Values Of Interplanar Spacing Research Articles

Effect of Thermal Activation on the Structure and Electrochemical Properties of Carbon Material Obtained from Walnut Shells.

A simple activation method has been used to obtain porous carbon material from walnut shells. The effect of the activation duration at 400 °C in an atmosphere with limited air access on the structural, morphological, and electrochemical properties of the porous carbon material obtained from walnut shells has been studied. Moreover, the structure and morphology of the original and activated carbon samples have been characterized by SAXS, low-temperature adsorption porosimetry, SEM, and Raman spectroscopy. Therefore, the results indicate that increasing the duration of activation at a constant temperature results in a reduction in the thickness values of interplanar spacing (d002) in a range of 0.38-0.36 nm and lateral dimensions of the graphite crystallite from 3.79 to 2.52 nm. It has been demonstrated that thermal activation allows for an approximate doubling of the specific SBET surface area of the original carbon material and contributes to the development of its mesoporous structure, with a relative mesopore content of approximately 75-78% and an average pore diameter of about 5 nm. The fractal dimension of the obtained carbon materials was calculated using the Frenkel-Halsey-Hill method; it shows that its values for thermally activated samples (2.52, 2.69) are significantly higher than for the original sample (2.17). Thus, the porous carbon materials obtained were used to fabricate electrodes for electrochemical capacitors. Electrochemical investigations of these cells in a 6 M KOH aqueous electrolyte were conducted by cyclic voltammetry, galvanostatic charge/discharge, and impedance spectroscopy. Consequently, it was established that the carbon material activated at 400 °C for 2 h exhibits a specific capacity of approximately 110-130 F/g at a discharge current density ranging from 4 to 100 mA/g.

Green synthesis and characterization of silver doped ZnO particles

Green Synthesis is a chemical-free, economic, efficient, eco-friendly, and less time-consuming technique for the production of various nanoparticles. In the present study, green synthesized silver doped ZnO particles are synthesized. Silver nanoparticles are synthesized using Neem leaves and Silver salt (Silver Nitrate, AgNo3). Leaves extract act as a reducing agent for this synthesis. EDAX confirms the formation of Ag nanoparticles and ZnO particles. ZnO nanoparticles were successfully synthesized by the co-precipitation method, zinc acetate dehydrate and sodium hydroxide was used as precursor material. The green synthesized Ag nanoparticles are doped with ZnO. The synthesized particles were then characterized through XRD and UV–Vis spectrophotometry. The values of interplanar spacing and lattice parameters obtained were consistent with its standard values. The band gap of ZnO nanoparticles got reduced with doping Ag nanoparticles.

Enhancing high frequency magneto-dielectric performance with exchange-coupled garnet/spinel ferrite (Y3Fe5O12/Mg0.4Cd0.4Co0.2Fe2O4) composites

Yttrium iron garnet ferrite (YIG), with good magnetic and dielectric properties, was mixed with doped magnesium spinel ferrite (Y3Fe5O12(x)/Mg0.4Cd0.4Co0.2Fe2O4(1-x) (x = 0.3, 0.6, 0.9)) to attain high permittivity and permeability with low magneto-dielectric losses. We have reported the synthesis and enhanced structural, magnetic and magnetodielectric properties of composites for miniaturized antenna applications. The X-ray diffraction (XRD) patterns of all the composites were analysed using the Rietveld method, which confirmed that they exhibited a crystalline structure with a cubic spinel and cubic garnet phase. XRD spectra confirm that the spinel ferrite phase dominates over the garnet ferrite phase in the x = 0.3 composite, whereas it is the opposite for the other composites. In contrast to the parent ferrites, it has been observed that the composites (x = 0.3, 0.6, 0.9) exhibit a higher value of the crystallite size ‘D’ and a lower value of the lattice constant ‘a’. The composite with the x = 0.3 composition has the least porosity and a high relative density. From field emission scanning electron microscopy (FESEM), it has been ascertained that the materials possess a grain size ranging from 0.57 to 0.8μm, with a larger grain size for the x = 0.9 composite, while the x = 0.3 composite has the smallest grain size. Transmission electron microscopy (TEM) scans have corroborated the FESEM micrographs’ findings, indicating that the grains within the composites’ structure exhibit agglomeration. The calculated values of inter-planar spacing of the samples using high-resolution TEM (HR-TEM) matches well with the XRD results. A magnetic study reveals that the composite with x = 0.3 has a good exchange-coupling, the highest coercivity value of 99.2 Oe and a magnetization value of 41 emu/g. The composite with x = 0.3 also has the highest permittivity value of ∼19.5, a permeability value of ∼2.8, but low dielectric and magnetic losses of ∼0.009 and ∼0.002, respectively. These low losses and a high miniaturization factor of ∼7.2 at high frequency (14 GHz) make it a potential candidate for high-speed satellite antenna applications.

