Phase Size Distribution Research Articles

The effect of contact resistance on electrical conductivity in filled elastomer materials

This paper is focused on studying the charge transport between the particles in filled elastomer composites, and suggests a new modeling approach that would allow predicting the electrical conductivity of this material. Our approach is based on a combination of non-equilibrium Green's function (DFTB-NEGF) analysis for atomic-level electron quantum transport, and effective medium theory for calculating the said macroscopic transport properties of the material. The model can be used for predicting macroscopic material conductivity based on the information of material microstructure received by electron microscopy; explain changes of conductivity in deformed material and with temperature variation, and finally it can assist in finding the optimal material parameters such as particle shape, size distribution, and volume fraction to maximize the performance. The results of our modeling re-attest the known phenomenon that the electrical conductivity in percolated network is always dominated by direct particle-to-particle charge transport. We studied the electrical conductivity in a medium of high volume fraction of metallic particles dispersed in polymer matrix where thin polymer matrix layer covalently attached to the metallic particle contacts, and the thin polymer layer undergoes high local shear strain when hard particles slide along each other during deformation. These conditions allow the redistribution of electron density from metal to the polymer, and the conductance through normally insulating matrix can become comparable with the pinpoint conductance through the metal. These conditions can only occur in the place of direct particle contacts, therefore all criteria for percolated conductive network hold valid in this case. The integral conductance of thin “sandwiched” polymer layer strongly, but predictably depends on local contact geometry, mostly on particle surface curvature at place of contact. This allows predicting composite conductivity from the properties of each phase, loading, and particle shape and size distributions. Further, the conductance of polymer chain can significantly increase with the fluctuations of molecular shape caused by temperature and/or deformation. We infer that this effect is responsible for the major part of strain and temperature dependence of the conductivity that has been reported in the literature, although particle orientation and stacking at larger deformations may also contribute to the strain dependence.

Selective Laser Melting of In Situ TiB/Ti6Al4V Composites: Formability, Microstructure Evolution and Mechanical Performance

In the present study, a series of in situ TiB/Ti6Al4V composites were fabricated using selective laser melting. The formability, microstructure evolution and mechanical properties of the as-built samples added with different contents of TiB2 were studied. It is found that the densification level is related to both the content of TiB2 and laser energy density. The added TiB2 reinforcement particle can spontaneously react with titanium and then form the TiB phase. The needle-like TiB phase tends to transform into dot-like particles with the decrease in energy density. Additionally, with the increase in TiB2 content, the TiB phase is coarsened due to the increased nucleation rate and more reactions. The grain morphology is found to largely depend on the translational speed of solid–fluid interface determined by the temperature gradient and cooling rate. Also, the microhardness of the as-built TiB/Ti6Al4V composites is obviously improved. More interestingly, as the energy density increases, the microhardness of the as-built TiB/Ti6Al4V composites firstly increases and then decreases due to the synergy of grain size and different morphologies and distribution of TiB phases. The wear resistance of TiB/Ti6Al4V composites is far superior to that of Ti6Al4V alloy owing to the increased microhardness resulted from the uniform distribution of the hard TiB phase in the matrix.

The effects of additives in to heat treatment temperature and time on the crystallinity of lithium silicate glass-ceramic

