. Typical ferrimagnetic character with small coercivity and saturation magnetization was found. We carried out that anomalous influence of Cu2+ ion substitution respectively to the Mg1-xCuxFe2O4 ferrite powder manifested in heat generation ability rise up to x=0.6. The subsequent sharp reducing of this characteristic were accompanied by the main phase crystal structure distortion followed by phase separation to cubic and tetragonal structure. This was matched by in an increase of ferrite particles crystallite size and size distribution appearance. The saturation magnetization and Curie temperature dependencies observed for powders via Cu substitution was explained by phase composition, the cations distributions between ferrite sublattices, modulation of exchange interaction.

Performance engineering of dye sensitized solar cells (DSSC) using Ag modified titania as photoanode

Present work reports the fabrication of silver (Ag) modified titania photoanode as an efficient photoanode for Dye Sensitized Solar Cell (DSSC). Pristine and Ag modified Titania nanomaterials were prepared using sol gel method. The structural analyses confirm the high crystallinity of the samples with crystallite size distribution in nanorange. TEM micrograph confirms that the synthesized nanomaterials are in uniform size. A red shift is observed in the UV DRS spectra compared to pristine Titania and which confirm the incorporation of Ag inside titania. A prototype DSSC was fabricated using the pristine and modified Titania as photoanode, Ruthenium dye as sensitizer, I-/I-3 as redox electrolyte and platinum counter electrode. The cell with Ag modified titania photoanode showed 15 times enhanced photoconversion efficiency (PCE) than the pristine one. This improved performance of the Ag modified DSSC can be ascribed to reduced recombination and improved charge carrier transport of electrons/holes at the interfaces.

Enhanced dielectric properties of Nanocrystalline Ba(1-x)SrxTiO3 (x=0 and 0.3) ceramics

In this paper, we report the enhancement of the dielectric constant of barium titanate (BTO) through partial substitution of strontium to barium and crystallite size reduction through a high power ultrasonic treatment. The sample under investigation is Ba1-xSrxTiO3 or BST with x = 0 and 0.3 compositions prepared through mechanical alloying of SrCO3, BaCO3 and TiO2 precursors as the feedstock. All mechanically alloyed samples were crystalline powders with a single phase as confirmed by an x-ray diffractometer (XRD). The mechanically alloyed materials were consisted of multi-crystallite particles as confirmed both by XRD data analysis and particle size evaluation. Subject to an additional ultrasonic treatment, the multi-crystallite particles were fragmented toward mono-crystallite particles with the mean crystallite size about 52 nm after 12 hours irradiation. Even a smaller mean crystallite size (18 nm) with a narrower crystallites distribution then that of BTO was obtained in Ba1-xSrxTiO3 with x = 0.3. Such a narrow crystallite size distribution with a small mean crystallite size has superior dielectric constant over those of BTO and doped BTO with a large mean crystallite size. The highest dielectric constant of 3000 was obtained at a frequency of 273 Hz in doped BTO after 12 hours ultrasonic irradiation. The value is 12 times higher than those of BTO and doped BTO with a large crystallite size.

Importance of precursor type in fabricating ZnO thin films for photocatalytic applications

Here, the importance of choosing an appropriate precursor with right molarity for the fabrication of zinc oxide (ZnO) films by spray pyrolysis for the photocatalytic application is reported. Films were grown on glass substrates by using three different zinc precursors such as zinc acetate, zinc chloride, and zinc acetylacetonate. The structural, morphological, and optical characterizations were performed on the ZnO films. A preferential orientation along (002) plane, crystallite size distribution in the range 21–59nm, and the nanostructures such as nanothorns, hexagonal nanorods, hexagonal layers and elongated grains, were acquired from the characterization studies. Further, the photocatalytic activity was tested using indigo carmine dye, obtaining 100% of dye degradation using the ZnO thin films deposited with zinc acetate, whereas films from zinc chloride and zinc acetylacetonate precursors showed 20% and 10% of degradation respectively.

Fabrication and study of sol-gel ZnO films for use in Si-based heterojunction photovoltaic devices

This paper considers the use of zinc oxide thin films prepared via the sol-gel route as an n-type layer in heterojunction ZnO/Si solar cells. The ZnO films were prepared via a simple spin-coating technique using zinc acetate dihydrate as a zinc precursor, isopropanol as a solvent and monoethanolamine as a stabilizing agent. Optical, structural and morphological properties of ZnO were investigated for thin films grown from sol-gel solutions with different concentrations both on glass and silicon substrates. As such, a distribution of crystallite sizes and surface topology parameters corresponding to various zinc acetate dihydrate concentrations were obtained to elucidate optimal film deposition conditions. Correlation between thin film morphology and structural characteristics of ZnO thin films was made based on atomic-force microscopy studies. Finally, our results on fabrication, characterization and simulation of ZnO/Si heterojunctions for use as photovoltaic devices are presented. Although noticeable rectifying and photovoltaic properties were observed for Al/Si/ZnO/Ti/Au devices, there appears to exist a considerable room for device improvement with simulation studies suggesting that efficiencies of the order of 24% may be obtained for devices with optimal silicon wafer passivation, i.e. with lifetimes of the order of 1000 μs.

