SS Sample Research Articles

Foam and emulsion properties of crude saponin extract from saffron (Crocus sativus L.) corm

The emulsion and foam stability of the crude saponin extract from the saffron corm (SS) were compared with commercially available saponin (CS) and Tween 60 (T60). The purity of the SS sample was calculated relative to CS and showed a value of 84.43%. Most stable emulsions with the smallest oil droplet size were acquired with T60. Also, T60 showed the lowest surface tension, interfacial tension, and the lowest contact angle. However, a reduction of interfacial tension and surface tension up to 77% and 32% was recorded for SS, respectively. Commercially available saponin indicated the best foam stability regarding film drainage, coalescence, and bubble disproportionation due to its highest solution viscosity. The antioxidant activity of samples was evaluated regarding the FRAP assay and the DPPH free radical scavenging activity. The results showed FRAP values of 2.41 and 1.20 mmol L−1 Fe (II)/100 g sample, and DPPH IC50 values of 2103 and 2326 mg kg−1 for CS and SS, respectively. The investigation showed that SS can form stable emulsions and abundant and persistent foams. Our results provide valuable insights for using saffron corm saponin extract as a new potential natural surfactant for selected applications of the food and pharmaceutical industries.

Crystallization behavior of CMAS + sea salt mixture and its effect on the mixture penetration into thermal barrier coatings

When aero-engines are operated in dusty and near-sea environments, thermal barrier coatings (TBCs) are threatened by coupling corrosion of calcium-magnesium-alumina-silicate (CMAS) and sea salt. Investigating the crystallization behavior of CMAS + sea salt that affects the melt penetration into TBCs is the key to seeking protection methods against coupling corrosion. In this study, the crystallization temperature range and crystalline products of CMAS + sea salt were investigated. The results indicated that the crystallinity of CMAS + sea salt is affected by temperature. CMAS, CMAS+5SS (95 wt% CMAS + 5 wt% sea salt), and CMAS+10SS (90 wt% CMAS + 10 wt% sea salt) were crystalized initially at 1000 °C, but the crystallinity was low. At 1100 °C, more crystallization occurred, with diopside (CaMgSi2O6), akermanite (Ca2MgSi2O7), and anorthite (CaAl2Si2O8) being precipitated. With the temperature increasing to 1200 °C, wollastonite (CaSiO3) instead of akermanite was precipitated in both CMAS and CMAS+5SS samples, while the CMAS+10SS sample became almost amorphous glass with little crystallization indicating that higher sea salt content narrows the crystallization temperature range. Moreover, at the appropriate crystallization temperature (1100 °C), the addition of sea salt in CMAS played a depolymerization role and promoted discrete precipitation of dendritic akermanite, which reduced the crystalline layer compactness increasing the threat of mixture penetration into TBCs.

Investigations on the temperature-dependent tribological behaviour of spark plasma sintered CNT-304 SS self-lubricating nanocomposites

ABSTRACT Herein, we report the tribological behaviour of CNT-304 stainless steel composites at room (28°C) and high temperatures (200°C). Nanocomposites of various CNT concentrations, namely 0.2, 0.5, 1.0, 2.0, 3.0, and 4.0 wt%, were prepared. A significant amount of grain refinement resulted in an increase in CNT loading. A tribological study was carried out at 28°C and 200°C. Wear resistance was found to enhance with an increase in CNT concentration at both temperatures. However, a slightly higher wear rate was observed at 200°C for the samples with CNT content < 3 wt% than their corresponding low-temperature values. About 86%, 91% drop-in wear rate was seen in 2.0 wt% CNT-304 SS, and 4.0 wt% CNT-304SS, respectively, as compared to pure SS at 28°C, which is 54% and 88% decrease at 200°C and is very promising. The decrease in wear volume with CNT content at both temperatures can be ascribed to the self-lubricating and reinforcing nature of CNTs in the metal matrix composites. Severe abrasive wear in the pristine SS samples was slowly changed to mild abrasive and lubricated wear in composites. A systematic study on the tribological behaviour of CNT-SS composites can shed light on the benefits and detriments of using them for various applications. Highlights Incorporation of CNTs into 304 SS matrix caused grain refinement. Wear rate decreased with CNT content and 4.0 wt% CNT-SS showed minimum wear rate while pristine gave the maximum at both 28°C and 200°C. About 86% and 54% decrease in wear rate were observed for 2.0 wt% CNT-304 SS at 28°C and 200°C respectively as compared to the pristine 304 SS sample. Wear rate at 200°C was slightly more than that of room temperature (28°C) for CNT content < 3 wt%. The 3.0 wt% CNT-304 SS and 4.0 wt% CNT-304 SS showed nearly the same wear rate at both ambient and 200°C test.

