Fluxing Agent Research Articles

Examining the properties, behaviour in firing and potential application of coal mine overburden for stoneware ceramics

Purpose. A binary mixture of a ceramic body was studied, incorporating overburden from a coal mine site in Bontang, East Kalimantan, Indonesia. This overburden material has been tested for the manufacture of stone-ceramic body. Methods. The initial characterization of overburden materials includes testing the chemical composition by XRF analysis and mineral content by XRD analysis on raw materials and overburden exposed to high temperature. The composition of ceramic specimens is a mixture of 85% overburden material and 15% fine sand. Firing temperatures in the range of 900-1100°C were applied to the ceramic body specimen. Then, ceramic properties, such as physical color, plasticity, shrinkage, water absorption and density were analyzed. Findings. The results show that the ceramic specimen experiences densification when exposed to high temperature in this range, which in turn contributes to low water absorption and high flexural strength. This ultimately results in low water absorption below 1.0% at 1100°C, which is favorable for stoneware type of ceramics. The mechanical properties of specimen at 1000°C is in accordance with stoneware body standard. In addition to this, it is believed to be more energy efficient, since the low firing temperature is sufficient to achieve the stoneware specification. Originality. The binary clay-based ceramic have been tested using coal mine overburden and river sand with a high Fe2O3 content. Together with the presence of alkali oxides and calcium in the raw materials, this can potentially reduce the use of fluxing agent. A comprehensive study has been conducted on the characteristics, firing effect and application of stoneware. Practical implications. Some ceramic prototypes from this result were also made using a rotary technique and heated in this temperature range. Since overburden is generally considered to be backfill material, the selective clay material application for ceramics can provide the potential to stimulate local product innovation by utilizing easily available overburden materials.

Fluidization-melting characteristics of fly ash from municipal solid waste incineration

Fly ash (FA) from municipal solid waste incineration contains hazardous substances such as dioxins, furans, and heavy metals. Melting FA has proved to be an effective method for reducing volume and mass, while also rendering the waste harmless. However, during the melting process, the addition of a fluxing agent with calorific value is currently necessary to increase melting capacity and reduce energy consumption, which presents a challenge. To tackle this issue, a fluidization-melting technology for a fuel/FA mixture is proposed, wherein a fuel source is employed in the melting process, producing ash that can serve as a fluxing agent. To test this approach, rice husk (RH) was utilized as fuel in a small-scale fluidization-melting test. The objective of this study was to examine the operation parameters of the platform and the characteristics of the resulting product, and to evaluate the harm reduction effect of the slag and its potential for resource utilization. The operating temperature was set at 690 °C in the thermal modification unit and at 1450 °C in the melting furnace, resulting in stable operation and continuous liquid slag discharge. The leaching toxicity of heavy metals in the obtained slag was lower than the standard limit, achieving harmless disposal of FA. However, the resource utilization potential of the obtained slag is limited due to its failure to meet the criteria of vitrified substance and environmental quality requirements. These limitations could be addressed by promoting the combustion of carbon in the melting furnace and accelerating the cooling rate of the slag in the quenching unit.

Increased NIR photoluminescence of Egyptian blue via matrix effect optimization

The exceptionally high NIR photoluminescence of the ancient pigment Egyptian blue is due to its very stable phase cuprorivaite (CaCuSi4O10). This compound has recently attracted significant attention, leading to numerous applications for sensors, luminescent solar concentrators, energy-saving, and biomedicine. Here we report an innovative manufacturing process for producing high-grade cuprorivaite, characterized by fine crystal grains and a significantly increased NIR photoluminescence emission. The unprecedented ultra-high NIR emission (quantum yield ΦEM ≈ 30 %) is almost three times higher than the best one reported so far. This is an important turning point for the extension of applications of cuprorivaite to new sectors and can greatly boost its exploitation. The new high-efficiency cuprorivaite is obtained by solid-state synthesis, using silica nanoparticles as a starting material and avoiding fluxing agents. No doping with rare-earths or other elements has been employed, making synthesis straightforward and sustainable. The material obtained has been fully characterized in terms of crystalline, morphological, and optical properties and compared to cuprorivaite obtained through traditional melt-flux synthesis. The main difference observed is that the tiny crystals obtained through the new synthesis method are practically devoid of the glassy phase, rich in copper and impurities, that is instead largely present in Egyptian Blue pigment synthesized with traditional melt-flux synthesis. We speculate that this glassy phase is responsible for the partial suppression of the intrinsic photoluminescence of cuprorivaite, demonstrating how limiting the glassy phase can increase the external quantum efficiency of Egyptian blue.

