Uncalcined Powder Research Articles

Pulse ultrasonication leaching approach for selective Li leaching from spent LFP cathode material

ABSTRACT Lithium-iron-phosphate (LFP) batteries are a type of battery whose usage is increasingly expanding due to their features and low production costs. The recovery of precious metals from discarded LFP batteries, resulting from their growing utilization, holds significance from both environmental and economic perspectives. Hydrometallurgical recycling of LFP has gained attention due to its cost-effectiveness and environmental considerations. This study explores the application of ultrasound-assisted leaching as an alternative to conventional hydrometallurgical leaching processes, yielding promising results. The utilization of ultrasound facilitates efficient Li solubility within a short duration of 15 min, eliminating the need for prolonged leaching times. Moreover, selective Li solubility was achieved without the use of additional oxidizing agents through the calcination of the LFP cathode powders. In the ultrasonic leaching of uncalcined powders, a Li dissolution efficiency of 98.60% was obtained, while the Fe dissolution efficiency remained at 32.46%. However, in the ultrasonic leaching of calcined powders, the Li dissolution efficiency was 90.66% within 15 min, while the Fe leaching efficiency remained at 4.88%. Thermodynamic models were employed to elucidate all leaching processes, and the influential parameters were discussed. Furthermore, Al current collectors were successfully recycled, resulting in the production of amorphous Al2O3 powders.

Effect of thermal and densification processes on reaction and conventional sinterings of a hydrolyzed calcium phosphate phase

Thermal processes resulting in the densification of compacts of an uncalcined powder (UPC) and of the powder calcined at 700 °C for 1 h (CPC), obtained from a hydrolyzed powder with a primary molar ratio of Ca/P = 1:1 obtained by the nitrate synthesis were studied during heating under reaction and conventional sintering modes up to 1100 °C. Due to desorption, decomposition, crystallization and phase transformation processes, the density of the UPC increased stepwise and finally reached 95% of the theoretical density of the formed biphasic HA/β-TCP product with a 52/48 ratio compared to 67% and a 0.55/0.45 ratio in the CPC. Because the annealing time at 1100 °C was negligible (about 1 min), a proper completing sintering to produce high quality ceramics from such UPC phases seems very promising.

Novel Method for NTC Thermistor Production by Aerosol Co-Deposition and Combined Sintering.

A novel three-stage process to produce NTCR sensors is presented. In this process, an uncalcined powder mixture of NiO and Mn2O3 was deposited onto an alumina substrate via aerosol co-deposition (AcD). Then, an electrode structure was screen-printed onto the surface and the composite film was sintered in a multifunctional temperature treatment. Thereby, the sintering of the electrode, the formation of the NiMn2O4 spinel and the removal of film strains took place simultaneously. This enabled a significant reduction in energy demand and workload. The manufactured sensors, both as first prototypes, as well as miniaturized chip components, were characterized by a single-phase cubic NiMn2O4 spinel structure, mechanical stability and electrical properties that were similar to those of classical NiMn2O4 bulk ceramics or tempered aerosol deposited (AD) NiMn2O4 films. Particularly noteworthy was the high reproducibility and low variation of the NTCR parameters, such as the specific resistivity at 25 °C ρ25, the electrical resistance at 25 °C R25 and the thermistor constant B. The NTCR parameters were as aging-stable as for NiMn2O4 bulk ceramics or tempered NiMn2O4 AD-films and could even be further improved by thermal post-treatment.

Innovative polyetherimide and diatomite based composites: influence of the diatomite kind and treatment

In this work innovative composites were developed, using as polymeric matrix polyetherimide (PEI), a high performance thermoplastic, and as natural filler two different kinds of diatomaceous earth, i.e. uncalcined and calcined. The uncalcined powder was amino-functionalised to improve its chemical compatibility with the matrix, whereas the calcined one was submitted to a purification treatment with HCl to remove possible contaminants.Mechanical tests and microstructural characterisation were carried out to evaluate the influence of the filler kind, of its content (i.e. 1–10wt.%) and of its amino-functionalisation or purification in the case of uncalcined and calcined diatomite, respectively, on the composites performance. The collected results show an increase of Young's modulus with the filler content, particularly in the case of amino-functionalised diatomite, suggesting a good chemical compatibility between filler and matrix. This is substantiated by the scanning electron microscopy (SEM) observation of the fracture surface of samples after tensile test.

