XRD Intensities Research Articles

Reduction Reactivity of Low Grade Iron Ore-Biomass Pellets for a Sustainable Ironmaking Process

Currently, fossil fuels are still the primary fuel source and reducing agent in the steel industries. The utilization of fossil fuels is strongly associated with CO2 emissions. Therefore, an alternative solution for green steel production is highly recommended, with the use of biomass as a source of fuel and a reducing agent. Biomass’s growth consumes carbon dioxide from the atmosphere, which may be stored for variable amounts of time (carbon dioxide removal, or CDR). The pellets used in this study were prepared from a mixture of low-grade iron ore and palm kernel shells (PKS). The reducing reactivity of the pellets was investigated by combining thermogravimetric analysis (TGA) and laboratory experiments. In the TGA, the heating changes stably from room temperature to 950 °C with 5–15 °C/min heating rate. The laboratory experiments’ temperature and heating rate variations were 600–900 °C and 10–20 °C/min, respectively. Additionally, the reduction mechanism was observed based on the X-ray diffraction analysis of the pellets and the composition of the reduced gas. The study results show that increasing the heating rate will enhance the reduction reactivity comprehensively and shorten the reduction time. The phase change of Fe2O3 → Fe3O4 → FeO → Fe increases sharply starting at 800 °C. The XRD intensities of Fe compounds at a heating rate of 20 °C/min are higher than at 10 °C/min. Analysis of the reduced gas exhibits that carbon gasification begins to enlarge at a temperature of 800 °C, thereby increasing the rate of iron ore reduction. The combination of several analyses carried out shows that the reduction reaction of the mixture iron ore-PKS pellets runs optimally at a heating rate of 20 °C/min. In this heating rate, the reduced gas contains much higher CO than at the heating rate of 10 °C/min at temperatures above 800 °C, which encourages a more significant reduction rate. In addition, the same reduction degree can be achieved in a shorter time and at a lower temperature for a heating rate of 20 °C/min compared to 10 °C/min.

Impact of Radio Frequency Plasma Power on the Structure, Crystallinity, Dislocation Density, and the Energy Band Gap of ZnO Nanostructure

The aim of this study is to investigate the effect of radio frequency (RF) plasma power on the morphology, crystal structure, elemental chemical composition, and optical properties of ZnO nanostructure using a direct current magnetron sputtering technique. This study emphasized that the growth rate and surface morphology of the polycrystalline ZnO were enhanced as the radio frequency (RF) plasma power increased. This can be observed by fixing other parameters such as the growth time, substrate temperature, and chamber partial pressure. The RF plasma power alteration from 150 to 300 W can produce uniform nanograin, spheroid, and nanorods. Additionally, the RF plasma power alteration leads to the alteration in the ZnO nanorod diameter from 14 to 202 nm. It was observed that the XRD intensities are increased at higher plasma powers. This, perhaps, can be inferred from the transformation of the granular microcrystals to the needlelike or platelike large crystals, as already examined using SEM images. This also has an impact on the average crystalline size, which increased from 10 to 40 nm on increasing the RF plasma power. Moreover, the increase of the RF plasma power has an obvious impact upon the optical band-gap energy, which was accordingly decreased from 3.26 to 3.22 eV. Finally, the absorption band edge was shifted to a lower-energy region due to the quantum size effect at the nanorange.

Electrochemical Nanostructuring of Electrodeposited Cu2o Thin Film for Efficient Hydrogen Reduction

Cu2O is an intrinsic p-type semiconductor with a direct bandgap of 2 eV and its conduction band edge lies 0.7 V negative of hydrogen reduction potential which makes it a promising photocathode for water splitting. This study emphasizes the modification of the surface of Cu2O thin films to facilitate the separation of photogenerated charge carriers as well as increase the electrode-electrolyte contact area. Mesoporous Cu2O is realized by holding a thin film of electrodeposited Cu2O at a positive potential (0.4 V ‒ 1 V vs. Ag/AgCl) in buffered Na2SO4 (pH 5) . The treated films are found to have mesoporous structure with 10-30 nm thick flakes on its surface. No phase change is observed in electrochemically treated Cu2O thin films although the XRD intensities of all peaks are slightly lower indicating material loss. This morphological conversion is attributed to Cu2O dissolution in acidic media as trace copper ions are detected in the solution. The modified Cu2O photocathode can lead to a better device performance due to increased surface area and improved charge transport. Figure 1