Study of the Synthesis Variables in the Preparation of CoAl2O4 Pigment Using Microwaves to Reduce Energetic Consumption

Due to the importance of optimizing the manufacture of ceramic pigments, motivated by the increase in prices of both raw materials and energy, and the need to control manufacturing parameters to obtain optimal conditions for the preparation of ceramic inks, two synthesis routes (traditional route and coprecipitation) and two calcination methods (traditional oven and microwave oven) are proposed to obtain the blue ceramic pigment CoAl2O4 with the aim of minimizing the use of mineralizers or flux agents and reducing energy consumption in its manufacturing. The pigments prepared were characterized by thermal analysis and structurally by XRD and SEM, with particle sizes below 300 nm observed. Finally, the colorimetric coordinates of glazed tiles with the pigments obtained were characterized. In all cases, the microwave-assisted synthesis increased the color intensity, considerably decreasing the temperature and calcination time, obtaining a particle size under 300 nm with a very narrow size distribution, and substantially improving the energy cost of its preparation and the color development of the final product. The viability of the combination of synthesis by coprecipitation and microwave calcination as a method of industrial preparation of ceramic pigments has been demonstrated.

Improving the transient thermal response and ablation properties of epoxy‐modified silicone rubber composites by adding fluxing agent

AbstractIn this work, transient thermal response and ablation behavior of liquid silicone rubber composites containing fluxing/ceramic forming fillers were investigated under different heat flows using an oxyacetylene flame. The results indicated that the introduction of zinc borate (ZB) and aluminum oxide (Al2O3) effectively reduced the temperature at various depths of the samples, and they improved the thermal insulation properties and lowered pyrolysis rates. The above finding was attributed to the heat absorption arising from water release and melt filling as well as the vitrified reaction of solid melt due to the decomposition of ZB. Besides, the melting and exfoliation of Al2O3 and the formation of aluminum silicate (Al2SiO5) caused heat absorption effect. Additionally, the mass ablation rates and line ablation rates increased with rising heat flows coupling with a decrease of compressive strength of the char layers. In a nutshell, the effect of adding ZB/Al2O3 on the thermal insulation behavior of epoxy‐modified vinyl silicone rubber (EMVSR) composites under different heat flows was elucidtaed. This work served as a reference for the design and preparation of flexible ablative materials for thermal protection applications.

Mineralogical and physico-chemical characterization of alluvial clays from Bamendou-Balessing (West Cameroon): Suitability for ceramics

The alluvial clays of Bamendou-Balessing (West Cameroon) are characterized to evaluate their potential for ceramic products. Four representative samples collected in the study area were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), differential thermal analysis (DTA) coupled with thermogravimetry analysis (TG), X-ray fluorescence (XRF) and physical analyses (particle size distribution and consistency limits). Firing properties of the specimens making from alluvial clays were determined. The alluvial clays are composed of clay minerals (45–64 wt%) dominated by kaolinite (92–98 wt%) with variable contents of illite (1–7 wt%) and vermiculite (0–2 wt%). The non-clay mineral phases are quartz (19–38 wt%) associated with variable proportions of K-feldspar (1–17 wt%) gibbsite (2–5 wt%) and goethite (1–12 wt%). The thermal behavior of the clayey samples shows dehydration of gibbsite and goethite at 281–288 °C and dehydroxylation of kaolinite at 521–524 °C. SiO2 (34.5–47.4 wt%), Al2O3 (25.4–29 wt%) and Fe2O3 (4.8–15.2 wt%) are the main major oxides. Samples G and YG present the most suitable physico-mechanical properties for fired bricks between 850 and 1100 °C (i.e. water absorption 19–29%, bulk density 1.49–1.81 g/cm3, compressive strength 12–23 MPa, metallic sonority, good cohesion). On the contrary, the samples R and B show poor physico-mechanical properties during firing due to their low fluxing agent (feldspar) content and high Fe2O3 content (9–15 wt%). The neoformation of mullite, spinel and cristoballite at 1100 °C occurs in specimens favoring the densification of the ceramic body.

