Major Crystalline Phase Research Articles

Optimization of Mn-Zn ferrite doping in phosphate-based glass ceramics for enhanced hyperthermia efficiency and bioactivity

This study investigates the effects of Mn-Zn ferrite (MZF) content and heat treatment temperature on the structural, mechanical, magnetic, and bioactive properties of Na2O-CaO-P2O5 glass ceramics. Various MZF contents (5MZF, 10MZF, 20MZF, and 40MZF) were incorporated into the glass ceramics and subjected to heat treatment at different temperatures (600, 650, 700, and 800 °C). The results demonstrated that increasing the MZF content significantly enhanced the mechanical properties, including Vickers hardness, Knoop hardness, and Young's modulus. For example, the Vickers hardness values increased from 5.6 GPa in 5MZF samples to 7.1 GPa in 40MZF samples. X-ray diffraction analysis revealed the presence of major crystalline phases, such as Ca2P2O7 and Na4Ca(PO3)6, with NaFe3P3O12 and (Zn,Mn)Fe2O4 appearing in samples with higher MZF content. Magnetic measurements indicated that the 40MZF samples treated at 700 °C reached a satisfactory hyperthermia temperature of 43 °C within 16 min. Bioactivity tests showed a decrease in bioactivity with increasing MZF content, whereas cytotoxicity assays confirmed that all MZF-Na2O-CaO-P2O5 bioactive glass ceramics were non-toxic, maintaining over 100 % cell viability after 24 h. These findings suggest that MZF-containing glass ceramics have potential applications in the biomedical field, particularly when enhanced mechanical and magnetic properties are required.

Investigating Nanoindentation and Wear Properties of Spark Plasma Sintered Ti48Al48Cr2Nb2 Alloy

This work studied spark plasma sintered Ti48Al48Cr2Nb2 alloy for their nanoindentation and wear properties. Results showed an improvement in nanoindentation properties of the compacts with an increase in holding time from 5min to 7.5min for the heating rate of 50°C/min and 100°C/min. X-ray diffraction (XRD) analysis showed the intensity of diffraction peaks of two major crystalline phases of Ti3Al2.25Nb0.75 and γ-TiAl. Scanning electron microscopy (SEM) images of sintered compacts possessed varied microstructures due to different sintering parameters. The nearly lamellar structure showed a good balance of yield stress and fracture toughness. Wear tracks SEM analysis revealed the worn surface morphologies and the sample sintered for 7.5 min at the eating rate of 50°C/min sustained the least damage evident by the shallow grooves and narrow wear track. Profilometer measurements revealed the wear track depth and width, confirming the degree of wear for the samples sintered at varied conditions.

Investigation of the effect of Tideglusib on the hydroxyapatite formation, crystallinity and elasticity of conditioned resin-dentin interfaces

To investigate the effect of dentin infiltration with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs) on hydroxyapatite formation, crystallinity and elasticity of conditioned resin-dentin interfaces. Dentin conditioned surfaces were infiltrated with NPs or TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nanoindentation to determine the modulus of elasticity, X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-filed imaging. TDg-NPs provoked peaks narrowing after the diffraction-intensity analysis that corresponded with high crystallinity, with an increased modulus of Young after load cycling in comparison with the samples treated with undoped NPs. New minerals, in the group of TDg-NPs, showed the greatest both deviation of line profile from perfect crystal diffraction and dimension of the lattice strain, i.e., crystallite, grain size and microstrain and 002 plane-texture. The new minerals generated after TDg-NPs application and mechanical loading followed a well defined lineation. Undoped NPs mostly produced small hydroxyapatite crystallites, non crystalline or amorphous in nature with poor maturity. Tideglusib promoted the precipitation of hydroxyapatite, as a major crystalline phase, at the intrafibrillar compartment of the collagen fibrils, enabling functional mineralization. TDg-NPs facilitated nucleation of crystals randomly oriented, showing less structural variation in angles and distances that improved crystallographic relative order of atoms and maturity. Nanocrystals inducted by TDg-NPs were hexagonal prisms of submicron size. Thermal challenging of dentin treated with TDg-NPs have provoked a decrease of functional mineralization and crystallinity, associated to immature hydroxyapatite. New polycrystalline lattice formation generated after TDg-NPs infiltration may become correlated with high mechanical performance. This association can be inferred from the superior crystallinity that was obtained in presence of tideglusib. Immature crystallites formed in dentin treated with undoped NPs will account for a high remineralizing activity.

