Scanning Transmission Electron Microscopy Observations Research Articles

0-D/3-D heterojunction composite constructed by decorating transition metal oxide nanoparticle on peony-like ZnO hierarchical microstructure for improved photodegradation of palm oil mill effluent

A series of transition metal oxide nanoparticles decorated on peony-like hierarchical porous ZnO (MO/ZnO, where MO = CuO, WO3 and Nb2O5) was synthesized using a precipitation-ultrasonic method. The X-ray diffraction, energy dispersive X-ray and fourier-transform infrared spectroscopy findings indicated the existence of both MO and ZnO in the composites. The field-emission scanning electron microscope and transmission electron microscope observations revealed that the MO nanoparticles were well dispersed onto peony-like ZnO hierarchical microstructure. Furthermore, the enhanced visible light absorption abilities of MO/ZnO were confirmed by UV–vis diffuse reflectance spectroscopy. The photocatalytic effectiveness of MO/ZnO was investigated by palm oil mill effluent (POME) degradation under UV irradiation. Among them, Nb2O5/ZnO composite exhibited the best photodegradation efficiency (91.7%) and the highest rate constant (0.0102 min−1) after 240 min irradiation. Moreover, a complete decolorization of POME was observed after 30 min irradiation using Nb2O5/ZnO composite. The phytotoxic effects of POME against the Vigna radiata seeds also reduced greatly after photocatalytically treated using Nb2O5/ZnO composite. Meantime, the product revealed great photocatalytic stability with the degradation efficiency retained more than 80% after 4 cycles. The radical trapping experiment demonstrated that hydroxyl radical and photogenerated hole played major role in POME degradation. The outstanding photoactivity of Nb2O5/ZnO composite can be explicated by efficient charge separation between Nb2O5 and ZnO where the evidence can be obtained from photoluminescence and terephthalic acid-photoluminescence probing analyses. The present study to construct these heterojunction composites can provide an innovative view to design highly effective photocatalytic system for the treatment of industrial wastewater.

Strain relaxation and spinodal decomposition in composition adjusted TiO2-VO2 films on TiO2(100) substrates

In this study, we investigate the process of strain relaxation and spinodal decomposition in TiO2-VO2 films on TiO2(100) substrates. Herein, the film composition was adjusted to Ti0.2V0.8O2 for the relaxation of the in-plane tensile c-axis strain in the films. A 115 nm thick Ti0.2V0.8O2 solid-solution film is epitaxially grown on a rutile-type TiO2(100) substrate using a pulsed laser deposition technique, and is annealed inside the spinodal region. Reciprocal space mapping measurements show that the in-plane tensile c-axis strain is almost fully relaxed in the solid-solution film. Scanning transmission electron microscopy (STEM) observation results reveal that the annealed film causes spinodal decomposition along the c-axis direction, forming vertically aligned multilayer structures. The STEM observations also suggest the presence of interfacial misfit dislocations along the c-axis, indicating the generation of plastic strain relaxation along the c-axis in the film. Composition analysis reveals that the Ti-V interdiffusion between the film and substrate is considerably suppressed. The overall results of this study show that the composition adjustment to Ti0.2V0.8O2 is effective for strain relaxation along the in-plane c-axis and occurrence of spinodal decomposition with reduced Ti-V interdiffusion in the TiO2-VO2 films on TiO2(100). Our study helps establish a method for the formation of nanostructures via spinodal decomposition in the TiO2-VO2 films.

Influence of tool rotational speed on the evolution of microstructure and mechanical properties of precipitation-hardened Aluminium 6061 butt joint during friction stir welding

The present investigation aims to evaluate the influence of varying tool rotational speed (rotation per minute, rpm) on the mechanical properties and microstructural evolution within friction stir welded aluminium alloyAA6061-T6 joints. The effects of rpm underthe constant tool travel speedwere investigated by optical microscopy, field emission scanning electron microscopy (FESEM)and transmission electron microscopy (TEM)observation, tensile, fracture and micro-hardness test. Special attention was paid to the formation and evolution ofprecipitates.Results revealed that the tool rotational speedof 1300 rpmproduces highest hardness reaching to ∼69 HVN at the nugget zone (NZ), which could be attributed to the higher intensity of nano-sized re-precipitation. This specific tool rotational speed of 1300 rpm has been determined to be suitable to achieve the maximum joint efficiency of 70.6%. Significantly, the NZ is characterized with small equiaxed dynamically recrystallized grains. In a noteworthy findings, the NZ showed mostly either free from strengthening precipitate or trace of small tiny re-precipitates, while the thermo-mechanically affected zone (TMAZ) contains coarse precipitates with deformed and dynamically recovered grains. On the other hand, there was obvious grain growth with increasing rpm, substantiating more heat involvement with favourable thermal gradient. The experiment concludes thatthe rotational speed has an considerable effect on the precipitation characteristics, dislocation property and existence of finer second phase intermetallic compounds (IMC),which arethe predominant factors controlling the joint property.

