Formation Of Fcc Phase Research Articles

Comparative Study of Callistemon citrinus (Bottlebrush) and Punica granatum (Pomegranate) Extracts for Sustainable Synthesis of Silver Nanoparticles and Their Oral Antimicrobial Efficacy.

A comparative study was applied to investigate the potential of Callistemon citrinus (bottlebrush) flower extract (BBE) and Punica granatum (pomegranate) peel extracts (PPE) for the sustainable synthesis of the silver nanoparticles, Ag-BBE and Ag-PPE, respectively. The synthesis process of Ag NPs using the selected extracts was applied under optimized conditions. Hence, the effect of the selected plant's type on the different characteristics of the synthesized green Ag NPs was investigated. The UV-Vis spectroscopy revealed the presence of the characteristic silver peaks at 419 and 433 nm of the Ag-BBE and Ag-PPE, respectively. The XRD spectra reported the fcc phase formation of Ag NPs. The TEM results highlighted the morphological features of the synthesized Ag NPs. with a size range of 20-70 nm, and with 10-30 nm for Ag-BBE and Ag-PPE, correspondingly. The Raman spectra revealed characteristic silver bands in the Ag-PPE and reflected some bands related to the natural extract in the Ag-BBE sample. The antimicrobial activity and statistical analysis investigation were conducted against four selected oral pathogens (Staphylococcus aureus (SA), Candida albicans (CA), Staphylococcus epidermidis (S. epi), and Enterococcus faecalis (EF)). Both tested extracts, BBE, and PPE, revealed potential effectivity as reducing and capping agents for Ag NP green synthesis. However, the synthesized NPs demonstrated different features, depending on the used extract, reflecting the influence of the plant's biomolecules on the nanoparticles' properties.

A machine learning framework for discovering high entropy alloys phase formation drivers

In the past years, high entropy alloys (HEAs) witnessed great interest because of their superior properties. Phase prediction using machine learning (ML) methods was one of the main research themes in HEAs in the past three years. Although various ML-based phase prediction works exhibited high accuracy, only a few studied the variables that drive the phase formation in HEAs. Those (the previously mentioned work) did that by incorporating domain knowledge in the feature engineering part of the ML framework. In this work, we tackle this problem from a different direction by predicting the phase of HEAs, based only on the concentration of the alloy constituent elements. Then, pruned tree models and linear correlation are used to develop simple primitive prediction rules that are used with self-organizing maps (SOMs) and constructed Euclidean spaces to formulate the problem of discovering the phase formation drivers as an optimization problem. In addition, genetic algorithm (GA) optimization results reveal that the phase formation is affected by the electron affinity, molar volume, and resistivity of the constituent elements. Moreover, one of the primitive prediction rules reveals that the FCC phase formation in the AlCoCrFeNiTiCu family of high entropy alloys can be predicted with 87% accuracy by only knowing the concentration of Al and Cu.

Insights on phase formation from thermodynamic calculations and machine learning of 2436 experimentally measured high entropy alloys

Both CALPHAD (CALculation of PHAse Diagrams) and machine learning (ML) approaches were employed to analyze the phase formation in 2436 experimentally measured high entropy alloy (HEA) compositions consisting of various quinary mixtures of Al, Co, Cr, Cu, Fe, Mn, and Ni. CALPHAD was found to have good capabilities in predicting the BCC/B2 and FCC phase formation for the 1761 solid-solution-only compositions, excluding HEAs containing an amorphous phase (AM) or/and intermetallic compound (IM). Phase selection rules were examined systematically using several parameters and it was revealed that valence electron concentration (VEC)< 6.87 and VEC> 9.16 are the conditions for the formation of single-phase BCC/B2 and FCC, respectively; and CALPHAD could predict this with essentially 100% accuracy. Both CALPHAD predictions and experimental observations show that more BCC/B2 alloys are formed over FCC alloys as the atomic size difference between the elements increases. Four ML algorithms, decision tree (DT), k-nearest neighbor (KNN), support vector machine (SVM), and artificial neural network (ANN), were employed to study the phase selection rules for two different datasets, one consisting of 1761 solid-solution (SS) HEAs without AM and/or IM phases, and the other set consisting of all the 2436 HEA compositions. Cross validation (CV) was performed to optimize the ML models and the CV accuracies are found to be 90.4%, 94.1%, 93.8%, 89.7% for DT, KNN, SVM, and ANN respectively in predicting the formation of BCC/B2, BCC/B2 + FCC, and FCC; and 92.9%, 96.3%, 96.9%, 92.3% for DT, KNN, SVM, and ANN respectively in predicting SS, AM, SS + AM, and IM phases. Sixty-six experimental bulk alloys with SS structures are predicted with the trained ANN model, and the accuracy reaches 80.3%. VEC was found to be most important parameter in phase prediction for BCC/B2, BCC/B2 + FCC, and FCC phases. Electronegativity difference and FCC-BCC-index (FBI) are the two dominating features in determining the formation of SS, AM, SS + AM, and IM. A separation line ΔHmix=29×VEC−247 was found in the ΔHmix-vs-VEC plot to predict the formation of single-phase BCC/B2 or FCC with a 96.2% accuracy (ΔHmix = mixing enthalpy). These insights will be very valuable for designing HEAs with targeted crystal structures.