Sintering, microstructure and mechanical properties of anorthite-based ceramics prepared from iron-extracted steel slag

Steel slag is a promising source of ceramic materials, but it causes a waste of iron resources and inferior ceramic performance because the slag contains over 30 % iron oxides. To deal with this problem, we proposed a two-step utilization process for steel slag, including iron extraction by smelting reduction and ceramics preparation from residual slag. In this work, the effect of the reduced slag addition on phase constituents, microstructure, and properties of this novel ceramic was studied. The major crystalline phase is anorthite for all the ceramics. Although abundant liquid is expected theoretically in conventional ceramics at 1175 °C, it did not achieve vitrification until 1250 °C. The slag addition plays different roles in sintering under various slag contents. After introducing 15 wt% slag, the sintering and pore elimination are accelerated significantly because of the slag’s fluxing effect although the ceramic shows no change in the theoretical liquid content. The ceramics have no advantage in producing liquids with further increasing the slag content. Therefore, limited densification is observed with 30 wt% slag addition owing to the lack of liquid phase. Fortunately, solid solution diopside is largely generated in the anorthite matrix with 45 wt% slag addition, greatly enhancing the ion diffusion and grain growth. This effect contributes to a highly dense and uniform sintered structure with small rounded pores at 1175 °C, at which its flexural strength increases by 92 % compared to the conventional ones. However, a higher slag addition in the ceramic should be avoided to ensure satisfactory structure integrity.

Synthesis of the acidic/magnetic catalyst x-MoO3/Ni0.5Zn0.5Fe2O4 by combustion reaction and evaluation of its catalytic potential/reuse in biodiesel production

The objective of this work was to synthesize a new catalyst x-MoO3/Ni0.5Zn0.5Fe2O4 using the combustion reaction method and to evaluate its catalytic potential and reuse in biodiesel production from waste oil, optimizing the process through experimental design. The catalysts were characterized in terms of structure by X-ray diffraction and phase quantification by Rietveld refinement, surface area by the Brunauer-Emmett-Teller technique, experimental density by helium pycnometry, acidity tests by ammonia desorption at programmed temperature, chemical analysis by X-ray fluorescence, morphology by scanning and transmission electron microscopy, and catalytic properties. The products of the simultaneous transesterification and esterification reactions were characterized by gas chromatography and acidity index. The results indicate the formation of catalysts with surface area ranging from 1.5 to 1.7 m2/g and density ranging from 4.5 to 5.1 g/cm3, composed of major crystalline phases of MoO3 in the orthorhombic configuration and cubic Ni0.5Zn0.5Fe2O4 ferrite, with total acidity ranging from 70 to 182 μmol/g of NH3. Morphological characterization revealed that the catalyst comprises irregular plates of various sizes and shapes with a wide range of cluster sizes. In the simultaneous transesterification and esterification reactions of residual oil, the catalysts were active under all conditions tested, with emphasis on the catalyst containing 50 % Mo ions and 50 % Ni0.5Zn0.5Fe2O4 presenting the best catalytic performance with a conversion of 95 % in ethyl esters and a reduction of 71 % in acidity, with a service life of 6 cycles, an average conversion of 90 % and good thermal and structural stability after use. The experimental design was significant and predictive, with a confidence level of 95 %. Statistical analysis identified that all input variables (temperature, time, and amount of catalyst) were significant for the adopted design. The new catalyst composed of molybdenum, iron, nickel, and zinc has a positive impact on biodiesel synthesis from frying oil and ethanol.