Formation, conversion, and elimination of intermediate spinel phase in MgO/kaolin mixture firing for cordierite

AbstractCordierite ceramic is usually used for diesel particulate filter owing to its excellent low thermal expansion coefficient and high thermal shock resistance properties. However, the co‐exited intermediate spinel phase can deteriorate the thermal and mechanical performances of cordierite ceramic product, because the spinel phase has much higher thermal expansion coefficient comparing to that of cordierite. In this study, two methods are utilized to reduce the spinel impurity in the cordierite ceramic. On the one hand, rational reaction resources were introduced to decrease spinel production. The formation of intermediate spinel phase is systematically researched by X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman characterizations and the results clarified the preference of path “Enstatite + Mullite → Cordierite” for less spinel production in comparison to path “Enstatite + Al2O3 → Cordierite + Spinel.” Additionally, MgO was introduced as fluxing agent to promote liquid‐phase sintering, thus facilitating the conversion of spinel. On the other hand, the sintering schedule was improved by introducing a holding temperature gradient to promote the diffusion of Si4+ and further promote the conversion of spinel into cordierite. With these methods, the residual spinel phase is minimized, the resulting high‐purity cordierite has a 47% reduction in the thermal expansion coefficient from 3.07 × 10−6/K to 1.63 × 10−6/K compared to the original cordierite sample.

Phase evolutions, microstructure and physico-mechanical properties of ceramics from Meiganga kaolin: effect of Na/K2O and CaO addition

ABSTRACT This paper examines the potential use of pegmatite and marble as additives in amalgamation with Meiganga kaolin to produce stoneware products capable to resist high temperatures as well as enhancement the mechanical characteristics. Two series of ceramic products were formulated by partly replacing kaolin with 0, 3, 5 and 7 wt% of both pegmatite and marble wastes. The specimens were sintered at 1000°C, 1050°C and 1100°C. Fired ceramic samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and the microstructure of the products was determined using an environmental scanning electron microscope and energy-dispersive X-ray spectroscopy. Also, the physico-mechanical properties were evaluated. Results divulged that, the addition of pegmatite or marble to kaolin enhances the strength of the ceramic body and act as a fluxing agent by promoting vitrification and glassy phase in clay after firing. The highest flexural strength results were observed with 7 wt% of pegmatite added at 1100 °C, with an increase ~ 35% compared to the control sample. High silica and alumina contents in pegmatite fill in voids, providing densification matrices. The incorporation of pegmatite allows to obtain a ceramic with better mechanical properties and energy saving as compared by the conventional ceramic.

Tunable photoluminescence of intrinsic oxygen vacancies and Bi3+/Eu3+/Li+ tridoped BaZnOS for application in wLEDs

Quaternary wide-band-gap oxychalcogenides (MZnOS, M = Ca, Sr, and Ba) are underexplored inorganic semiconductors compared with pure chalcogenides or oxides, in which more dopants could be simultaneously coordinated by oxide and chalcogenide anions. In this kind of materials, color-tunable photoluminescence (PL) could well be obtained without destructing structure. Due to the need of complex conditions for synthesis compared with Ca(Sr)ZnOS, the unique structure of BaZnOS remains largely unexplored as host for application in lighting/display fields. Spectroscopic measuring combined with XPS and DFT computational studies on pristine BaZnOS reveal that the weak multi-colored self-PL were originated from the intrinsic trap states of oxygen vacancies (VO2+, VO+ and VO0). The crystallographic occupancies of dopants Bi3+/Eu3+ and Li + at Ba2+ and Zn2+ sites, respectively were proved based on the Rietveld refinements and crystal chemistry rules. Tunable and thermally stable PL in the regions of cyan, white and even yellow could be systematically obtained from the BaZnOS: Bi/Eu via changing concentrations of dopants with the help of energy transfer (ET) from the host to dopants as well as Bi to Eu. The effect of unlit Li+ is acting both as charge balancer and fluxing agent for reducing calcination temperature and improving PL efficiency. Finally, as a proof-of-concept experiment, the BaZnOS: Bi/Eu/Li phosphor converted white light emitting diode (pc-wLED) was fabricated and produced attractive performances including high CRI of 82.5, low CCT of 4024 K, CIE coordinates of (0.3462, 0.3531), and luminous efficiency (LE) of 16.5 lm/W. Altogether, the stable Bi/Eu/Li tridoped BaZnOS phosphor is a promising candidate to be applied in lighting/display fields.