Microstructures and properties of AlCrFeNiMnx high-entropy alloy coatings fabricated by laser cladding on a copper substrate

In this study, AlCrFeNiMn x high-entropy alloy coatings (x=0, 0.5, and 1) were successfully prepared on a copper substrate by laser cladding. The influence of Mn addition was investigated on the phase constituent, microstructure, and mechanical properties of the HEA coatings. Due to the high-entropy effect, the AlCrFeNiMn x HEA coatings comprised only simple BCC and FCC structure phases. Moreover, the addition of Mn elements inhibited the formation of FCC phases due to the variation of ΔG mix , ΔH mix , δ, ∆x and VEC value. The addition of Mn leads to solute effect, so the grains were significantly refined with an increase in Mn content. When the Mn content was 0.5, good comprehensive mechanical properties were obtained with an average Vickers hardness of 625 HV, average friction coefficient value of 0.42, and a mass loss of 1.02 mg. • AlCrFeNiMn x HEA coatings are prepared on a copper substrate by laser cladding. • The addition of Mn inhibited the formation of FCC phase of the AlCrFeNiMn x HEAs. • The addition of Mn can significantly refine grains of the AlCrFeNiMn x HEAs. • The addition of Mn can improve the mechanical properties of the AlCrFeNiMn x HEAs.

Synchronous enhancement of the strength and ductility in a metastable β-Ti alloy by a new refined α phase mechanism

Grain refinement is a fascinating method to improve both strength and plasticity of metallic materials. In particular, grains below the micrometer scale can produce significant strengthening effects while avoiding progressive stress localization and early failure of the alloy and then improving the plasticity. A new α grain refinement mechanism, FCC phase-stress delocalization, is found in hot-rolled metastable β titanium alloys. The fragmentation process of α phases followed the formation of FCC phase → accumulation of dislocation and stress localization on the α/β phase interfaces → FCC phase as a site to release the stress concentration and promote the formation of grooves → the final refinement completed via developing grooves. At the same time, it is researched by TEM that the orientation relationship (OR) between the α and the FCC phase is P-type and B-type, and the variant selection of the FCC phase occurs. Furthermore, the highest ultimate tensile strength (UTS) ~1210.3 MPa and excellent elongation (EL) ~22.5% were obtained under the R90 sample. Such significant performance breakthroughs are attributed to the occurrence of ultra-fine α grain and the FCC phase, which breaks the trade-off between strength and ductility.

Effect of Sn on synthesis of nanocrystalline Ti-based alloy with fcc structure

Abstract The effect of the amount of Sn on the formation of fcc phase in Ti−13Ta−xSn (x=3, 6, 9 and 12, at.%) alloys was studied. The alloys were synthesized by mechanical alloying using a planetary mill, jar and balls of stabilized yttrium. Using Rietveld refinement, it was found that the obtained fcc phase has crystallite size smaller than 10 nm and microstrain larger than 10−3. Both conditions are required to form an fcc phase in Ti-based alloys. For all samples, the microstructure of the fcc phase consists of equiaxial crystallites with sizes smaller than 10 nm. The largest presence of fcc phase in the studied Ti alloy was found with 6 at.% Sn, because this alloy exhibits the largest microstrain (1.5×10−2) and crystallite size of 6.5 nm. Experimental data reveal that a solid solution and an amorphous phase were formed during milling. The necessary conditions to promote the formation of solid solution and amorphous phases were determined using thermodynamic calculations. When the amount of Sn increases, the energy required to form an amorphous phase varies from approximately 10 to approximately −5 kJ/mol for 3 and 12 at.% Sn, respectively. The thermodynamic calculations are in agreement with XRD patterns analysis and HRTEM results.