Polylactide single-polymer composites with a wide melt-processing window based on core-sheath PLA fibers

Polylactide (PLA) single polymer composites (SPCs) were prepared using PLA nonwovens made of core-sheath PLA fibers as raw materials by hot-pressing. The core and sheath materials were poly(l-lactide) (PLLA) and PLA with d-lactide of about 10mol% (PLA90), respectively. The melt processing window of PLA SPCs reached more than 40°C. The effects of hot-pressing temperature on the crystallinity, the size distribution of crystallites, the lamellar thickness and mechanical property of PLA SPCs were significant while those of hot-pressing pressure were small. The strong interfacial adhesion between matrix and reinforcement led to high mechanical properties of PLA SPCs. For pure PLA materials prepared at 180°C, the tensile strength (σb), elongation at break (εb), the work of rupture (W) and impact strength (αcU) were only 19MPa, 1.8%, 0.15J, and 2.8kJ/m2, respectively while those of the SPCs prepared at 130–160°C were 47–65MPa, 15–32%, 9–22J, and 14.9–67.2kJ/m2, respectively. With the increase of hot-pressing temperature, the σb, W and αcU decreased.

Structural, Magnetic and Mossbauer Studies of Magnesium Ferrite Nanoparticles Prepared by Hydrothermal Method

Magnesium ferrite (MgFe2O[Formula: see text] being a soft magnetic material with fast frequency response, high a.c. heat power generation and high biocompatibility, is widely used in biomedical fields such as targeted drug delivery, magnetic hyperthermia, etc. This paper reports the synthesis of magnetic MgFe2O4nanoparticles by hydrothermal method using chloride salts of metal ions. The effect of calcination on the structural and magnetic properties is studied by XRD, FTIR, VSM and Mossbauer spectrum analysis. Fine particles in the size range 3–24[Formula: see text]nm are obtained. On calcination, crystallite size increases and lattice parameter decreases. From the magnetic characterization, it is seen that the magnetic properties mainly depend on crystallite size and cation distribution. The mixed spinel states of the prepared materials are confirmed from the FTIR and Mossbauer spectrum analysis. The doublet spectrum obtained in the Mossbauer studies indicates the superparamagnetic relaxation at room temperature.

Adjusted interactions of nickel nanoparticles with cobalt-modified MgAl2O4-SiC for an enhanced catalytic stability during steam reforming of propane

Steam reforming of propane (SRP) for the stable production of hydrogen-rich reformates was investigated using the Ni-supported on the cobalt-modified SiC-embedded MgAl2O4 support (denoted as NCMAS). The adjusted interactions of the Ni nanoparticles with the cobalt-modified SiC-embedded MgAl2O4 (MgAl2O4-SiC) and its crystallite size distributions largely altered the catalytic activity and stability of NCMAS. The introductions of SiC on the NCMAS, where SiC has a higher thermal conductivity, also increased the dispersion of smaller MgAl2O4 grains with the less formations of inactive NiAl2O4 species, which resulted in the higher catalytic activity with smaller formations of unreformed light hydrocarbons. The positive roles of cobalt promoter on the MgAl2O4-SiC matrices were mainly attributed to the suppressed aggregation of nickel nanoparticles by their strong and intimate interactions with the cobalt-modified MgAl2O4. The effects of cobalt promoter at an optimal 5wt%Co in the MgAl2O4-SiC (NCMAS(5)) enhanced the oxidation-resistance of the nickel nanoparticles with less formations of inactive metal aluminates by being reversibly re-reduced under the SRP reaction conditions. These phenomena further lessen coke depositions by intimately interacting with highly dispersed oxophilic cobalt or cobalt aluminate species. The optimal NCMAS(5) was applied to derive kinetic parameters using Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanisms, and the reasonable activation energy of 73 kJ/mol and optimal operating parameters to maximize hydrogen production by SRP reaction was estimated in terms of the reaction conditions such as space velocity, feed ratio and reaction temperature.

High resolution residual stress gradient characterization in W/TiN-stack on Si(100): Correlating in-plane stress and grain size distributions in W sublayer

Residual stress gradient characterization by the ion beam layer removal method (ILR), using a milling step of 10nm, was applied to W/TiN stacks processed on thermal SiO2-insulated standard silicon wafers. The stress profiles indicate a pronounced stress gradient with high tensile, as well as compressive stress concentrations in polycrystalline W and amorphous TiN sublayers ranging between 3.5 and −4GPa. Electron backscatter diffraction shows that the W sublayer exhibits zone T microstructure with nano-sized crystallites in the nucleation region at the interface to TiN and above that columnar or V-shaped grain morphology typical for competitive grain growth. In the W sublayer, the stress distributions correlate well with this in-plane crystallite size distribution on the base of a Hall-Petch mechanism, reaching a tensile maximum in the transition region between the nucleation layer and the region with columnar microstructure.