The glass powders were prepared from binary system of 45 wt.% Li2O and 55 wt.% SiO2 and melted in platinum crucible (90% Pt- 10% Rh) at 1195 °C for 1:15 hr. The glass molten was rapid cooled in cold water at 3°C and the produced frit was milled in agate mortar and four sample groups were prepared. In the first group the temperature changes of heat treatment 750, 800, 850, 900 and 950°C was studied. Second group the time changes of heat treatment 2, 4, 6, 8 and 10 hr. was examined. Third group the addition effect of P2O5 4, 7, 11, 14 and 18 wt.% as nucleating agent was studied. Fourth group the addition changes of nucleating agent mixing P2O5 and TiO2 (quarter of P2O5 percentages as same above) was inspected. XRD, AFM and optical microscope had been done for all four group specimens. Crystalline phase percentages were calculated from XRD histogram by GSAS (General Structure Analysis System) and EXPGUI. The grain size distribution and average diameter of the crystalline phases for all four group specimens were calculated by AFM measurement. The density and mass fraction of crystalline phases were calculated by optical microscope image analyses by image J 1.52i. The results indicated good crystalline phase percentages, phases density, mass fraction and average diameter on nano-scale for 4 wt.% of (3 wt.% P2O5- 1 wt.% TiO2), heat treated at temperature 950°C for 6 hrs.

Phase Structure of Block and Gradient Copolymers of Butyl Acrylate and Styrene

The structure of n-butyl acrylate–styrene block and gradient copolymers of various compositions is studied in detail, and their glass transition temperatures are determined. Influence of the architecture of copolymer macromolecules on the glass transition temperature is considered. Histograms of the size distribution of phases are constructed, and the density distribution of domains over the cross section of the dispersed phase is estimated. Schematic representations of the structure of the block and gradient copolymers are proposed, and their features are analyzed.

Synchrotron radiation-based materials characterization techniques shed light on molten salt reactor alloys

From a safety point of view, it is important to study the damages and reliability of molten salt reactor structural alloy materials, which are subjected to extreme environments due to neutron irradiation, molten salt corrosion, fission product attacks, thermal stress, and even combinations of these. In the past few years, synchrotron radiation-based materials characterization techniques have proven to be effective in revealing the microstructural evolution and failure mechanisms of the alloys under surrogating operation conditions. Here, we review the recent progress in the investigations of molten salt corrosion, tellurium (Te) corrosion, and alloy design. The valence states and distribution of chromium (Cr) atoms, and the diffusion and local atomic structure of Te atoms near the surface of corroded alloys have been investigated using synchrotron radiation techniques, which considerably deepen the understandings on the molten salt and Te corrosion behaviors. Furthermore, the structure and size distribution of the second phases in the alloys have been obtained, which are helpful for the future development of new alloy materials.

The Effect of annealing temperature on corrosion resistance and microstructure of Zr-Sn-Nb-Fe alloy

The Ti-2Al-2.5Zr titanium alloy plate in beta phase water quench at different times of the reentry after annealing is implemented while primary phase number and size distribution of samples are obtained. This research is carried out on corrosion behavior in 3.5% [mass fraction] NaCl solution. Experimental study showed that after the beta phase water quenching Ti-2Al-2.5Zr titanium alloyed after 500 oC annealing when partial recrystallization happened. There seems to be lots of tiny dispersion in the alloy that was annealed with its samples of six-party [HCP] structure of Ti, Zr, Al phase 2 with the dimension below 100 nm. Reaching 500 oC when the rate of annealing at a primary phase of the sample at 550 oC is low 90% of the primary phase is less than 100 nm. The changing of the rule of present decreasing also triggers little difference overall. Precipitation in the process of annealing Zr [Nb,Fe,Cr] 2is less that proves to be good for corrosion resistance.

Influence of heat treatment under hot isostatic pressing (HIP) on microstructure of intermetallic-reinforced tool steel manufactured by laser powder bed fusion

Microstructure and properties of as-built laser powder bed fusion (LPBF) steels differ from the conventional ones, and they may contain some porosity and lack of fusion. Therefore, post-treatments, including hot isostatic pressing (HIP), are used to densify the material, and tailor the properties of the final product. Usually, HIP is performed as an operation separate from heat treatment. In the present investigation a new approach was used, in which the whole cycle of the heat treatment was carried out in HIP under pressure, and the influence of HIP on microstructure of an advanced stainless maraging tool steel manufactured by LPBF was investigated. For a comparison, a conventional steel grade of the same chemical composition, after a heat treatment at the same temperature-time conditions, was also characterized. The microstructure of the steel was investigated by means of advanced microscopy and atom probe tomography. The influence of the manufacturing route, heat treatment and HIP on microstructure, austenitic phase fraction and size distribution of precipitates was investigated, and the role of high pressure in stabilization of austenite in the microstructure was discussed. It was concluded that since HIP influences phase transformations, a fundamental understanding of the influence of HIP on microstructure is necessary, and development of new post processing regimes guaranteeing the best performance of the material is required.