Effects of growth temperature and thickness on structure and optical properties of Ga2O3 films grown by pulsed laser deposition

A series of Ga2O3 films grown on sapphire substrate by pulsed laser deposition with different growth temperature (400–1000 °C) and different thickness (69–332 nm) were studied by X-ray diffraction, optical transmittance and spectroscopic ellipsometry. The phase was transformed from amorphous to polycrystalline β-Ga2O3 structure with increasing growth temperature. Refractive indexes increase with increasing thickness or growth temperature of the films in the transparent area, where the effect of film thickness is much more significant than that of growth temperature. The Urbach tail observed in absorption edge by ellipsometry combined with the transmittance spectra and the XRD intensities illustrate that higher growth temperature or thicker thickness can improve the crystal quality of films. The band gap of Ga2O3 films decrease with increasing growth film thickness and elevated experimental temperature (25–600 °C), and the quantitative analysis of temperature-dependent band gap was conducted by using the Varshni equation.

Enhancement of Osteoblastic-Like Cell Activity by Glow Discharge Plasma Surface Modified Hydroxyapatite/β-Tricalcium Phosphate Bone Substitute.

Glow discharge plasma (GDP) treatments of biomaterials, such as hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) composites, produce surfaces with fewer contaminants and may facilitate cell attachment and enhance bone regeneration. Thus, in this study we used argon glow discharge plasma (Ar-GDP) treatments to modify HA/β-TCP particle surfaces and investigated the physical and chemical properties of the resulting particles (HA/β-TCP + Ar-GDP). The HA/β-TCP particles were treated with GDP for 15 min in argon gas at room temperature under the following conditions: power: 80 W; frequency: 13.56 MHz; pressure: 100 mTorr. Scanning electron microscope (SEM) observations showed similar rough surfaces of HA/β-TCP + Ar-GDP HA/β-TCP particles, and energy dispersive spectrometry analyses showed that HA/β-TCP surfaces had more contaminants than HA/β-TCP + Ar-GDP surfaces. Ca/P mole ratios in HA/β-TCP and HA/β-TCP + Ar-GDP were 1.34 and 1.58, respectively. Both biomaterials presented maximal intensities of X-ray diffraction patterns at 27° with 600 a.u. At 25° and 40°, HA/β-TCP + Ar-GDP and HA/β-TCP particles had peaks of 200 a.u., which are similar to XRD intensities of human bone. In subsequent comparisons, MG-63 cell viability and differentiation into osteoblast-like cells were assessed on HA/β-TCP and HA/β-TCP + Ar-GDP surfaces, and Ar-GDP treatments led to improved cell growth and alkaline phosphatase activities. The present data indicate that GDP surface treatment modified HA/β-TCP surfaces by eliminating contaminants, and the resulting graft material enhanced bone regeneration.

Structural-disorder and its effect on mechanical properties in single-phase TaNbHfZr high-entropy alloy

Equiatomic TaNbHfZr refractory high-entropy alloys (HEAs) were synthesized by arc-melting. The HEAs were annealed at 1800 °C for different times, at maximum up to 8 days. Their on average body-centered cubic (bcc) solid-solution structure was confirmed by X-ray (XRD) and neutron (ND) diffraction, respectively. The HEAs are characterized by high average values of the static atomic displacements from the ideal lattice positions and the local internal strain. The short-range clustering (SRC) of a subset of atoms, enriched in Hf and Zr takes place perpendicular to the <100> directions. Furthermore, it becomes increasingly interconnected as a function of the annealing time. This is revealed by the evaluation of diffuse XRD intensities, high-resolution transmission electron microscopy (HRTEM) images, and atom probe tomography (APT). The local structural disorder and distortions at the SRC were modeled by molecular dynamics (MD) relaxations. The hardness and compressive yield strength of the as-cast HEA is found to be many times of what can be expected from the rule of mixture. The yield strength further increases by 76% after 1 day of annealing, which can be explained by a strengthening mechanism resulting from the SRC. With further annealing to 4 days, a minor phase with hexagonal close packed (hcp) structure and rich in Hf and Zr nucleates at the larger connecting nodes of the SRCs.