Microstructure, mechanical, and corrosion resistance properties of Al0.8CrFeCoNiCux high-entropy alloy coatings on aluminum by laser cladding

High-entropy alloys (HEAs) were used to improve the hardness, wear resistance, and corrosion resistance of steel surfaces by laser cladding due to their outstanding mechanical and corrosion resistance properties. However, there are only a few literary works on the improvement of wear resistance on the aluminum alloy surface by HEAs. In this work, the wear performance of laser cladded Al0.8CrFeNiCoAlCux HEA coating on aluminum alloy with different Cu contents was investigated in detail. Moreover, phase structure, microstructure, bonding shear strength, and corrosion resistance of HEA coatings were studied by XRD, SEM, tensile device, and electrochemical workstation. The result shows that with the increase of the Cu content, the structure of the coatings changed from BCC1 and BCC2 phases to BCC1, BCC2, and FCC1 phases. Evident cracks were observed in the Al0.8CrFeCoNi HEA coating. Meanwhile, when x = 0.25, the cracks disappeared, but the bonding shear strength was 79.6 MPa, only 34.7% of the substrate. At 0.5 ≤ x ≤ 1, the bonding shear strength of the Al0.8CrFeCoNiCux HEA coatings went above 175.2 MPa. As Cu promotes the formation of FCC phase, the hardness of the Al0.8CrFeCoNiCux HEA coating decreased as the Cu content increased. The effect of Cu on wear resistance has the same trend as with hardness. The wear rate of Al0.8CrFeCoNiCu0.5, Al0.8CrFeCoNiCu0.75, and Al0.8CrFeCoNiCu HEA alloys is only 3.4%, 4.02%, and 5.42%, respectively, of the substrate. The wear mechanisms of the substrate are that of delamination fracture and serious adhesion wear, while the wear mechanisms of Al0.8CrFeCoNiCux (0.5 ≤ x ≤ 1) HEA coatings are that of adhesive and abrasive wear. The corrosion resistance of Al0.8CrFeCoNiCux (0.5 ≤ x ≤ 1) HEA is better than that of the substrate in 1 mol l−1 H2SO4 solution. Al0.8CrFeCoNiCu0.5 has the best corrosion resistance that is characterized by pitting and intergranular corrosion.

Effects of Ti and Cu on the Microstructure Evolution of AlCoCrFeNi High-Entropy Alloy During Heat Treatment

The microstructure evolution of AlCoCrFeNiTi0.5 alloy and AlCoCrFeNiCu alloy during heat treatment was systematically studied, to reveal the influence rules of chemical activity of adding element on the microstructure evolution of AlCoCrFeNi system. Owing to the negative mixing enthalpy with the constituent elements, Ti element was mainly dissolved in the Al–Ni-rich phases, and aggravated the lattice distortion of B2 phase. The structure variation of BCC phase by adding Ti inhibited the formation of FCC phase and enhanced the precipitation of σ phase during heat treatment. Owing to the positive mixing enthalpy with constituent elements, Cu element tended to be repelled to the ID region and formed metastable Cu-rich FCC1 phase which would transform into Cu–Al–Ni-rich FCC2 phase with increasing temperature. The addition of Cu inhibited the precipitation of σ phase during heat treatment. Adding Ti maintained the stable dendritic morphology, while adding Cu reduced the thermal stability of microstructure. Two dramatic morphology changes occurred at 1000 °C and 1100 °C in the AlCoCrFeNiCu alloy. The lattice distortion of phase in AlCoCrFeNiTi0.5 alloy was aggravated with increasing temperature up to 800 °C, then relaxed together with the dissolution of σ phase when temperature was above 900 °C. The variation in lattice distortion dominated the hardness of AlCoCrFeNiTi0.5 alloy. With increasing heating temperature, the increasing volume fraction of region with FCC structure due to the transformation between FCC phases, and the pronounced coarsening in microstructure due to the reduced thermal stability, resulted in the mainly decreasing trend in the hardness of AlCoCrFeNiCu alloy.