Composition modification and plasma vitrification of bottom ash from industrial hazardous waste incineration

Industrial hazardous waste (IHW) incineration bottom ash (BA) contains high-content acidic oxides and a limited amount of basic oxides. This contributes to the vitrification of the BA sample, although it causes a high melting temperature and viscosity. Unfortunately, basic fluxing agents play a negative role in the durability of glassy slag. Hence, the industrial BA melting process requires a comprehensive and accurate composition modification method. In this study, the basicity, complete liquid phase temperature, and viscosity-temperature performance of a BA sample were investigated. The BA sample was melted using a thermal plasma system. Furthermore, environmental sound quality analysis was performed, including the toxicity characteristic leaching procedure and acid loss rate. The results indicate that the BA sample may be directly vitrified, although the melting temperature and viscosity need to be modified. Comprehensively, it was found that 15% CaO addition is the most suitable choice. The BA composition modification sample melted completely, slagging smoothly, transformed mostly to the vitrification state, and the index values of the environmental sound quality analysis were dramatically reduced. It has been proven that appropriate composition modification can not only guarantee the stable BA melting process but also favor the vitrification and solidification of heavy metals.

Comparative Study of the Synthesis of a Red Ceramic Pigment Using Microwave Heat Treatment

In this study, a new red ceramic pigment has been developed within a perovskite structure, and microwave heat treatments have been applied. Those red ceramic pigments within the YAlO3 system doped with chromium with the nominal composition Y0.98Al0.98Cr0.04O3 were synthesized by traditional routes and alternative methods like coprecipitation. Also, heat treatment has been studied comparing a traditional electric and microwave kiln. Different flux agents have been incorporated to improve the synthesis reaction. Prepared pigments have been characterized by X-ray diffraction (XRD) as having a predominant phase of perovskite structure, which is responsible for the red shade, and a minority garnet phase that causes more brown colorations. Studies by Ultraviolet-Visible spectroscopy gave rise to a series of absorption bands that indicate the presence of Cr(III) in the octahedral position corresponding to perovskite and Cr(IV) corresponding to garnet in both the octahedral and tetrahedral positions. The perovskite phase is favored with the use of flux mix, corroborating the UV-visible results and being more pronounced in traditional high temperature thermal treatments. The coprecipitation route has been studied to increase the reactivity of the particles given their nanometric size; however, this reactivity favors a greater appearance of undesirable garnet phases with both types of flux. Scanning Electron Microscopy (SEM) micrographs offer information obtained from the secondary electrons of predominantly cubic crystalline phases with sizes between 1 µm and 2 µm in pigments synthesized via the traditional method and sizes less than 1µm together with the glassy phase in pigments synthesized via coprecipitation. Microwave thermal treatments have been studied, obtaining pigments with a majority structure of perovskite and garnet at lower temperatures and relatively short synthesis times. The feasibility of use in porous single-fired ceramic glazes has been studied, whose chromatic coordinates have been collected using an Ultraviolet-Visible Spectrophotometer based on the CIEL*a*b* system.

Preparation of Coal Gangue-Based Porous Ceramics and Its Application on Pb2+ Cycling Adsorption

The presence of lead in wastewater poses a significant threat to human health. To address this issue, coal gangue-based porous ceramics (CGPC) were developed to remove Pb2+ in wastewater. Coal gangue (CG) waste from Lvliang City, Shanxi province in China was used as raw material, and porosity was introduced through the addition of a pore-forming agent and an extrusion molding process. Properties of CGPC were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) to explore its adsorption mechanism. The researchers examined the impact of pH, dosage of adsorbent, initial concentration, duration of adsorption, and temperature on the adsorption efficiency of CGPC. The CGPC of best performance had a porosity of 32.91% and compressive strength of 20.5 MPa prepared at 800 °C under nitrogen atmosphere with 10 wt% Na2CO3 pore-forming agent and 8 wt% CaO-MnO2 combined fluxing agent. The removal rate of Pb2+ in simulated lead-containing wastewater with a concentration of 200 mg/L reached 99.63%, and the maximum adsorption capacity was 32.15 mg/g. The adsorption process of Pb2+ by CGPC involves chemical adsorption and ion exchange. After being regenerated for seven cycles with 1 mol/L NaOH as the desorption agent, the removal rate of Pb2+ by CGPC still had 72%.