A note on the reaction between sputter co-deposited Mn and Si and formation of the MnSi phase

Mn and Si were magnetron co-sputtered on Si (100) substrates and annealed in the temperature range of 773-848 K in Ar atmosphere to obtain MnSi. The results were tested by XRD, high resolution SEM (HRSEM), 4 points probe measurements and AES. The activation energy calculated on the basis of XRD intensity is in the range of 0.43-0.71 eV. The Mehl-Johnson relation was applied for the determination of the activation energy interval. The HRSEM thicknesses evaluated are related to the intensity measurements. The constants appearing in the Mehl-Johnson equation were determined by graphical iteration. The activation energy calculated on the basis of film thickness is almost exactly the same as that obtained by XRD intensity measurements being in the range of 0.43 – 0.73. The results of the activation energy evaluation of MnSi formation and the method relating XRD intensities to the thickness are discussed.

Effect of the Quartz Particle Size on XRD Quantifications and Its Implications for Field Collected Samples

The aims of the present study were to assess the effect of the quartz particle size on XRD quantifications, and use it to develop models for correcting the measured quartz concentrations of samples collected from the field. Seven nearly monodispersed pure quartz dusts, with mass median aerodynamic diameters (MMAD) ranging from 0.70 to 10.84 μm, were prepared by a liquid sedimentation device, and their unit XRD intensities (UI) were measured using the NIOSH Method 7500. The results show that UI increases (from 063 to 1.14) along with the rise in MMAD of the pure quartz dust. To examine the impact of the above results on quantifying field collected samples, both total dust and respirable dust samplings were conducted at seven different workplace environments. The results show that the quartz particles contained in all collected total dust samples (MMAD=5.18-16.7 μm, GSD=2.08-2.88) were coarser in their particle sizes than that of the reference quartz standard (NIST-SRM 1878; MMAD=2.16 μm, GSD=1.55), and the measured total quartz particle concentrations (C_m) were 16.6-22.5% lower than the corresponding true concentrations (C_t). However, for respirable dust samples (MMAD=1.37-3.95 μm, GSD=1.978-2.87), since collected quartz particle sizes could be either finer or coarser than that of the reference standard, both underestimation and overestimation were found in the present study (C_m/C_t=0.881-1.09). To correct the measured concentrations of field collected samples, correcting models were developed based on the MMADs of the collected quartz particle samples and their corresponding UIs. This study yields correcting factors for the respirable fraction (CR_f) as CR_f=1.50-0.67×[1-exp(-0.69×MMAD)] (R^2=0.996, n=7). However, the obtained CR_f should be used with caution if the collected samples were found with quartz particle sizes falling outside the size range of the present study.

Setting solution concentration effect on properties of a TTCP/DCPA-derived calcium phosphate cement