Silver nanoparticles (AgNPs) fabricating potential of aqueous shoot extract of Aristolochia bracteolata and assessed their antioxidant efficiency

This research was performed to evaluate the silver nanoparticles (AgNPs) fabricating potential of aqueous shoot extract of Aristolochia bracteolata and also assess the free radicals scavenging potential of synthesized AgNPs. The results obtained from this study showed that the aqueous shoot extract of A. bracteolata has the potential to synthesize the AgNPs and it was initially confirmed by color change in the reaction blend as yellow to dark brownish. Subsequently, a clear absorbance peak was found at 425 nm in UV–visible spectrum analysis. The functional groups involved in the capping and stabilization of AgNPs were confirmed by Fourier Transform-Infrared spectroscopy (FTIR) analysis and recorded about 10 sharp peaks 3688, 3401, 2980, 2370, 1948, 1642, 1480, 1280, 782, and 628 cm−1. The Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) observations revealed that the predominant shape of the AgNPs was spherical and size ranged from 41.43 to 60.51 nm. Interestingly, the green fabricated AgNPs showed significant free radicals scavenging activity and were confirmed with ferric reducing assay, 1, 1-diphenyl-2-picryl-hydrazyl (DPPH), H2O2 radicals, and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals scavenging activity. Thus, after a few in-vivo antioxidant studies, Aristolochia bracteolata-mediated AgNPs can be considered as an antioxidant agent.

Ultra-high temperature flexure and strain driven amorphization in polycrystalline boron carbide bulks

The temperature dependence of the flexural strength of sintered boron carbide was studied. At temperatures above 2000 °C, B 4 C showed an ultrahigh flexural strength exceeding 1 GPa which was accompanied by a change in the deformation mechanism from brittle fracture to plastic deformation . Scanning transmission electron microscopy (STEM) observations revealed that the amorphization can be of microstructural origin for the observed plasticity in B 4 C at temperatures above 2000 °C and a strain rate of 3•10 −3 s −1 . The amorphization occurs inside of the severely deformed grains. Flexural tests below 2000 °C provided evidence for the formation of stacking faults or dislocations, which are ordinary defects after the flexural tests. The results at 2000 °C suggest that the magnitude of the tensile stresses imposed on the B 4 C grains during deformation in flexure and the total strain transferred to a ceramic during the deformation process play the dominant role in the crystalline-amorphous transformation.

Ready-to-use binder-free Co(OH)2 plates@porous rGO layers/Ni foam electrode for high-performance supercapacitors.

In this work, an outstanding nano-structured composite electrode is fabricated through the co-deposition of Co(OH)2 nanoplates and porous reduced GO (p-rGO) nanosheets onto Ni foam (NF). Through field emission scanning electron microscopy and transmission electron microscopy observations, it was confirmed that porous reduced graphene oxide sheets are completely wrapped by uniform hexagonal Co(OH)2 plates. Due to the unique architecture of both components of the prepared composite, a high surface area of 234.7 m2 g−1 and mean pore size of 3.65 nm were observed for the Co(OH)2@p-rGO composite. The constructed Co(OH)2@p-rGO/NF composite electrode shows higher energy storage capability compared to that of Co(OH)2/NF and p-rGO/NF electrodes. The Co(OH)2/NF electrode shows specific capacitances of 902 and 311 F g–1 at 5 and 30 A g–1, while the Co(OH)2@p-rGO/NF electrode delivers 1688 and 1355 F g–1 under the same current loads, respectively. Furthermore, when the current load was increased from 1 to 30 A g–1, 74.5% capacitance retention was observed for the Co(OH)2@p-rGO/NF electrode, indicating its outstanding high-power capability, while the Co(OH)2/NF electrode retained only 38.5% of its initial capacitance. The fabricated Co(OH)2@p-rGO/NF//rGO/NF ASC device shows an areal capacitance of 3.29 F cm−2, cycling retention of 91.2% after 4500 cycles at 5 A g−1 and energy density of 68.7 W h kg−1 at a power density of 895 W kg−1. The results of electrochemical tests prove that Co(OH)2@p-rGO/NF exhibits good performance as a positive electrode for use in an asymmetric supercapacitor device. The prepared porous composite electrode is thus a promising candidate for use in supercapacitor applications.

