Solid-state Melting Research Articles

Ba4B14O25: A Deep Ultraviolet Transparent Nonlinear Optical Crystal with Strong Second Harmonic Generation Response Achieved by a Boron-Rich Closed-Loop Strategy.

Discovering new deep ultraviolet (DUV) nonlinear optical (NLO) materials is the current research hotspot. However, how to perfectly integrate several stringent performances into a crystal is a great challenge because of the natural incompatibility among them, particularly wide band gap and large NLO coefficient. To tackle the challenge, a boron-rich closed-loop strategy is supposed, based on which a new barium borate, Ba4B14O25, is designed and synthesized successfully via the high-temperature solid-state melting method. It features a highly polymeric 3D geometry with the closed-loop anionic framework [B14O25]8- constructed by the fundamental building blocks [B14O33]24-. The high-density π-conjugated [BO3]3- groups and the fully closed-loop B-O-B connections make Ba4B14O25 possess excellent NLO properties, including short UV cutoff edge (<200nm), large second harmonic generation response (3.0 × KDP) and phase-matching capability, being a promising DUV-transparent NLO candidate material. The work provides a creative design strategy for the exploration of DUV NLO crystals.

Thermoluminescence studies of NaMgF3:Tb for gamma dosimetry applications

NaMgF3 is a recognized sensitive thermoluminescence (TL) dosimeter but it shows fading at room temperature which limits its use as a radiation dosimeter. It is important to improve this parameter of NaMgF3 for its potential application in the field of radiation dosimetry. Thus, the current work focuses on enhancing the dosimetric properties of NaMgF3 exclusively the TL fading characteristics. In the present study, Tb doped NaMgF3 has been synthesized by two different methods i.e. solid state reaction method (SSR) and melting method (MT). A comparative and detailed TL studies have been carried out after irradiation with gamma rays which has not been reported so far. Detailed analysis of TL and Photoluminescence (PL) properties reveal that NaMgF3:Tb prepared via MT shows good luminescence properties in comparison to SSR and previously reported results. Thus, Tb doped NaMgF3 synthesized by melting method can be a potential dosimeter for the detection of gamma rays.

Electrochemical Control for Corrosion in Molten Chloride Salts

Concentrated solar power (CSP) with thermal energy storage (TES) has the ability to help solve the renewable energy grid integration challenge with its electricity dispatch capability. However, utility-scale adaption of CSP-TES has been slow due to the high levelized cost of electricity (LCOE). One avenue for cost reduction is the increase in operating temperature of the CSP plant to increase the thermal efficiency of the Carnot cycle. This requires finding a new salt blend with higher thermal stability up to 800 ℃. A ternary MgNaK chloride salt is a prime candidate with its low cost, high thermal stability, and good heat transfer properties. However, its commercial deployment is challenged by the high corrosion rates, leading to the use of expensive alloys; thus, increasing the capital cost and maintenance cost of the CSP plant.A corrosion control system in MgNaK chloride salts using active metals such as Mg has been demonstrated under laboratory conditions. This mitigation strategy involves controlling the corrosive impurities, such as MgOHCl, by using liquid Mg. The elemental Mg scavenges oxygen and water derived impurities and provides redox reaction control by shifting the electrochemical potential of the alloys towards cathodic protection while Mg acts as the sacrificial oxidant. However, employment of Mg is challenged in the cold temperature section of the CSP plant (400 – 550 ℃) due to its slow dissolution kinetics in the solid state (melting point of 650 ℃).Here, we propose an electrochemical approach using bulk Mg anodes and W cathodes to provide corrosion control. We used electrolysis to enhance dissolution kinetics of solid Mg to the molten salt at temperatures relevant to the cold section of the CSP plant (500 ℃). Our data suggests electrolysis of Mg effectively enhances the rates of removal of corrosive impurities from molten chloride salts. Preliminary results indicate significant opportunity for the electrochemical process to be scaled up commercially. The novel approach eliminates impurities in-situ from oxygen and moisture ingress in the CSP plant, in turn reducing corrosion rates and therefore reducing capital and maintenance cost of the CSP plant.