The present work was to investigate the effects of concentration of (NH(4))(2)HPO(4) (diammonium hydrogen phosphate) setting solution on properties of a tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)--derived calcium phosphate cement. Experimental results indicated that working/setting time of the cement paste decreased with increasing (NH(4))(2)HPO(4) concentration of the setting solution. After being immersed in Hanks' solution for 1 day or longer, the XRD intensities of initial TTCP and DCPA phases largely decreased, while apatite phase became dominant. More residual TTCP phase was observed in the 1 day-immersed cement prepared from higher concentration setting solutions. Compressive strength of the cement immersed for 1 day was consistently higher than that immersed for 30 min or 7 days. After being immersed for 1 day, the average CS value reached a maximal value (59 MPa) as (NH(4))(2)HPO(4) concentration was increased to 0.6 M, beyond that the cement strength decreased and maintained in a relatively high range of 47-54 MPa. Cells incubated with conditioned medium of Al(2)O(3) powder and with blank medium exhibited similar average viability values (0.80 and 0.78, respectively). The OD value with extractions of cement decreased with increasing (NH(4))(2)HPO(4) concentration of the setting solution. The average 0.25, 0.5 and 0.6 M--OD values were 0.78, 0.67 and 0.66, respectively. When setting solution concentration was greater than 0.6 M, the OD value sharply declined to 0.47.

Mechanochemical processing of serpentine with ammonium salts under ambient conditions for CO2 mineralization

This paper assesses the suitability of mechanochemistry as a convenient low-energy processing option in CO2 mineralization. Whereas some success has been reported in milling alkaline earth-containing minerals under gaseous CO2, this work focuses instead on a purely solid-state approach towards two key objectives: (a) Mg extraction from serpentine using ammonium bisulfate; and (b) direct or indirect CO2 sequestration using ammonium bicarbonate in a natural extension of its role as “CO2 carrier” in the chilled ammonia scrubbing process. In Mg extraction work, dry milling of serpentine with ammonium bisulfate gave respectable yields (>60% Mg) as boussingaultite [(NH4)2Mg(SO4)2·6H2O] in 2 to 4 h. In CO2 sequestration, dry milling anhydrous magnesium sulfate with ammonium bicarbonate yielded only mixed sulfate products. Carbonation of the heptahydrate, epsomite, was found to proceed via ammonium magnesium carbonate hydrate [(NH4)2Mg(CO3)2·4H2O], which dissolves incongruently to yield nesquehonite [MgCO3·3H2O]. The modest conversion (∼30%) is probably due to equipartition of Mg into the double sulfate co-product. A similar route is followed in magnesia and brucite, in which the existence of an amorphous native carbonate precursor to nesquehonite in the same molar ratio (Mg : CO2 = 1) was inferred from inconsistency in the XRD intensities. This was largely responsible for the high carbonation yields in the unwashed products, ∼70% and ∼85% in MgO and Mg(OH)2, respectively, as confirmed by TG-FTIR. The same intermediate is probably formed in serpentine, but it is apparently soluble in the aqueous mineral environment. When the unwashed product is subjected to mild thermal consolidation, stable hydromagnesite [Mg5(CO3)4(OH)2·4H2O] is formed in ∼20% yield after milling for 16 h. Possible identities for the amorphous precursor are briefly considered.

Twin growth and its interaction with precipitates

New models for twin growth and its interaction with precipitate in Inconel-718 are proposed in this paper. The measured accumulated XRD intensities to represent the quantity of the Ni 3 Nb( δ) phase are in agreement with its dissolution in twin/grain interior and precipitation again in twin/grain boundary. Present result shows that twin growth is associated with and similar to a “wave front” movement of twin boundary mainly resulting from the assistance of sufficient vacancies and solute atoms from dissolved Ni 3 Nb( δ) phase diffusing from the twin interior toward the twin boundary to build up the existed twin. This leads to the overall free energy reduction and results in twin growth. Furthermore, possible interaction of twin growth meeting NbC particle is also discussed.

Rapid synthesis of pervoskites (KNbO 3, SrTiO 3) and spinel (LiMn 2O 4) in presence of α-glycine with finished end product

Addition of Amino acid α-glycine to pervoskites like potassium niobate (KNbO 3) and strontium titanate (SrTiO 3) is seen to reduce the temperature of synthesis by several 100 degrees leading to formation of fine end product. Reduction of the grain size as much as 27% has been recorded in KNbO 3. The XRD Intensities were found to depend on the molar proportion of glycine. The average particle size of the KNbO 3 product with glycine is found to be in order of 140–290 nm having maximum tetragonal distortion of 1.206. SrTiO 3 synthesised in presence of glycine shows needle shaped structures with reduction in white aggregates. Glycine helps in liberation of carbon dioxide with fishy odour thereby leading to the early phase formation. Studies on LiMn 2O 4 spinel used in rechargeable lithium batteries in this direction have been included.