Effect of annealing on grain growth and Y segregation behavior in tetragonal ZrO2 thin film

AbstractIn order to fabricate tetragonal yttria stabilized zirconia samples with large grain size, 3 mol% Y2O3 doped zirconia thin films were grown on (0001) α‐Al2O3 substrate by pulsed laser deposition (PLD) followed by subsequent high temperature annealing. The thin film samples were annealed at 1200°C, 1250°C, 1300°C, and 1350°C in order to obtain larger grain size without Y segregation. The microstructure and chemical composition of these annealed films were analyzed using atomic force microscopy, scanning transmission electron microscopy, and energy‐dispersive X‐ray spectroscopy. The as‐grown thin film was found to be composed of [111]‐oriented grains of ∼100 nm connected with small‐angle tilt boundaries. Based on analysis of annealed thin films, it was revealed that grain growth of tetragonal zirconia occurred anisotropically. Cross section scanning transmission electron microscopy observations revealed that such grain growth behavior is affected by the step‐terrace structures of the sapphire substrate. Energy‐dispersive X‐ray spectroscopy showed that Y was found to distribute almost uniformly below 1300°C but to segregate at the grain boundaries at 1350°C. As a conclusion, the 1300°C‐annealed sample shows the largest grain size with homogeneous Y distributions.

Analysis of the Morphology and Structure of Carbon Deposit Formed on the Surface of Ni3Al Foils as a Result of Thermocatalytic Decomposition of Ethanol.

This article presents the results of investigations of the morphology and structure of carbon deposit formed as a result of ethanol decomposition at 500 °C, 600 °C, and 700 °C without water vapour and with water vapour (0.35 and 1.1% by volume). scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) observations as well as energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), and Raman spectroscopic analyses allowed for a comprehensive characterization of the morphology and structure of cylindrical carbon nanostructures present on the surface of the Ni3Al catalyst. Depending on the reaction mixture composition (i.e., water vapour content) and decomposition temperature, various carbon nanotubes/carbon nanofibres (CNTs/CNFs) were observed: multiwalled carbon nanotubes, herringbone-type multiwall carbon nanotubes, cylindrical carbon nanofibers, platelet carbon nanofibers, and helical carbon nanotubes/nanofibres. The discussed carbon nanostructures exhibited nickel nanoparticles at the ends and in the middle part of the carbon nanostructures as catalytically active centres for efficient ethanol decomposition.

Microscopic Corrosion Process and Electrochemical Property of JLF-1 Steel (Fe-9Cr-2W) in the Molten Salt, LiF-NaF-KF

In order to establish a molten salt blanket, the microscopic corrosion of JLF-1 steel (Fe-9Cr-2W) was investigated by comparing with its alloying elements (pure Fe, Cr, and W) and pure Ni. Impedance measurements in LiF-NaF-KF at 500°C and scanning electron microscope and transmission electron microscope observations were performed. The charge transfer resistance of JLF-1 steel was similar to that of pure Fe, three times higher than that of pure Cr, and ten times lower than that of pure W and Ni. The concentration of W in JLF-1 steel was higher near the surface than at the bulk, which also indicated the higher corrosion resistance of W than Fe and Cr. For corrosion resistance of JLF-1 steel, the degradation by 9 mass % Cr was more effective than the improvement by 2 mass % W. The dominant corrosion was the intergranular corrosion at lath boundaries, leading to lath dropout for JLF-1 steel, the intergranular corrosion along grain boundaries for pure Fe, pitting corrosion for pure Cr, and entire surface corrosion for pure W and Ni.

The effect of severe plastic deformation on the IF steel properties, evolution of structure and crystallographic texture after dual rolls equal channel extrusion deformation

This paper presents some results of the influence of severe plastic deformation on the microstructure evolution, grain refinement aspect, and mechanical properties of ultra-low carbon steel. Ti-stabilized experimental IF steel was deformed at a room temperature with unconventional SPD process—dual rolls equal channel extrusion (DRECE). Mechanical properties and structure of ferritic steel in initial state and after selected steps of deformation were investigated. The mechanical properties were determined by static tensile tests carried out at a room temperature and microhardness research. The structural investigations involved using scanning transmission electron microscopy observations, electron back scattered diffraction and measurements of the crystallographic texture. The DRECE process affects the evolution of the structure. The microstructural investigations revealed that the processed strips exhibited a dislocation cell and grain structures with mostly low angle grain boundaries. The electron backscattering diffraction (EBSD) examination showed that the processed microstructure is homogeneous along the strips thickness. The mechanical properties of the DRECE-processed IF steel strips increased with an increase the number of passes.

