Crystallographic Properties Research Articles

Electrical and thermoelectrical properties of Bi2−xNaxTe3 alloys

For the first time, Bi 2 Te 3 alloys, which have long been known as promising thermoelectric materials for room temperature applications, have been doped with Na atoms to enhance their thermoelectric performance. Bi 2 Te 3 and Bi 2−x Na x Te 3 alloys were prepared by mono-temperature melting synthesis. Their structural, crystallographic properties and surface morphology were investigated by XRD and SEM analyses. All the prepared alloys showed perfect crystalline structure of single Bi 2−x Na x Te 3 phase. The thermoelectric properties of the synthesized alloys were measured in the temperature range of 273–473 K. Electrical conductivity of the concerned alloys were measured by the standard four probe method and studied as a function of temperature, showing metal-like behavior. Na-doping enhanced the electrical conductivity significantly due to enhancing of the carrier concentration. The Seebeck coefficient of all alloys exhibited a positive sign, confirming the p-type conduction. Significantly high Seebeck coefficient values were observed at high temperatures. The maximum value was recorded at 266 μV K − 1 for Bi 2 Te 3 at 473 K. Electronic thermal conductivity of the prepared alloys was estimated from Wiedemann-Franz equation. A remarkable reduction of the electronic thermal conductivity was observed against temperature, in correspondence with the electrical conductivity. The materials thermoelectric power factor was calculated based on electrical conductivity and Seebeck coefficient measurements. Also, the power factor was investigated as a function of temperature. The largest value was found for the most Na-doped samples at 299.6 µW/mK 2 , observed at 413 K. • Bi 2 Te 3 and Bi 2−x Na x Te 3 alloys were prepared by mono-temperature melting synthesis. • Thermoelectric measurements were carried out in the temperature range 273–473 K. • The maximum power factor was observed at 299.6 µW/mK 2 , observed at 413 K.

Room-temperature polymer-assisted additive manufacturing of microchanneled magnetocaloric structures

Magnetic refrigeration is an energy-efficient, sustainable, environmentally-friendly alternative to the conventional vapor-compression cooling technology. There are several magnetic refrigerator device designs in existence today that are predicted to be highly energy-efficient, on condition that suitable working materials can be developed. This challenge in manufacturing magnetocaloric devices is unresolved, mainly due to issues related to shaping the mostly brittle magnetocaloric alloys into thin-walled channeled regenerator structures to facilitate efficient heat transfer between the solid refrigerant and the heat exchange fluid in an active magnetic regenerator (AMR) cooling device. To address this challenge, a novel extrusion-based additive manufacturing (AM) method has been developed to 3D print microchanneled magnetocaloric structures. The printing ink consists of magnetocaloric powders, a polymer binder, and multiple solvents to achieve desirable shear-thinning property, which is critical for a robust printing process. Acting as a sacrificial binding agent for the magnetic powders, the polymer binder holds the 3D printed structures in place and is removed subsequently using a two-step heat-treatment process. To demonstrate the effectiveness of the fabrication process, spatially designed microchannels with minimum dimensions of 150 µm were achieved using nanoscaled La 0.6 Ca 0.4 MnO 3 powders (diameter~10 nm). Results indicate that the crystallographic properties and magnetofunctional response of the sintered 3D printed samples are comparable to that of the precursor powders. Overall, this study provides a promising route for realizing low-cost magnetic regenerators, thus potentially eliminating one of the main barriers to the commercialization of magnetic cooling technology. • Room temperature extrusion-based method for 3D printing magnetocaloric structures. • Significant magnetocaloric response in 3D printed LCMO scaffolds (ΔS=4.9 J/kg-K at 5 T). • Microchanneled magnetocaloric structures with record spatial resolution (dia∼150 µm). • Overcoming a crucial barrier to the commercialization of magnetic cooling technology.