Anomalous phase composition in the two-phase region of DyFe3−xAlx (x≤1.0)

The structure transitions and phase relationships of DyFe3−xAlx compounds have been investigated by X-ray powder diffraction. Our XRD results show that each of the compounds with x≤0.45 crystallizes in the rhombohedral PuNi3-type structure with space group R3¯m and Z=9; for the 0.8≤x&lt;1.0 compounds, each has a hexagonal structure of the CeNi3 type with space group P63/mmc and Z=6; and each of the samples with 0.45&lt;x&lt;0.8 is a two-phase mixture of the PuNi3- and CeNi3-type structures. The calculated XRD intensities of the DyFe3−xAlx compounds with x=0.2, 0.33, 0.4, and 0.45 indicate that Dy occupies the 3a and 6c sites, Fe and Al distribute randomly on the 18h site, and the 3b and 6c sites are exclusively occupied by Fe, which agrees well with those of our experimental XRD patterns. The XRD intensities of the DyFe3−xAlx compounds with x=0.8 and 1.0 have also been calculated and found to agree with the experimental results with Dy on the 2c and 4f sites, Fe and Al at the 12k site, and Fe at the 2a, 2b, and 2d sites. In the two-phase region with x=0.45–0.8, the values of unit-cell parameters and phase compositions are linearly dependent on the value of x, indicating that the two phases are constituted by the same composition x with different stacking arrangements. This abnormal two-phase equilibrium is further confirmed by the structural analysis of the DyFe2.33Al0.67 (or x=0.67) sample. The samples with x=1.1 and 1.2 were also analyzed, and each found to be a mixture of more than two phases.

Periodic density functional theory calculations for 3-dimensional polyacetylene with empirical dispersion terms

We report periodic B3LYP density functional theory calculations for three-dimensional (3D) trans-polyacetylene (t-PA) fibers. Empirical dispersion terms, as proposed by Grimme, are included with an appropriate re-scaling to yield the B3LYP+D* method implemented in CRYSTAL06. The dispersion corrections are critical for obtaining correct unit cell parameters. In our calculations the out-of-phase P2(1)/n structure turns out to be a transition state for the interchain relative translational motion, which lies about 0.35 kcal mol(-1) above the two symmetrically located in-phase P2(1)/a minima. These results provide a possible new explanation for the observed XRD intensities. Our calculations should also be useful for comparison with more costly non-empirical treatments of 3D PA and other pi-conjugated polymers.

Preparation and characterization of Bi0.4Te3.0Sb1.6 nanoparticles and their thin films

Abstract In this article, we perform a preliminary study to assemble micro-size thermoelectric devices with low-cost fabrication by a preparation of nanoparticles and their thin films. Bi 0.4 Te 3.0 Sb 1.6 nanoparticles with an average size of approximately 50 nm are fabricated by a beads-milling method. The nanoparticle solution is prepared by mixing with toluene and a surfactant, and thin films with 1 μm thick are deposited on Al 2 O 3 substrates by a printing method. The thin films are sintered at temperatures ranging from 300 to 500 °C for 60 min in hydrogen ambient. We investigate the thin film structures and the thermoelectric properties at room temperature. As the sintering temperature increases, hexagonal-shaped crystals are grown on the film surface while the atomic composition is almost constant throughout all the sintering temperatures. The XRD patterns indicate that all the nanoparticle thin films are found to mostly exhibit the same XRD intensities and have multiple peaks correspond to each other. The in-plane electrical conductivity of the thin films increases but the Seebeck coefficient decreases as the sintering temperature increases. As a result, the best performance of the thermoelectric power factor of 1.3 μW/(cm K 2 ) is achieved at a sintering temperature of 350 °C.