Effects of Cr2O3 doping on crystallization behavior and electrochemical properties of Li2O–Al2O3–TiO2–P2O5–SiO2 glass-ceramics

Bulk glass-ceramic solid electrolytes of the Li2O–Al2O3–TiO2–P2O5–SiO2 system were prepared by melt-quenching and one-step heat treatment method in this work. The effects of the gradual substitution of Al3+ by Cr3+ and the elevation of the heat treatment temperature on the phase composition, microstructure, and ionic conductivity of the solid electrolytes were systematically investigated. The results show that the major crystalline phase is LiTi2(PO4)3, and the conductivity of the glass-ceramics initially enhances and then decreases as the Cr2O3 content increases from 0 mol% to 3 mol%. The highest conductivity is obtained when the Cr2O3 content is 2 mol%, measuring 4.45 × 10−4 S/cm at 25 °C. Additionally, the mechanism of the surface exfoliation of the glass-ceramics and the enhancement achieved by doping with Cr3+ are explained according to microstructure analysis. This work provides a simple method to enhance the electrical conductivity and physical properties of LATP glass-ceramic solid electrolytes, which is of great significance for the design of lithium-ion solid electrolytes.

Preparation, properties and formation mechanism of transparent anorthite-based glass-ceramic glaze with high hardness

The transparent anorthite-based glass-ceramic glaze was prepared at 1200 °C by mineral raw materials. The effect of ZnO content on the structures and properties of the anorthite glass-ceramic glaze was studied by XRD, SEM-EDS, HR-TEM, high temperature microscope, micro-Vickers hardness tester and comprehensive thermal analyzer. Furthermore, the formation mechanism of anorthite was investigated systematically. The results reveal that the introduction of ZnO results in the decrease of melting temperature, elimination of the diopside, reduction of the thermal expansion coefficient, and improvement of the mechanical properties of the glazes markedly. The major crystalline phases of glazes change from the coexistence of anorthite and diopside to single anorthite with the increase of ZnO content from 0 wt% to 6.45 wt%, and the relative anorthite content increases from 26.87 wt% to 49.83 wt%. Both the size and number of anorthite grains with a distribution of the card structure gradually increases as increasing the ZnO content. The increase of anorthite improves the scattering ability of visible light and then reduces the transparency of the glaze. The Vickers hardness and flexural strength of glazes improve from 5.26 GPa and 45.95 MPa to 7.20 GPa and 72.79 MPa, respectively. The thermal expansion coefficient decreases from 6.328 × 10−6/°C to 5.781 × 10−6/°C (600 °C). Anorthite crystal generates from the reaction of genhlenite, SiO2 and Al2O3 at 1100 °C, and the gehlenite forms through the reaction of metakaolin and CaO. The study shows that the plate-like anorthite crystallizes when the content of ZnO is 3.33 wt%, the Vickers hardness of glass-ceramic glaze is 6.56 GPa with a great transparency.

Bactericidal efficiency of silver nanocomposites obtained using Brewer’s spent grains

Silver nanocomposites were prepared using extracts resulting from different extraction methods of brewer’s spent grains (BSG) herein called BW3. Extracts were prepared using solvent (acetone and methanol aqueous solutions, and water) extraction methods, ultrasonic and microwave-assisted methods, and alkaline-acid hydrolysis.Extraction conditions influenced the composition of extract solutions differing in the amount of Na, K, P, Mg, Ca, Zn, and SO4−, Cl−, and NO3– anions, wherein predominantly varying contents of P and anions influenced the properties of the nanocomposites. Nanocomposites exhibited three major crystalline phases, namely, Ag3PO4 (9–74 wt%), Agmet (25–84 wt%), and AgCl (∼1–5 wt%) with different Ag crystallite sizes. Nanoparticles of different Ag phases were capped by organic structures consisting of chemical groups such as C–OH, C = O, C–OOH, –NH, and –PH. The thermal stability of the nanocomposites increased with increasing Agmet phase content.The minimum inhibitory concentration (MIC) of nanocomposites for Escherichia coli was as low as 4 μg mL−1. The antibacterial efficiency depended on the amount of (i) Ag+ ions from different Ag phases and their solubility, (ii) positively charged P and N hydrogen forms, (iii) negatively charged C groups and vacancies, and (iv) Ag phases crystallite size.