Ternary system of TiO2 confined chitosan–polyaniline​ heterostructure photocatalyst for the degradation of anionic and cationic dyes

Herein, report the preparation of TiO 2 tethered chitosan–polyaniline​ composite (TiO 2 @CS–PANI) by heterogeneous chemical polymerisation​ technique. The crystallographic, morphological and optical properties of the fabricated TiO 2 @CS–PANI composite was described with the aid of powder X-ray diffraction (PXRD), Fourier transform infra red (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), photoluminescence (PL) and thermogravimetry-differential scanning calorimetric (TGA-DSC) analysis. The diffuse reflectance spectra (DRS) evaluation confirmed that the TiO 2 @CS–PANI band gap was reduced compared to that of TiO 2 from 3.2 eV to 2.98 eV. The prepared photocatalyst was utilised for the degradation of toxic Methylene Blue (MB) and Methyl Orange (MO) dye molecules from water in visible light photocatalysis, and is studied in detail. The initial dye concentration of 30 mg/L and photocatalyst dosage of 100 mg were used to investigate the degradation capacity of the composite. The TiO 2 @CS–PANI composite shows extreme degradation efficiency of 92.3% and 89.5% towards MB and MO dyes, respectively. The photocatalyst offers an improved reusability up to five successive cycles. The results established that the TiO 2 @CS–PANI composite could be used as an effective photocatalyst to mineralise toxic dye molecules containing water/wastewater. • A heterogeneous chemical polymerisation method was adopted for the preparation of TiO 2 @CS-PANI photocatalyst. • The band gap of the composite was found to be 2.98 eV. • The composite exhibited high efficiency for the degradation of MB and MO dyes. • The hydroxyl radical was engaged as the primary reactive species. • The stability and reusability performance of the composite was established.

Characterization of pulp calcifications and changes in their composition after treatments with citric acid and ethylenediaminetetraacetic acid solutions.

The ectopic calcifications of non-mineralized tissues can occur in several forms throughout life, such as pulpal calcification. The presence of pulp stones is a challenge in endodontic treatment because they partially or fully obliterate the pulp chamber hindering access to root canals and their subsequent shaping. This study aimed to determine their crystallographic properties and evaluate the capacity of citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) to promote the demineralization of pulp calcifications. The samples were obtained from patients with indications of endodontic treatment, and the radiographic examination was suggestive of pulp stone in at least one permanent tooth. The samples were isolated and analyzed by scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). The Fourier Transform by high resolution-transmission electron microscopy, Raman microscopy, and X-ray diffraction (XRD) were used to identify the mineral phase and crystallographic characteristics. To evaluate the effect of CA and EDTA on the crystallinity of calcifications, they were submerged into these two individual solutions and the changes were assessed in situ by Raman spectroscopy. The SEM images obtained from calcifications demonstrated irregular morphologies. EDX of sample surfaces shows a high presence of oxygen, carbon, calcium, and phosphorous, however, other elements such as sodium, magnesium, nitrogen, chlorine, potassium, sulfur, and zinc were identified in less quantity. According to Raman, XRD, and high-resolution transmission electron microscopy, the predominant mineral phase identified in the pulpal calcification was a poor crystallinity apatite. According to in situ analyses, the effect of CA and EDTA was observed on the signals of PO4 3- and CH2 groups corresponding to inorganic and organic components. The changes with CA were evident at 7min while the effect of EDTA was observed until 15 min of treatment. All results indicate that pulp stones have a heterogeneous composition principally composed of apatite with low crystallinity. The solubility of these pathological minerals is adequate using solutions such as EDTA or CA; however, the effectivity depends on the mineralization grade of calcifications, time, and concentration of exposition to this chemical.

Surface fractality and crystallographic texture properties of mixed and mono metallic MOFs as a new concept for energy storage devices

Herein, fractality, morphology and crystallography studies as a novel approach were introduced to evaluate the effect of inorganic nodes on energy storage device performances of Ni/Co-BTC and Ni/Zn-BTC mixed metallic (MM) and Ni-BTC, Zn-BTC, and Co-BTC mono metallic (mM) MOFs electrode materials. Through XRD data, crystallographic texture studies were pursued by calculating crystallite size (D), interplanar space (dhkl), strain and dislocation density (ε,δ), and texture coefficients (TC(hkl)). Besides statistical studies, the Areal Autocorrelation Function (AACF) via AFM analysis was developed to investigate morphological features. Fractality results of electrochemical and physical methods verified the reliability of these methods for describing the pseudocapacitive nature of MM-MOF and mM-MOF electrode materials. Based on our findings, compared with mM-MOFs, Ni/Co-BTC and Ni/Zn-BTC MM-MOF electrodes with the beneficiary of the synergistic effect of mixed-metallic cations, smaller crystallite size (D=21.53 nm), higher maximum height (Sz=21.64 nm) with larger fractal dimensions (Df=2.58), and more interface width roughness (RMS=2.65 nm) offers an impressive architecture capable of pseudocapacitance storing charge. Therefore, Ni/Co-BTC and Ni/Zn-BTC MM-MOF electrodes offer the specific capacity of 263.8 and 203.3 mA h g−1 at 2.5 A g−1 with a dominant contribution of battery-like features.