Phase transformation, morphology, DC electrical resistivity and dielectric properties investigations of properties of manganese doped barium titanate nanoparticles

In this work, manganese (Mn) doped barium titanate BaTi1-xMnxO3 nanoparticles with varying composition of Mn (x = 0.0, 0.10 and 0.20) were prepared by using sol–gel self-ignition wet chemical route. The influence of Mn doping on crystal structure, infra-red, morphology, DC electrical resistivity and frequency dependent dielectric studies was systematically investigated. To know the crystalline nature and purity of the prepared samples, a non-destructive X-ray diffraction (XRD) tool was used. The analysis of XRD results revealed that pure BaTiO3 and BaTi1-xMnxO3 with x = 0.1, samples show tetragonal structure and for higher Mn content (x = 0.20) shows the hexagonal structure. The values of interplanar spacing, Miller indices, etc. were used to determine the unit cell parameters, X-ray density and unit cell volume. The highest intensity peak (110) observed in XRD pattern was considered to determine the crystalline size and which is found to be in the range of 3 to 8 nm. Scanning electron microscopy (SEM) technique was employed to study the surface morphology. SEM analysis confirm the dense nature of the grains with hexagonal shape for x = 0.2. EDX results confirm the presence of Ba, Ti, Mn and O elements as per the stoichiometric proportion. The functional groups and chemical bonds of Mn doped BaTiO3 were obtained by Fourier transform infrared spectroscopy (FTIR). The temperature dependant DC electrical resistivity studies were performed by standard two probe technique. The conductivity plot exhibits negative temperature coefficient (NTC). The activation energy and resistivity both decreased with Mn doping. The dielectric properties such as dielectric constant (ε′), dielectric loss (ε″) and dielectric loss tangent (tan δ) were studied by means of LCR-Q meter. The variation of these parameters as a function of frequency shows the exponential decrease. The dielectric constant and dielectric loss reduces, whereas dielectric loss tangent increase on Mn doping. The ac conductivity increases with frequency.

Effect of Fe Doping on Photocatalytic Dye-Degradation and Antibacterial Activity of SnO2 Nanoparticles

A simple hydrothermal method is utilized to synthesize iron-doped tin oxide nanoparticles (Fe-SnO2 NPs) at various doping concentrations. The structural characterization using XRD, Raman, and FTIR measurements confirmed the incorporation of Fe ions into the SnO2 lattice without any deviation in the tetragonal crystal system of SnO2 nanoparticles. SEM and HRTEM images show the spherical-shaped nanoparticles with agglomeration. The values of interplanar spacing ([Formula: see text]-value) calculated from the HRTEM lattice are consistent with the XRD results. Further, optical analysis revealed a red shift in the optical absorption band and a decrease in the band gap energy with an increase in Fe-dopant concentration. The decrease of PL emission peak intensity with Fe doping revealed the generation of singly charged oxygen vacancies. The H2O2-assisted photocatalytic degradation efficiency of Fe-SnO2 NPs investigated against crystal violet dye indicated an efficiency of 98% for 0.05 M Fe-SnO2 NPs within 30 minutes under visible light illumination. In addition, the effects of pH, scavengers, and reusability of the catalyst are tested. The antibacterial behavior of Fe-SnO2 NPs against Escherichia coli is examined by using the colony count method, and the inhibition rate was found to be 49, 65, 70, and 78% for pure, 0.01, 0.03, and 0.05 M Fe-SnO2 NPs, respectively.