CuPbBi5S9 thermoelectric material with an intrinsic low thermal conductivity: Synthesis and properties

CuPbBi5S9 compounds have been investigated as gladite for years. However, there have been no significant studies on their physical and chemical properties. This work demonstrates that upon alloying with moderate Cu, Pb, Bi, and S using an appropriate preparation method, quaternary CuPbBi5S9 compounds can exhibit excellent figure of merit ZT within the temperature range 298–723 K. A low average velocity, low Young’s modulus and Debye temperature, and large Grüneisen parameter, determined experimentally, indicate strong lattice anharmonicity in CuPbBi5S9 crystals. Furthermore, density functional theory calculations (local vibration of low-frequency acoustic phonons) justify the low lattice thermal conductivity of CuPbBi5S9 compounds. Because of the low thermal conductivity (0.514 W m−1K−1) and a relatively high power factor (293 μW m−1K−2), a maximum ZT of 0.42 was achieved at 723 K for CuPbBi5S9 prepared by mechanical alloying combined with solid-state melting. Thus, CuPbBi5S9 materials are promising candidates for use as high-performance thermoelectric materials in the intermediate-temperature range.

Production of hydrogen and multi-walled carbon nanotubes by ethanol decomposition over Fe/CeO2 catalysts

ABSTRACT Fe/CeO2 catalysts with different ferrum loading were prepared by solid state melting method. Ethanol decomposition on those catalysts at different temperature (600, 700, and 800°C) has been studied. To evaluate the catalytic performance in ethanol decomposition, gaseous and solid products produced from ethanol decomposition were collected and analyzed; H2 and multi-walled carbon nanotubes (MWCNTs) were obtained. In these experiments, ethanol decomposition on Fe (30 wt%)/CeO2 at 600°C showed the maximum H2 yield (the maximum H2 yield was 94%, which was higher than that of previous reports). In addition, other gaseous products include CH4 and CO were observed, but CO2 was not be detected. The content of H2, CO, and CH4 were 60 ~ 80%, 20 ~ 25%, and 0 ~ 10%, respectively. MWCNTs have formed in ethanol decomposition process, the quality and purity of MWCNTs increase with increasing temperature, and the material with the carbon-encapsulated metal structure was obtained.

Paramagnetic surface defects in LiMgPO4

The samples of LiMgPO4 were synthesized by the solid state reaction and melting methods. The EPR spectra obtained at 300 K and 115 K are indicative of the existence of charged defects in LiMgPO4. The main imperfections are identified as a radical CO−3 (g = 2) and a singly charged oxygen vacancy (g1 = 2.45, g2 = 2.20, g3 = 2.00). The presence of carbon-containing groups is proved by Raman spectroscopy. The assumption is made that the defects are located mainly on the surface of the grains. Thermoluminescent characteristics of LiMgPO4 annealed in atmospheres with different pO2 demonstrate that the surface defects impair the efficiency of LiMgPO4 as a dosimetric material.

Interactions at the planar Ag3Sn/liquid Sn interface under ultrasonic irradiation

The interactions at the interface between planar Ag3Sn and liquid Sn under ultrasonic irradiation were investigated. An intensive thermal grooving process occurred at Ag3Sn grain boundaries due to ultrasonic effects. Without ultrasonic application, planar shape of Ag3Sn layer gradually evolved into scalloped morphology after the solid-state Sn melting, due to a preferential dissolution of the intermetallic compounds from the regions at grain boundaries, which left behind the grooves embedding in the Ag3Sn layer. Under the effect of ultrasonic, stable grooves could be rapidly generated within an extremely short time (<10s) that was far less than the traditional soldering process (>10min). In addition, the deepened grooves leaded to the formation of necks at the roots of Ag3Sn grains, and further resulted in the strong detachment of intermetallic grains from the substrate. The intensive thermal grooving could promote the growth of Ag3Sn grains in the vertical direction but restrain their coarsening in the horizontal direction, consequently, an elongated morphology was presented. All these phenomena could be attributed to the acoustic cavitation and streaming effects of ultrasonic vibration.