Effects of surface roughness on bending properties of rolled AZ31 alloy

This study investigated the effects of mechanical-polishing-induced surface roughness and the direction of polishing lines on the bending properties of a rolled AZ31 alloy. To this end, three-point bending tests were performed on one sample without polishing lines (SS sample) and two samples with polishing lines—one in which the polishing lines were parallel to the rolling direction (RS-RD sample) and the other in which they were parallel to the transverse direction (RS-TD sample). In all three samples, macrocracks were formed in the width direction on the outer surface, where tensile stress was predominantly generated in the longitudinal direction. However, the macrocracks formed in the SS sample were curved because of the merging of uniformly formed fine microcracks, whereas those formed in the RS-TD sample were linear owing to the formation of relatively coarse microcracks along the polishing lines. The bendability of the samples was in the order of SS > RS-RD > RS-TD, and their limiting bending depths were 4.8, 4.6, and 4.4 mm, respectively. In the presence of mechanical-polishing-induced surface roughness, polishing lines perpendicular to the direction of the major stress (i.e., tensile stress along the longitudinal direction) resulted in a greater degree of stress concentration on the outer surface of the bending specimen. This higher stress concentration promoted the formation of undesirable {10–11} contraction and {10–11}–{10–12} double twins—which typically act as crack initiation sites—and thereby facilitated crack generation and propagation. Consequently, the surface roughness caused premature fracture during bending deformation, which, in turn, caused deterioration of the bendability of the rolled Mg alloy.

Dynamics of microbial communities during biotransformation of nitrofurantoin

The purpose of this research was to investigate the biodegradation of nitrofurantoin (NFT), a typical nitrofuran antibiotic of potential carcinogenic properties, by two microbial communities derived from distinct environmental niches – mountain stream (NW) and seaport water (SS). The collected environmental samples represent the reserve of the protected area with no human intervention and the contaminated area that concentrates intense human activities. The structure, composition, and diversity of the communities were analyzed at three timepoints during NFT biodegradation. Comamonadaceae (43.2%) and Pseudomonadaceae (19.6%) were the most abundant families in the initial NW sample. The top families in the initial SS sample included Aeromonadaceae (31.4%) and Vibrionaceae (25.3%). The proportion of the most abundant families in both consortia was remarkably reduced in all samples treated with NFT. The biodiversity significantly increased in both consortia treated with NFT suggesting that NFT significantly alters community structure in the aquatic systems. In this study, NFT removal efficiency and transformation products were also studied. The biodegradation rate decreased with the increasing initial NFT concentration. Biodegradation followed similar pathways for both consortia and led to the formation of transformation products: 1-aminohydantoin, semicarbazide (SEM), and hydrazine (HYD). SEM and HYD were detected for the first time as NFT biotransformation products. This study demonstrates that the structure of the microbial community may be directly correlated with the presence of NFT. Enchanced biodiversity of the microbial community does not have to be correlated with increase in functional capacity, such as the ability to biodegradation because higher biodiversity corresponded to lower biodegradation. Our findings provide new insights into the effect of NFT contamination on aquatic microbiomes. The study also increases our understanding of the environmental impact of nitrofuran residues and their biodegradation.

