Heating Stage Microscope Research Articles

The B2O3/SiO2 ratio and dwelling time dependent crystallization behavior, phase formation, microstructural features, and thermal behavior of SrO-CaO-Al2O3-ZnO-B2O3-SiO2-TiO2 glass system

In the present study, the SrO-CaO-ZnO-Al2O3-B2O3-SiO2-TiO2 - based glass system is studied to investigate the effect of B2O3/SiO2 ratio and heat treatment dwell time on crystallization, phase development, and microstructural features in monolithic glass. The density of glasses increases with the increase in B2O3/SiO2 ratio as B2O3 has a higher molar mass than SiO2. The XRD patterns revealed that an increase in B2O3/SiO2 ratio facilitates the crystallization as evident in the case of glass of largest B2O3/SiO2 ratio (? 0.4) at 10 h dwelling at 850?C. However, at higher dwell time i.e. 20 and 30h, all glass specimens transformed to glass-ceramic, indicating a vital role of heat treatment time on crystallization. Scanning electron microscopic examination revealed that with the increase in the B2O3/SiO2 ratio, the anisotropic growth of crystals increases which is prominent for the glass having B2O3/SiO2 ratio (? 0.4). In addition, the corresponding temperature for various thermal events like sintering, softening, half-sphere, and melting is evaluated as a function of temperature at varying heating rates with the help of a heating stage microscope. The increase in heating rate, enhance the temperature for sintering, softening, and melting due the delayed arrival of required thermal energy as recorded in the heating stage microscope system.

Elevating clean energy through sludge: A comprehensive study of hydrothermal carbonization and co-gasification technologies

This study explores the recycling challenges of industrial sludge, owing to its non-recyclable properties and associated environmental problems. To promote sustainable energy utilization, a novel approach combining hydrothermal carbonization and co-gasification was employed to facilitate the conversion from waste to energy. The industrial sludge was pretreated in the batch-type hydrothermal treatment unit at 180–220 °C, followed by co-gasification. The experimental results indicate that pretreating the sludge at the hydrothermal temperature of 200 °C maximized its thermal decomposition, leading to a rougher structure with obvious cracks, eventually transforming into numerous fragmented small particles. At 1100 °C with a blending mass ratio of 1:1, the sludge hydrochar at 200 °C significantly enhanced the reactivity of coal char, exhibiting the gasification reactivity index R0.9 of 1.57 times higher than that of untreated char. Using the in-situ technique with the heating stage microscope, it was first observed that the addition of pretreated sludge coal chars underwent gasification in the shrinking core mode, displaying a significant ash melt flow phenomenon. Based on the in-situ X-ray diffraction, it was discovered that more amorphous structures were formed by the reaction of Fe with other minerals in the sludge-coal blended char after hydrothermal carbonization at 200 °C. With pretreatment at the hydrothermal temperature of 200 °C, the sludge can increase the specific surface area of the blended char and facilitate the cracking of carbon crystals during co-gasification. Its specific surface area and the Raman spectroscopic ratio ID1/IG were 1.76 and 1.17 times that of coal char, respectively. Collectively, this study highlights the potential for energy recovery from industrial sludge, contributing to sustainable waste management in the chemical industry.

Effects of phosphorus on the fusion characteristics of synthetic ashes with different Al2O3/CaO ratios

In this paper, five series of synthetic ashes with different Al2O3/CaO ratio mass ratios were prepared, and the ash fusion temperatures (AFTs) of the samples with different percentages (5–20 wt%) of phosphorus pentoxide (P2O5) added were measured under a mild reducing atmosphere to study the effect of phosphorus on the fusion characteristics of the ashes in different compositions. X-ray diffraction (XRD), thermodynamic equilibrium calculations, and high-temperature heating stage microscopy (HHSM) were used to investigate the mechanism of phosphorus in changing the fusion characteristics of the ash. The results showed that the addition of P2O5 produced the least effect on AFTs of samples with an Al2O3/CaO ratio of 6:4. For lower Al2O3/CaO ratios (classified as peralkaline), the addition of P2O5 caused a decrease-increase-decrease trend in AFTs, while for higher Al2O3/CaO ratios (classified as peraluminous), the AFTs of samples were decreased by phosphorus. The stronger affinity of P2O5 for CaO and Al2O3, compared to that of SiO2, was noticed and led to a shift of main minerals in the slag from silicates to phosphates and to the isolation of SiO2. In addition, the phosphorus-bearing samples followed the same “melt-dissolution mechanism” as the phosphorus-free samples.