Phenomena of Intergranular Liquid Film Formation in Technology

The phenomena of the first order phase transition (two-dimensional melting) of grain boundary at temperatures 0.6 - 0.9 TS0 (of the solid state melting point), discovered by the author (1971), is a fundamental property of solid crystalline materials. This finding leads to a principal revision of the scientific concepts of the solid state of substance. The phenomenological description and justification of the finding are developed. The generalized equation of Clausius-Clapeyron type for two-dimensional phase transition was obtained by applying the mathematical tools of the film thermodynamics. The equation has been used for calculating the grain boundary phase transition(GBPhT) temperature TSf of any metal, which TSf value lies within the range of (0.55 - 0.86) TS0. The investigation outcomes are applied to develop the methodology for more effective hard coating formation by synthesis of nanosize nitrides and carbonitrides in surface layers of steels and nickel alloys using a thermo-chemical processing (TChP). Production of an overall nitrogen concentration gradient from 4% to 0.5% at within surface layers leads to formation of modified coatings with a stepped change in properties. The mechanical behavior of new tools at the industrial tests indicated a higher heat resistance (nickel alloys), high resistance to surface wears and fragile breaks-down (chromium tool steels). A short overview of the results of some graded alloys characterization is presented.

Cu6Te3S – a Cu-filled Cr3Si-structure variant

Abstract A solid state melting and annealing route was used to prepare Cu6Te3S, a copper telluride sulfide representing a filled variant of the Cr3Si structure type. The title compound exhibits a reversible phase transition at 404 K which was confirmed by thermal analysis, temperature dependent X-ray single crystal and powder diffractometry. Both polymorphs crystalize cubic in space groups P 4 ¯ 3 n $P\bar 43n$ and P213, respectively. X-ray photoelectron spectroscopy (XPS) was performed to evaluate the electronic structure of Cu6Te3S and to determine the oxidation state of Cu in the title compound.

Reply to comments on the inter-planar structures and lamellar packing of short and long chain zinc (II) n-alkanoates

The room temperature structure of zinc carboxylates from the butanoate to eicosanoate, adduced from single crystal and powder diffraction, solid state 13C NMR and FT-Infrared spectroscopies, density measurements and molecular calculations show carboxyl moieties coordinated to tetrahedral zinc (II) atoms via bridging bidentate bonding. The hydrocarbon chains exist in the fully extended all-trans conformation and are tilted at ca. 60° with respect to the metal planes. Moreover, the compounds crystallize in a monoclinic crystal system where the a axis is the principal axis, irrespective of chain length. Furthermore, whilst the short chain homologues (nc<9) are packed within a lamellar as a bilayer, for the long chain length adducts the hydrocarbon chains are arranged as “overlapping” lamellar bilayers, which are not in the same plane. Odd–even alternation in the infrared, solid state 13C NMR, density and melting point data is due to greater intra-lamellar inter-planar van der Waals interactions as a result of different packing intimacies between odd and even chain compounds. However, for short chain compounds, nc<9, the hydrocarbon chain do not overlap; hence, odd–even alternation is not observed for these compounds.

Effect of Sintering Temperature on Structural and Morphological Properties of Europium (III) Oxide Doped Willemite

Willemite- (Zn2SiO4-) based glass ceramics doped with various amounts of europium oxide (Eu2O3) were prepared by solid state melting and quenching method. Effect of sintering temperature (600–1000°C) on structural and morphological properties of the doped samples was investigated. Phase composition, phase evolution, functional groups, and microstructure analysis were, respectively, characterized using X-ray diffractometer (XRD), fourier transform infrared spectroscopy, field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray. XRD analysis detected the presence of rhombohedral crystalline phase in the doped samples sintered at different temperatures. FE-SEM and bulk density results confirmed that doping of the willemite with Eu2O3effectively enhanced densification. The microstructural analysis of the doped samples showed that the average grain size increased with the increase of sintering temperature.

Laser modification of the materials surface layer – a review paper

Abstract The state of laser processing in surface materials modification in Poland is reported, based on own experience, coworkers and coauthors results, as well the literature review. The curriculum concerning historical development of lasers and laser technology in Poland, laser-matter interaction, as well basis of different laser techniques applied in materials surface engineering (solid state hardening, melting, alloying, cladding, ablation, shot peening, cleaning and texturing) are reviewed, and compared with results of coauthors, as well with a wide range of Polish authors papers. Finally, it is concluded that overall state of research on laser application in surface engineering in Poland is well developed and still growing industrial application is observed.