A Novel Mesoporous Activated Carbon Derived from Calliandra calothyrsus via Physical Activation: Saturation and Superheated

In this work, both pyrochar and activated carbon were prepared by physical activation (i.e., saturation and superheated) by involving a thermal agent as a comparison. The effects of three agents on the pore development of activated carbon from a new material, Calliandra calothyrsus, were observed in detail. The BET surface area and the iodine index of the prepared activated carbon were used as pyrochar selection. Proximate, ultimate, XRD, FTIR, TGA, and SEM were used to characterize the physical and chemical properties of the product. Pyrochar pores were found to develop significantly at 350 °C, indicated by an increase in the BET surface area and iodine index. Pyrochar from a temperature of 350 °C was then selected as a precursor of activated carbon. S–SS and SS–S activated carbon samples were declared to have the highest iodine index (870 mg/g) and the highest BET surface area (642 m2/g), respectively. The pore distribution data showed that the superheated agent widened the pore and provided an active site for iodine adsorption, while the saturation agent resulted in a narrower pore for an increase in the BET surface area. S–SS has a lower C fraction and higher O fraction than SS–S. The SS–S samples have both Vol and Volmic for an increased BET surface area. The number of aromatic layers and –OH functional groups of the S–SS sample is more convenient for iodine enhancement than for increasing the BET surface area. Less water droplets and greater energy from superheated resulting pores widen, increasing the aromatic layer and providing additional functional groups.

Influence of initial relative densities on the sintering behavior and mechanical behavior of 316 L stainless steel fabricated by binder jet 3D printing

Compared with other 3D printing methods, binder jet 3D printing (BJ3DP) shows the great potential for obtaining large-scale complex parts with high efficiency and low cost. However, understanding the sintering behavior of powders is one of the challenging topics in BJ3DP. In this work, on the basis of the thermo–elasto–viscoplastic constitutive law model, the sintering behavior of 316 L stainless steel (316 L SS) cuboids prepared by BJ3DP with different initial relative densities (relative densities of green parts), i.e., 49.5%, 51.5% and 53.5%, was investigated via finite-element numerical simulations. It suggested that the shrinkage decreased as the initial relative density increased, resulting from that a higher initial relative density would provide higher sintering stress. Additionally, precise shrinkage and final relative densities of the BJ3DP samples were quantitatively predicted via numerical simulations, and the simulated results were in good agreement with experimental results. According to the experimental results, a final relative density of ~98.7% could be achieved in the BJ3DP 316 L SS sample with an initial relative density of 53.5% after sintering, showing a yield strength of ~308 MPa and an ultimate tensile strength of ~601 MPa along with a total elongation of ~59.4%.

Effects of precipitate origin and precipitate-free zone development on the tensile creep behaviors of a hot-rolled Mg-13wt%Gd binary alloy

In heat-resistant Mg Gd based alloys, the relationship between the collective effects of precipitate origin and precipitate-free zone (PFZ) development on the creep resistance is still unclear. In this work, a hot-rolled Mg-13wt%Gd binary alloy was treated by solid solution (SS sample) and peak aging (AA sample). After peak aging, static precipitated β ′ phases were widely generated and PFZs were directly formed along both sides of the grain boundaries in AA sample. Tensile creep tests were performed at 523 K on both SS and AA samples. During creep testing, dynamic precipitated β ′ phases were gradually generated in SS sample while the β ′ phases persisted as large scales in AA sample. The dominant creep mechanisms of SS sample were twinning and cross-slip composed by < a > dislocations, since the late occurrence and low density of β ′ phases failed in hindering the movement < a > dislocations at the beginning of steady creep stage. On the contrary, the large-scale β ′ phases reduced the space for dislocation movement and succeeded in retarding cross-slip, leading to pyramidal < c + a > slip being the main creep mechanism of AA sample. Besides, PFZs were formed in SS sample (from zero to ~1.1 μm) while they became narrower in AA sample (from ~5 μm to ~1.7 μm). The large decreased ratio of PFZ width, the large scale of static precipitated β ′ phases and the resultant pyramidal < c + a > slip effectively enhanced the creep resistance of AA sample. Accordingly, AA sample behaved a higher creep resistance in comparison to SS sample at 523 K. It is hoped that the roles of precipitate origin and PFZ development in the creep properties can enrich the theories and methods in improving the service performance of Mg Gd series at medium to high temperatures. • Wide PFZs and large-scale static precipitates are obtained after peak aging. • For peak-aged alloy, PFZs are narrowed during creep and creep resistance rises. • For solid solute alloy, PFZs are widely developed and creep resistance falls. • Static precipitates can retard a -cross slip whereas dynamic precipitates fail. • As a -cross slip is delayed, pyramidal slip is activated to enhance creep resistance.