The Crystallization, Microstructure, and Dielectric Characteristics of MgO–Al2O3–SiO2–TiO2–CeO2 Materials for Microwave Applications

In this article, the impacts of varying CeO2 contents and heat‐treatment procedures on the crystallization, microstructure, and dielectric characteristics of MgO–Al2O3–SiO2–TiO2–CeO2 (MASTC) materials are investigated. In this research, it is indicated that perrierite, rutile, and α‐cordierite are the major crystalline phases in the materials. An increased CeO2 content promotes the formation of perrierite and inhibits the precipitation of α‐cordierite and rutile in the glass ceramics. An appropriate amount of CeO2 content contributes to a dense microstructure and improves the dielectric characteristics of the samples. However, an excessive amount of CeO2 deteriorates the densification and dielectric characteristics of the MASTC materials. Furthermore, heat‐treatment temperature and duration also have a significant impact on the crystallization, microstructure, and dielectric performance of the materials. The MASTC material with 20.2 wt% CeO2, heat‐treated at 1100 °C for a duration of 3 h, possesses superior characteristics with a density of 3.14 g cm−3, a permittivity of 11.1, and a Q × f factor of 17 357 (14 GHz).

Reduction of Firing Temperature by Utilization of Secondary Materials for the Synthesis of Forsterite Ceramics

The main aim of this research was to investigate the effect of the addition of coal fly ash as a secondary waste material on the synthesis and properties of forsterite ceramics. The utilization of fly ash as a raw material, which contains flux oxides, reduce the necessary firing temperature for the synthesis of forsterite ceramics in comparison with forsterite ceramics synthetized from high purity or industrial materials, while preserving its refractory properties. The results revealed that forsterite was synthesized as a major crystalline phase in all samples. The optimal firing temperature for obtaining good physico-mechanical parameters was found to be between 1400-1600°C for high purity or industrial materials, while mixtures containing fly ash could achieve similar parameters at lower firing temperatures between 1200-1300°C. The decrease in refractoriness was found to be within acceptable limits for utilization as a refractory material. These findings demonstrate the potential for cost reduction and energy savings through the use of secondary waste materials and reduced firing temperature in the synthesis of forsterite ceramics.

Cold‐cap structure in a slurry‐fed electric melter

AbstractAs glass batch is charged into an electric melter, a cold cap forms on the glass melt surface. Heat transfer to the cold cap from the molten glass below and the melter atmosphere above determines the melting rate. A mathematical model of the cold cap and the experimental kinetic data of the feed‐to‐glass conversion that were collected for several simulated low‐activity and high‐level waste melter feeds allowed us to develop relationships between the internal structure of the cold cap, its properties, its thickness, and the internal heat transfer. This contribution shows the distribution of major crystalline phases and the cumulative evolution of gases within the cold cap. It also examines the temperature, conversion degree, and heating rate the melter feed is experiencing during the passage through the cold cap and their effects on the cold‐cap bottom temperature and morphology, which are important for the computational fluid dynamics simulations of melters.

Investigation of critical properties of Cassava (Manihot esculenta) peel and bagasse as starch-rich fibrous agro-industrial wastes for biodegradable food packaging.