A framework for polydisperse pulp phase modelling in flotation

Froth flotation is one of the most widely-used mineral processing operations. The pulp zone in flotation tanks is polydisperse in general and serves as a medium for the interaction between the solid particles and the gas bubbles in a liquid continuum, leading to particle–bubble attachment/detachment and bubble coalescence/breakage phenomena. To better predict the hydrodynamics and inform the design of efficient flotation equipment, it is therefore important to accurately model and simulate the evolution of the size distribution of the dispersed phases. This has created an urgent need for a framework that can model the pulp phase in an efficient manner, which is not currently available in the literature. The available software products are not efficient enough to allow for a tractable modelling of industrial-scale flotation cells and in some cases they cannot model the polydispersity of the dispersed phase at all. This work presents an efficient numerical framework for the macroscale simulation of the polydisperse pulp phase in froth flotation in an open-source finite element computational fluid dynamics (CFD) code that provides an efficient solution method using mesh adaptivity and code parallelisation. A (hybrid finite element–control volume) finite element framework for modelling the pulp phase has been presented for the first time in this work. An Eulerian–Eulerian turbulent flow model was implemented in this work including a transport equation for attached and free solid particles. Special care was taken to model the settling velocity of the free solids and the modification of the liquid viscosity due to the presence of these particles. Bubble polydispersity was modelled using the population balance equation (PBE), which was solved using the direct quadrature method of moments (DQMOM). Appropriate functions for bubble coalescence and breakage were chosen in the PBE. Mesh adaptivity was applied to the current problem to produce fully-unstructured anisotropic meshes, which improved the solution efficiency, while all simulations were executed on a multicore architecture. The model was validated for 2D simulations of a bubble column against experimental results available in the literature. After successful validation, the model was applied to the simulation of the pulp phase in a flotation column for monodisperse and polydisperse solids. Polydispersity of the solids was modelled for the first time in this work using three separate solid size classes. A clear dependence of the flotation rate on the particle size was noticed and the monodisperse solids simulations were shown to over-predict the flotation rate. Other than flotation, this open-source framework can be used for the simulation of a variety of polydisperse multiphase flow problems in the process industry.

Microstructural study of phase separation in (GeS3)100-xAgx and (GeS2)100-xAgx chalcogenide glasses

Microstructure of (GeS3)100-xAgx (x = 0, 5, 10, 15, 20, 25) and (GeS2)100-xAgx (x = 0, 5, 10, 15, 20) has been studied by scanning electron microscopy. It is found that the glasses of both systems are phase separated: (GeS3)100-xAgx for 5 ≤ x ≤ 20 at.% and (GeS2)100-xAgx for 10 ≤ x ≤ 15 at.%. Morphology of coexisting phases is essentially dependent on the glass composition. The phase-separation is very pronounced in (GeS3)100-xAgx glasses and is diminished in (GeS2)100-xAgx as indicated by the size and spatial distribution of majority and minority phases.