Preparation of visible light photocatalyst by interface reaction between tungsten-molybdenum oxide and copper clusters

A tungsten-molybdenum solid solution oxide ((Mo,W)O3) powder was prepared using hydrothermal processing. The crystal structure of the obtained powder was orthorhombic WO3 type with 0.22M H2O per unit chemical formula weight. This powder was dehydrated and transformed into monoclinic WO3 type structure by heat treatment at 500°C in air. When uncalcined powder was modified with Cu by impregnation with a CuCl2 solution and subsequent firing at 500°C in air, photocatalytic decomposition activity against gaseous 2-propanol (IPA) was achieved under visible light illumination. Results suggest that Cu(W1−xMox)O4 was formed on the (Mo,W)O3 powder surface by the Hedvall effect during its phase transition, and that the Z-scheme became feasible between (Mo,W)O3 and Cu(W1−xMox)O4.

Nanostructured MnCo2O4 synthesized via co-precipitation method for SOFC interconnect application

Nanostructured manganese cobaltite spinel oxide (MnCo2O4) was successfully synthesized by co-precipitation method. X-ray diffraction (XRD) results revealed that the molar ratio of OH−/NO3− = 1.5 in the precipitation stage is more appropriate for achieving MnCo2O4 phase. The results of thermal analysis (TGA/DTA) along with the XRD results revealed that the MnCo2O4 phase remains stable up to 1050 °C. Morphological studies show that by increasing the calcination temperature from 350 to 550 and 1000 °C, morphology of the particles varies from plate-like to quasi spherical and polyhedral shape, respectively. Density and porosity measurement of cold pressed and sintered samples showed that by employing un-calcined powder, a dense sample with 98% of the theoretical density could be obtained at the sintering temperature of 1000 °C. Selected synthesized powders were coated on the AISI 430 ferritic stainless steel coupons and the results demonstrated that using un-calcined powder, leads to the formation of a highly dense and adhesive coating layer due to the very high tendency of un-calcined powder for densification.

Enhanced pyroelectric properties of PZT/PVDF-TrFE composites using calcined PZT ceramic powders

The effects of calcined lead–zirconate–titanate (PZT) powders on the electric properties of PZT/polyvinylidene-trifluorethylene copolymer (PVDF-TrFE) composites thick films were studied in this paper. Firstly, the PZT powders synthesized by hydrothermal method were calcined at different temperatures ranging from 300°C to 900°C, and then the PZT/PVDF-TrFE composites films were produced by casting PZT/PVDF-TrFE suspension onto the indium-tin-oxide (ITO)-coated glass substrates. Electric properties, including dielectric and pyroelectric performances of thick films consisting of PZT powders calcined at different temperatures were tested. The highest pyroelectric coefficient obtained in the sample using 700°C calcined PZT powders was 96 μCm-2K-1, which was 20% higher than the composites made of uncalcined powders. Additionally, the highest detectivity figure-of-merit (FOM) (F D ) of the composite was 1.36 × 10-5Pa-1/2, which increased about 13.5% compared to the one using uncalcined powders.

Facile Synthesis of Monodisperse Porous ZnO Spheres by a Soluble Starch-Assisted Method and Their Photocatalytic Activity

In this study, monodisperse porous ZnO spheres were fabricated by a facile and low-cost soluble-starch-assisted method. The as-obtained samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV−vis diffuse reflectance spectroscopy (DRS), thermogravimetric and differential scanning calorimetry (TG−DSC), Fourier transform infrared (FTIR) spectroscopy, and Brunauer−Emmett−Teller (BET) analysis. The Raman spectra revealed that the uncalcined powders were composed of ZnO and starch. The BET analysis showed that mesopores (25 nm) and macropores (180 nm) coexisted in the typical porous ZnO spheres. The photocatalytic activities of the as-obtained ZnO samples were evaluated in the photocatalytic degradations of aqueous solutions of rhodamine B (RhB) and 4-nitrophenol (4-NP) at room temperature. A possible growth mechanism of the as-obtained porous ZnO spheres is also...

Synthesis and characterization of La 0.85Sr 0.15Ga 0.80Mg 0.20O 2.825 by glycine combustion method and EDTA combustion method

The powders of La 0.85Sr 0.15Ga 0.80Mg 0.20O 2.825(LSGM) were synthesized by glycine combustion method (GCM) and EDTA combustion method (EDTACM). XRD results show that the main phase (LSGM) exists in the uncalcined powders synthesized by GCM. The LSGM materials are composed of the main phase without secondary phases when calcined at 1300 °C. The LSGM materials contain fewer amounts of secondary phases than those prepared by EDTACM at the same calcination temperature. The conductivities of LSGM increase with the increase of testing temperature. The ionic conductivities of LSGM prepared by GCM and EDTACM were calculated to be 0.053 S cm −1 and 0.060 S cm −1 at 800 °C, respectively. The curve of ln(σ T) vs. 1/ T exists two straight lines. It indicates that activation energy of oxygen-vacancy motion at lower temperatures is greater than that at higher temperatures.