Structural characterization of char during co-gasification from torrefied sludge and Yangchangwan bituminous coal

The present study aims to investigate the physico-chemical structural evolution characteristics of char structure of CO2 atmosphere torrefaction pretreated sludge with Yangchangwan bituminous coal (YC) during co-gasification. The co-gasification reactivity of torrefied sludge and YC was measured using a thermogravimetric analyzer. The co-gasification reactivity of torrefied sludge with YC was thoroughly explored in depth by in situ heating stage microscope coupled with traditional characterization means of char sample (Scanning electron microscope, nitrogen adsorption analyzer, laser Raman spectroscopy). The results show that the gasification reaction rate of sludge treated under CO2 atmosphere and coal blended char was better than other char samples at 1100–1200 °C. The torrefied sludge under CO2 atmosphere promoted its thermal decomposition to the maximum extent, so that it eventually was transformed into a large number of small broken particles. The specific surface area and ID1/IG ratio of blended char of torrefied sludge under CO2 atmosphere and YC were 1.70 and 1.07 times higher than that of YC, respectively. The in situ technique revealed that YC char with the addition of torrefied sludge undergo gasification by shrinking core modes and the presence of obvious ash melting flow phenomenon. It was more obvious than that of YC.

Reappraising Crystallization Kinetics with Overgrowth Chronometry: an in Situ Study of Olivine Growth Velocities

Abstract We investigated the early stages of olivine crystal growth via in situ seeded experiments in a single plagioclase-hosted melt inclusion, using a heating stage microscope. Each experiment was subjected to a cooling ramp of 7800°C/h followed by an isothermal dwell at 19°C, 38°C, 57°C, 77°C, 96°C or 129°C of undercooling. The seeds (6–16 μm in diameter Ø) grew into large crystals (Ø 80–169 μm) in 3 to 30 min through the symmetrical development of tabular, skeletal, and dendritic overgrowths as the undercooling of the system increased. Time-resolved image processing and incremental measurements of the overgrowth thicknesses indicate up to three stages of crystal growth: an acceleration stage, a linear (constant growth rate) stage, and a deceleration stage. At the isotherm, the growth velocities reach a stable maximum that in all experiments corresponds to the period of linear growth. The highest linear values are measured at the $\left\{101\right\}$ interfaces, from 2.1 × 10−8 m/s at 19°C of undercooling to 4.8 × 10−7 m/s at 129°C of undercooling. Crystal growth is slower at other interfaces, in the ranges 1.9–7.6 × 10−8 m/s and 4.5 × 10−9 – 7.6 × 10−8 m/s for the $\left\{100\right\}$ and $\left\{001\right\}$ forms, respectively. Growth in the $<010>$ dimension appears limited to less than 2.4 × 10−8 m/s at 129°C of undercooling. We constrain the uncertainty on these growth velocities, which includes the environmental conditions (± 8.6°C on the nominal undercooling) and the measurements of crystal lengths (underestimated by <16% at most fast interfaces). A systematic and comprehensive review of 19 pre-existing datasets indicates that our linear growth velocities are faster than most growth rates determined at comparable undercoolings. Growth rates determined as half crystal lengths divided by total time are intrinsically low estimates of the true maximum, linear growth velocities, because the total time includes periods of slower or non-growth, and measured crystal dimensions are subject to projection foreshortening or truncation. These errors can lead to values that are several times to several orders of magnitude lower than the true maximum growth rates. This study completes and refines previously published data on the crystallization kinetics of olivine, highlighting the sensitivity of growth rates to specific environmental conditions and measurement methods. We emphasize the importance of symmetrical growth and true maximum growth velocities for interpreting olivine growth histories.

In-situ analysis of the sintering behavior of coal ash and a phosphorus-rich biomass ash under gasification condition

The relatively high contents of some ash-forming elements (Na, K, Ca, Mg, P) in biomass ash can cause serious ash-related problems (deposition, slagging, corrosion, etc.) during the co-gasification of coal and biomass, influencing the stable operation of gasifier. The sintering behavior of Jincheng coal ash (JCA) and a phosphorus-rich Jatropha seed cake ash (JSCA) were investigated by in-situ heating stage microscopy, while the sintering mechanism was revealed by phase studies employing X-ray powder diffraction and thermodynamic modelling. Results indicated that the sintering temperature of blended ashes reached the minimum at the 20 wt% blending ratio of JSCA in the coal-biomass ash mixture. The high sintering temperatures of JCA and JSCA were due to the extensive mullite and quartz crystallization in the high acidic JCA system and the widespread formation of K–Ca phosphate and K–Mg phosphate in the high basic JSCA system, respectively. The transition of the phosphorus from fluxing effect to refractory effect on the sintering of ash mixture was identified at the 20 wt% blending ratio of JSCA. It was also found that the role of mullite and quartz decreased, while the role of anorthite, gehlenite, leucite, and calcium phosphate increased with increasing JSCA content, leading to the lowest sintering temperature. Finally, the variation trend of sintering temperatures against the JSCA additions was in accord with the change of the liquidus temperatures that was calculated by thermodynamic modelling. These observations can be used for the potential prediction of the ash sintering temperature in the coal-biomass gasifier.

