Polyhedral Grains Research Articles

Investigation of Sr-substituted Ba1-xSrx(Zn1/3Nb2/3)O3 complex perovskites: structural, electrical and electrochemical properties

Herein we report the structural, dielectric and electrochemical properties of Ba1-xSrx(Zn1/3Nb2/3)O3 (BSZN, 0 ≤ x ≤1) solid solution synthesised by solid-state reaction. A complete substitutional solid solution was obtained, wherein the BSZN cubic perovskites of the space group of Pmm were obtained at x ≤ 0.6 while the pseudo-cubic phases were discernible at x > 0.6. The nano-sized crystallites, as determined by both Scherrer and Williamson-Hall analyses, supported the claim of large polyhedral grains of 0.1 to 0.3 μm by FE-SEM. Both ε′ and tan δ were found to vary consistently with increasing dopant concentration, except for an anomalous observation for the composition, x = 0.6 with the lowest tan δ of 0.0783 and the highest ε′ of 27.5. Such phenomenon could be attributed to the combined effects of larger grain size, higher relative density and stronger polarisation per molar volume. The impedance analysis revealed that these BSZN perovskites were of the negative temperature coefficient of resistance (NTCR) type. The combined plots of imaginary modulus (M″) and impedance (Z″) against frequency showed the short-range movement of localised charge carriers, suggesting a non-Debye-type relaxation process.

Elevating carbonation efficiency and CO2 capture capacity of steel slag by sodium tripolyphosphate (STP): The role of CaCO3 morphology modification

Carbonation degree significantly impacts the volume stability of steel slag powder. To elevate the carbonation efficiency of steel slag and thereby alleviate the volume unsoundness of steel slag powder, sodium tripolyphosphate (STP) was used to enhance the micro morphology of CaCO3 and accelerate Ca leaching and CO2 diffusion. Three methods for assessing CO2 uptake were employed to reliably determine the degree of carbonation. Results indicate that steel slag added with 0.05 wt% STP obtained a promotion exceeded 80 % in CO2 uptake. Additionally, STP increased the CO2 capture capacity of steel slag by 24.84 %. Under the influence of STP, the expansion of steel slag paste was reduced by up to 31.45 % following an autoclaving test. The formed micro CaCO3 particles in carbonated steel slag without STP were polyhedral grains and a dense carbonation layer was formed around calcium silicate. Contrastively, CaCO3 formed in the carbonated STP incorporated steel slag were conical or acicular particles and consequently generated a porous layer. The porous microstructure provided “tunnels” for the continuous CO2 diffusion and Ca2+ leaching and hence maintained relatively higher reaction speed throughout the carbonation process. Furthermore, STP also played the role as a chelator which accelerated the leaching of Ca2+.

Influence of the Isothermal Transformation Temperature on the Structure and Properties of Low-Carbon Steel

Purpose. The study is aimed at evaluating the effect of the isothermal transformation temperature on the structure and properties of low-carbon steel. Methodology. The material for the study was a 3 mm diameter wire made of mild steel with the following chemical composition: 0.21% C, 0.47% Mn, 1.2% Si, 0.1% Cr, 0.03% S, 0.012% P. The 0.3 m long wire samples were subjected to austenitizing at 920 °C for 8...9 min, after which they were held isothermally for 11 min at temperatures of 650...200 °C, followed by cooling in air. The strength, plastic properties, and strain hardening coefficient were determined from the analysis of tensile curves. Findings. It was found that a decrease in the temperature of isothermal transformation, starting from 450...400 °C, increases the amount of Widmannstätten ferrite due to the disappearance of polyhedral ferrite grains. At the same time, the number of areas with locally located dispersed cementite particles similar to pearlite colonies increases, and bainite crystals appear. Against the background of a sharp decrease in the strain hardening coefficient in the range of 450...400 °C, the ability of the bainite phase to undergo plastic deformation should be considered one of the reasons for the delay in density reduction. Originality. The effect of steel hardening with a decrease in the pearlite transformation temperature is based on the grinding of ferrite grains, an increase in the amount of Widmannstätten ferrite, and the dispersion of pearlite colonies. The strengthening effect of steel with a bainite structure is based on an increase in the degree of supersaturation of the solid solution with carbon atoms and dispersion hardening by particles of the carbide phase. Practical value. The optimal structural state of steel intended for the manufacture of such critical elements as a support beam, railroad car bogie, etc. is a mixture of phase components with different dispersion and morphology, and their quantitative ratio is determined by the operating conditions of a particular product.