Strengthened passivation and mechanism of 316L stainless steel in hot diluted sulfuric acid solution by connecting to Pd electrode

Purpose The purpose of this paper is to study the variations of composition and properties of the passive film on 316 L stainless steel surface in 80°C, 0.5 mol L-1 H2SO4 + 2 mg L-1 NaF solution, is helpful to understand the mechanisms of corrosion resistancethe of plated Pd on 316 L ss. Design/methodology/approach The variations of composition and properties of the passive film on 316 L stainless steel surface in 80°C, 0.5 mol L-1 H2SO4 + 2 mg L-1 NaF solution after connected to Pd electrode were studied with methods of potential monitor, X-ray photoelectron spectroscopy analysis and electrochemical impedance spectrum (EIS) measurement. Findings By connecting to a Pd electrode, the potential of the SS sample increased from the active region to the passive region. By connecting to the Pd electrode, the contents of Cr, Cr(OH)3 and Fe3O4 in passive film increased obviously. With increased Pd/SS area ratio, the Cr(OH)3 content in passive film increased but the Fe3O4 content changed little. The results show that after connecting to Pd the corrosion resistance of the passive film on 316 L stainless steel increases obviously, which may be attributed to the more compact passive film because of higher Cr, Cr(OH)3 and Fe3O4 contents and less point defects in the film. Originality/value The effects and mechanism of Pd on passivation of SS was studied.

A detailed study on electrochemical performance and cell viability of nano-YSZ-coated 316L SS sample for dental applications

Development of biocompatible dental implants has attained significant impact in dental industry. In the present work, we report for the development of biocompatible nano-Yttria-stabilized Zirconia (YSZ) coatings on 316L stainless steel (316L SS) obtained by EPD process followed by sintering at air atmosphere. The surface morphology and electrochemical performance of nano-YSZ-coated 316L SS were investigated to evaluate its corrosion behavior in artificial saliva medium. The surface morphology and composition of the coatings were characterized by XRD, Raman, and FESEM with EDAX, respectively. The electrochemical performance of the uncoated metal and nano-YSZ-coated 316L SS samples were evaluated in artificial saliva medium using electrochemical techniques such as Open Circuit Potential – time measurement (OCP), Electrochemical Impedance Spectroscopy (EIS), and Cyclic Potentiodynamic Polarization (CPP). The nano-YSZ-coated 316L SS thin film possess significant electrochemical and biocompatibility properties compared to uncoated metal. Nano-YSZ-coated 316L SS (70 V, 5 min, 800 °C) acts as an active and also as a good barrier against corrosive ions and resists ions penetration from artificial saliva to the metal surface.