The utilization of silica sand beneficiation cake as a fluxing agent in production of clay brick

The utilization of silica sand beneficiation cake as a fluxing agent in production of clay brick

Flame retardancy, combustion, and ceramization behavior of ceramifiable flame‐retardant room temperature vulcanized silicone rubber foam

AbstractTwo types of ceramifiable flame‐retardant room temperature vulcanized (RTV) silicone rubber foam containing mica power (MP) were prepared by using glass powder (GP) as fluxing agents and aluminum hydroxide (ATH) as flame‐retardant agent, respectively. The flame retardant, combustion behavior, and thermal stability of ceramifiable flame‐retardant RTV silicone rubber foams were investigated. The results show that GP is not conducive to the flame retardancy and thermal stability improvement of the foams. On the contrary, MP and ATH can significantly improve the flame retardancy and thermal stability at high temperatures of the foams. The foams with addition of MP and ATH can reach to a high limiting oxygen index value of 35.8 with V‐0 rating in the vertical combustion test, and the total heat release and total smoke production of the foams are 21.0% and 61.7% lower than of the pure RTV silicone rubber foam, respectively. Furthermore, the structural and morphological changes of the foams under different pyrolysis conditions were studied, so as to reveal its ceramifiable mechanism under different fire scenarios. The results show that GP does not promote the formation of more char residue during pyrolysis, but it can greatly lower the ceramifiable temperature, resulting in a superior ceramic phase char residue. The foams including MP and ATH have a high char residue content; nevertheless, a comparatively higher temperature is necessary to create ceramic phase char residue.

An archaeometric contribution to the interpretation of blue-green glass beads from Iron age Central Italy

Several types of (mostly) blue-green glass beads from Iron-Age archaeological sites in Central Italy were studied using a range of spectroscopic techniques: portable X-Ray Fluorescence spectrometry, Fibre Optics Reflectance Spectroscopy, Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectrometry, micro-Raman spectroscopy and Laser Ablation Inductively Coupled Plasma Mass Spectrometry. Complementary information was gathered from each technique and discussed in the frame of the archaeological typology of the objects. The systematic evaluation of the results allowed us to draw some conclusions on the raw materials employed for primary production and to highlight some provenance indicators in the glass. Some of the beads found in the Iron Age (IA) contexts were preliminarily attributed to the Final Bronze Age (FBA) production based on their typology, and the compositional data obtained in this work confirmed that they were low magnesium high potassium (LMHK) glass, typical of FBA in the Italian peninsula. Other beads were assigned to low magnesium glass (LMG) or high magnesium glass (HMG), thus giving further information on the fluxing agents employed in the Early Iron Age (EIA) and beyond. Colour variations among the beads reflected their chemical composition, with different bead typologies coloured in a specific way. In some instances, it was possible to establish different origins for the colouring raw materials. The provenance of the samples was difficult to place, but the chemical evidence suggested a subdivision within the raw glass used to produce the beads: for one set of samples, a local origin of the glass could be hypothesised, whereas several production sites in the Near East were suggested for most of the beads considered in this study. Some preliminary clues for the local working of imported glass were also highlighted for one typological group.

Development and Performance Characterization of Lightweight Foam Glass Mixed with Coal Waste

Waste glass and fly ash are used as main raw materials, borax is used as fluxing agent, and calcium carbonate is used as foaming agent to prepare foam glass. The main factors affecting the performance of foam glass and the appropriate ratio and process were obtained by single factor test and orthogonal test. The macroscopic physical properties such as thermal conductivity and porosity of the product and XRD, DSC-TG and SEM microscopic performance tests were carried out. The results show that the CaCO3 content is 2%, the fly ash content is 10%, the foaming temperature is 875 °C, and the foaming time is 30 min. The thermal conductivity of the obtained foam glass can reach 0.050 W/(m•k). When the fly ash content is 20%, the compressive strength of the foam glass can reach 6.5 MPa.

Investigation of the presence of metallic phases in brazilian tin-slags

The supply chain of Sn presents social and environmental risks that could threaten the availability of cassiterite, while secondary materials, such as tin-slags, stand as an alternative source for smelters. In this context, this work investigated the presence of occluded metallic phases in Brazilian tin-slags. Chemical analyses of different slags revealed that this fact could be related to high ZrO2 levels, which was also supported by different thermodynamic studies. It was indicated that minor additions of CaO could diminish the melting temperature of these slags, contributing towards the precipitation of metallic prills. Smelting experiments were performed between 1773-1573K with a tin-slag concentrate using limestone as a fluxing agent. It was verified that metallic prills were mostly precipitated in the bottom of the crucible above 1673K. However, at 1573K, a mixture of metallic and oxidized phases was obtained, indicating that low working temperatures lead to losses of Sn in the final slag as metallic inclusions. Further additions of limestone improved the coalescence but did not allow efficient precipitation of these metallic prills. Temperature measurements were performed in a 150 kVA EAF during slag processing, and it was verified that tapping of metal/slag occurred partially below 1573K, justifying the presence of metallic prills in the studied slags. Therefore, an optimization of the process relies both on the dilution of ZrO2 content by a controlled addition of fluxing agents, as well as by an increase in working temperatures. Alternatively, magnetic separation can be used to recover occluded metallic particles from final slags.