Growth and Properties of GaN by Vapor Transport Epitaxy

Highly c-axis oriented poly-crystalline GaN with a dimension of <TEX>$1{\sim}3\;{\mu}m$</TEX> was deposited on <TEX>$c-Al_2O_3$</TEX> substrate by vapor transport epitaxy (VTE) method at the temperature range of <TEX>$900{\sim}1150^{\circ}C$</TEX>. XRD intensities from (00'2) plane of grown GaNs were increased with reaction conditions which indicate the improvement of the crystal quality. In the PL spectra measured at 10 K, the spectrum composed with the neutral-donor bound exciton-related emission at 3.47 eV, crystal defect-related emission band at 3.42 eV and with its phonon replicas. The fact that intensity of <TEX>$I_2$</TEX> were increased and FWHM were decreased with growth conditions means that the quality of GaN crystals were improved. With this simple VTE technology, we confirm that the GaNs were simply deposited on sapphire substrate and crystal quality related to optical properties of GaN grown by VTE were relatively good. PL emission without deep level emission in spite of polycrystalline structure can be applicable to the fabrication of large area and low cost optical devices using poly-GaN grown by VTE.

Preparation of double-sided epitaxial Yb124 films by coating-pyrolysis process

Double-sided epitaxial YbBa 2Cu 4O 8 (Yb124) films were grown on 20 × 20 mm 2 LaAlO 3(0 0 1) substrates by coating-pyrolysis process. The Yb124 film, prepared through an annealing path with a heating rate of 10–20°C/min up to 780°C, exhibited very strong XRD intensities corresponding to the c-axis orientation. Inductive superconducting transitions were recognized at 77.4 and 77.6 K for both sides.

High-resolution X-ray diffraction analysis of cubic GaN grown on (0 0 1)GaAs by RF-radical source molecular beam epitaxy

Cubic GaN epilayers were grown on atomic hydrogen treated (001)GaAs substrates by RF-radical source molecular beam epitaxy. The crystalline quality was characterized by a high-resolution X-ray diffractometer. It was found that high-quality c-GaN can be grown at temperatures above 680°C; the FWHM of (002)GaN rocking curve was as small as 80–90arcsec. In order to further precisely investigate how and to what extent the h-GaN phase is included in the c-GaN layer, the X-ray reciprocal space maps were measured for the X-ray beams incident along both 〈110〉 and 〈11̄0〉 azimuths. It was found that the stacking faults exist predominantly on {111}A planes. The inclusion of h-GaN was estimated by comparing the integrated XRD intensities for h-GaN {101̄1} and c-GaN(002) planes. It was found that the inclusion of h-GaN phase drastically decreased with increasing growth temperature above 680°C to reach about 4×10−3 (or below) at temperatures of 710–740°C.

Pulsed laser deposition of CdWO 4

Pulsed laser depositions of CdWO 4 thin films are carried out in the presence of O 2 using targets of CdWO 4(010) single crystals and pressed CdO and WO 3 powder mixtures. CdWO 4(002) peaks are observed on Si(111), CaF 2(111), mica(001) and glass substrates by ablating CdWO 4(010) single crystals. CdWO 4(002) and (111) peaks are detected in the films prepared on glass substrate using CdO and WO 3 mixed powders and the relative XRD intensities change as a function of atomic ratio of CdO to WO 3 used. The thin film with the stoichiometric composition of CdWO 4 can be prepared by selecting appropriate CdO WO 3 ratio in the mixed oxide target and the film shows a photoluminescence similar to CdWO 4.

Grain orientation in sol-gel derived Ln 2Ti 2O 7 ceramics ( Ln = La, Nd)

Sol-gel derived La 2Ti 2O 7 and Nd 2Ti 2O 7 exhibited preferential grain orientation on sintering. The extent of orientation is quantified in terms of the Lotgering orientation factor from the XRD intensities of pellets sintered at different temperatures. The microstructural studies indicated extensive orientation with sintering and also a change in morphology of the grains from acicular to large platelets.