Tm&lt;sup&gt;3+&lt;/sup&gt;/Yb&lt;sup&gt;3+&lt;/sup&gt; Codoped YAG Glass-Ceramic Formed in Silicate Glass System

Based on the analysis of glass formation region of Y2O3-Al2O3-SiO2 glass system, the glass composition 5Li2O-18Y2O3-29Al2O3-48SiO2 (LYAS) in mol% central in the glass formation region of Y-Al-Si glass system was chosen for present work. The Tm3+ and Yb3+ were introduced as activators in LYAS glass. The glass samples were prepared by the high-temperature solid-state melting and then the derived YAG glass-ceramic was obtained by heat-treating the precursor glass. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis results indicate that the lattice constant of the obtained glass-ceramic is consistent with the pure YAG phase. The primary crystallite size is calculated to be 46nm and the crystal grains grow with excellent orientation (444) in the internal network. The secondary particle size is estimated to be ~8μm and the large grain size is owing to the particles aggregation. The crystal grains distributed uniformly in the glass matrix, and consistent well with the XRD analysis results.

Tm&lt;sup&gt;3+&lt;/sup&gt;/Yb&lt;sup&gt;3+&lt;/sup&gt; Codoped YAG Glass-Ceramic Formed in Silicate Glass System

Based on the analysis of glass formation region of Y2O3-Al2O3-SiO2 glass system, the glass composition 5Li2O-18Y2O3-29Al2O3-48SiO2 (LYAS) in mol% central in the glass formation region of Y-Al-Si glass system was chosen for present work. The Tm3+ and Yb3+ were introduced as activators in LYAS glass. The glass samples were prepared by the high-temperature solid-state melting and then the derived YAG glass-ceramic was obtained by heat-treating the precursor glass. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis results indicate that the lattice constant of the obtained glass-ceramic is consistent with the pure YAG phase. The primary crystallite size is calculated to be 46nm and the crystal grains grow with excellent orientation (444) in the internal network. The secondary particle size is estimated to be ~8μm and the large grain size is owing to the particles aggregation. The crystal grains distributed uniformly in the glass matrix, and consistent well with the XRD analysis results.

Thermodynamic properties of potassium nitrate–magnesium nitrate compound [2KNO3·Mg(NO3)2

The Mg(NO3)2–KNO3 binary system phase diagram has a congruent melting compound, 2KNO3·Mg(NO3)2. The thermodynamic properties for this compound are not available in the literature. In this study, the nitrate compound was synthesized and the melting point and heat capacity were determined using differential scanning calorimetry (DSC). Two endothermic peaks were observed at 404.8K and 468.83K corresponding to solid state transition and melting of the compound with the enthalpies of transitions as 2.71kJ/mol and 20.73kJ/mol, respectively. The heat capacity data as function of temperature are fit to polynomial function and thermodynamic properties like enthalpy, entropy and Gibbs energies of the compound as function of temperature are subsequently deduced.

Synthesis of amorphous MgO-rich peridotitic starting material for laser-heated diamond anvil cell experiments – application to iron partitioning in the mantle

We report the preparation of the starting material reflecting the complex composition of the Earth's mantle. With this aim, we synthesized two types of material: sol–gel and glass obtained by aerodynamic levitation. Thanks to their high homogeneity and reactivity, these materials are suitable for experimental petrology under extreme conditions, conducted in laser-heated diamond anvil cell. We then used this mantle analog to investigate the iron partitioning between high pressure phases under lower mantle conditions during solid-state reaction and partial melting of the material. Iron preferentially partitions into the (Mg,Fe)O, but the presence of aluminum slightly enriches iron in the silicate phase (Kpv−fp=0.41±0.04) compared to similar experiments in an Al-free system.