Moinui Flow on Mauna Loa: transport and deposition of an olivine crystal cargo in a compound basaltic lava flow

The Moinui lava flow on the west flank of Mauna Loa, Hawai`i, is a 32-km-long pāhoehoe basalt flow, between 760 and 1500 years old, characterised by the presence of two generations of olivine: 2–5-mm-sized glomerocrystic clusters of equant polyhedral grains, and dendritic plates. Both generations are distributed throughout the flow field from the vent at 3400 m above sea level to the ocean. We mapped roadcut outcrops in detail to investigate the internal geometry and emplacement mechanisms of the flow, and sampled these outcrops to collect quantitative textural data on the two olivine populations in 2D and 3D, with a view to understanding emplacement processes in general, and the factors controlling the growth, transport, and deposition of phenocryst olivine in particular. Roadcut outcrops reveal complex geometries of interconnected tube-fed sheet lobes, with the main control being pre-existing topography: drained tubes with flanking sheet lobes were developed on the seaward slope of the volcano, whereas tumuli were developed on the flat coastal plain topography. The internal architecture of the flow field is consistent with current hypotheses of emplacement by breakout and inflation of flow lobes from tube-fed internal pathways. Concentrations of up to 30% olivine represent settling of the larger size-fraction of the transported load, with no evidence for superimposed effects of flow differentiation.Implied effective viscosities were around 1000 Pa s. The glomerocrystic population was inherited as pre-existing crystal clusters derived from a sub-volcanic chamber, rather than by synneusis (random collision and aggregation) post-eruption, whereas the plate population was probably generated by a burst of nucleation related to degassing and supercooling during the vent eruption. Other than this, there is no evidence for substantial growth of the transported olivines during flow.

Influence of synthesis route on structural properties of SnFe2O4 spinel phase via methods of co-precipitation, sol–gel and solvothermal: morphology, phase analysis, crystallite size and lattice strain

In this study, regarding to the wide applications of spinel ferrites in various fields such as Li ion-batteries, photocatalysts, and optoelectronics, the structural and morphological properties of tin ferrite oxide (SnFe2O4) nanoparticles are investigated using X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM). The sol–gel, solvothermal, and co-precipitation methods were used to synthesize the SnFe2O4 nanoparticles, and the effect of annealing temperatures at T = 350 °C, 450 °C, and 550 °C was investigated. The XRD results confirmed the formation of tin ferrite spinel phase at an annealing temperature of 350 °C with a preferred peak (311). Crystallite size (D) and strain (ε) of SnFe2O4 nanoparticles was determined in region 20–45 nm and 2–4 × 10–4, respectively, using the Scherer, Williamson–Hall, and Rietveld computational methods. The results showed that the crystallite size in the samples increased with increasing annealing temperature. This increase is attributed to the reduction of defects, imperfections and lattice strain, which leading to an increase in the lattice constants and unit cell volume in the nanocrystalline structure. The Rietveld method determine smaller crystal sizes compared to the Williamson–Hall and Scherer methods because it can correct for peak broadening by taking into account all instrumental factors. The FESEM images of the synthesized nanostructures of SnFe2O4 showed cubic and polyhedral grains with cluster growth and an average grain size of 50–80 nm. According to the crystal structure of tin ferrite spinel, the cubic morphology confirmed the formation of this structure. The average crystallite size and grains in the synthesized samples was determined using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analysis, respectively. The formation conditions of the SnFe2O4 spinel phase and other phases in the synthesis process at different temperatures and dependence of structural parameters was studied by various structural models for the samples.

Analysis of Biocompatible Metallic Materials used in Medicine

The paper presents the results of the analysis of two biocompatible materials, Kirschner wires of different thicknesses. Kirschner wires (K-wires) are stainless steel pins used in surgery to fix bone fragments and to provide an anchor for skeletal traction. The K-wires are produced in different diameters. In the present work, a scanning electron microscopy and light microscopy were employed to document the microstructure of two K-wires with different thicknesses. Before observation, the wires were prepared by a standard metallographic procedure (grinding and polishing) followed by electrolytic etching. The chemical composition was determined by studying the wires using quantitative energy-dispersive X-ray spectrometry. It has been found that the chemical composition of the materials corresponds to Cr-Ni stainless steel. In the thick Kirschner wire (sample no. 1) a deformed microstructure after drawing was observed. Sample no. 2 (thin Kirschner wire), on the other hand, consisted of polyhedral austenitic grains, which were formed after recrystallization annealing. Furthermore, isolated microparticles were observed and assigned to titanium nitride. A Vickers hardness test was also performed on the samples. It has been found that the hardness of sample no. 1 was 428.8 HV 0.5. The average hardness of sample no. 2 was 213.4 HV 0.5. It can be concluded that recrystallization annealing decreases the hardness of the material. The K-wires with smaller diameter are thus easier to bend which facilitates their fixation in human body.