Comparative observation of the flow behavior of low- and high-temperature ashes of biomass

Biomass ashes are frequently known for their limiting effects in thermochemical conversion processes. Thus, a comprehensive understanding and prediction of the temperature-depending behavior of the ashes is indispensable for practical applications. In the present study, the flow behavior of low-temperature ash (LTA) and high-temperature ash (HTA) of biomass is investigated in detail and monitored by in situ methods. For this purpose, the mineral matter formation and transformation of both ashes are studied by X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis. A combination of heating-stage microscope and scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (SEM-EDX) has enabled a systematic identification of the microstructures and observations of LTA and HTA. The results have illustrated an associated release of K and Cl and the formation of new mineral phases in the remaining material during ashing at increased temperature. Both ashes have exhibited flow temperatures below 1100 °C and a rarely observed behavior of higher characteristic temperatures for LTA than for HTA is detected. From the heating-stage microscopy, the ashes have given evidence to a significant formation of slag at the characteristic temperatures and a viscosity-driven behavior at the characteristic points of ash fusion. Based on these results, a conclusion can be drawn regarding the usability of this biomass for high-temperature conversion processes on the industrial scale.

Glass-ceramic joining of Fe22Cr porous alloy to Crofer22APU: interfacial issues and mechanical properties

This work deals with the joining of porous Fe22Cr ferritic stainless steel to a dense Crofer22APU plate by using a silica-based, Ba-containing glass-ceramic. The chemical and interfacial stability and the mechanical properties of the joints were evaluated before and after thermal ageing at 700 °C for 500hrs. The sintering behaviour of the glass was assessed by using heating stage microscopy (HSM) to study the influence of a porous metal substrate on the shrinkage of the joining material. Scanning electron microscopy revealed that there were no defects or cracks at the porous alloy/glass-ceramic interface for both the as-joined samples and the samples after thermal ageing at 700 °C for 500 h. However, at this exposure temperature, the porous alloy started to form an oxide scale at the interface with the glass-ceramic and the internal surface of the porous alloy. Finally, the evaluation of the mechanical properties by tensile testing showed that the properties were not affected by thermal ageing at 700 °C.

Shear-thinning sacrificial ink for fabrication of Biosilicate® osteoconductive scaffolds by material extrusion 3D printing

Osteoconductive scaffolds are required to stimulate and enhance the regenerative potential of cells in bone tissue engineering applications. Additive manufacturing (AM), popularly known as 3D printing, has been widely used to fabricate these porous structures. In this study, bioceramic scaffolds based on highly bioactive glass-ceramic (Biosilicate®) were developed and characterized using a hydrogel as sacrificial ink for material extrusion 3D printing. A paste containing Biosilicate as solid filler was developed from a sacrificial ink whose formulation is based on poly(ethylene glycol) (PEG-400) with 7.5% (w/w) Laponite® nanoclay as rheological modifier. Initially, the rheological behaviors of the sacrificial ink (PL) and of the ceramic paste with 70% (v/v) Biosilicate (PL-BioS) were evaluated. Viscosity of the PL increased with addition of Biosilicate, showing a shear-thinning behavior appropriate to material extrusion 3D printing. After that, samples were 3D printed and dried at 20 and 50 °C. The dimensional characteristics of the samples were evaluated and compared, and showed that drying at 20 °C resulted in lower degree of shrinkage and mass loss before sintering. Preliminary heating stage microscopy tests were performed to define the sintering parameters, and then the scaffolds were sintered at 900 °C for 5 h at a heating rate of 1 °C/min. The sintered scaffolds were analyzed by FTIR, XRD, and SEM. These characterizations showed that the PL was eliminated from the structure with no significant change in scaffold composition, which remained intact after this process, and that the residual Laponite improved scaffold strength with formation of micropores internally to the filaments. An in vitro biological study confirmed the nontoxic behavior of the developed scaffolds on NHI-3T3 fibroblast-like cells, showing suitable cell adhesion, growth and proliferation on their surface, which are associated with good osteoconductive properties. In conclusion, the use of PL gels combined with Biosilicate is promising for ceramic ink formulation, considering that shear-thinning materials facilitate the 3D printing process. Moreover, preliminary mechanical and biological results reveal the potential of the sintered scaffolds for use in bone tissue engineering.