Structural investigations on the fertilizer component K2Ca2Si2O7

Polycrystalline material as well as single crystals of the fertilizer component K 2 Ca 2 Si 2 O 7 have been prepared by solid state reactions and melting experiments, respectively. The compound is hexagonal (space group P 6 3 / m , a = 9.8020(5) A, c = 13.8781(5) A, V = 1154.76(9) A 3 , D calc = 2.815 g/cm 3 , Z = 6). The crystal structure was solved by direct methods using a sample that was subject to twinning by merohedry and subsequently refined to a residual of R (| F |) = 0.044 (551 independent observed reflections ( I >2σ( I )), 59 parameters). K 2 Ca 2 Si 2 O 7 can be classified as a sorosilicate based on disordered [Si 2 O 7 ]-moieties. The dimers are arranged in 5.2 A wide layers perpendicular to [001] centered at about z ≈ ¼ and z ≈ ¾. Charge compensation within the structure is accomplished by K + - and Ca 2+ -cations distributed among a total of six independent sites within the asymmetric unit. Basically, two types of coordination environments of the non-tetrahedral cations can be distinguished: M (2) and M (4) are surrounded by six nearest oxygen neighbours in form of distorted octahedra. The coordination spheres around M (1), M (3) and M (5) can be approximately described as trigonal prisms. In case of M (5) the prism is capped by three additional oxygen atoms. By sharing common faces the octahedra and the prisms are linked into one-dimensional columns running parallel to [001]. The relative alignment of these non-intersecting columns corresponds to a hexagonal rod packing with parallel rods. The [Si 2 O 7 ]-dimers provide linkage between the columns, thus the whole structure can be considered as a mixed polyhedral framework where the two fundamental building units are connected via common corners. The remaining irregularly coordinated M (6)-atoms in turn are situated in cavities of the network. The structural relationship of the present compound with a family of rare-earth silicates with general composition A 3 BSi 2 O 7 is discussed.

Microstructure and thermal properties of quasi-equal rare earth substitution Y0.5Gd0.5Ba2Cu3O6.94 superconductor

Abstract Sintering effects in YBa2Cu3Oz samples with quasi-equal rare earth substitution have been investigated. It has been shown that the Y-123 type compound can be formed when gadolinium is partially substituted (in this case 50% atomic substitution) for yttrium. The superconducting compound was obtained by the optimized ceramic method, including solid-state reaction, melting and sintering, controlled by X-ray diffraction. The microstructure was investigated by SEM and energy dispersive X-ray analyses. An AC susceptibility measurement has shown that T c =93 K. Temperature-dependece of the thermal conductivity (4.5–300 K) of the polycrystalline Y0.5Gd0.5Ba2Cu3O6.94 sample was also measured.

Structure Chemical Aspects of Silver(I) Chalcogenide Halides and Preparation of the x = 1 Member of the Solid Solution Ag5Te2Cl1–xBrx

The maximum grade of substitution to be reached in solid solutions Ag5Te2Cl1−xBrx by solid state melting reactions starting from the elements, is x = 0.65. Using solvothermal synthesis in aqueous ammonia solution, the area of stability can be extended to pure bromide (x = 1). X-Ray diffraction experiments have substantiated the isostructural features of Ag5Te2Br compared with the chlorine analog. At r. t. Ag5Te2Br crystallizes monoclinically, in the β -Ag5Te2Cl structure type, with lattice parameters of a = 14.000(5), b = 7.702(3), c = 13.856(6) Å , β = 90.61(4)°, space group P21/n. A topological approach, first introduced for the characterization of complex structures of silver(I) (poly)chalcogenide halides, has been transferred to the Ag5Q2X system. Based on this formalism the anion substructures can be described by simple nets or strands created by the connection of positions at distances close to or even larger than the sum of the van der Waals radii. In case of the present system, only honeycomb-like telluride nets and halide strands are necessary to explain the complex anion substructure. A deeper understanding of the physical properties, like the anisotropic silver mobility, can be achieved by this topological approach which was not possible with other structure description models.

Heat Capacities of Tetracene and Pentacene

New solid state heat capacity data for tetracene and pentacene are reported in the temperature range (258 to 600) K. The heat capacity measurements were performed using the step method with a Setaram Micro DSC III calorimeter (Institute of Chemical Technology, Prague) and a Setaram TG-DSC 111 (University of Alberta) calorimeter. These new heat capacity data are shown to be in good agreement with one another and with several solid state constant-pressure heat capacity estimation methods and quantum mechanical calculations. The new results highlight errors in the solid state heat capacity and melting point databases for polynuclear aromatic hydrocarbons.