Development and optimization of trivalent chromium electrodeposit on 304L stainless steel to improve corrosion resistance in chloride-containing environment

In this study, we developed and optimized a trivalent chromium coating electrodeposited on 304L stainless steel (SS) from a Cr-trivalent bath. The results reveal that the Cr coatings at all bath temperatures except for 80 °C showed clusters of polyhedral grains, however, the grain sizes decreased with an increase in bath temperature. Also, the coatings deposited at bath temperatures of 30, 50, and 60 °C experienced networks of cracks, which decreased in population density as temperature increased. However, the coatings deposited at bath temperatures of 70 and 80 °C were crack-free due to surface modification, confirmed by 3D profile results with an advanced power spectral density and a multi-Gaussian histogram analysis. The mechanical test results demonstrate that the adhesion and wear resistance of the Cr-coatings formed on the SS substrate significantly improved, with the optimal coefficient of friction of 0.18. Likewise, electrochemical behavior observations of the Cr coatings show that pitting resistance improved with the increase in bath temperature conditions, as shown in the pitting potential values which increased from 272.6 mV to 436.2 mV as bath temperature increases from 30 °C to 80 °C. From this study, it is proposed that the Cr-coatings deposited at a bath temperature of 80 °C presents the optimal coating performance concerning a combination of all the target qualities aimed, such as better tribological behavior and improved pitting resistance. Thus, enabling the establishment of an innovative method to overcome the conventional issues encountered in Cr electrodeposition of SSs.

Microstructure evolution, crystal structure, Raman analysis, bond characteristics and enhanced microwave dielectric properties of Zn1-xCuxZrNb2O8 solid solution ceramics

The Structural factors of ceramic materials significantly affect microwave dielectric properties. Consequently, the structure–performance mechanism is essential for providing insight into material discovery and performance refinement. In the present work, Zn1-xCuxZrNb2O8 ceramics were synthesized through oxygen-assisted sintering procedures. The controversy of lattice vibrations was clarified and complete Raman vibration with complete mode assignments were provided for the first time through density functional theory and symmetry analysis. Intrinsic properties, including lattice energy, bond ionicity, thermal expansion coefficient, Raman vibrational states and bond energy, were calculated and the structure–performance relationships were established based on crystal structure refinement, density functional theory, chemical bond theory and Raman analyses. X-ray diffraction patterns and crystal structure refinement indicate a pure phase with the wolframite structure. The smaller ionic radii of Cu2+ ions led to a decrease in cell volume, which could account for the blueshift of the Ag mode at around 340 cm−1. Through Cu2+ substitution, the grain growth was further promoted and morphology evolution from polyhedral grain to rod shape was observed, which may be attributed to grain amalgamation. From chemical bond theory, Cu2+ substitution leads to the decrease in the dielectric constant, which is related to a decrease in the Nb–O bond ionicity (fiNb-O). The improvement in Q×f value is attributed to the high lattice energy of Nb–O bond (UNb–O), low FWHM at 845 cm−1 and large grain size. τf values are strongly impacted by the bond energies of the Zn/Cu–O bonds in the Zn1-xCuxZrNb2O8 ceramic crystals. Remarkably, microwave dielectric performance of the composition x = 0.06, sintered at 1175 °C, where εr = 27.9, Q×f = 73,200 GHz (@7.14 GHz) and τf = −40 ppm/°C, provide potential for millimeter-wave applications.