Structure and energy of the (101) twin boundary in hot-deformed Nd-Fe-B magnets

Revealing the atomic structure and energy of twin boundaries in compounds has been a challenge, especially for compounds with complex crystal structure such as the tetragonal Nd2Fe14B phase in Nd-Fe-B magnets. In this paper, a large number of (101) twin boundaries were observed in grain-coarsening regions of hot-deformed Nd-Fe-B magnets. The atomic structure and twin boundary energy of the (101) twin boundaries were investigated based on the atomic-scale high-angle annular dark field scanning transmission electron microscopy observation and first-principles calculations. The (101) twin boundary has a considerably low energy of 0.008 J/m2. The mechanism of twin-assisted grain coarsening was proposed.

Photocatalytic performance of coupled semiconductor ZnO–CuO nanocomposite coating prepared by a facile brass anodization process

Coupled semiconductor metallic oxides have been largely taken into consideration due to the photocatalytic application. In this work, ZnO–CuO coating nanocomposite was fabricated by simple anodic oxidation of alpha brass at different anodizing times. The crystalline structure of hexagonal ZnO and monoclinic CuO phases were demonstrated by X-ray diffraction (XRD). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) observation indicated the heterostructure formation of ZnO flower-like and CuO patches-like after 30 min anodizing. Brunauer-Emmett-Teller (BET) method was conducted for specific surface area measurement of the samples. Cyclic voltammetry (CV) and Pourbiax diagram indicated that the brass oxidation process starts with the formation of ZnO followed by CuO formation. Diffuse reflectance spectroscopy (DRS) demonstrated that the band gap energy of the ZnO–CuO nanocomposite narrowed by raising anodizing time owing to the formation of the Cu(3d) energy state near the Zn (3d) valence band. Photoluminescence (PL) spectra revealed that the lifetime of the photo-excited electron-hole increased by the effective combination between CuO and ZnO in anodized brass after 30 min. The photocatalytic performance of ZnO–CuO nanocomposites with different anodization times was estimated by the degradation of 2 mg/L methylene blue (MB) and colorless phenol solution under visible light irradiation. After 30 min, the anodized brass with an estimated 3 eV band gap energy exhibited 54 and 49% degradation of MB and phenol, respectively, after 300 min, which was the highest efficiency among all the samples. Also, the highest photo-degradation was obtained at 8 mm2/mL of surface area to volume of dye solution. Recyclability results showed only a 5% drop-in photocatalytic activity after three cycles. Finally, the photo-degradation mechanism was proposed based on the role of holes and hydroxyl radicals, using various scavengers.

A half-shear-half-shuffle mechanism and the single-layer twinning dislocation for [formula omitted] mode in hexagonal close-packed titanium

Among the twinning modes in hexagonal close-packed (HCP) metals, the mechanism for {112¯2}〈112¯3¯〉 mode is particularly confusing and controversial. In the literature reports, there are three possible second invariant planes, i.e. the K2 planes for {112¯2}〈112¯3¯〉 twinning mode: {112¯4¯} which has been widely accepted and corresponds to a three-layer zonal twinning dislocation; {112¯2¯} that is deemed unfavorable; and (0002) which has only been observed in atomistic simulations and corresponds to a single-layer twinning dislocation. {112¯4¯} was predicted by classical twinning theory and the experimentally measured magnitude of twinning shear s in titanium and zirconium seemed to agree well with the prediction. However, {112¯4¯} has never been verified in simulations which show that (0002) should be the K2 plane. This conflict has not been resolved due to the lack of experimental observation of the structure of twinning dislocations. In this work, scanning transmission electron microscopy (STEM) observations are conducted to resolve the twin boundary structure in deformed pure titanium on the atomic scale, combined with atomistic simulations. Atomic resolution STEM unambiguously shows that the twinning dislocation only involves a single twinning plane and the K2 plane is (0002), which is consistent with the atomistic simulations. The STEM results also reveal a half-shear-half-shuffle process which is manifested by a unique twin boundary structure generated by the glide of single-layer twinning dislocations. To explain these results, the lattice correspondences of all three K2 planes are examined in great detail. In particular, shear and shuffle required in the lattice transformations are analyzed inside the framework of classical theory. These analyses explain well why (0002) is the more favorable K2 plane than {112¯4¯} and {112¯2¯}, and properly resolve the conflict between the prediction of the classical twinning theory and the simulation results.