Influence of bi-phasic TiO2 as a low-temperature curable electron transport layer for efficient perovskite solar cells

Electron transporting layers play an important role in controlling the photovoltaic performance and stability of perovskite solar cells. Biphasic TiO2 nanoparticles are successfully synthesised by the solvothermal method. A low-temperature curable bi-phasic TiO2 layer consisting of brookite and rutile TiO2 was successfully developed by the spin coating technique. The effect of solvothermal synthesis's reaction time (5 h,10 h and 20 h) on brookite and rutile concentration is thoroughly studied. The optical, crystallographic and morphological properties are characterised effectively to analyse the bi-phasic nature of synthesised TiO2 nanoparticles. The effect of bi-phasic TiO2 nanoparticles concentration as an electron transport layer (ETL) in perovskite solar cells (PSCs) was studied by engineering a low-temperature curable TiO2 nanoparticle deposition methodology. The interparticle connection attained at low temperatures in brookite TiO2 is used to attain PSCs with high power conversion efficiency (PCE). The electrical properties and current–voltage measurements of the bi-phasic TiO2 ETL were evaluated thoroughly. PSC was fabricated with 75 % brookite and 25 % rutile TiO2 particles as ETL exhibited the highest PCE of 14 %, with an open circuit voltage of 1.1 V and a current density of 17.4 mA/cm2, which is effectively co-related with the change in brookite-rutile concentration.

The crystallographic structure and properties of novel quaternary nanolaminated rare-earth-Cr-based i-MAX phases

Seven novel inherently nanolaminated transition metal carbides, (Cr2/3R1/3)2AlC (R = Gd, Tb, Dy, Ho, Er, Tm, Lu) with R in-plane chemical ordering in the carbide sheet, have been synthesized and found to be crystallized in Cmcm orthorhombic structure with monotonously decreased lattice parameters due to lanthanides constrictions. Linear antiferromagnetism is found for R = Gd and gradually changed to paramagnetism for R = Er, Tm and Lu through nonlinear magnetic configurations with gradually decreased ordering temperature. Compared with Cr2AlC benchmark, the Vickers hardness is significantly higher, leading to higher compressive fracture strength and better wear resistance. After compression at high temperature, nanoscale co-existence of the C2/c monoclinic and orthorhombic structure is observed, which is caused by the random stackings and high-density slidings within ab plane. The further first-principle calculations confirm the close thermal stability of both two structures.

Multimodal analysis of Zr substitution effects on magnetic and crystallographic properties in (Sm1−xZrx)(Fe0.8Co0.2)12 compounds with ThMn12 structure

SmFe12-based compounds containing Zr atoms have been recognized as candidates for novel high-performance permanent magnet materials with a high saturation magnetization. Partial substitution of Sm with Zr in (Sm1−xZrx)(Fe0.8Co0.2)12 has been known to enhance the magnetization of the compound. This study focused on (Sm1−xZrx)(Fe0.8Co0.2)12 single-crystalline films to evaluate the effects of Zr substitution for Sm on their structural and magnetic properties via systematic multimodal analysis. X-ray absorption fine structure (XAFS) and scanning transmission electron microscopy indicated a selective occupation of the Sm site by Zr atoms without disturbing the Fe sublattices. The chemical shift in the Zr-K edge XAFS spectra suggested electron transfer from Zr to the Fe band. Soft X-ray magnetic circular dichroism analysis proved that the magnetic moment of Sm was two orders of magnitude smaller than the magnetic moments of Fe and Co, and its contribution to the total magnetization was negligible. The partial substitution of Sm with Zr resulted in a volumetric expansion and c-axis length elongation despite Zr having a smaller atomic radius, which is unique to (Sm1−xZrx)(Fe0.8Co0.2)12 without structure-stabilizing elements such as Ti, V, and Si. This anisotropic expansion is explained by an increase in the magnetic moment and magnetic interactions in the Fe8f site, which is induced by the electron transfer from Zr to Fe8f atoms. Thus, we conclude that the electron transfer from Zr to the Fe8f atoms principally drives magnetization enhancement in (Sm1−xZrx)(Fe0.8Co0.2)12 single-crystalline films.