Effects of Boron Content on microstructure and mechanical properties of AlFeCoNiBx High Entropy Alloy Prepared by vacuum arc melting

The AlFeCoNiBx (x = 0, 0.05, 0.10, 0.15, 0.2) high entropy alloys are prepared by vacuum arc melting. The effect of B on the microstructure and mechanical behaviors of the alloys are systematically investigated. X-Ray Diffraction results and Electro-Probe Microanalyzer results show that small amount of B atoms are dissolved into B2 matrix and the other B atoms result in the formation of FCC phase. The addition of B content leads to transformation of microstructure from pure B2 phase to “B2 phase + particle FCC structure” and then to “B2 phase + eutectic structure”. Eutectic structure consists of FCC1 phase and FCC2 phase. FCC1 phase is rich in Co and Ni and FCC2 phase is rich in B, Fe and Co. With the increase of B content, grain size of B2 phase firstly reduce and then increase. By increasing the B content from 0 to 0.2, fracture strength and plastic strain increase from 850 MPa to 2293 MPa and 0.07 to 0.27 respectively. The increase of yield strength is due to the solid solution strengthening and fine grain strengthening of boron atom. While, the increase of plasticity is due to the formation of FCC eutectic structure.

Grain refinement and FCC phase formation in AlCoCrFeNi high entropy alloys by the addition of carbon

To refine grains and improve the mechanical properties of the AlCoCrFeNi HEA (high entropy alloy), a series of (AlCoCrFeNi)100–xCx (x = 0–8, atomic ratio) HEAs were prepared, the alloying effects of C (carbon) on the microstructure and mechanical properties of the HEA were investigated. The results showed that C addition had potential in refining grains; the grains size decreased with increasing C content until 2%. When the C content was more than 1.5%, the second phase (FCC phase) was generated, its fraction increased with the increase of C content. During solidification, C atoms accumulated on the grains surface and inhibited grains growth, which contributed to the refinement of grains size. When the C content was more than 2%, the second phases (FCC phase) were formed. The compressive strength and fracture strain reached the maximum value respectively (3.3 GPa and 35%) when the C content was 1.5%. The grains size decreased with the increase of C content from 0% to 1.5%, which contributed to the increase in compressive strength and fracture strain.

Properties of atomized AlCoCrFeNi high-entropy alloy powders and their phase-adjustable coatings prepared via plasma spray process

In this study, the adjustment of the phase constitution of AlCoCrFeNi high-entropy alloy (HEA) coatings was achieved using a plasma spray process with vacuum gas-atomized powders. The as-prepared AlCoCrFeNi powders were of pure BCC phase and the particles were in spherical shape. The FCC phase began to form above 600 °C, and its degree of crystallinity increased with annealing temperature, resulting in a reduced saturation magnetization. Two Curie temperatures were observed in as-atomized powders: the first was around 220 °C and was reversible; the second was contributed by the irreversible FCC phase transformation over 600 °C. When depositing the AlCoCrFeNi coating using the plasma spray process, the ratio of the FCC phase increased with increasing spraying current and argon flow rate. However, the phase constitution of the AlCoCrFeNi coatings was also influenced by powder size. With coarse powders (60–90 μm), the formation of FCC phase was suppressed, even as the current and gas flow were increased to 750 A and 50 l/min, respectively. The physical properties, such as porosity, hardness, and saturated magnetization, of plasma-sprayed AlCoCrFeNi can hence be adjusted by tuning its phase constitution.

