Alumina Crucible Research Articles

The reaction of Li6.5La3Zr1.5Ta0.5O12 with water

The Li-ion conductor “Li6.5La3Zr1.5Ta0.5O12” (LLZT) with garnet structure is prepared by solid-state reaction in an alumina crucible; its stability in water is investigated at room temperature. A Li+/H+ exchange is characterized by TGA, 7Li and 27Al MAS NMR, neutron diffraction, and TEM. In water, Li+/H+ exchange leads to a new garnet oxide “Li6.5−xHxLa3Zr1.5Ta0.5O12” (H-LLZT) with space group Ia–3d; the lattice parameter of H-LLZT is increased by the exchanged protons. Both LLZT and a grain boundary phase LiAlO2 are unstable in water. The exchanged protons in H-LLZT displace Li from the octahedral sites bridging the 24d tetrahedral sites; they form a strong OH bond that distorted the site. The amorphous phase LiAlO2 in the grain boundary dissolves on exposure to water, which inhibits Li-ion transport across the grain boundary.

ChemInform Abstract: Single Crystal Growth and Structural Characterization of Ternary Transition‐metal Uranium Oxides: MnUO4, FeUO4, and NiU2O6.

AbstractSingle crystals of MnUO4 (I) are prepared from U3O8 and MnCl2 in a molten CsCl flux (alumina crucible, 900 °C, 12 h).

ChemInform Abstract: Molten Salt Synthesis of Tin Doped Hematite Nanodiscs and Their Enhanced Electrochemical Performance for Li‐Ion Batteries.

AbstractSn4+ doped Fe2O3 nanodiscs (5% Sn) are synthesized by the mixed molten salt method from mixtures of Fe(NO3)3, SnCl4, NaCl, and KCl (alumina crucible, 550 °C, 8 h).

ChemInform Abstract: Structural Transition at 360 K in the CaFe5O7 Ferrite: Toward a New Charge Ordering Distribution.

AbstractThe title ceramic is prepared by solid state reaction of CaO, Fe2O3, and Fe in a ratio of 1:2:1 (alumina crucible, 1100 °C for 24 h and 900 °C for 48 h).

ChemInform Abstract: Synthesis, Single Crystal Growth and Properties of Sr5Pb3ZnO12.

AbstractPolycrystalline Sr5Pb3ZnO12 is prepared by firing a stoichiometric mixture of SrCO3, Pb3O4, and ZnO in air (alumina crucible, 800 °C, 36 h).The compound crystallizes similar to the known compounds Sr5Pb3MO12 (M: Co, Ni, Cu) in the space group P$\bar 6$2m (powder XRD).

ChemInform Abstract: Pr1.33Pt4Ga10: Superstructure and Magnetism.

AbstractPr1.33Pt4Ga10 single crystals are prepared from the elements using excess Ga as flux (alumina crucible in evacuated silica ampoule, 1150 °C, 4 h, 2; ≈10% yield).

ChemInform Abstract: Synthesis and Crystal Chemistry of Microporous Titanates Kx(Ti,M)8O16 Where M: Sc—Ni.

AbstractSingle crystals of potassium titanate hollandites K1.5Sc1.5Ti6.5O16, K1.4Ti8O16, K1.5V1.5Ti6.5O16, K1.5Cr1.5Ti6.5O16, K1.6Ni0.8Ti7.2O16, K1.4Mn1.4Ti6.6O16, K1.5Fe1.5Ti6.5O16, K1.5Co0.75Ti7.25O16, and K1.6Ni0.8Ti7.2O16 are prepared by a flux method from transition metal oxides and KCl in a molar ratio of 1:10 (alumina crucibles, 1473—1573 K, 12 h).

ChemInform Abstract: New Kagome Metal Sc3Mn3Al7Si5 and Its Gallium‐Doped Analogues: Synthesis, Crystal Structure, and Physical Properties.

AbstractSingle crystals of the new title compound are prepared from a Sc/Mn/Al/Si mixture with a molar ratio of 3:3:30:5 using Al as a reactive flux (alumina crucible, 1100 °C, 8 h).

Preparation of lithium ion conductive Al-doped Li7La3Zr2O12 thin films by a sol–gel process

Thin films of garnet-type Al-doped Li7La3Zr2O12 (LLZ) are prepared by the sol–gel process. Thin films are prepared on MgO substrates by a dip-coating process using a precursor sol from Zr-alkoxide and Li, La and Al nitrates. After the dip-coating, the dried films are calcined at 450 °C to get precursor films. When the precursor films are heat-treated at 900 °C in an alumina crucible, La2Zr2O7 is mainly obtained. With coexistence of Li2CO3 powders in the crucible during the heat-treatment at 900 °C, thin film of polycrystalline cubic LLZ is obtained. Addition of an ionic surfactant, lithium dodecylsulfate, improves the quality of the thin films, and the thin film heat-treated at 900 °C with coexistence of Li2CO3 powders in the crucible shows the ionic conductivity of 2.4 × 10−6 S cm−1 at 25 °C.