Cassava peel and bagasse are fibrous, starch-rich agro-industrial wastes, which cause severe environmental impacts upon their disposal. However, these can be raw materials for biodegradable food packaging. In this study, their morphological, chemical, thermal properties, crystalline phases, and chemical compositions were investigated, and potential utilisation as alternative biodegradable food packaging matrices has been assessed. Residual starches in cassava peel and bagasse were morphologically similar with that of commercial cassava starch, whereas potassium (8570±56mg/kg), and calcium (5300±147mg/kg) were highly abounded in peel and bagasse respectively. The major crystalline phase, α-amylose dihydrate, for cassava peel (97.1 (2)%) and bagasse (99.0 (3)%) point towards the presence of starch. Calcium and silicon reported to be in crystalline phases respectively, in the forms of quartz and whewellite. These beneficial characteristics suggested the potential valorisation of cassava peel and bagasse with special interest as matrices for biodegradable food packaging.

Phases in fine volcanic ash

Volcanic ash emissions impact atmospheric processes, depositional ecosystems, human health, and global climate. These effects are sensitive to the size and composition of the ash; however, datasets describing the constituent phases over size ranges relevant for atmospheric transport and widely distributed impacts are practically nonexistent. Here, we present results of X-ray diffraction measurements on size-separated fractions of 40 ash samples from VEI 2–6 eruptions. We characterize changes in phase fractions with grainsize, tectonic setting, and whole-rock SiO2. For grainsizes < 45 μm, average fractions of crystalline silica and surface salts increased while glass and iron oxides decreased with respect to the bulk sample. Samples from arc and intraplate settings are distinguished by feldspar and clinopyroxene fractions (determined by different crystallization sequences) which, together with glass, comprise 80–100% of most samples. We provide a dataset to approximate glass-free proportions of major crystalline phases; however, glass fractions are highly variable. To tackle this, we describe regressions between glass and major crystal phase fractions that help constrain the major phase proportions in volcanic ash with limited a priori information. Using our dataset, we find that pore-free ash density is well-estimated as a function of the clinopyroxene + Fe-oxide fraction, with median values of 2.67 ± 0.01 and 2.85 ± 0.03 g/cm3 for intraplate and arc samples, respectively. Finally, we discuss effects including atmospheric transport and alteration on modal composition and contextualize our proximal airfall ash samples with volcanic ash cloud properties. Our study helps constrain the atmospheric and environmental budget of the phases in fine volcanic ash and their effect on ash density, integral to refine our understanding of the impact of explosive volcanism on the Earth system from single eruptions to global modeling.

Novel PbO@C composite material directly derived from spent lead-acid batteries by one-step spray pyrolysis process

A one-step spray pyrolysis process is investigated for the first time in the field of spent lead-acid batteries (LABs) recycling. The spent lead paste that derived from spent LAB is desulfurized and then leached to generate the lead acetate (Pb(Ac)2) solution, which is then sprayed directly into a tube furnace to prepare the lead oxide (PbO) product by pyrolysis. The low-impurity lead oxide product (9 mg/kg Fe and 1 mg/kg Ba) is obtained under the optimized conditions (the temperature of 700 °C, the pumping rate of 50 L/h, and the spray rate of 0.5 mL/min). The major crystalline phases of the synthesized products are identified to be α-PbO and β-PbO. In the spray pyrolysis process, Pb(Ac)2 droplets are sequentially transformed into various intermediate products: H2O(g)@Pb(Ac)2 solution, Pb(Ac)2 crystals@PbO, and the final PbO@C product. Owning its carbon skeleton structure, the recovered PbO@C product (carbon content of 0.14%) shows better performance than the commercial ball-milled lead oxide powder in battery tests, with higher initial capacity and better cycling stability. This study could provide a strategy for the short-route recovery of spent LABs.