Fabrication of superhydrophobic and self cleaningPVA‐silicafiber coating on304L SSsurfaces by electrospinning

AbstractIn this work superhydrophobic coating with self cleaning property is fabricated on 304L SS samples directly using a simple one step electrospinning process followed by silane treatment by using polyvinyl alcohol (PVA) and tetraethyl orthosilicate solution. A maximum water contact angle of 169.2° ± 2.1° is obtained at an electrospinning potential of 15 kV for 2 h, with a distance of 18 cm between the collector and needle. The hierarchical nanostructures thus formed on 304L SS composed of poly(vinyl alcohol)‐silica microbeads and nanofibers. The surface morphologies are optimized by varying the electrospinning voltage, time, distance between needle and the collector and aging duration of the precursors. Attenuated total reflectance‐infrared spectroscopy studies at different stages of preparation confirmed the presence of PVA/SiO2composite nanofibers deposited on the 304L SS surface. The reaction of SiO2nanofibers with hexamethyl disilazane resulted in the formation of SiOSi bonds that provided water repellent property. The developed SHP surface coating on 304L SS sample showed dynamic bouncing of water droplets and excellent self cleaning performance. The sample retained the SHP behavior in chloride solutions with different ionic strengths and pH.

Effect of Different Synthesis Methods on Structural, Morphological and Magnetic Properties of La&lt;sub&gt;0.7&lt;/sub&gt;Ba&lt;sub&gt;0.25&lt;/sub&gt;Nd&lt;sub&gt;0.05&lt;/sub&gt;MnO&lt;sub&gt;3&lt;/sub&gt;

La0.7Ba0.25Nd0.05MnO3 (LBNMO) compounds were synthesized using two different methods, namely are solid-state reaction (SS) and sol-gel (SG). All samples were heat-treated at 1200 °C for 12 hours. The investigation on structural, morphological, and magnetic properties was carried out by X-Ray Diffractometer (XRD), Scanning Electron Microscope (SEM), and Vibrating Samples Magnetometer (VSM) at room temperature. From the Rietveld refinement, both samples have formed a rhombohedral structure with an R-3c (167) space group. The average crystallite size was calculated using the Scherrer formula and Williamson-Hall (W-H) method for comparison. It was shown that the crystallite size of the sample produced by the SG method has larger than the SS method. This result is fairly consistent with the result obtained from SEM analysis, which shows that the average grain for the SG sample is larger than of the grain of the SS samples. From the magnetic hysteresis curve, the magnetization saturation value for the SG was higher and sharper than that of the SS sample. These confirm the occurrence of the double exchange interaction in the samples, which is mainly associated with the reduction of bandwidth and grain size.

Construction of a novel corrosion protective composite film based on a core-shell LDH-Mo@SiO2 inhibitor nanocarrier with both self-healing/barrier functions

Layered Double Hydroxides (LDHs) are well-known nanomaterials for the construction of self-healing corrosion protective composite coatings with controlled release ability of the active corrosion inhibitors. In this paper, the LDH surface has been modified with SiO2 nanoparticles through a sol-gel method, and then its active corrosion inhibition behaviors in the saline solution and sol-gel film were investigated by polarization, electrochemical impedance spectroscopy (EIS) and salt spray tests. XRD, TGA, and FE-SEM tests were conducted to characterize the constructed LDH particles. The results demonstrated that the LDH(Mo)SS sample provided superior active inhibition efficiency in the solution and coating phases due to the controlled release ability of the LDH particles intercalated with MoO42− anions as well as the barrier properties of this sample.

Efficient methods by active learning Kriging coupled with variance reduction based sampling methods for time-dependent failure probability

For efficiently estimating the time-dependent failure probability, two new methods named as the active learning Kriging (AK) coupled with importance sampling (AK-co-IS) and AK coupled with subset simulation (AK-co-SS) are proposed. The proposed methods are based on the fact that the AK coupled with Monte Carlo simulation (AK-MCS) method has been proved to be a very efficient method. However, for problem with small time-dependent failure probability or long service time, the size of candidate sample pool generated by MCS would be so large that the efficiency of AK-MCS is reduced. Therefore, the AK-co-IS and AK-co-SS are proposed to highly enhance the computational efficiency by greatly reducing the candidate sample pool size. And these two methods reduce the candidate sample pool size respectively by searching the optimal time-dependent design point to increase the ratio of failure samples and converting a rare event simulation problem into sequence of more frequent event ones. Through iteratively constructing the AK model to be convergent by the U-learning function in the IS and SS sample pools, respectively, the computational cost of estimating the time-dependent failure probability would reduce drastically compared with AK-MCS. Several examples are used to illustrate the efficiency and accuracy of the proposed methods.