Temperature-dependent photoluminescence of CuAlO2 single crystals fabricated by using a flux self-removal method

The temperature-dependent behavior of p-type transparent semiconducting oxide CuAlO2 single crystals prepared by using a flux self-removal method in alumina crucibles was investigated through transmittance and photoluminescence (PL) measurements at temperatures from 12 K to room temperature. The low-temperature (12 K) PL spectrum shows two weak, broad emission peaks, one at 3.52 eV and the other at 3.08 eV, which we assign to excitonic emission and to defectrelated emission originating from copper vacancies. The positions of the PL peaks as functions of temperature exhibit a normal behavior satisfying the standard Varshini law, and the Debye temperature is found to be θD = 610 ± 80 K. The exciton-binding energy of the CuAlO2 single crystal is estimated to be 49 meV from the PL intensity change with temperature.

ChemInform Abstract: KNa3Mn7(PO4)6: 2D Spin‐Frustrated Magnetic Material with a Diamond‐Like Chain Structure.

AbstractSingle crystals of the title compound are prepared by solid state reaction of Na2CO3, Mn(OAc)2, NH4H2PO4, and KF (alumina crucible, 1153 K, 40 h).

ChemInform Abstract: Quaternary Arsenides ACdGeAs2 (A: K, Rb) Built of Ethane‐Like Ge2As6 Units.

AbstractKCdGeAs2 (I) and RbCdGeAs2 (II) are prepared by solid state reactions of stoichiometric mixtures of the elements (alumina crucible in evacuated silica tube, 650 °C (I) and 600 °C (II), 10 d).

ChemInform Abstract: The Luminescence Properties of Novel α‐Mg2Al4Si5O18:Eu 2+ Phosphor Prepared in Air.

AbstractBlue emitting α‐Mg2Al4Si5O18:Eu 2+ phosphor is prepared via conventional solid‐state reaction of stoichiometric amounts of MgO, Al2O3, H2SiO3, and Eu2O3 using excess La2O3 as a flux (alumina crucible, air, 1300 °C, 6 h).

ChemInform Abstract: A Single‐Component White‐Emitting CaSr2Al2O6:Ce3+, Li+, Mn2+ Phosphor via Energy Transfer.

AbstractSamples of CaSr2Al2O6:xCe3+,xLi+ (0.01 ≤ x ≤ 0.09) and CaSr2Al2O6:0.03Ce3+,0.03Li +,yMn2+ (0 ≤ y ≤ 0.07) are prepared by solid state reactions of CaCO3, SrCO3, Al2O3, CeO2, and MnCO3 (alumina crucibles, 10%H2/N2, 1400 °C, 6 h).

The use of ceramic sludge and recycled glass to obtain engobes for manufacturing ceramic tiles

The aim of this work was the valorization of two wastes that are classified as Class I according to the Brazilian Standard ABNT NBR 10004:2004 in order to obtain a ceramic engobe for the production of single-fire ceramic tiles. Ceramic sludge from a wastewater treatment plant of a ceramic tile manufacturer and recycled glass were used to obtain a frit in order to make the sludge and glass inert in a vitreous matrix. Thus, a representative amount of the ceramic sludge was collected, dried, and characterized by chemical analysis, X-ray diffractometry, and thermal analyses (differential thermal analysis, thermogravimetric analysis, and dilatometric analysis). Furthermore, the ceramic sludge was assessed according to the ABNT NBR 10004:2004. Seven formulations containing ceramic sludge contents varying from 20 to 80 wt% and recycled glass contents varying from 12 to 48 wt% and using calcite, dolomite, ulexite, and saltpeter as raw materials were prepared. Each formulation was melted in a laboratory kiln using alumina crucibles at 1420 °C for 1 h, and the melts were poured into water at room temperature to produce frits. Each frit was milled, and the coefficient of thermal expansion was determined by dilatometry. The results show that the studied ceramic sludge presented high contents of barium and fluoride. The main identified crystalline phases were α-quartz, zircon, illite, and barium silicate. The coefficient of thermal expansion after heat treatment was 5.6 × 10−6 °C−1. Once characterized, the feasibility of applying these wastes as raw materials for the production of ceramic frits was evaluated. The results of the dilatometric analysis, glaze fluidity flow test, and visual analysis showed that the incorporation of these wastes would allow for the obtainment of ceramic frits for producing ceramic engobes. Thus, three formulations of engobe were prepared and heat-treated at 1150, 1165, and 1175 °C. The engobes were characterized (XRD, determination of brightness, colorimetry, and microstructural analysis by optical microscopy) and showed suitable properties for use in the production of ceramic tiles. Engobe E3, which presented the highest ceramic sludge content, was selected for an industrial test. The results of a visual analysis and water spot test showed that the investigated engobe, compared with a commercial engobe (engobe reference), could be used in the production of glazed ceramic tiles.