Synthesis and characterization of Sr- and Mg-doped Lanthanum gallate electrolyte materials prepared via the Pechini method

The powders of Sr- and Mg-doped lanthanum gallate (La 0.85Sr 0.15Ga 0.80Mg 0.2O 2.825; LSGM) were synthesized by the Pechini method. The XRD pattern indicates that the main phase (LaGaO 3) exists in the uncalcined powders. The LSGM materials are composed of the main phase without secondary phases when calcined at 1400 °C. The LSGM materials contain fewer amounts of secondary phases than those prepared by the sol–gel method and solid-state reaction method at the same calcination temperature. TEM image of the powders indicate that the average grain size is about 80 nm. The conductivity increases with the testing temperature increasing. The curve of ln( σT) vs 1/ T exists two straight lines intersecting at T * ( T * is about 602 °C). It indicates that activation energy of oxygen-vacancy motion at lower temperatures is greater than that at higher temperatures.

Nano-crystallinite hydroxyapatite synthesized by neutralization with the assist of citric acid

Bioactive hydroxyapatite (HA) powders with nano-crystallinity were prepared by an economic way, i.e. the neutralized route, during which a supersaturated suspension of lime chelated with citric acid was titrated by orthophosphoric acid diluted with deionized water or ethanol. The crystal behaviors of HA powders were characterized by X-ray diffraction and Fourier transform infrared spectra. It was found that uncalcined powders were amorphous calcium phosphate, while the crystallinity increased significantly after calcined at 800 °C and their crystal sizes synthesized with aqueous and ethanol solutions were determined as 54.8 and 85.4 nm, respectively. The inhibition of crystal growth was attributed to the chelating reagent, resulting in the B-substituting CO32− ions to PO43− groups and causing a-axis shortened and c-axis lengthened in the crystal cell.

Effect of sintering conditions on characteristics of PbTiO 3–PbZrO 3–Pb(Mg 1/3Nb 2/3)O 3–Pb(Zn 1/3Nb 2/3)O 3

In this work, the piezoelectric ceramic system of the Pb[(Zr 1− y Ti y ) 0.74(Mg 1/3Nb 2/3) 0.20(Zn 1/3Nb 2/3) 0.06]O 3, 0.47≤ y≤0.57, with composition close to the morphotropic phase boundary (MPB) is studied. From the results of X-ray diffraction and piezoelectric measurement, ceramics near y=0.51 are found at the MPB between the tetragonal and pseudocubic perovskite. The effects of sintering time and packing powders on the properties of Pb[(Zr 0.49Ti 0.51) 0.74(Mg 1/3Nb 2/3) 0.20(Zn 1/3Nb 2/3) 0.06]O 3 (PZT–PMN–PZN) ceramic are discussed. Dielectric and piezoelectric properties have maximum values at the sintering temperature of 1250 °C for 3 h. Longer sintering time causes excessive PbO loss and a resultant variation in composition, which leads to an inhomogeneous microstructure and the emergence of a pyrochlore phase. The pyrochlore phase is detrimental to the dielectric and piezoelectric properties. The PZT–PMN–PZN piezoceramics system, which has excellent dielectric and piezoelectric properties, uses uncalcined powder of the main component as the packing powder to provide a positive vapor pressure.

Effect of calcination of the mixture of alumina powder and aqueous magnesium solution on the microstructure and properties of sintered bodies

Abstract The influence of calcination of the mixture of alumina powder and aqueous magnesium solution on the microstructure and properties of sintered bodies was investigated. The dry pressing technique was applied to formgreen bodies using granules prepared by spray drying both calcined and uncalcined alumina powders. Density, fracture strength and Weibull modulus were measured, and the microstructurewas evaluated for sintered specimens prepared from calcined and uncalcined powders. Direct observation of the internal structure of sintered bodies was also applied to obtain information on the variation of defect distribution in sintered bodies. The effects of calcination on the properties and microstructure of sintered bodies are discussed, and it is concluded that the uniform mixing of alumina and magnesium source was responsible for the excellent properties of alumina ceramics made from the calcined powder.

Synthesis of biphasic ceramics of hydroxyapatite and β-tricalcium phosphate with controlled phase content and porosity

Biphasic porous ceramics of hydroxyapatite and β-tricalcium phosphate have been prepared. The process was based on solid state reactions of brushite with calcium carbonate. The optimum heat treatment conditions for producing pure stoichiometric HA, β-TCP and a biphasic composite of HA and β-TCP with definite phase composition were identified by the methods of thermal analysis, X-ray diffraction and IR absorption spectroscopy. As a gas-forming agent, a certain amount of uncalcined powder was mixed with the corresponding precalcined powder to produce porous ceramics with different microporosities. Foam ceramics with macropores have been prepared by a dipping technique. The pore structure was examined using scanning electron microscopy.