Microstructures and Interface Magnetic Moments in Mn2VAl/Fe Layered Films Showing Exchange Bias.

Heusler alloys are a material class exhibiting various magnetic properties, including antiferromagnetism. A typical application of antiferromagnets is exchange bias that is a shift of the magnetization curve observed in a layered structure consisting of antiferromagnetic and ferromagnetic films. In this study, a layered sample consisting of a Heusler alloy, MnVAl and a ferromagnet, Fe, is selected as a material system exhibiting exchange bias. Although the fully ordered MnVAl is known as a ferrimagnet, with an optimum fabrication condition for the MnVAl layer, the MnVAl/Fe layered structure exhibits exchange bias. The appearance of the antiferromagnetic property in the MnVAl is remarkable; however, the details have been unclear. To clarify the microscopic aspects on the crystal structures and magnetic moments around the MnVAl/Fe interface, cross-sectional scanning transmission electron microscope (STEM) observation, and synchrotron soft X-ray magnetic circular dichroism (XMCD) measurements were employed. The high-angle annular dark-field STEM images demonstrated clusters of MnVAl with the L2 phase distributed only around the interface to the Fe layer in the sample showing the exchange bias. Furthermore, antiferromagnetic coupling between the Mn- and Fe-moments were observed in element-specific hysteresis loops measured using the XMCD. The locally ordered L2 phase and antiferromagnetic Mn-moments in the MnVAl were suggested as important factors for the exchange bias.

Effects of tilted magnetocrystalline anisotropy on magnetic domains in Fe3Sn2 thin plates

We studied effects of tilted magnetocrystalline anisotropy on the magnetic domains in a bubble-hosting magnet ${\mathrm{Fe}}_{3}{\mathrm{Sn}}_{2}$. With increasing the in-plane uniaxial magnetocrystalline anisotropy, the magnetic ground state in ${\mathrm{Fe}}_{3}{\mathrm{Sn}}_{2}$ thin plates changes from disordered stripe domains to stripe domains with preferred orientation. Through transport of intensity equation analysis, we further characterized the transition from skyrmion bubbles to biskyrmionlike configurations with increase in the tilted in-plane magnetocrystalline anisotropy when an out-of-plane magnetic field was applied. In addition, differential phase contrast scanning transmission electron microscopy (DPC-STEM) observations and micromagnetic simulations were carried out to confirm that the biskyrmionlike configurations were type-II bubbles. We show that, in addition tilting a magnetic field to induce misalignment between the magnetic field and the easy magnetization axis, tilting the uniaxial magnetic anisotropy can also be used to stabilize type-II bubbles. Our results also indicate DPC-STEM can help to distinguish between type-II bubbles and biskyrmions.

Crystallization behavior of two Al-Ni-Co-Gd amorphous alloys with selected Ni/Co ratios

Metallic ribbons of Al86NixCoyGd6 composition with different ratio of nickel and cobalt, (x/y = 1 and 3), were produced by standard planar flow casting method in amorphous state. Phase transformation follows upon heat treatment in 5 crystallization stages. Detailed microstructural characterizations (e. g. scanning electron diffraction experiments) were carried out to explain unusual phenomenon shown in x-ray diffraction data, calorimetric and complementary resistometry measurements bound to the second transformation stage. The observed phenomenon was proven to be connected to a observed reordering on the sub-nanometer scale without previous chemical rearrangement forming from amorphous matrix surrounding fcc-Al(Ni) nanocrystals, appearing as a second and single transformation step. Kinetics of crystallization was studied by differential scanning calorimetry and further monitored by electrical resistivity measurements. The transformation sequence up to 850 K is explained by X-ray diffraction and supported with detailed scanning transmission electron microscopy and energy dispersive spectroscopy observations.