Investigation of Degree of Undercooling of Fe-O Alloy on Al2O3 Substrate

An Fe-O drop of ~0.4 g in an alumina crucible was quenched from ~2200 K (~1927 °C) at a cooling rate of −87 K/s by flowing He gas at a flow rate of 25 L/min STP. A deep undercooling of approximately 200 K was obtained regardless the oxygen content in the sample. According to the classical nucleation theory, the contact angle between a solid Fe nuclei and the Al2O3 substrate was estimated to be 53 (±4) deg.

ChemInform Abstract: Flux Growth of Yb6.6Ir6Sn16 Having Mixed‐Valent Ytterbium.

AbstractSingle crystals of the title compound are grown in an indium flux starting with a mixture of Yb, Ir, Sn, and In in the molar ratio of 3:2:6:30 (alumina crucible, 1000 °C for 5 h and 850 °C for 48 h, <95% yield).

Effect of Microstructure and Elemental Composition on Electrode Interfacial Impedance of Li7La3Zr2O12-based Batteries

Introduction Solid state batteries offer increased safety, high voltage stability, and simpler electrolyte chemistry than organic electrolytes. Their inherent protection from dendrite growth gives the capability to use metallic lithium anodes. Recent advances have improved conductivity to within an order of magnitude of organic electrolytes at room temperature. However, interfacial resistance between electrodes and the electrolyte remains a pressing concern. In a typical planar battery, this high resistance per area is magnified by low interfacial surface area.Elemental composition has a significant effect on the conductivity of a garnet electrolyte. The conductivity of the garnet fluctuates an order of magnitude based on a lithium stoichiometry of 6 to 7 in the Li7-xLa3Zr2-xTaxO12series. It has also been demonstrated that aluminium composition at the grain boundaries associated with higher temperature sintering increases conductivity. It stands to reason lithium activity extremes at the electrode interfaces effects would cause local variations in electrolyte composition and affect the conductivity.This study aims to address some of these concerns using a systematic study of the anode-electrolyte interface and the cathode-electrolyte interface. We investigate the elemental composition of the interface, as well as the effect of greatly increased surface area through a highly microporous electrolyte scaffold containing the cathode and anode material. Experimental Procedure Li7La3Zr2O12 garnet was produced in a conventional solid state method. 10% excess LiOH-H2O and stoichiometric amounts of La2O3 and ZrO2were ball milled in ethanol for 24 hours. The milled materials were added to an alumina crucible, calcined at 900 ºC for 4 hours, and milled again.A colloidal deposition of this slurry is prepared with polyvinyl butyral (PVB), benzyl butyl phthalate (BBP), and Solsperse dispersant in ethanol.Calcined powder is added to toluene and ethanol solvents with a binder system containing PVB, BBP, and menhaden fish oil as a dispersant. This preparation is milled for two days, then degassed in preparation for tape-casting.After tape-casting, tapes are drop-coated with the colloidal slurry and another tape is applied on top. This structure is held at 500ºC for 1 hour to burn off binders then heated to 1100 ºC for 1 hour. This produces a three layer porous-dense-porous scaffold of electrolyte that will maintain electronic isolation between electrodes.Symmetric cells with two cathodes are produced by infiltrating a glycine/metal-nitrate solution into the pores of each side and combusting. For two-anode symmetric cells, lithium is lightly pressed into both sides at 350 ºC.Electrochemical impedance spectroscopy was performed between room temperature and 300 ºC using a 10 mV amplitude between 10 MHz and 100 mHz.Electron energy loss spectroscopy was performed on a 2100F TEM equipped with a Gatan Tridiem post-it column energy filter. Results Figure 1 shows a cross section of a lithium-penetrated Li-garnet scaffold showing the fracture plane of the garnet(light) fully coated by the lithium (dark). Figure 2 shows the Nyquist plot of a full cell made with a lithium-penetrated scaffold. The bulk conductivity shown in the inset is fairly low at 20 Ω compared to the 1000 Ω overall cell impedance.