Fast ion conduction and stable [Na-Si-P] glass-ceramic solid electrolyte mixed with hafnium and scandium ions: Application to Na-ion full cell

NASICON type glass and glass-ceramic electrolyte materials have become very attractive choices recently to integrate into any Na+ ion storage system. This investigates glass and glass-ceramic electrolytes using the formula: 45(Na2O + NaF)-10SiO2-35P2O5-(10-x)HfO2-xSc2O3 (labeled as [NSP]90(10-x)HfScx; x = 0, 2, 4, 6, 8, 10 mol%) via the high energy mechanical milling followed by heat treating for different schedules. The thermal stability parameter (ΔT = Tc-Tg) and bulk conductivity are obtained to be highest for [NSP]90(10-x)HfScx glass electrolyte before and after heat treatment. XRD results revealed of Glass-ceramic powder that NASICON type Na3Sc2(PO4)3 and triclinic Na2HfSi2O7 major crystalline phases, which are reported to be highly conductive and stable. [NSP]90Hf4Sc6 −12 h glass-ceramic electrolyte stabilizes more against Na- metal than its corresponding [NSP]90 (10-x)HfScx glass electrolyte. The lowest interfacial resistance of [NSP]90Hf4Sc6 −12 h is observed than its pristine ell, directly ascribes the compatibility of Na metal-[NSP]90Hf4Sc6-12 h/Na electrolyte combination. The irreversible capacity and stability of full cell NVMP/[NSP]90Hf4Sc6/NVZn is also explored in light of the oxidation and redox reaction behavior.

Preparation of lightweight ceramsite by stone coal leaching slag, feldspar, and pore-forming reagents

In this study, lightweight ceramsite was prepared by stone coal leaching slag (SCLS), feldspar, and various pore-forming reagents via the roasting process, and the effect of raw meal ratio, roasting temperature, and roasting dwelling time on ceramsite features was investigated through orthogonal and single-factor experiments. The bulk density of ceramsite decreased from 900.0 to 762.0 kg/m3 when the content of Fe2O3 increased from 0 to 6 %. Under the optimal conditions (SCLS: feldspar: Fe2O3 = 65: 29: 6 and roasting at 1150 °C for 25 min), the ceramsite possessed a bulk density of 762 kg/m3 and water absorption of 2.4 %, which meet the Chinese standards for ceramsite (GB/T 17431.1–2010). The adsorption of the ceramsite was then characterized by different adsorption models and adsorption–desorption curves. The specific surface area of prepared ceramsite was 1.717 m2/g, which was suitable to produce adsorption materials. X-ray diffraction (XRD) results showed that the peak intensity of quartz and feldspar decreased and the cristobalite phase appeared with the increase in temperature, which helps to enhance the strength of sintered ceramsite. The major crystalline phases of the prepared ceramsite were quartz, feldspar, hematite, and cristobalite at 1,150 °C. The leaching concentration of heavy metals in ceramsite was far below the limited value of GB 5085.3–2007, which means that heavy metals were wrapped inside ceramsite. This study demonstrates a practical use for SCLS, potentially eliminating its damage to the environment, and provides guidance for SCLS-based ceramsite production.

Effect of heat treatment on dielectric and ferroelectric properties of BST ceramics

Barium Strontium Titanate (Ba0.9Sr0.1TiO3) ceramic powders were prepared by solid-state sintering technique and were uniaxially pressed and sintered at different temperatures of 1000 °C, 1050 °C,1100 °C, 1150 °C and 1200 0C for three hours. The physical, phase composition, microstructure, dielectric and ferroelectric properties of the BST ceramics were investigated. BaTiO3 was the major crystalline phase formed in ceramics. With the increase in the sintering temperature, the density was observed to be increased. Grain boundaries were clearly observed in the micrographs of FESEM for the ceramic samples sintered at high temperatures. Ferroelectric hysteresis was observed for the BST ceramic samples. At room temperature, the dielectric constant of the BST ceramic samples was observed to be increased with the increase of sintering temperature.