A population balance model for large eddy simulation of polydisperse droplet evolution

In the context of many applications of turbulent multi-phase flows, knowledge of the dispersed phase size distribution and its evolution is critical to predicting important macroscopic features. We develop a large eddy simulation (LES) model that can predict the turbulent transport and evolution of size distributions, for a specific subset of applications in which the dispersed phase can be assumed to consist of spherical droplets, and occurring at low volume fraction. We use a population dynamics model for polydisperse droplet distributions specifically adapted to a LES framework including a model for droplet breakup due to turbulence, neglecting coalescence consistent with the assumed small dispersed phase volume fractions. We model the number density fields using an Eulerian approach for each bin of the discretized droplet size distribution. Following earlier methods used in the Reynolds-averaged Navier–Stokes framework, the droplet breakup due to turbulent fluctuations is modelled by treating droplet–eddy collisions as in kinetic theory of gases. Existing models assume the scale of droplet–eddy collision to be in the inertial range of turbulence. In order to also model smaller droplets comparable to or smaller than the Kolmogorov scale we extend the breakup kernels using a structure function model that smoothly transitions from the inertial to the viscous range. The model includes a dimensionless coefficient that is fitted by comparing predictions in a one-dimensional version of the model with a laboratory experiment of oil droplet breakup below breaking waves. After initial comparisons of the one-dimensional model to measurements of oil droplets in an axisymmetric jet, it is then applied in a three-dimensional LES of a jet in cross-flow with large oil droplets of a single size being released at the source of the jet. We model the concentration fields using $N_{d}=15$ bins of discrete droplet sizes and solve scalar transport equations for each bin. The resulting droplet size distributions are compared with published experimental data, and good agreement for the relative size distribution is obtained. The LES results also enable us to quantify size distribution variability. We find that the probability distribution functions of key quantities such as the total surface area and the Sauter mean diameter of oil droplets are highly variable, some displaying strong non-Gaussian intermittent behaviour.

Preparation of Various Platinum Rare Earth Metal Alloy Nanoparticles and Their ORR Performance

Polymer electrolyte hydrogen fuel cells and their application can contribute to a sustainable future energy landscape. A significant contribution to their costs originates from the platinum-based catalyst. To this date platinum cobalt alloy nanoparticles are the industry standard catalysts to facilitate the sluggish Oxygen reduction reaction (ORR). It has been demonstrated that platinum rare earth metal alloy nanoparticles have high ORR activities which is retained during accelerated stress tests (AST) [1]. The very negative reduction potential of the rare earth metals (-2.0 V to -2.5 V) pose great challenges on the synthesis of its respective platinum alloys with the right properties such as alloy phase and particle size distribution [2]. Last year we showed the successful synthesis of small Pt3Y alloy nanoparticles using potassium vapor as the reducing agent at mild temperatures around 400 °C. Herein we demonstrate the synthesis of platinum alloy nanoparticles of gadolinium, cerium and lanthanum using the same method. Furthermore, we investigated the phase stability of different alloys towards acid leaching and the ORR performance before and after AST. The Pt3Y alloy phase appears to be stable against acid leaching, in contrast to Pt2Y and all of the synthesized alloy phases of Gd, Ce and La. However, a lattice strain (shown by XRD) and traces of the respective rare earth element in the catalyst surface (shown by XPS) in combination with promising ORR results justify further investigation into these catalysts. [1] Hernandez-Fernandez, P., Masini, F., McCarthy, D. N., Strebel, C. E., Friebel, D., Deiana, D., ... Chorkendorff, I. (2014). Mass-selected nanoparticles of PtxY as model catalysts for oxygen electroreduction. Nature Chemistry, 6(8), 732–738. https://doi.org/10.1038/nchem.2001[2] Knudsen, B. P. (2016). Synthesis of Platinum Rare Earth Alloy Catalysts for Fuel Cells.