Evaluation of the effect of high-speed sintering on the mechanical and crystallographic properties of dental zirconia sintered bodies

There are only a few reports investigating the effects of high-speed sintering on the properties of dental zirconia. In this study, we investigated the effects of high-speed sintering on the crystal phase, mechanical properties, microstructure, and LTD resistance of 3 mol. % and 4 mol. % Y2O3 stabilized zirconia (3Y and 4Y zirconia). In both 3Y and 4Y zirconia, yttria distribution in the zirconia sintered body was suppressed and the LTD resistance was improved by high-speed sintering. High-speed sintering slightly reduced the mechanical properties of 3Y and 4Y zirconia, but they showed clinically sufficient mechanical properties. From the above results, it was concluded that high-speed sintered 3Y and 4Y zirconia are sufficiently clinically acceptable.

Synthesis and characterization of bifunctional Ru doped La-based perovskites for magnetic refrigeration and energy storage systems

In this study, the effect of Ru additive on the crystallographic, magnetic, and electrocatalytic properties of LaBiBaMnO3 manganite was investigated for magnetic refrigeration and energy storage systems. XRD analysis of La0·62Bi0·05Ba0·33MnO3 (LBBM) and La0·62Bi0·05Ba0·33Mn0·90Ru0·10O3 (LBBMR) manganites prepared by solid state method reveals that the samples have a rhombohedral structure and the average grain size of perovskites are found to be below 3 μm. From the temperature-dependent magnetization measurements, it was observed that the value of Curie temperature (TC) decreased from 334 K for LBBM to 327 K for LBBMR with the substitution of Mn with 10% Ru. In parallel with the decrease observed in TC with Ru contribution, a decrease in magnetic entropy value was also observed. The substitution of 10% Ru reduced the onset potential 51 mV for oxygen evolution reaction (OER) and 74 mV for oxygen reduction reaction (ORR). The electrode activity of OER at 10 mA cm−2 was obtained at around 0.976 V. Ru substitution and increasing scan rate to 100 mV s−1 increased the current density and lowered onset potential for OER. The ORR efficiency of LBBM catalysts boosted up to 60% with the durability test for 6 h. The increased cathodic Tafel slope from −255.1 mV dec−1 to −120.4 mV dec−1 with 10% Ru substitution suggests that a fast charge transfer for ORR activity due to Ru-occupied Mn-sites in the structure. LBBMR sample achieved bifunctional properties as ORR/OER performance and magnetic cooling applications by substituting Mn with 10% Ru.

Tuning of Morphological, Crystallographic and Optoelectronic Properties in Electrodeposition of CuSCN for Device Applications