In-situ formation of thin-film like β′'-alumina layers on α-alumina substrates

The in-situ formation of layers consisting of β′'-alumina on high purity polycrystalline α-alumina substrates was investigated. The direct synthesis of sodium and potassium β′'-alumina layers was possible in a mixture of uncalcined powders of stoichiometries close to the β′'-alumina phase in a temperature-time window between 1200 and 1400 °C and 1 h to 12 h.

Sintering behaviour of precursor mullite powders and resultant microstructures

Crystallization and sintering behaviour of two structurally different diphasic precursor mullite powders were studied. Powder derived from boehmite and colloidal silica formed mullite at around 1250 °C and could be sintered to high density at this temperature by viscous flow sintering. Calcination of the powder up to 1000 °C did not affect its sinterability but the weight loss decreased from 20% for the uncalcined powder to 5% for the 1000 °C calcined powder. In contrast, powder derived from aluminium sulfate and colloidal silica formed mullite at around 1200 °C and did not sinter much by the viscous flow, but showed enhanced solid-state sintering behaviour compared with crystalline mullite powders. Calcination of the powder at temperatures below mullite formation temperature did not affect its sinterability. Microstructural examinations revealed that dense mullite obtained by sintering of powder derived from aluminium sulfate-colloidal silica had much finer grain size (~135 nm) than that obtained from the boehmite-colloidal silica mixture (~1500 nm) and the fine grain size of the mullite was stable up to 1300 °C upon long heat treatments (120 h).

Sintering studies on submicrometre-sized Y-Ba-Cu-oxide powder

The isothermal sintering behaviour of submicrometre-sized (<50 nm) powders of single-phase YBa2Cu3O x (123) and unreacted stoichiometric mixture of submicrometre-sized (<50 nm) powders of BaCO3, Y2O3 and CuO (which on calcination at 1173 K gives YBa2Cu3O x ) was investigated through dilatometry under different sintering atmospheres. The sintering rate of the powder compacts was impeded by the presence of oxygen. The activation energies,Q, of sintering were determined to be 1218 kJ mol−1 in argon, 1593 kJ mor−1 in air and 2142 kJ mol−1 in oxygen. A decrease in the apparent sintered density with increasing oxygen partial pressure was also observed. X-ray diffraction and thermal analyses (thermogravimetry and differential thermal analysis) showed no reaction during sintering of the single-phase product. Pellets fabricated from uncalcined powder exhibit two stages of sintering, one between 1073 and 1173 K having an activation energyQ=627kJ mol−1, and a second one above 1173 K withQ=383.7 kJ mol−1. A.c. susceptibility, resistivity and critical current density were determined as a function of the temperature of the sintered samples.

Rapid Formation of the 110 K Phase in BI‐Pb‐Sr‐Ca‐Cu‐O through Freeze‐Drying Powder Processing

Three techniques for processing Bi‐Pb‐Sr‐Ca‐Cu‐O (BPSCCO) powders were investigated: dry‐mixing, sol‐gel formation, and freeze‐drying. It was found that sintering for 120 h at 850°C is required to form nearly single‐phase (Bi,Pb)2Sr2Ca2Cu3O10‐y by dry‐mixing, whereas sintering for 30 h at 840°C was sufficient to form the 110 K (2223) phase when freeze‐drying was used. The sol‐gel route was found to be intermediate in efficiency between these two techniques. Freeze‐drying provided highly reactive, intimately mixed, and carbon‐free precursors. The presence of carbonates in the uncalcined powders was the major cause of phase segregation and sluggishness of the 110 K phase formation.

Preparation and characterization of precursor powders for yttria-doped tetragonal zirconia polycrystals (Y-TZP) and Y-TZP-Al2O3 composites

Precursor powders for the preparation of tetragonal 2.5 mol% Y2O3-ZrO2 containing 0 to 30 wt% Al2O3 were made by coprecipitation. The behaviour of this powder during calcination from room temperature to 1200° C was studied using differential thermal analysis. X-ray diffraction and transmission electron microscopy methods, and measurements of surface area. The uncalcined powder was essentially amorphous. On heating alumina-free powder, zirconia crystallized at 485° C: for increasing alumina content, zirconia crystallized from an amorphous aluminous matrix at increasing temperatures (850° C for 20 wt% Al2O3), while the crystallite size decreased and the surface area of the powder increased. The zirconia first crystallized as cubic, but transformed to the tetragonal form near 1100° C. The alumina crystallized as corundum at 1200° C. No monoclinic zirconia could be detected when calcined aluminous material was cooled to room temperature. The sintering behaviour of the calcined powder is discussed.