Surface micro-structuring of type 304 stainless steel by femtosecond pulsed laser: effect on surface wettability and corrosion resistance

This paper presents results on femtosecond (fs) pulsed laser-based surface micro-structuring of type 304 stainless steel (304 SS). Post laser treatment surface wettability and corrosion resistance investigation are reported. SS sample surfaces have been micro-structured using a typical laser fluence of ~ 0.9 J/cm2 for varying sample scanning speed in the range 25–1000 µm/s. Dense array of micro-protrusions have been generated without formation of a crater for an optimized target scan speed exceeding 200 µm/s. Static water contact angle (WCA) measurement indicated super-hydrophilic behavior immediately after laser treatment. However, hydrophilicity (wettability) was found to decrease with storage time with sample becoming highly hydrophobic (WCA: 144° ± 5°) within 50 days after laser treatment. Corrosion resistance of the laser-treated samples was measured by potentio-dynamic polarization technique. Fs laser micro-structured SS has shown poorer corrosion resistance in comparison to pristine surface. Observed poorer corrosion resistance of laser-treated surface has been explained on the basis of surface chemical composition and surface roughness. The results demonstrated that corrosion resistance increased with increasing hydrophobicity of the SS surface.

The influence of synthesis conditions on the redox behaviour of LiFePO4 in aqueous solution

To contribute to the knowledge on the influence of synthesis procedure on the intercalation kinetics of lithium ions into phospho-olivines, LiFePO4/C composite samples (LFPC) were synthesized in two ways, the first one in a sol-gel procedure (SG), and the other in a solid-state reaction (SS). The X-ray diffractograms (XRD) of both samples overlapped with that of pure LiFePO4, taken from the crystallographic database. Scanning electron microscopy pictures indicated the high degree of interparticle sintering, which caused a considerable agglomerate growth. The results of potentiodynamic measurements in aqueous LiNO3 solution revealed that for SS sample, three times higher initial capacity from that of SG one, (amounting to 74 mAh g−1 at 5 mV s−1). However, capacity fade on rising scan rate is much more expressed for SS sample than for SG one. We suggest that a different degree of material utilization due to the incomplete coverage of olivine particles by carbon explains this difference. The technique of separation of diffusion and capacitance currents was applied in a kinetic analysis, but it was shown to be inappropriate. We suggest the inapplicability of classic CV theory to the intercalation system accompanied by phase transition. Instead, a model of ohmic resistance determination of process kinetics was considered. LFPC-SS sample delivers three times larger capacity in LiNO3, amounting to 74 mAh g−1 at 1 mV s−1.

Experimental Evaluation of Mechanical and Tribological Behaviours of Gas Nitride treated AISI 316LN Austenitic Stainless Steel

Austenitic stainless steel is limited to utilize directly in numerous industries on account of its low surface hardness. Hence, in this work, an effort has taken to enhance the surface hardness of austenitic stainless steel type AISI 316LN Stainless Steel (316LN SS) by Gas Nitride (GN) technique. The GN was done on 316LN SS at 520°C for 42 hours. The GN was done in two phases to limit the white nitride layer. The GN treatment enhances the surface hardness from 210 HV25g (untreated 316LN SS sample) to 1230 HV25g (GN treated sample). The GN treatment produces a thick and uniform nitride layer on the 316LN SS. The tribolgical test conclude that the GN layer on 316LN SS eliminates adhesion bonds at the contact points and show smooth surface even after 1000m sliding distance. Consequently, the GN treatment was not just reduce the friction and also formed an excellent wear resistance GN layer on the 316LN SS substrate.