Separation of Dy from Nd-Fe-B Magnet Scraps Using Molten Salt Electrolysis

IntroductionThe demand for Dy-added Nd-Fe-B magnets is rapidly increasing because these magnets are indispensable for high-performance motors in electric vehicles (EVs) and hybrid electric vehicles (HEVs). These magnets need to possess sufficient thermal stability for use in such motors in high-temperature environments. The addition of Dy is necessary to improve the thermal stability of Nd-Fe-B magnets. However, there is the concern about a shortage of rare earth metals because of the uneven distribution of rare earth resources. Against this background, it is necessary to develop an inexpensive and environmentally friendly recovery/separation process for rare earth metals, especially the recovery of Dy from Nd-Fe-B magnet scraps.We proposed a new separation and recovery process for Dy from Nd magnet scraps using molten salt electrolysis and an alloy diaphragm [1-3]. The new separation and recovery process was first applied to chloride melts [4-6], and the present study focused on the separation of Dy from Nd-Fe-B magnet scraps in a molten LiCl-KCl system. The anodic dissolution of RE (Dy, Nd, etc) using Nd-Fe-B magnet electrodes and electrowinning of Dy using Ni electrodes were carried out in a molten LiCl-KCl system at 723 K.ExperimentalAll chemicals were anhydrous reagent grade. The LiCl-KCl eutectic (LiCl:KCl = 58.5:41.5 mol%) was placed in a high purity alumina crucible, and kept under a vacuum for more than 24 hrs at 473 K to remove water. All experiments were performed in LiCl-KCl eutectic melts under a dry Ar atmosphere at 723 K. A chromel-alumel thermocouple was used for temperature measurements. The anodic working electrodes were Nd-Fe-B magnets (20 mm × 10 mm × 1.5 mm) wound Ni wires (5 mm × f 1 mm, 99 %). The composition of Nd-Fe-B magnet was 20 mass%Nd, 5mass%Dy, 65mass%Fe, 1mass%B, etc. The cathodic working electrodes were Mo and Ni plates (20 mm × 10 mm × 0.2 mm, 99 %). The reference electrode was an Ag wire immersed in LiCl-KCl containing 1 mol% of AgCl. The potential of this reference electrode was calibrated with reference to that of a Li+/Li electrode, which was prepared by electrodepositing Li metal on a Mo wire. The counter electrode was a glassy carbon rod (50 mm × f 5 mm, Tokai Carbon Co., Ltd.). The samples were prepared by potentiostatic electrolysis. After electrolysis, the samples were rinsed with distilled water. Cross-sections of these samples were also observed by SEM. The compositions of the samples were analyzed by EDX.Results and discussionAnodic potentiostatic electrolysis at 1.70 V and 2.20 V for 12 h were conducted using Nd-Fe-B magnet electrodes. From a cross-section of a sample obtained at 1.70 V, it was found that RE in the outer layer was selectively dissolved but RE in the inner layer remained. On the other hand, the Nd-Fe-B magnet was almost dissolved, and the original form was disappeared.After anodic potentiostatic electrolysis at 2.20 V, cathodic potentiostatic electrolysis was conducted at 1.00 V for 5 h using a Mo plate in order to removed Fe dissolved into the bath from the Nd-Fe-B magnet. The electrodeposited Fe was observed on a Mo plate. Furthermore, based on the results of previous works [5], cathodic potentiostatic electrolysis was conducted at 0.65 V for 4h, 12 h using Ni plates in order to recover Dy selectively. The SEM analysis showed that the alloys formed. From the EDX analysis of formed alloy, the molar ratio of Dy/Nd in the alloy samples are found about 10 for 4 h and 16 for 12 h. These results suggested that the separation of Dy and Nd could be achieved.

Protective Engobes for Si3N4 Ceramics Sintered in Air-Atmosphere Furnace

Silicon nitride ceramics were sintered at 1640°C in an air-atmosphere furnace using an alumina crucible, alumina packing powder, and protective Al2O3 engobes as well as glass ceramic engobes obtained from the system SiO2-ZnO-Al2O3 The Si3N4 composite was prepared from β-Si3N4 powder with addition of MgO and Al2O3 as sintering aids. It was found that the densest silicon nitride ceramic with only partial oxidation was the sample covered with the Al2O3 engobe. Three phases were identified by XRD analysis: β-Si3N4, α-Si3N4, and Si2N2O. The obtained results are promising and encourage continuous research in this field to ensure protection from and prevention of intensive oxidation.