Mechanism of polishing lutetium oxide single crystals with polyhedral diamond abrasive grains based on molecular dynamics simulation

Lutetium oxide single crystal is an excellent laser crystal material with the advantages of low phonon energy, high thermal conductivity, and high laser-induced damage threshold. Polishing is an important method to achieve ultrasmooth, damage-free surfaces of lutetium oxide wafers. The diamond abrasive grains used in mechanical polishing are mainly in the form of blocks, flakes, and balls. In this study, the molecular dynamics simulation method is used to simulate the process of polishing a lutetium oxide single crystal with different shapes of polyhedral diamond abrasive grains, and the polishing force, subsurface damage, and material removal are analyzed. Results show that the compressive stress and thickness of the machined amorphous layer in the subsurface are minimum at the vertex contact position and maximum at the face contact position. The values at the sphere and edge contact positions are somewhere in between. In terms of material removal, polyhedral and spherical abrasive grains have a plowing effect on the material removal process. However, the vertices and edges of polyhedral abrasive grains can be more easily cut into the workpiece than spherical abrasive grains, so polyhedral abrasive grains are conducive to the removal of materials in specific cases.

Pharmacognostic Survey on Paeonia Broteri – An Iberian Endemism

The genus Paeonia (Paeoniaceae) includes perennial plants distributed throughout the northern hemisphere and some of these are used in traditional medicine and cultivated as ornamental species. Paeonia broteri is endemic to Iberian Peninsula and the current paper is the first report on a pharmacognostic survey on its roots, leaves and corresponding powders. Using light and scanning electron microscopy, simple and compound polyhedral starch grains, with a fissure-type hilum and no striae, are recorded in the root phelloderm cells and the presence of idioblasts with druse-type calcium oxalate crystals, in addition to isolated stone cells, are also common. Irregular and sinuous epidermal cells can be detected on both leaf surfaces and anomocytic stomata, with an elliptical-rounded shape, are only on the abaxial face. In leaves, druse-type calcium oxalate crystals appear along the vascular tissues. The histochemical tests allowed the in situ localization of some chemical groups and the most relevant detected were polyphenols and terpenoids.

The arrival of millets to the Atlantic coast of northern Iberia

Despite being one of the most important crops in the recent prehistory of Eurasia, the arrival and exploitation of millets in the westernmost part of Europe are still largely underexplored. Here and for the first time, we report multipronged biomolecular evidence of millet consumption along the Atlantic façade of northern Iberia through a combination of radiocarbon dating, stable isotopes, and dental calculus analyses on the human individuals found in the burial site of El Espinoso cave (Asturias, Spain). The high-resolution chronological framework established for individuals placed the burials between 1235 and 1099 cal. BC. The discovery of high δ13C values on their bone collagen and the identification of polyhedral starch grains within their dental plaque underline the relevance of C4 plants in their diet and highlights the timing of the systematic consumption of millets in the Late Bronze Age. Our data support previous regional archaeobotanical evidence and establish a more precise chronology of the dispersal of millets into northern Iberia during the Bronze Age, becoming an essential crop until the arrival of maize from America after AD 1492. This study emphasizes the importance of multidisciplinary methods to ascertain the origin and development of agricultural practices during recent prehistory.

Magnetic-Property Assessment on Dy-Nd-Fe-B Permanent Magnet by Thermodynamic Calculation and Micromagnetic Simulation.

Heavy rare-earth (HRE) elements are important for the preparation of high-coercivity permanent magnets. A further understanding of the thermodynamic properties of HRE phases, and the magnetization reversal mechanism of magnets are still critical issues to obtain magnets that can achieve better performance. In this work, the Nd-Dy-Fe-B multicomponent system is investigated via the calculation of the phase diagram (CALPHAD) method and micromagnetic simulation. The phase composition of magnets with various ratios of Nd and Dy is assessed using critically optimized thermodynamic data. γ-Fe and Nd2Fe17 phases are suppressed when partial Nd is substituted with Dy (<9.3%), which, in turn, renders the formation of Nd2Fe14B phase favorable. The influence of the magnetic properties of grain boundaries (GBs) on magnetization reversal is detected by the micromagnetic simulations with the 3D polyhedral grains model. Coercivity was enhanced with both 3 nm nonmagnetic and the hard-magnetic GBs for the pinning effect besides the GBs. Moreover, the nucleation and propagation of reversed domains in core-shell grains are investigated, which suggests that the magnetic structure of grains can also influence the magnetization reversal of magnets. This study provides a theoretical route for a high-efficiency application of the Dy element, realizing a deterministic enhancement of the coercivity in Nd-Fe-B-based magnets.