Microstructure and mechanical properties of a SiC containing advanced structural ceramics

The fracture toughness of SiC-AlN structural ceramics can be improved by obtaining fine grain size distribution of both SiC and AlN phases and a weak SiC-AlN interfacial solid solution layer which helps in crack deflection. In order to achieve this, a SiC containing ceramics i.e. 55wt.%SiC+45wt.%AlN is prepared by spark plasma sintering (1850 °C/50 MPa/5 min.). High density (96.6%) with a very fine grain microstructure comprising of intimate mixture of both the SiC and AlN phases are obtained in the product. Vol% & wt% of SiC & AlN phases estimated through the EDS mapping and Rietveld analysis are found to be 54 vol% & 46 vol%, and 54.2 wt% & 45.8 wt% respectively. Formation of solid solution layer between hexagonal AlN (a = 3.1114 Å, c = 4.9792 Å) and hexagonal SiC (a = 3.081 Å, c = 5.031 Å) phase is confirmed indirectly by change in AlN lattice parameter and directly by EDS mapping. Electron probe micro analysis (EPMA) study reveals that, the solid solution between AlN and SiC phase is formed by mainly diffusion of SiC in AlN phase. Young modulus and hardness of the SPS product are similar to those reported in the literature. The product shows higher indentation fracture toughness (6.7 ± 0.9 MPa.m0.5 and 4.8 ± 0.6 MPa.m0.5 obtained using Median and Palmqvist crack model respectively) than the fracture toughness of a well known ultra-high temperature structural material i.e. ZrB2–20SiC (3.9 ± 1.1 MPa.m1/2). The indentation cracks are found to initiate at the AlN-SiC interface (Hv1263–1641) and are found to propagate along either the AlN phase (Hv1434–1720) or AlN-SiC interface. The cracks are found to stop when these encounter either SiC phase (Hv1896–2476) or porosity. The higher value of fracture toughness may be attributed to the mismatch in coefficient of thermal expansion (CTE) of SiC and AlN phase, fine grain size distribution, secondary crack generation and a weak AlN-SiC interfacial solid solution layer which helps in crack deflection. This product may find potential application as high temperature structural material since SiC containing materials exhibits outstanding high temperature oxidation and corrosion resistance.

Effect of Heat Treatments on the Mechanical and Electrochemical Corrosion Behavior of 38CrSi and AISI 4140 Steels

The aim of this investigation was to compare the microstructural, mechanical and electrochemical corrosion characteristics of 38CrSi steel with widely used AISI 4140 steel under various heat treatment processes to widen its field of applications. Experimental steels 38CrSi and AISI 4140 were subjected to austenitizing at 900 °C for 30 min followed by annealing, quenching in oil and quenching followed by tempering at 400 °C for 120 min. Microstructure of 38CrSi and AISI 4140 steels was characterized by light optical and scanning electron microscopy. Tensile, Charpy impact toughness and Rockwell hardness testing techniques were used to evaluate the mechanical properties. Electrochemical corrosion behavior was evaluated by a Tafel scan in tape water. Results show that microstructure of both steels comprised of ferrite and pearlite after annealing, packets and blocks of lath martensite with retained austenite after quenching and tempered lath martensite with retained austenite after quenching, and tempering with varying grain size distribution and volume fractions of different phases. Hardness and tensile properties of both steels varied in quite identical manner, while impact toughness of both steels varied in inverse manner. 38CrSi steel was found to be brittle, while AISI 4140 steel exhibited excellent properties under all heat treatment processes. In 38CrSi, the corrosion rate decreases as compared to the as-received sample from 0.515 to 0.486 mpy in quenching and tempering heat treatment, while in AISI 4140 steel the corrosion rate decreases during quenching from 0.620 to 0.472 mpy.

THEORETICAL-EXPERIMENTAL POSSIBILLITIES OF MICROSTRUCTURE QUANTIFICATION OF DISPERSION STRENGTHENED MATERIALS

<p>The present paper is devoted to the possibilities to classify the spatial arrangement of the elements (features) of a stochastic process with geometrical objects. The fundamental quantities describing point processes were introduced. Experimental possibilities of structural objects determination, possibilities of evaluation of the size distribution of the secondary phases, testing of planar point structures (estimation of the process intensity, square method and characteristics of the second order) were estimated. Interparticle distances, namely mean interparticle distance, mean minimum distance, mean visibility and mean path of spherical contact were defined. Selected processes were described and demonstrated from simulated realizations on Al-Al<sub>4</sub>C<sub>3 </sub> dispersion strengthened material, prepared by a powder metallurgy method of reaction milling. Interparticle distances of Al<sub>4</sub>C<sub>3</sub> particles were evaluated. Polygonal methods and quadrant counts method were used for characterization of the particle arrangement.</p>