Eco-friendly synthesis of silver nanostructures using medicinal plant Vernonia amygdalina Del. leaf extract for multifunctional applications

Ethiopian medicinal plant, Vernonia amygdalina Del. mediated green silver nanostructures (V-SNS) were successfully synthesized for the first time. The surface amalgamation of biomolecules of plant leaf extract around Ag nanostructures has also been approved by the most advanced techniques which were employed to characterize the NSs. The presence of absorbance maxima, λmax at 454 nm confirms the formation of V-SNS. UV-DRS studies revealed the band gap of 2.09 eV for NSs. The role of biomolecules as capping agents for V-SNS was authenticated by FT-IR spectra. The presence of four sharp peaks in the XRD pattern of NSs confirmed the highly crystalline nature of NSs. The TGA-DTA studies revealed that Ag NS is thermally stable above 570 °C. The purity of the NSs was corroborated by SEM-EDAX analysis. The average particle size of V-SNS was deduced to be 35.24 nm. In addition, TEM micrographs revealed the presence of V-SNS with varieties of nano-sized shapes. TEM-HRTEM-SAED analysis authenticated the presence of silver NS with interplanar spacing values of 0.248 nm and 0.243 nm which conformed to Ag (111) lattice fringes of silver. The V-SNS showed significant synergistic antibacterial influence versus S. aureus, E. coli, P. aeruginosa, and E. aerogenes. The uppermost zone of inhibition of 18 mm was inscribed against P. aeruginosa bacteria. The better electrochemical properties of V-SNS electrode as revealed by cyclic voltammograms, Nyquist and Bode plots make it suitable for potential electrochemical sensor application. V-SNS exhibited better photocatalytic activities against Acid orange 8 and Acid red 88 dyes.

An Investigation on Microstructural, Morphological, Optical, Photoluminescence and Photocatalytic Activity of WO3 for Photocatalysis Applications: An Effect of Annealing

The presence of carcinogenic dyes in industrial wastewater is a serious problem that hazards the water bodies and nano-catalysts are key members that are used to purify it. Therefore, this work investigates the synthesis of tungsten oxide (WO3) nanoparticles with various annealing temperatures in the range of 100–600 °C by the co-precipitation method for photocatalysis applications. The improvement in crystallinity of the nanoparticles achieved through annealing temperature and the crystallite size was an increase from 10 to 34 nm. The structural parameters of the prepared samples were characterized using XRD reveals the formation of stable monoclinic structure. FESEM morphological images confirmed the formation of irregularly shaped nanoplates. HRTEM and SAED patterns confirmed the growth of nanocrystalline WO3 nanoparticles. Parameters like (hkl) planes and interplanar spacing values obtained from HRTEM studies agreed well with the results of XRD. The elemental presence and chemical compositions were confirmed from EDS and XPS studies, respectively. The presence of functional groups has been verified through FTIR spectroscopy studies. Considerable decrements in the energy gap of WO3 NPs were observed with annealing from 2.89 to 2.61 eV. The defects/oxygen deficiencies were examined through photoluminescence. The photocatalytic performance of WO3 NPs was assessed by degrading the methylene blue dye. The parameters obtained from Pseudo first-order kinetic studies confirmed that 600 °C annealed WO3 NPs have higher photocatalytic activity.