{332} and {112} Twin Variant Activation during Cold-Rolling of a Ti-Nb-Zr-Ta-Sn-Fe Alloy

Deformation twinning is a phenomenon that causes local shear strain concentrations, with the material either experiencing elongation (and thus a tensile stress) or contraction (compressive stress) along the stress directions. Thus, in order to gauge the performance of the alloy better, it is imperative to predict the activation of twinning systems successfully. The present study investigates the effects of deformation by cold-rolling on the {332}<113> and {112}<111> twin variant activation in a Ti-30Nb-12Zr-5Ta-2Sn-1.25Fe (wt.%) (TNZTSF) alloy. The Ti-30Nb-12Zr-5Ta-2Sn-1.25Fe (wt.%) alloy was synthesized in a cold crucible induction levitation furnace, under an argon-controlled atmosphere, using high-purity elemental components. The TNZTSF alloy was cold-deformed by rolling, in one single step, with a total deformation degree (thickness reduction) of ε ≈ 1% (CR 1), ε ≈ 3% (CR 3), and ε ≈ 15% (CR 15). The microstructural investigations were carried out with the SEM-EBSD technique in order to determine the grain morphology, grain-size distribution, crystallographic orientation, accumulated strain-stress fields and Schmid Factor (SF) analysis, all necessary to identify the active twin variants. The EBSD data were processed using an MTEX Toolbox ver. 5.7.0 software package. The results indicated that the TNZTSF alloy’s initial microstructure consists of a homogeneous β-Ti single phase that exhibits equiaxed polyhedral grains and an average grain-size close to 71 μm. It was shown that even starting with a 1% total deformation degree, the microstructure shows the presence of the {332}<113> twinning (()[] active twin variant; Schmit factor SF = −0.487); at a 3% total deformation degree, one can notice the presence of primary and secondary twin variants within the same grain belonging to the same {332}<113> twinning system (()[] primary twin variant—SF = −0.460; ()[] secondary twin variant—SF = −0.451), while, at a 15% total deformation degree, besides the {332}<113> twinning system, one can notice the activation of the {112}<111> twinning system (()[] active twin variant—SF = −0.440). This study shows the {332}<113> and {112}<111> twinning variant activation during cold-deformation by rolling in the case of a Ti-30Nb-12Zr-5Ta-2Sn-1.25Fe (wt.%) (TNZTSF) alloy.

Practical insights into the recycling of green mussel shells (Perna Viridis) for the production of precipitated calcium carbonate

The study presented a powder processing method involving calcination and subsequent carbonation in the synthesis of precipitated calcium carbonate (PCC) for recycling green mussel shells, which contain a high calcium carbonate content. The purity of portlandite [Ca(OH)2] as a result of calcination and subsequent moisture absorption during storage was verified using the XRD-Rietveld method. Further quantitative XRD Rietveld analysis of the PCC product confirmed the presence of vaterite (55.20 wt.%) and calcite (44.80 wt.%) minerals after carbonation process of the calcined powder product. The SEM examination of this product revealed particle aggregates of non-uniform polyhedral and cubical grains of varying small and large sizes. The FTIR analysis also confirmed that calcination and subsequent hydration of mussel shell powder yielded pure portlandite, whereas the carbonation yielded PCC polymorphism. As a result, this powder processing method is simple to scale and reduces the cost of PCC synthesis, which is critical for practical applications. The current study demonstrated that the powder processing method for recycling green mussel shells as starting materials in biomedical applications is technically feasible.

Study on grinding force of Si3N4 ceramics in random rotation grinding with truncated polyhedral grains

Study on grinding force of Si3N4 ceramics in random rotation grinding with truncated polyhedral grains

Phase field modeling of diamond-silicon carbide ceramic composites with tertiary grain boundary phases

Phase field simulations are used to study effects of microstructure features on overall strength and ductility of polycrystalline ceramic composites. The material of present interest is a diamond-silicon carbide (SiC) blend with a grain boundary (GB) phase consisting of much smaller SiC grains, graphitic inclusions, and porosity. Homogenized properties—elastic moduli and surface energy—used in the phase field representation of the GB phase are obtained from a novel approach involving bounds from elastic homogenization theory. Extensive parametric calculations on synthetic microstructures with smoothed polyhedral grains are used to deduce trends in structure-property-performance relations. Results suggest that peak strength, for a fixed fraction of GB phase, can be increased by the following prescriptions: increasing bulk diamond content, reducing porosity, reducing graphite content, and distributing any unavoidable defects uniformly rather than randomly. For the assumed constitutive behavior of the GB phase, graphite appears less deleterious than pores of the same average volume fraction, and median defect concentration appears to be more important than randomization of distributions at low volume fractions. More complex interrelations among microstructures, model features, and material responses are also revealed, for example effects of anisotropic fracture, inelastic dilatation associated with crack opening, and twin variant selection in the SiC phase.