Influence of pH and Fe doping on structural and physical properties of Mg0.95Mn0.05-xFexO (x = 0, 0.04) nanoparticles

We investigate the effects of pH and Fe doping on the size, structural and physical properties of Mg0.95Mn0.05-xFexO (x = 0, 0.04) nanoparticles. All the nanoparticles were synthesized by the sol-gel autocombustion method by varying the pH of the solution. Furthermore, the phase purity, size, and size distribution of the nanoparticles were studied by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Irrespective of the pH, Rietveld refinement analysis of the XRD data reveals single crystallographic cubic phases with MgO-type wurtzite structure (space group Fm3¯m) along with a lattice parameter of 4.2121(8) Å for x = 0.0 and 4.2083(5) Å for x = 0.04. This change in lattice parameter with Fe doping is due to the smaller size of Fe2+ (78 p.m.) compared with Mn2+ (83 p.m.). The size of the nanoparticles increases monotonically from approximately 10 nm to approximately 16 nm for x = 0.0 and from approximately 18 nm to approximately 23 nm for x = 0.04 with increasing pH. SEM micrographs of the powders show highly agglomerated nanoparticles with porous and irregular morphology. The TEM findings support the XRD results, showing that the nanoparticles increase in size with increase in pH. Because Raman modes should be absent in bulk MgO and present in MgO nanoparticles, the strong intensity of the three Raman modes at approximately 380 cm−1, 470 cm−1, and 608 cm−1 further supports the formation of small nanoparticles of Mg0.95Mn0.05-xFexO (x = 0, 0.04). The decrease in peak intensity with increase in pH suggests an increase in the size of the nanoparticles. The peak at 470 cm−1 corresponds to a transverse optical phonon, while the peak at 380 cm−1 corresponds to a transverse acoustic phonon.

Synthesis Temperature Influence on the AlMgB14 Phase Composition

The influence of the synthesis temperature on the phase composition, size distribution, and morphology of AlMgB14 particles, obtained by direct interaction of powders of elementary Al, Mg, and B with the addition of free carbon in vacuum 10 – 2 Pa at 1200 – 1400°C, was studied. The synthesized powders were analyzed by means of x-ray diffraction, SEM, EDX, and laser diffraction. The highest mass content of the main phase AlMgB14 (94%) was obtained at synthesis temperature 1200 – 1300°C with 1 h soaking. Impurity MgAl2O4 as well as magnesium-depleted spinel and AlB12 were recorded at soaking temperature above 1300°C.

Microstructural Analysis of Powder Metallurgy Tool Steels in the Context of Abrasive Wear Behavior: A New Computerized Approach to Stereology

The present work describes a new methodology designed to characterize the microstructures of tool steels containing carbide hard phases, with the focus set on their abrasive wear resistance. A series of algorithms were designed and implemented in MATLAB® to (i) recognize each of the features of interest, (ii) measure relevant quantities and (iii) characterize each of the phases and the alloy in function of attributes usually neglected in wear description applications: size distribution, shape and contiguity of the hard phases. The new framework incorporates new parameters to describe each one of these attributes, as observed in SEM micrographs. All three aforementioned stages contain novel contributions that can be potentially beneficial to the field of materials design in general and to the field of alloy design for severely abrasive environments in particular. Models of known geometry and micrographs of different powder metallurgy steels were analyzed, and the obtained results were compared with the obtained by the linear intercept method. The relation between the new parameters and the ones available in the scientific literature is also discussed.