Effect of Al and MgO on the simultaneous alloying of diamond wire saw silicon waste and Ti-bearing blast furnace slag

Diamond wire saw silicon waste (DWSSW) and Ti-bearing blast furnace slag (TBFS) are industrial solid wastes that contain large amounts of Si and Ti, whose accumulation unnecessarily wastes resources. In this paper, DWSSW and TBFS were mixed and melted in an induction furnace by simultaneous alloying, and Ti and Si were recovered by a Si-Ti alloy. In addition, the optimal material ratio of DWSSW and TBFS was determined. 10–30% reducing agent Al and 5–15% fluxing agent MgO were added to explore the effect of additives on the co-processing of DWSSW and TBFS. The results showed that Al promoted the reduction of Ti and the recovery of Si. When 20% Al was added, the recovery ratio of Ti in TBFS reached 95.62%, and the recovery ratio of Si reached 80.53%. Adding MgO changed the slag composition, simplified the slag structure, and reduced the viscosity. The recovery ratio of Ti from TBFS reached 96.18% when 15% MgO was added. The two additives promoted the alloying co-processing of DWSSW and TBFS, which provided a more efficient clean utilization process for these two solid wastes.

Luminescence Properties of Y3F[Si3O10]:Ln3+ (Ln = Eu, Tb, Er) with Thalenite-Type Host Lattice and Crystal Structure of Tm3F[Si3O10

With Tm3F[Si3O10], a new representative of the Ln3F[Si3O10] series could be synthesized by the reaction of Tm2O3, TmF3 and SiO2 (molar ratio: 1:1:3), applying an excess of CsBr as a fluxing agent in gas-tightly sealed platinum crucibles for eight days at 750 °C, and designed to yield Tm3F3[Si3O9] or Cs2TmF[Si4O10]. Single crystals of Tm3F[Si3O10] (monoclinic, P21/n; a = 725.04(6), b = 1102.43(9), c = 1032.57(8) pm, β = 97.185(7)°; Z = 4) appear as pale celadon, transparent, air- and water-resistant rhombic plates. According to its thalenite-type structure, Tm3F[Si3O10] contains catena-trisilicate anions [Si3O10]8− and triangular [FTm3]8+ cations. The three crystallographically different Tm3+ cations are coordinated by seven plus one (Tm1) or only seven anions (Tm2 and Tm3) exhibiting a single F− anion for each polyhedron, additional to the majority of O2− anions. Furthermore, the luminescence properties of the isotypic colorless compound Y3F[Si3O10] doped with Eu3+ (red emission), Tb3+ (green emission) and Er3+ (yellow and infrared emission), respectively, are reported in presenting their different excitation and emission spectra.

Systematic study of the effect of K2TiF6 flux content on the microstructure and mechanical properties of Al–B4C composites

Al–B4C Metal matrix composites (MMCs) possess several attractive properties such as high hardness, superior resistance to impact and wear, excellent resistance to chemical agents, neutron absorption capability, etc. While stir-casting is the most economic route for fabricating these MMCs, this requires mitigating the poor wettability and improving the interfacial bonding between B4C particles and Al-melt. Inorganic K2TiF6 salts are generally added to the Al-melt as fluxing agents to enhance wettability. However, a systematic study of the effect of K2TiF6 flux content on the microstructure and mechanical properties of Al–B4C MMCs is still lacking. This work intends to fill this gap. Al-alloy 6061 reinforced with 6 wt% B4C and different amounts of K2TiF6 flux additions (40 wt%, 70 wt%, and 100 wt% with respect to the amount of B4C) were fabricated by combined stir-casting + squeeze-casting. A detailed analysis of the microstructure and mechanical properties of the composites was performed both in the as-cast condition and after T6 heat treatment. It was ascertained that the retention efficiency of the B4C particles in the matrix improved with increasing flux content due to an improvement in the interfacial bonding through the formation of Ti-rich intermetallic phases, and this resulted in an increase in the strength and hardness of the MMCs. Several mechanisms such as grain refinement, load transfer, coefficient of thermal expansion mismatch, and stiffness mismatch contributing to the strengthening of the MMC have been considered in detail to determine their relevance in the fabricated composites.