A force model for face grinding using digital graphic scanning (DGS) method

The prediction of grinding force has great significance in improving grinding quality and efficiency. This paper presents a predictive force model in plunge facing grinding considering both the cutting mechanism of single grain and the random nature of wheel topography. The model includes cutting deformation force and frictional force, which mainly depend on undeformed chip cross-section area and wear flat area of grains. In order to overcome the difficulties for calculating the cross-section area of irregular polyhedral grains, a digital graphic scanning (DGS) method is proposed in this research. Single grain scratch test and hardness test are carried out to obtain the model coefficients. The validation experiments performed on a face grinding machine show a good match of the predictive and measured forces for different grinding parameters.

Structural, optical and photocatalytic properties of Ni doped BiFeO3 nanoparticles

This paper presents synthesis and study of Structural, Optical, and Photocatalytic properties of bismuth ferrite (BFO) and nickel doped bismuth ferrite (BiFe1-xNixO3) nanoparticles. The synthesis of BiFeO3 and BiFe1-xNixO3 (x = 0.02, 0.04) are done by Sol-Gel method. After synthesis the samples of pure and transition metal ion (Ni) doped bismuth ferrite have been studied by using X-ray diffractometer (XRD), X-ray Photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscope and Raman Spectroscopy. Optical properties are studied by using UV–vis spectroscopy using different wavelengths (range 300–800 nm). Photocatalytic properties are also studied by degradation of MB dye using prepared samples as photocatalyst. XRD patterns shows that all the prepared samples are crystalline and crystallinity increased by Ni-doping and shifts in XRD peaks by Ni-doping shows the distortion in the structure of BFO. Raman spectroscopy also indicates the rhombohedral distorted structure of Ni-doped BFO in R3C space group. FESEM micrographs shows that Ni-doped BFO has polyhedral and spherical shape grains and Ni doping cause reduction in grain size. Optical band gap reduced due to Ni-doping is shown by the UV–Vis spectroscopy results and Tauc’s plots. The increase in reduction of MB dye due to Ni-doping shows the enhanced photocatalytic properties of BFO by Ni doping.

Doping effects in (Ba0.85Ca0.15)(Hf0.1Ti0.9)O3 lead-free piezoelectric ceramics prepared via powder injection moulding using simple binder

To improve densification of the (Ba0.85Ca0.15)(Hf0.1Ti0.9)O3 (BCHT) ceramics prepared via powder injection moulding, MnO2 and Li2CO3 were used as sintering aids. The BCHT ceramics doped with different Mn- and Li-amount prepared by powder injection moulding in which paraffin was used as injection binder, have rather pure perovskite structure with complicated polymorphic ferroelectric phase coexistence. Polyhedral grains combined with nearly round shape grains with increased relative density and larger gains size were obtained at appropriate doping amount, related to the formation of liquid phase during sintering and increased mobility of ions due to the generation of point defects caused by heterovalent cations doping. TheMn- and Li-doped BCHT ceramics are displacement driven ferroelectrics with apparent diffused transition characteristic at different extent, relating to the morphotropic phase boundary composition and the variation of point defects induced by doping. Comparable or surpassing electrical performance was acquired, especially the dielectric breakdown strength was increased due to the improved sinterability. With appropriate doping amount, piezoelectricity larger than 300 pC/N can be obtained in the Mn- and Li-doped BCHT ceramics poled under low electric field.

Structural properties of Al2O3–MgO–C refractory composites improved with YAG nanoparticle hybridized expandable graphite

Abstract The structural properties of Al2O3–MgO–C refractories were measured with the addition of YAG nanoparticle hybridized expandable graphite (EG) powder as a partial replacement of graphite in the refractory composition. The experimental findings showed that the refractories fabricated with YAG nanoparticle hybridized EG exhibited a considerable improvement in structural properties (strength, toughness, Weibull modulus) as compared to that of refractories developed with conventional graphite compositions. These improvements in structural properties can be attributed to the formation of a well-sintered framework of EG embedded polyhedral YAG grains throughout the matrix microstructure of these new class of refractory composites. Mechanisms of microstructure evaluation and toughening in Al2O3–MgO–C refractory composites are proposed.