Synthesis and characterization of magnetic nanoparticles from raffinate of industrial copper solvent extraction plants

Abstract Magnetite nanoparticles successfully produced from the raffinate of an Iranian industrial copper solvent extraction unit. Removal of iron from leach solution is important for successful operation of hydrometallurgical recovery of copper. It includes reduction of Fe3+ to Fe2+ followed by precipitation of Al3+ as Al(OH)3, oxidation of Fe2+ to Fe3+ (the theoretical ratio for stoichiometric, Fe3+/Fe2+ = 2) and finally synthesize of nano-sized magnetite. Two different Fe2+ oxidation agents namely H2O2 and O2 were used. Using XRD, FTIR, FESEM, and TEM analysis, the phase structure, morphology, and size distribution of magnetic nanoparticles, produced under different conditions, were evaluated and compared. Under optimum conditions spherical magnetic nanoparticles with an average size of about 25 ± 3 nm can be produced. The XRD analysis of produced nanoparticles after purification of raffinate showed the slight formation of aluminum hydroxide, goethite and hematite phases. In addition, the VSM results indicate the highly ferromagnetic behavior for samples at the room temperature with a saturation magnetization of 41.25 emu/g.

Phase behavior and hot storage characteristics of asphalt modified with various polyethylene: Experimental and numerical characterizations

Phase behavior is crucial to multi-phase materials, which intensively affects macro-performance of materials. Polymer modified asphalt is a typical multi-phase material and widely applied in paving industry. This paper presents the fundamental understanding of phase behavior and hot storage characteristics of polyethylene (PE) modified asphalts. The influence of polymer structure on phase behavior was studied by experimental and numerical approaches. Experimentally, four typical PE modified asphalts were selected to prepare thin film slides of asphalt, which were subjected to isothermal annealing and observed under fluorescence microscopy (FM). The morphology evolutions were evaluated by statistical size distribution. Storage stability was further evaluated by tube test. Numerically, microstructure evolutions and storage stability were described by phase field method. The results showed that the scope of PE phase size distribution becomes wider during annealing. Linear low-density PE shows a relative slow separation. Phase-field model perfectly describes the experimental microstructure evolution. Polyethylene structural parameters significantly affect the phase behavior. Lower crystalline, higher melt flow index (MFI) as well as more branched molecule promotes the swelling of PE particle and the interaction of constituents. Moreover, differences in density and viscosity between PE and asphalt greatly accelerate the separation in the vertical direction.

Structural and Luminescence Properties of Li3Y2(BO3)3 Synthesized by Solid-State Reactions

A new binary metal borate compound, trilithium diyttrium orthoborate, Li 3 Y 2 (BO 3 ) 3 was successfully synthesized by a solid-state reaction at 1000°C using the initial reactants of Li 2 CO 3 , Y 2 O 3 , and H 3 BO 3 (mole ratio 1.5:1:3). The phase analysis, crystallinity and size distribution of Li 3 Y 2 (BO 3 ) 3 was investigated by X, ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM). It was found that single phase Li 3 Y 2 (BO 3 ) 3 crystallizes in orthorhombic crystal system with refined unit cell parameters of a=8.9228, b=9.5840(7), c=20.4469Å, Z=9, and represent the space group of Pmmm. Particles size distribution estimated from the SEM images are in the range of 20 to 200 µm. The luminescence properties of Li 3 Y 2 (BO 3 ) 3 were investigated by using steadystate photoluminescence (PL) measurement as a function of temperature. The spectra are dominated by transitions related to defects present in the sample, in the visible region of the spectrum. A relatively low intensity band-to-band transition was also observed at high energy side of the spectrum centered at around 3.33 eV. This peak is decomposed to two close peaks at 3.32 and 3.35 eV using Gauss fitting. From the temperature behavior of peak energies of these emissions, the band gap of Li 3 Y 2 (BO 3 ) 3 is estimated to be 3.35 eV for the first time.