Cellulose nanofiber-reinforced rubber composites prepared by TEMPO-functionalization and elastic kneading

Aqueous dispersion consisting of 2,2,6,6-tegramethylpyperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TEMPO-CNFs), dodecyltrimethylammonium chloride (DTMACl), and diethylene glycol (DEG) was oven-dried at 40 °C for 1 d to prepare a dried product. The soft and bulky TEMPO-CNF/DTMACl/DEG material was added to a carboxy group-containing nitrile-butadiene rubber (XNBR) followed by removal of all the DEG molecules by vacuum drying at 80 °C for 8 h. The mixture was then subjected to kneading with high shear forces using a two-roll mill at 20–30 °C (i.e., elastic kneading), followed by pressing at 170 °C for 20 min to prepare cross-linked XNBR composite sheets consisting of TEMPO-CNF and DTMACl. The XNBR composite sheet containing 9.9 vol% TEMPO-CNF had an average tensile strength, storage modulus at 23 °C, work of fracture, and elongation at break of 19 MPa, 47 MPa, 2.7 MJ/m3, and 230%, respectively, whereas those of the reference cross-linked XNBR sheet were 11 MPa, 11 MPa, 0.9 MJ/m3, and 220%, respectively. Scanning transmission electron microscopy observation revealed unique fibrillated and cluster-like structures of the TEMPO-CNF were likely responsible for the excellent mechanical and thermal properties. The proposed process is industrially viable for conventional kneading processes to prepare composite rubber sheets with good mechanical and thermal properties.

Effect of Pre-Stretch on the Precipitation Behavior and the Mechanical Properties of 2219 Al Alloy.

The influence of pre-stretch on the mechanical properties of 2219 Al alloys sheets were systematically investigated, with the aim of examining the age-strengthening in parts draw-formed from as-quenched sheets. The precipitation was characterized based on differential scanning calorimetry (DSC) analysis and transmission electron microscope (TEM) observation of specimens of as-quenched and quenched-stretched condition to address the influence of pre-stretching. A tensile test was performed to evaluate the effect on mechanical properties. The introduction of pre-stretching endues increased yield strength (YS) and thus can be helpful to exert the potential of the alloy. Peak YS of 387.5 and 376.8 MPa are obtained when specimens pre-stretched for 10% are aged at 150 and 170 °C, respectively, much higher than that obtained in the non-stretched specimens (319.2 MPa). The precipitation of Guinier-Preston zone (G.P. zones) and the transition to θ″ shifts to a lower temperature when pre-stretched is performed. The high density of dislocations developed during the stretching contributes to the acceleration in precipitation. Quench-stretched specimens present a much quicker age-hardening response at the beginning stage, which endue higher peaked yield strength. The yield strength, however, decrease much more quickly due to the recovery that occurs during the aging processes. The study suggested the feasibility of aging draw-formed components of 2219 Al alloy to obtain high strength.

YIn0.9Mn0.1O3–ZnO NIR reflective nano-pigment exhibiting three different colors: Ochre, cyan blue, and deep blue

A set of NIR reflective nano-pigments displaying YIn0.9Mn0.1O3–ZnO stoichiometry was synthesized by sol-gel route. The dried gel precursor was calcined at different temperatures for 2h (550 ​°C, 650 ​°C, 750 ​°C, 800 ​°C, and 850 ​°C), observing the formation of three ochre pigments and two different blue shades. Precursors and final calcined pigments were characterized by thermogravimetry (TGA) and differential scanning calorimetry (DSC) analysis to monitor the NIR reflective pigments production and their thermal resistance. Fourier transform infrared (FT-IR) spectra were collected to know chemical changes obtained by calcination process. Crystalline phases and morphology of nano-pigments were studied using X-ray diffraction (XRD) and scanning transmission electron microscope (STEM) observation, respectively. The synthesized pigments showed near infrared (NIR) reflectance ability. The final color was evaluated according to CIE-1976L∗a∗b∗ method obtaining a standard identification of each color.

Nonsymmetrical Segregation of Solutes in Periodic Misfit Dislocations Separated Tilt Grain Boundaries.

Interfacial segregation is ubiquitous in mulit-component polycrystalline materials and plays a decisive role in material properties. So far, the discovered solute segregation patterns at special high-symmetry interfaces are usually located at the boundary lines or are distributed symmetrically at the boundaries. Here, in a model Mg-Nd-Mn alloy, we confirm that elastic strain minimization facilitated nonsymmetrical segregation of solutes in four types of linear tilt grain boundaries (TGBs) to generate ordered interfacial superstructures. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy observations indicate that the solutes selectively segregate at substitutional sites at the linear TGBs separated by periodic misfit dislocations to form such two-dimensional planar structures. These findings are totally different from the classical McLean-type segregation which has assumed the monolayer or submonolayer coverage of a grain boundary and refresh understanding on strain-driven interface segregation behaviors.