Raman spectroscopy study of the wurtzite-zinc blende phase transition of bare CdSe nanoparticles

Structural and electronic properties characterization results show that the crystallographic structure of CdSe films, deposited by chemical bath synthesis, is controlled by the bath growth temperature. The synthesis parameters employed produced a set of nanostructured CdSe films on glass substrates with controlled crystal structure. The effect of bath temperature (Tb) on CdSe films was studied in the 0 ≤ Tb ≤ 80 °C range. The average crystal diameter (AD) of the films lies within the 7 ≤ AD ≤ 12 nm interval, where AD depends on the selected Tb. X-ray diffractograms (XRD) shown that at low Tb values the formation of the hexagonal wurtzite (WZ) is promoted while at the other extreme the cubic zinc-blende (ZB) crystalline structure dominates. It is observed that the WZ → ZB transition occurs at the critical temperature Tbc ~ 40 °C. The AD in each films for CdSe-NP’s was obtained from XRD analysis employing the Scherrer-Debye formula. The values of the lattice interplanar spacing (IS), determined from XRD analysis, as function of Tb increases continuously except at temperatures around Tbc where a local minimum is observed. The presence of stress acting on CdSe NP’s is identified by correlating the IS values with the crystalline structure: compression occurs for 0 ≤ Tb ≤ 40 °C, and tension for 50 ≤ Tb ≤ 80 °C. The band gap energy, obtained from optical absorption spectra, decreases monotonically but a local minimum is observed at Tbc = 40 °C. Results from Raman spectroscopy show that the CdSe Raman LO-mode hardens for Tbc as consequence of the WZ ↔ ZB structural transition.

ВЗАИМОСВЯЗЬ РАЗМЕРОВ И ФАЗОВОГО СОСТАВА МАССИВНЫХ АМОРФНЫХ СПЛАВОВ НА ОСНОВЕ Zr

Bulk amorphous Zr-based alloys are promising for their high mechanical properties and thermal stability. The predominate component of Zr in the alloy significantly improves its strength, ductility, corrosion resistance and melting point, which is important when creating various structural materials. The obtainment bulk of Zr-based alloys with an amorphous structure is not a trivial goal, but requires an ad hoc approach as the high degree of Zr oxidation and the necessary high rates of melt cooling limit realization of the amorphous state. At an insufficient cooling rate during quenching, the crystalline phases are formed, which causes change in the properties of the material itself, which in turn affects the field of practical application. Therefore, it is very important to have an idea about the change in a structure during manufacture since many properties of materials are structurally dependent.During the work, the amorphous, partially crystalline and crystalline samples of the amorphized alloy of Zr 55 Cu 30 Al 10 Ni 5 composition were obtained by levitation melting and quenching into copper moulds of variable diameter. The crystalline phases formed during quenching depending on the sizes of the sample and position in it were identified. Small differences between the values of interplanar spacing of the formed phases and the tabulated ones, which can be associated with partial substitution of atoms that leads to anisotropic lattice distortions were revealed and explained. In addition, during the work, differences in the phase composition after quenching and under decomposition of the amorphous phase during heating of the alloy of this composition were also revealed.

Comparison between axial residual stresses measured by Raman spectroscopy and X-ray diffraction in SiC fiber reinforced titanium matrix composite

Accurate measurement and analysis of residual stress state in the SiCf/Ti composites are crucial to optimizing their fabrication process and to understanding their failure mode, but they are still a challenge. In this work, SiCf/C/Ti17 composites with~48% fiber volume fraction, consisting of W-core SiC fibers (~100 m in diameter), turbostratic C coating (~2.5 m in thickness) and Ti17 matrix, are prepared by consolidating precursor wires fabricated by matrix-coated fiber method through hot isostatic pressing at 920℃/120 MPa/2 h; these samples are used for measuring their stresses. It is noted that turbostratic C coating, a necessary diffusion barrier layer between SiC fiber and Ti17 alloy matrix, bears the residual stress caused by the mismatch of thermal expansion coefficients between fiber and matrix during consolidation. It is found that the graphene planes are almost parallel to the axial direction of SiC fibers in the turbostratic C coating revealed by high magnification transmission electron microscope, and thus G peak position of C coating would be sensitive to stress state. Accordingly, micro-Raman spectroscopy is first used to measure the G peak positions of C coating under stress and stress-free state in the SiCf/C/Ti17 composite, respectively. Based on the position shift of G band caused by residual stress, the axial residual compressive stress of SiC fiber in SiCf/C/Ti17 composite is calculated to be~705.0 MPa. For comparison, X-ray diffraction method is also adopted to measure the interplanar spacing values of the Ti17 alloy matrix in different directions to obtain the spatial strains. During measurement, -Ti (213) high-angle diffraction peak is chosen to reduce test error, and then the different interplanar spacing values of -Ti (213) are obtained by varying the values of in three different directions at =0, 45 and 90. As three-axis-stress model is employed, the residual tensile stress of Ti17 alloy matrix in the axial direction of SiCf/C/Ti17 composite is~701.3 MPa, which is transformed through linear elastic theory into the residual compressive stress of SiC fiber of~759.4 MPa. The similar results confirm that it is reliable to characterize the residual stress in the SiCf/C/Ti17 composite with high-texture turbostratic carbon by both the Raman spectroscopy and the X-ray diffraction method.