Copper(I) thiocyanate (CuSCN) is known as a wide bandgap p-type semiconductor and recently demonstrated its high ability as a hole-transporting material in perovskite solar cells and light emitting diodes. Its thin film is usually fabricated by simple solution coating and drying [1]. In fact, little is known for physical properties of CuSCN, such as bandgap, band positions, optical transparency, carrier density and mobility.We have established methods to electrodeposit well-crystallized CuSCN thin films in various forms. Although the electrochemistry is fairly simple as limited by diffusion of 1 : 1 complex between Cu2+ and SCN- ions ([Cu(SCN)]+), the [Cu2+] : [SCN-] ratio, its absolute concentration and solvent can significantly alter the morphology and crystal orientation of resulting CuSCN [2].These unique features of the electrodeposition technique let us anticipate possibilities to tailor-tune physical properties of CuSCN to match the demands for device applications.In this study, we have carried out electrodeposition of CuSCN to vary its morphology and crystal orientation by tuning the bath composition and studied their band structure to explore the room for tuning its physical properties for thin film diodes and hybrid electroluminescence devices.Morphologies of CuSCN thin films electrodeposited from stoichiometric (REF), Cu-rich and SCN-rich baths are shown in Figs. 1 a-c. While the REF sample has an open structure made of relatively large bulky particles, the Cu-rich sample is dense, made of tiny grains to expose their hexagonally shaped top. On the other hand, the one from the SCN-rich bath show rectangular sides of the grains (Fig. 1 a) and strongly oriented to lay down the c-axis in parallel with the substrate.XRD patterns have found almost parallel orientation for the SCN-rich and a high degree of preference of the Cu rich to orient the c-axis of β-CuSCN perpendicular to the substrate.Although all these films indicate nearly the same energy gap of about 3.6 eV estimated by Tauc plot, significant difference was found for their work function (WF) measured by photoelectron yield spectroscopy (PYS) (Fig. 2). The threshold energy moved downwards from 5.23 to 5.66 eV vs. VAC from Cu-rich to SCN-rich film. The result indicates a high level of p-type doping in the presence of excess SCN-, probably due to increased concentration of Cu2+ as stabilized by SCN- bound to it.Simple devices as ITO / electrodeposited CuSCN / Aluminium were fabricated to examine their diode behaviour. While all of the devices employing the electrodeposited CuSCN thin films showed good rectifications in the J-V curves, the onset voltage determined that to observe 5 mA/cm2 moved from 1.21 to 2.57 V (ITO being positive) from Cu-rich to SCN-rich samples to confirm tunability of the device property by conditions of the electrodeposition. Successful operation of organic light emitting diode was also achieved by employing the electrodeposited CuSCN as a hole-injection layer. The device employing the electrodeposited CuSCN achieved a smaller turn-on voltage than that with spin-coated CuSCN in the I-V-L measurements.[1] Vinod E. Madhavan et al., ACS Energy Lett. 2016, 1, 1112−1117.[2] Lina Sun et al., Physics Procedia, 2011, 14, 12-24. Figure 1

Structural and magnetic properties of Ca3Mn2−xRuxO7(0<x≤0.9)

We here report on the study of the crystallographic and magnetic properties of layered perovskites ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2\ensuremath{-}x}{\mathrm{Ru}}_{x}{\mathrm{O}}_{7}$ ($x\ensuremath{\le}0.9$). We observe a solid solution between Mn and Ru atoms in the whole series and all samples present the same orthorhombic structure independently of the Ru content. Different magnetic structures, depending on the Ru content in the sample, have been determined using neutron powder diffraction. For low Ru doping ($x\ensuremath{\le}0.1$), there is a dominant $G$-type antiferromagnetic ordering in the perovskite bilayers but, differently from undoped ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$, the magnetic moments are located on the $ab$ plane. For higher Ru concentration ($x\ensuremath{\ge}0.3$), the predominant $G$-type ordering is preserved along the $y$ axis while an $A$-type component is developed along the $x$ axis and its intensity increases as Ru content does. This component is characterized by a ferromagnetic ordering in the $a$ direction of one of the $Mn(\mathrm{Ru}){\mathrm{O}}_{6}$ layers, coupled antiferromagnetically with the neighbor $\mathrm{Mn}(\mathrm{Ru}){\mathrm{O}}_{6}$ layer within the same bilayer. The study of the macroscopic magnetic properties shows that ferromagneticlike correlations are enhanced with increasing Ru content as deduced from the shift to higher temperature of the onset of the magnetic transition temperature. The magnetic transitions take place in two steps. At higher temperatures (140--200 K), short-range magnetic correlations are established. Tiny spontaneous magnetization is observed in the hysteresis loops with small coercive field. At ${T}_{\mathrm{N}}\ensuremath{\approx}115--125\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, long-range antiferromagnetic ordering is developed. The ferromagnetic component remains with a strong increase of coercivity. We discuss in the paper the possible origins of this ferromagnetic contribution.

Effect of Iron Isomorphic Substitution in Mg:Al and Zn:Al-Layered Double-Hydroxide Structures by Means of First Principle Calculations.

Layered double hydroxides (LDHs) are important components in terrestrial and extra-terrestrial environments. The presence of iron in these minerals provides them a wide potential application in environmental and materials sciences. In this work, the role of Fe in the crystallographic properties of LDHs M2+:M3+ 2:1 with Mg:(Fe,Al), Mg:Fe, Zn:(Fe,Al), and Zn:Fe is investigated by means of quantum mechanical calculations based on the density functional theory (DFT). Several relative proportions of Fe are studied. The cation ordering of these LDHs has been explored, finding useful insights for experimental synthetic paths of these minerals. The a and b cell parameters increase with the iron concentration. Some diffraction lines at high angle decrease in angle and increase in intensity with the increasing iron concentration. All of them agree with the experimental results. The iron substitutions tend to aggregate.