Crystalline microstructure of boehmites studied by multi-peak analysis of powder X-ray diffraction patterns

Nanocrystalline boehmite (gamma-aluminium-oxyhydroxide) is a material of industrial importance, the functionality of which follows from its crystalline microstructure. A procedure for preparing boehmite nanoparticles, comprising the formation of a precipitate by the alkalization of an aqueous solution of aluminium nitrate and subsequent hydrothermal aging, was previously elaborated. The application of an additive (maltitol or tartaric acid) to control the sizes and shapes of crystallites in the produced polycrystalline powder of boehmite was developed. The aim of this work is a study of the effect of the hydrothermal treatment time on nanocrystalline characteristics of boehmite, both in absence and in presence of the additive. The obtained materials were investigated by using X-ray diffraction (XRD) as principal technique and additionally by scanning and transmission electron microscopy. The multi-peak analysis of powder XRD patterns was applied to determine the prevalent crystallite shape, volume-weighted crystallite size distribution, and second-order crystalline lattice strain distribution being principal quantitative characteristics of the crystalline microstructure. Based on these characteristics, three types of the microstructure correlated with the production procedures were observed and discussed in detail. The nanoparticles of boehmites were found to be monocrystalline grains with characteristic habits and sizes of order of ten nanometers weakly dependent on the hydrothermal treatment time.

Structural and magnetic properties characterization of mechanically alloyed La substituted Ba(1-x)LaxFe12O19 (x = 0.07, 0.15 and 0.20)

This study reported the structural studies and magnetic properties of La-substituted barium hexaferrite (BHF) with Ba1-xLaxFe12O19 (x=0. 07, 0.15 and 0.20) constitutions. All samples were synthesized through mechanical alloying technique using BaCO3, La2O3 and Fe2O3precursors that were mechanically milled for 20 hours and successively sintered at 1200 °C to produce polycrystalline materials. The X-ray diffraction (XRD) method was employed to characterize the microstructure of synthesized materials. Structural analysis by refinement of XRD data showed that all sintered Ba1-xLaxFe12O19 (x=0.07, 0.15 and 0.20) samples are single phase material. The crystallite size of all samples was below 150 nm, with the mean size value decreased from 35 nm in sample of x = 0.07 to 23 nm in x = 0.20. This was accompanied by a change in crystallite size distribution toward the slim distribution. Magnetic properties characterization of La substituted BHF showed a substantial increase of coercivity as the fraction of La increased but the remanent magnetization decreased.The largest coercivity value of 315 kA/m was obtained in sample with x = 0.20 which is almost double when compared with low substitution of La (x = 0.07).

Unraveling Fundamental Descriptors for the Structural and Morphological Degradation of Pt Nanoparticles on Indium Tin Oxide Using in Situ Techniques

Enhancing stability of cathode catalysts for PEMFC applications under operating conditions is of great importance because state-of-art supports for nanoparticular Pt electrocatalysts suffer from carbon corrosion especially during start-stop procedure. Metal oxides have been proven to be viable alternatives because of their corrosion resistance and observed strong metal support interaction which is thought to enhance activity as well as stability of the catalyst [1-3]. Tin-based oxides excel by their thermal stability as well as high conductivity and are therefore promising candidates as alternative fuel cell support materials [4]. But the structural evolution of Pt-based nanoparticles under electrochemical conditions on oxides is still unknown. On high surface area carbon it has been shown by using in-situ SAXS studies that Pt nanoparticles grow due to Ostwald ripening and a dissolution/redeposition mechanism decreasing the electrochemical active surface area (ECSA) [5]. Here, we report on metal oxide supported Pt nanoparticles focussing on the structural evolution under electrochemical potential cycling applied to mimic fuel cell operating conditions. The Pt nanoparticles were synthesized using a solvothermal route and deposited on Indium Tin Oxide (ITO) resulting in homogenously distributed particles with well defined size. The electrocatalysts were extensively tested with respect to long-term electrochemical stability in order to investigate its potential as alternative carbon-free support material. We determined the evolution of crystal structure, composition, crystallite size and particle size distribution of the oxide support and the Pt nanoparticles by using in situ XRD and ASAXS. Additionally, we were able to follow the dissolution of the catalyst components during the electrochemical protocol using SFC ICP-MS setup. We can show that in case of ITO the size of Pt nanoparticles increases only slightly, whereas the mass-based catalytic activity decreases primarily due to changes of the support. Furthermore, our results show that we are able to unravel fundamental aspects of morphological degradation of Pt nanoparticles on non-carbon supports under electrochemical conditions. These results will help to understand stability determining properties of oxide supports leading to enhanced cathode electrocatalysts for a PEMFC. [1] A. Kumar, V. Ramani, J. Electrochem. Soc. 2013, 160, F1207-F15. [2] A. Lewera, L. Timperman, A. Roguska, N. Alonso-Vante, J. Phys. Chem. C 2011, 115, 20153-59. [3] T.T.H. Van, C.J. Pan, J. Rick, W.N. Su, B.J. Hwang, J. Am. Chem. Soc. 2011, 133, 11716-24. [4] H.-S. Oh, H.N. Nong, P. Strasser, Adv. Funct. Mater. 2015, 25, 1074-81. [5] X. Tuaev, S. Rudi, V. Petkov, A. Hoell, P. Strasser, Acs Nano 2013, 7, 5666-74.