Selective laser melting of an equiatomic AlCrCuFeNi high-entropy alloy: Processability, non-equilibrium microstructure and mechanical behavior

Abstract An equiatomic AlCrCuFeNi high entropy alloy (HEA) is fabricated successfully from the alloy powders using selective laser melting (SLM). Microstructural characteristics and mechanical behavior of SLMed AlCrCuFeNi samples under optimal SLM processing parameters are studied in detail. It is revealed that the SLMed AlCrCuFeNi HEA shows high crack sensitivity, and the optimum processing window is narrow. The formation of FCC phase is inhibited, resulting in a simple BCC solid solution to accommodate high lattice distortion and elastic strain induced by rapid cooling rate for the SLMed AlCrCuFeNi HEA. Moreover, unique fine columnar grains containing multiple ultrafine sub-grains structures appear within the molten pool and present a preferred orientation. Nano-scale Cu-rich phases precipitate and exhibit chain-like at HAGBs while granular shape at LAGBs. Also, anomalous alternating bright and dark structures containing B2 and A2 phases with the width about 22 nm appear at the sub-grain boundaries due to rapid solidification. The SLMed AlCrCuFeNi HEA possesses superior properties with a compression strength of 2052.8 MPa and a fracture strain of 6.8% compared to the corresponding casting material. Fracture analysis indicates that the SLM (0°) specimen exhibits quasi-cleavage fracture while the SLM (90°) specimen shows intergranular fracture. The grain boundary strengthening effect, preferential growth orientation of BCC grain and the existing microcracks are proposed to explain the anisotropy of compression properties.

Microstructural evolution, phase selection and properties of CoCrCuFeMn x Ni high-entropy alloys

Abstract Manganese was added to face-centered-cubic (fcc) high-entropy CoCrCuFeNi alloy to investigate the effects of Mn content on the microstructures, phase selection, and properties of CoCrCuFeMn x Ni. CoCrCuFeMn x Ni showed typical dendrite and interdendritic structures, and nanoprecipitates including Cu-rich cubic and Cr-rich acicular ones, were obtained in the interdendritic region. Calculated phase-selection-related parameters indicated that the formation of fcc phase was favored. Although two fcc structures were detected by X-ray diffraction, the interdendritic region showed body-centered-cubic, Cr-rich nanoprecipitates when x &lt; 0.5. It is worth noting that the CoCrCuFeMn2.0Ni interdendrites showed an amorphous phase. CoCrCuFeMn x Ni showed considerable ductility and increasing compressive strengths with increasing Mn content.

Effect of cobalt on microstructure and properties of AlCr1.5CuFeNi2Cox high-entropy alloys

The present paper investigates the effect of Co addition on the alloying behaviour, microstructure and the resulting properties of cast AlCr1.5CuFeNi2Cox high-entropy alloys intended to be used for high temperature applications. The elements Al, Cr, Cu, Fe, Ni and Co (Purity > 99) weighing approximately 800 g was melted in a high temperature vacuum induction furnace. The microstructure, phase transformation, density, microhardness and compressive strength of the samples were analysed using x-ray diffraction (XRD), scanning electron microscopes (SEM), Vickers microhardness tester and universal Testing machine. The crystalline structure of the alloys exhibits simple FCC and BCC phases. The microstructures investigation of the alloys shows the segregation of copper in the interdendritic region resulting in Cu-rich FCC phase. The addition of Co further enhances the formation of FCC phase resulting in the decrease in micro hardness value of the alloys, which varies from 471 HV to 364 HV with increase in the cobalt content from x = 0 to x = 1 (molar ratio). The similar decreasing trend is also observed for the compressive strength of the alloys.

Anomalous codeposition mechanism of Co-Ni alloy nanowires

The anomalous codeposition of Co-Ni nanowires occurs at potentials from −0.9 V to −1.6 V while the normal codeposition occurs at −3.0 V. We propose that hindrance of crystallization of Ni atoms can be responsible for the anomalous codeposition. The anomalous codeposition can be attributed to formation of hcp phase in deposition as the limited solubility of Ni in the hcp Co-Ni phase can block the deposition of Ni atoms onto the hcp lattice. The normal codeposition can be related to formation of fcc phase in deposition as the complete solubility of Ni in the fcc Co-Ni phase can lead to no hindrance of crystallization of Ni atoms.