BiVO4@WO3 S-scheme nanocomposite for visible light photocatalytic CO2 reduction

Significant efforts have been made in the recent times towards the synthesis of sustainable photocatalyst that are both eco-friendly and cost effective in terms of reduction of CO2. The outstanding properties exerted by bismuth, as BiVO4 in specific with respect to its highly facilitative band gap of 2.4 eV has been gaining considerate attention. In the present study, attempts have been made to dope WO3 onto BiVO4 as a means of reducing the recombination rates thereby facilitating the CO2 process. The characterisation results are indicative of the excellent crystallographic properties exerted by the material in addition to the supremacy over stand-alone BiVO4 (0.97 mA/cm2) and WO3 (0.23 mA/cm2) with respect to photocurrent response (1.69 mA/cm2). The catalyst survived 6 cycles of usage, indicative of its environmental and economic upper hand in addition to the greater rates of CO and H2 evolution (29.14 μmolg−1h−1 & 9.24 μmolg−1h−1)

Tuning the Porosity of Piezoelectric Zinc Oxide Thin Films Obtained from Molecular Layer-Deposited "Zincones".

Porous zinc oxide (ZnO) thin films were synthesized via the calcination of molecular layer-deposited (MLD) “zincone” layers. The effect of the MLD process temperature (110 °C, 125 °C) and of the calcination temperature (340 °C, 400 °C, 500 °C) on the chemical, morphological, and crystallographic properties of the resulting ZnO was thoroughly investigated. Spectroscopic ellipsometry reveals that the thickness of the calcinated layers depends on the MLD temperature, resulting in 38–43% and 52–56% of remaining thickness for the 110 °C and 125 °C samples, respectively. Ellipsometric porosimetry shows that the open porosity of the ZnO thin films depends on the calcination temperature as well as on the MLD process temperature. The maximum open porosity of ZnO derived from zincone deposited at 110 °C ranges from 14.5% to 24%, rising with increasing calcination temperature. Compared with the 110 °C samples, the ZnO obtained from 125 °C zincone yields a higher porosity for low calcination temperatures, namely 18% for calcination at 340 °C; and up to 24% for calcination at 500 °C. Additionally, the porous ZnO thin films were subjected to piezoelectric measurements. The piezoelectric coefficient, d33, was determined to be 2.8 pC/N, demonstrating the potential of the porous ZnO as an, e.g., piezoelectric sensor or energy harvester.

Functional analysis of the N-terminal region of acetylxylan esterase from Caldanaerobacter subterraneus subsp. tengcongensis.

Acetylxylan esterase from Caldanaerobacter subterraneus subsp. tengcongensis (TTE0866) has an N‐terminal region (NTR; residues 23–135) between the signal sequence (residues 1–22) and the catalytic domain (residues 136–324), which is of unknown function. Our previous study revealed the crystal structure of the wild‐type (WT) enzyme containing the NTR and the catalytic domain. Although the structure of the catalytic domain was successfully determined, that of the NTR was undetermined, as its electron density was unclear. In this study, we investigated the role of the NTR through functional and structural analyses of NTR truncation mutants. Based on sequence and secondary structure analyses, NTR was confirmed to be an intrinsically disordered region. The truncation of NTR significantly decreased the solubility of the proteins at low salt concentrations compared with that of the WT. The NTR‐truncated mutant easily crystallized in a conventional buffer solution. The crystal exhibited crystallographic properties comparable with those of the WT crystals suitable for structural determination. These results suggest that NTR plays a role in maintaining the solubility and inhibiting the crystallization of the catalytic domain.