Topographical, structural and hardness changes in surface layer of stainless steel-AISI 304 irradiated by fusion-relevant high energy deuterium ions and neutrons in a low energy plasma focus device

This paper aims to investigate the effects of fusion relevant intense pulse of energetic and high fluence deuterium ions and neutrons generated in a low energy (3.0kJ) plasma focus device (UNU/ICTP PFF) on stainless steel-AISI 304 samples. The irradiation was performed using different number of deuterium plasma focus shots (1, 3, 5 and 10) at a fixed axial distance of 8cm from the anode tip. X-ray diffraction spectra of irradiated samples indicated the structural phase transition from mixed ferittic-austenitic form in virgin AISI 304 SS sample to only austenitic form indicated by the presence of only γ-Fe diffraction peaks and increase in corresponding peak intensities. A small shift in all austenitic diffraction peaks towards the higher diffraction angles was observed indicating the decrease in lattice spacing by vacancy defects most probably due to energetic fusion neutrons. Field emission scanning electron microscopy and atomic force microscopy images showed the formation of nanometer sized particles on irradiated samples' surfaces. The size of nanoparticles initially decreased as the number of focus shots was increased from 1 to 3 and to 5, and later as the number of focus shots was increased to 10, the aggregations of the particles occurred to form bigger clusters. The sample surface hardness was found to decrease with increasing number of irradiation shots which can be attributed to the induction of vacancy defects by 2.45MeV fusion neutron irradiations and the increasing deposition of the copper ablated from the anode-top on the irradiated samples. The study clearly established that the plasma focus device provides intense fusion relevant pulses suitable for causing the topographical, structural and hardness changes on the surface of the irradiated SS AISI 304 which is one of the candidate materials for plasma facing components in fusion reactors.

Local Electrochemical Measurements in Bipolar Experiments for Corrosion Studies

AbstractIn this work, the local potential and local current were measured with paired Ag/AgCl reference microelectrodes during the corrosion of a 304L stainless‐steel (304L SS) sample in bipolar experiments. During a single experiment, it was possible to investigate both the anodic and cathodic domains corresponding to the corrosion of the stainless steel. From these local measurements in non‐contact mode, the current/potential curve was obtained, revealing the different reactivities of the 304L SS sample, over a large potential range. The polarisation curve was similar to that usually obtained in a classical three‐electrode configuration.

Effect of synthesis techniques on structural, magnetocaloric and critical behavior of Pr0.6Ca0.1Sr0.3Mn0.975Fe0.025O3 manganites

The effect of synthesis techniques on structural, magnetocaloric and critical behavior in Pr0.6Ca0.1Sr0.3Mn0.975Fe0.025O3 (PCSMFO) sample has been investigated. The sample was synthesized by two different methods: the solid-state reaction (SS) and Pechini sol–gel method (SG). X-ray diffraction analysis shows that our sample crystallizes in the orthorhombic structure with the Pbnm space group for both methods. Magnetic measurements show that our sample exhibits a ferromagnetic (FM)–paramagnetic (PM) transition with increasing temperature. The Curie temperature (TC) and magnetocaloric effect (MCE) of SS sample and SG sample were studied. A large magnetocaloric effect around Curie temperature is observed in our sample prepared by both methods. Moreover, the critical exponents β, γ, and δ determined as using the modified Arrott-plot (MAP), the Kouvel–Fisher method (KF), as well as the critical isotherm (CI) analysis. In both studied techniques, the Arrott plots show that the phase transition is of the second-order. Moreover, for the sample which is prepared by solid-state, the estimated critical exponents are close to those expected for mean-field model. For the SG sample, these exponents are close to those expected for 3D-dimensional Heisenberg and the value of critical exponents γ decreased and approached the 3D-Ising (γ=1.24). Interestingly, the change of the universality class can be explained by the reduction of grain size (D). The reduction of the grain size tends to create a transition phase from a long-range to short-range order in the system. These results suggest that the physical properties of our sample are strongly depended on the synthesis techniques.