Micro-characterization of Dust and Materials of Dust Origin at a Cement Industry Located in Bangladesh

Industrial dust generation from material processing is an uninterrupted phenomenon, hence analyzing materials of dust origin with dust particles is important to comprehend the entire scenario of occupational health exposure (OHE). In this study, we investigated the morphological, elemental, and mineralogical characteristics of engendered dust and materials of dust origin in the cement industry (CI) in Bangladesh. The dust samples were accumulated from dust collectors and the internal roadways of the CI to understand the nature of atmospheric dust of the CI. All the materials that could potentially be the sources of the dust of the CI were collected, including clinker, gypsum, limestone, fly ash, slag, and two types of cement products. Scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS), x-ray powder diffraction (XRD), and fourier-transform infrared spectroscopy (FTIR) were performed for the characterization. SEM micrographs showed the presence of fine (particles ≤ PM2.5) and ultra-fine (particles ≤ PM0.1) particles with diverse morphology in the studied samples. Ca, Si, Al, Mg, Fe, K, Na, Mo, and Ti were found as existing metallic elements in samples through the EDS technique. Several minerals of silicate, oxide, carbonate, and sulfate were detected with major crystalline phases of Portland cement by SEM-EDS, XRD, and FTIR analyses in samples; among which some are well documented as occupational hazards. The trace presence of organic carbon was observed in all FTIR spectra. The most significant outcome of this study is the detection of carcinogenic substances such as crystalline silica (quartz, cristobalite) and asbestoses (anthophyllite, chrysotile, and crocidolite) in samples. For instance, quartz was found in the dust of dust collectors while road dust of the CI showed the existence of both quartz and cristobalite. However, asbestoses were found only in source materials, but they could be released anytime during material handling, thus creating OHE.

Characterisation of a Complex CaZr0.9Ce0.1Ti2O7 Glass–Ceramic Produced by Hot Isostatic Pressing

The behaviour of Ce-containing zirconolites in hot isostatically pressed (HIPed) materials is complex, characterised by redox interactions between the metallic HIP canister that result in reduction of Ce4+ to Ce3+. In this work, a glass–ceramic of composition 70 wt.% CaZr0.9Ce0.1Ti2O7 ceramic in 30 wt.% Na2Al2Si6O16 glass was produced by HIP (approx. 170 cm3 canister) to examine the extent of the material–canister interaction. A complex material with six distinct regions was produced, with the extent of Ce reduction varying depending on the distance from the canister. Notably, the innermost bulk regions (those approximately 7 mm from the canister) contained only Ce4+, demonstrating that a production-scale HIPed glass–ceramic would indeed have a bulk region unaffected by the reducing environment induced by a ferrous HIP canister despite the flow of glass at the HIP temperature. Each of the six regions was characterised by XRD (including Rietveld method refinements), SEM/EDX and linear combination fitting of Ce L3-edge XANES spectra. Regions in the lower part of the canister were found to contain a significantly higher fraction of Ce4+ compared to the upper regions. Though zirconolite-2M was the major crystalline phase observed in all regions, the relative abundances of minor phases (including sphene, baddeleyite, rutile and perovskite) were higher in the outermost regions, which comprised a significantly reduced Ce inventory.

Enhanced magnetocaloric effect by modifying the intergranular phase via V-addition in La2/3Ca1/3MnO3 composites

Vanadium oxides (V2O5) with relatively low melting point (963 K) was found to be an effective sintering aid for forming multiphase nanocomposite of La2/3Ca1/3MnO3. The polycrystalline perovskites with a nominal composition of La2/3Ca1/3Mn1−xVxO3 (0 ≤ x ≤ 0.12) were prepared by the liquid-phase sintering method. The structure, magnetic properties and magnetocaloric effect (MCE) were investigated. The study on microstructure revealed that the composites consist of a major crystalline phase of La2/3 Ca1/3MnO3 and intergranular phases of Ca10V6O25 and La2MnO4.15 at the grain boundary. All the samples undergo the first-order phase transition at the Curie temperature. V-addition leads to a reduction of the Curie temperature, but significantly improves the MCE. The maximal magnetic entropy change of 3.8 J/kg K was achieved for x = 0.08 under an applied field of 0.5 T, almost twice as high as the un-doped sample. The result implies that the control of intergranular phases is a potential way to improve the MCE in perovskite manganites. The enhancement of MCE could be attributed to spin-polarized tunneling or spin-dependent scattering of polarized electrons at the grain boundaries.