The Evolution Rule of Three-Dimensional Structures of Graphite During Oxidation

The graphite oxidation samples with different degrees of oxidation were prepared from natural flake graphite via a modified Hummers method with controlled addition of KMnO 4. The evolution of oxygen-containing functional groups was analyzed by Fourier transform infrared spectrometry (FT-IR) and X-ray photoelectron spectroscopy (XPS). The evolution rule of three-dimensional (3D) graphite structures during oxidation has been verified via X-ray diffraction (XRD). Experimental results show that the evolution of the interplanar spacing of samples during oxidation can be approximately divided into four stages. When the dosage of KMnO 4 is 0.5 g per 1 g of graphite (g/g), a graphite intercalation compound (GIC) is formed through intercalating reactions, and a slight increase is observed in the values of d100 and d110, suggesting that the π–π interactions which decrease the length of carbon–carbon bonds were partially disrupted. Adding additional KMnO 4 initiates the second stage, in which GIC begins to oxidize. The insertion of oxygen-containing functional groups in the graphene basal plane leads to dramatic changes in the values of d100 and d110. The d100 is greatly reduced while d110 increases slightly. These trends are attributed to the fact that the basal plane is stretched during the oxidation process. Further addition of KMnO 4 in the third stage leads to relatively small increases in the values of d100 and d110. This result is consistent with the evolution rule of hydroxyl groups. In this research, the evolution rule of the value of d001 is also clearly demonstrated. When the concentration of KMnO 4 is not more than 3.0 g/g, the value of products d001 keeps gradually increasing, indicating that oxygen-containing groups continue to form bonds with carbons in the basal plane, and that additional water molecules are adsorbed between the layers of the samples. All the interplanar spacing values (d001, d100 and d110) are reduced significantly in the fourth stage, when the amount of KMnO 4 added up to 4.0 g/g. FT-IR and XPS analyses demonstrate that the decrease in the values of d100 and d110 is due to a reduction in the content of external hydroxyl groups. The change in d001 is attributed to the partial release of water molecules confined in the interlayer spaces between adjacent sheets are partly released.

XRD Study on D-Values of Modified PbTiO<sub>3</sub> Ceramics during Poling Process

The Calcium modified PbTiO3 ceramics with large piezoelectric anisotropy was poled in consecutive steps. X-ray diffraction (XRD) found that the values of inter-planar spacing, d002 and d200, increased with poling field at initial poling stages. A noticeable drop of the d¬002 and d200 at the coercive field was observed. The residual stresses measured by the  angle tilt method were introduced. The relations of d002-sin2ψ and d¬¬200-sin2ψ at different poling stages were simulated by a mathematic model. The linear terms in the model are related to the macro-stress which may cause an elastic deformation; the exponential term in the model is related to the micro-stress which may cause a plastic deformation by the 90o domain switch. The results show that macro-stress and micro-stress decreased and the decay speed along  angle increased as to the d002 lattice spacing. The residual stresses related to the d200 lattice spacing were almost not changed.