Comparison of magnetic anisotropy and structural properties in chemically ordered CoPt and FePt nanoparticles

The intrinsic magnetic properties of nanoparticles (NPs) can be accurately determined using highly dispersed NPs in a matrix. In this paper, we study chemically ordered CoPt and FePt NPs with a diameter of 3 nm embedded in an amorphous carbon matrix. Although both alloys exhibit almost the same magnetic and crystallographic properties in the bulk materials, they are completely different as NPs. We show that their magnetic anisotropy differs greatly. To understand the origin of such a difference, a fine crystallographic structure study has been performed using extended x-ray absorption fine structure. In that respect, the atomic relaxations appear to be different in both nanoalloys. Ab initio calculations of the atomic relaxation shed light on these experimental results, showing that the wide distance distribution in Co sublattice should strongly alter the magnetic anisotropy of CoPt NPs.

Performance Analysis of Chopped Fiber Composite Meta-Nano-Aramid IP for Transformer Bushings and to Analyze Environmental Impact

To study the effect of nano-SiO2 doping content on the properties of chopped fiber composite meta-nano-aramid insulating paper (IP) for transformer bushings, the laboratory-prepared chopped fiber composite meta-nano-aramid IP with different nano-SiO2 doping content is analyzed to assess its impact on the environment. The study has been carried out by considering crystallographic properties and morphology of chopped fiber composite meta-nano-aramid fiber, the influence-mechanism of nano-SiO2 doping content on the mechanical properties, the thermal stability and insulating properties of aramid paper. The experimental results show that the appropriate graft modification of nano-SiO2 enhances the thermal stability and mechanical properties of the meta-aramid (MA) insulating paper. It also shows lesser carbon emissions. When the results are compared with SiO2 without grafted silane coupling agent, SiO2 with a surface graft ratio of 6%, the former method (SiO2 without grafted silane coupling agent) shows a greater increase in the glass transition temperature of the MAIP. At the same time, it shows weakened molecular weight in terms of MSD. The proposed method shows more prominence in terms of the chain kinematic ability, the resistance to deformation, and shearing in terms of mechanical properties. When SiO2 with the graft ratio of 12% is observed, it does not show any improvement, and also the effects on thermal stability and mechanical properties of IP are not significant which is similar to grafting. After hot pressing at 245°C, 30 MPa for 5 min, the breakdown strength, and volume resistivity can reach as high as 37 kV/mm and 1.34 × 1015 Ω·cm respectively. The proposed method shows a significant environmental impact in terms of less emission of CO and CO2.

Preparation of Fe‐Pt Powders from Ingot by a Simple and Cost‐Effective Spark Erosion Device

AbstractFePt powders with 1 µm average particle size have been synthesized from bulk ingot with no need for cryogenic temperatures or conventional powder processing. This is achieved with a compact, cost‐effective spark erosion device which is simple to assemble, with no need of a mechanical workshop. The as‐synthesized powders show a disordered A1 phase with curie temperature, Tc = 300 °C. The effect of annealing on the transition from the disordered to the ordered phase and on the magnetic properties are investigated in situ by magnetic susceptibility measurements. The phase transition to the L10 phase (Tc = 445 °C) is complete at 630 °C where the coercivity increases from 0 to 0.3 T. A urther increase of the heating temperature has no effect on the magnetic and crystallographic properties.

Effects of high energy electron and X-ray irradiation on the morphology, microstructure and reflectivity of cast speculum metal mirror

The effects of irradiation of cast speculum metal mirrors using high-energy electrons (6 MeV and 9 MeV) and X-rays (6 MeV and 10 MeV) from a medical linear accelerator setup are studied in detail for the first time. Analyses using the techniques of X-ray diffraction, atomic force microscopy and Ultraviolet–Visible spectroscopy reveal that the irradiation causes some significant microstructural and morphological changes on the surface of speculum metal leading to the modifications of surface properties and hence the reflectivity of the material. From AFM morphology and XRD pattern, it is evident that the electron beam irradiation affects the surface topography and crystallographic properties of the material more at 6 MeV than 9 MeV. The optical studies suggest a significant reduction in Ultraviolet–Visible reflection after electron irradiation. However, X-ray irradiation of speculum metal provides an enhancement of reflection in the Ultraviolet–Visible region. Irradiation with high-energy electrons affects significantly the amount of absorption in the ultraviolet region. Moreover, an inverse relationship between crystallinity and visible reflectivity is inferred after electron and X-ray irradiations. These results may open up promising possibilities for this alloy to use in future space missions under high-energy irradiation due to its capacity to resist energetic particles and electromagnetic radiation without much material destruction.