Evolution of microstructure, mechanical and corrosion properties of AlCoCrFeNi high-entropy alloy prepared by direct laser fabrication

High entropy alloy (HEA) is an emerging class of engineering materials that shows promising potential for high temperature applications. These multi-component alloys are mostly fabricated by arc melting. In this study, direct laser fabrication (DLF) is utilized to prepare AlCoCrFeNi high entropy alloy at optimized operation parameters. The phase, microstructure, mechanical and corrosion properties of as-deposited alloy as well as samples aged at temperatures of 600 °C, 800 °C, 1000 °C and 1200 °C for 168 h have been investigated. The results show that high cooling rate during deposition inhibits the formation of FCC phase, leading to a nearly single B2 solid solution structure for as-deposited sample. After ageing at 800 °C, 1000 °C and 1200 °C, the microstructures exhibit intergranular needle-like and plate-like FCC phase precipitates and wall shaped FCC phase precipitates along grain boundaries. As the FCC phase is softer than B2 phase, the formation of the FCC phase during ageing results in reduced compressive yield strength accompanied with enhanced ductility. The potential difference between Fe-Cr rich FCC phase and Al-Ni rich B2 matrix means the alloy is susceptible to galvanic corrosion, with the B2 matrix corroding preferentially.

Structural, optical and magnetic properties of undoped NiO and Fe-doped NiO nanoparticles synthesized by wet-chemical process

Nanocrystalline nickel oxide (NiO) and ferrous doped NiO dilute magnetic nanoparticles have been prepared by wet-chemical method. The structural, composition, morphology, UV absorption and magnetic analysis of the prepared samples are characterized by XRD, FESEM, HRTEM, UV Spectra and VSM. XRD confirms the FCC phase formation. The FESEM and HRTEM used to found the structural parameters. The U–V absorption measurement shows the strong absorption at 313.24nm and 307.9nm for undoped NiO and Fe-doped NiO nanoparticles. The magnetic properties of these nanoparticles confirming the ferromagnetic behaviour at room temperature and has been attributed due to particle size effect.

Synthesis of Magnetic CuNi Nanoalloys by Sol-Gel-Based Pechini Method

Magnetic CuNi nanoalloys with different compositions were prepared by sol-gel-based Pechini method. A precursor material was prepared using citric acid, ethylene glycol, copper chloride and nickel chloride. The CuNi nanoalloys were obtained by calcination of the precursor material in H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> atmosphere at 600°C. The composition, structure, morphology and magnetic properties of the CuNi nanoalloys were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), high resolution transmission electron microscopy and vibrating sample magnetometry. AAS studies confirmed the expected Cu:Ni ratios in these nanoalloys. The XRD patterns showed the formation of fcc phase in the CuNi nanoalloys. The morphological characteristics of the CuNi nanoalloys show quasi-spherical particles with sizes in the range of 20-70 nm. Magnetic measurements reveal that the CuNi nanoalloys are typical soft magnetic materials.

Analysis of phase formation in multi-component alloys

An attempt has been made to predict phase formation using a CALPHAD-based approach for a large number of compositions that are known to form FCC, BCC and a mixture of FCC and BCC phases. The stable phase is assumed to be the first phase that is formed upon cooling from liquid state with the highest driving force. The driving force for other phases at the transition for various compositions is also presented. A comparison between the parametric approach of phase prediction by study of thermodynamic and topological parameters on one hand and the CALPHAD approach on the other is also presented. CALPHAD approach appears to predict BCC phase formation much more accurately than the FCC phase formation. The results indicate that solid solution formation in multicomponent alloys is favored when the ratio of ΔSconfig/ΔSfusion is greater than 1 and 1.2 for equiatomic and non-equiatomic alloys, respectively. The results also point out that BCC phase is favored when the atomic size difference is larger, which is reflected by a higher value of ΔSσ/k. Formation of FCC phase appears to be governed mainly by ΔHmix, while BCC phase governed by ΔSσ/k, which is representative of strain in the structure.

Synthesis of nanocrystalline Co–Ni alloys by precursor approach and studies on their magnetic properties

Nanocrystalline Co–Ni alloys with different compositions were prepared by polyol reduction of mixed cobalt nickel hydroxides. The precursors (mixed cobalt nickel hydroxides) were prepared by co-precipitation. Powder X-ray diffraction analysis indicated the formation of fcc phase in the alloys and their crystallite size in the range 17–25 nm. Scanning electron microscopy and transmission electron microscopy studies revealed the morphology of the particles as being close to spherical, and the energy dispersive X-ray analysis showed the stoichiometry of the alloys. The magnetization as a function of field and temperature of the alloys, measured using a superconducting quantum interference device, showed superparamagnetic behavior with negligible coercivity and remanence values.