Polycrystalline Silicon–Germanium Films Prepared by Aluminum-Induced Crystallization

The thin films were deposited on Al-coated glass and single-crystal Si substrates by traditional plasma-enhanced chemical vapor deposition with the mixture of , , and Ar at a low temperature of . The structure of the films was characterized by X-ray diffraction, Raman spectra, field-effect scanning electron microscopy, and atomic force microscopy. It showed that the Al layer was a very effective crystallization precursor for preparing the thin films. The polycrystalline thin films were the easiest to be formed when . Moreover, the (111) interplanar spacing values of the stress-free poly- thin films, with a lower concentration of crystallographic defects, were in accord with Vegard’s law. The grain size was sensitive to the annealing temperature and the Ge content. And, there was no surface roughening in the aluminum-induced crystallization poly- .

Strain effects on the energy band-gap in oxygenated CdTe thin films studied by photoreflectance

The incorporation of oxygen during the preparation of sputtered CdTe films produces a strong strain of the zincblende (cubic) lattice. First as a consequence of this, the energy band-gap shifts to lower energies and then, for larger strains, the degeneracy of the hole valence bands splits into two bands at the fundamental band-gap. These two transitions were measured using photoreflectance spectroscopy (PRS) as a function of the oxygen content. The energy band-gap shift resulting from tensile stress in the films was calculated using the elastic constants and deformation potentials for CdTe as well as the measured interplanar spacing values of the (1 1 1) CdTe X-ray diffraction peak.

Intercalation in hydrotalcite-like layered Zn/Al-double hydroxides with naphthalenedisulphonates

Hydrotalcite-like layered Zn/Al-double hydroxides (Zn/Al-HTs) with one of three naphthalenedisulphonates (NijDSs) as an interlayer guest dianion, were obtained as precipitates from weak alkaline solutions of NijDS admixed with calcined host powder. Two values of interplanar spacing were observed in the powder X-ray diffraction patterns of NijDS-intercalated Zn/Al-HTs with two guest isomers. Intercalated materials have been characterized by means of UV-vis diffuse reflectance spectroscopy, differential thermal analysis/thermogravimetry and X-ray photoelectron spectroscopy. A model has been proposed in which the organic dianion at the interlayer gallery region bridges two Al3+ cations in neighbouring layers of double hydroxides. The guest molecules have an orientation perpendicular to the internal surface of the layers for all NijDS-intercalated materials. Another orientation has been suggested in which the molecules tilt from the perpendicular position for two isomers of NijDS.

Thermal behaviour of hydroxyapatite intended for medical applications

Four commercial hydroxyapatites (both natural and synthetic) were tested to assess transformations of the chemical and crystalline structure following variation of temperature from 20 to 1600°C. The thermal behaviour of hydroxyapatite is relevant for biomedical applications such as plasma spraying of metallic implants. Thermogravimetric analysis showed a weight loss from each hydroxyapatite specimen, due to a release of structural H 20 molecules; all the specimens up to 1300°C were made of crystalline hydroxyapatite, determined by X-ray diffraction; at 1470°C they were made of both hydroxyapatite and calcium phosphate, but at 1570°C of calcium phosphate exclusively. The diffractograms of the hydroxyapatite coatings showed the same peaks as the original powders, so at the chosen plasma-spray procedure level no new phases were formed. The peak height was nevertheless lower in the plasma-sprayed hydroxyapatites for all interplanar spacing values, which indicated a lower degree of crystallinity, associated with a random structure derived from an alteration to the original crystalline network.

Grain boundary segregation in [100] symmetrical tilt bicrystals of an FeSi alloy

AbstractThe orientation and temperature dependences of the segregation of P, Si and C at [100] symmetrical tilt grain boundaries of an Fe‐3.5 at.% Si alloy were determined by AES analysis ofin situfractured bicrystals. The obtained anisotropy of the segregation enthalpy of all three elements is characterized by its low absolute values for the {013} and {012} boundaries. Both of these boundaries belong to the low classification levels after Paidar and possess high values of interplanar spacing which can be used as a simple geometric criterion of the boundary ‘specialty’. The data are consistent with the construction of the grain boundary segregation diagram showing the dependence of the segregation enthalpy on both the boundary orientation and the maximum solid solubility of the solute.