In-situ study of fractal properties of coal char particles during catalytic gasification

Interactions of potassium-based catalysts with Shenfu (SF) char during catalytic gasification was observed by an in-situ heating stage microscope. The effects of the gasification temperature (800–900 °C) and the catalyst loading (4.4%, 10%) on the reactivity of coal char were investigated. The heating stage microscopy was used to visualize the catalytic gasification process of coal char particles and the fractal theory was introduced to analyze the surface structure of coal char particles to reveal the gasification reactivity. The experimental results show that the fractal dimension of coal char particles is positively correlated with the carbon conversion rate, and the fractal dimension increases by increasing the gasification temperature and the catalyst loading. The relationship between the initial gasification reaction rate and the fractal dimension of coal char particles is consistent with that between the carbon conversion rate and the fractal dimension of coal char particles. There is an exponential relation between the fractal dimension of coal char and the char angle; the fractal dimension increases with the increase of coal char particle angle; and the fractal dimension of coal char particles can be used in the study of coal char catalytic gasification process.

Effect of phosphorus-based additives on ash fusion characteristics of high-sodium coal under gasification condition

Ash fusion characteristics and melting mechanism of two high-sodium coals including Luan (LA) and Hongshaquan (HSQ) with addition of ammonium dihydrogen phosphate and tricalcium phosphate under gasification condition were investigated to reveal reactions between phosphorus-based additives and high-sodium coal ash in detail. Methods such as ash fusion test, X-ray diffraction, and high temperature heating stage microscope were used for that purpose. High-sodium coal ashes have low ash fusion temperatures (AFTs) due to their high SiO2/Al2O3 ratio and alkaline and alkaline-earth contents. Low-temperature eutectics are formed between nepheline and akermanite, as well as anorthite and akermanite at 1210 °C and 1274 °C, respectively. Phosphorus has a higher affinity to alkaline and alkaline-earth metals for the higher ionic potential of acidic components than basic components. As a result, high melting point phosphates like Ca9MgNa(PO4)7, Ca9Fe(PO4)7, and Na3Ca6(PO4)5 are generated in coal ash with phosphorus-based additives. Additionally, when PO43-/Na molar ratio increases, contents of quartz and phosphates are also increased, which enhance the formation of skeleton structure with high AFTs. However, the formation of low-temperature eutectic mixtures of Fe-Na silicates accelerates the melting process of coal ash, which weak the enhanced AFTs of high-sodium coal by phosphorus-based additives. Furthermore, the melting mechanism of high-sodium coal ash with and without phosphorous-based additives follows the “melting-dissolution” mechanism.

Dancing and recrystallizing of Na2CO3 particles during catalytic gasification: Instructing the industrial catalysts loading procedures

The migrating of alkali at high temperature is closely related to catalytic gasification, activated carbon preparation and volatilization of alkali. In this work, a simple but effective and visible method was used to reveal the newfound migrating modes between Na2CO3 particles and coal char by situ heating stage microscope. Moreover, the effects of Na2CO3 migration on the gasification and the catalyst-loaded procedure were also evaluated. The video results recorded by microscope visually shows that Brownian motion and recrystallization of Na2CO3 particles contribute to the migration between Na2CO3 and coal during catalytic gasification. Brownian motion acts on the small Na2CO3 particles (<20 μm) and recrystallization acts on the big particles. The results show that Na2CO3 particles (<20 μm) actively moves at temperatures range of 660–730 °C, and when the moving Na2CO3 closes to the coal char particles, the coal char draws the jumping Na2CO3 particles, and the moving Na2CO3 particles adheres to the coal char surface. For the big Na2CO3 particles, lots of tiny particles can migrate to coal char by recrystallization in the surrounding of Na2CO3 particles, and the coal char has priority to attract the recrystallization of the tiny particle on the coal char surface. The Brownian motion and recrystallization complete Na2CO3 migration from Na2CO3 to coal, and Na2CO3 loaded by mechanical mixing can complete even Na dispersion as impregnation method does.

Study on high temperature gasification kinetics of coal char by TGA and in situ heating stage microscope

Study on high temperature gasification kinetics of coal char by TGA and in situ heating stage microscope

The characteristics of maceral in Huangling coal and its in-situ pyrolysis

In order to reveal the pyrolysis and coking characteristics of different components in coal, the macerals in Huangling coal were enriched by centrifugation, and the pyrolysis characteristics of macerals were studied. The transformation characteristics of macerals during pyrolysis were observed in-situ by heating stage microscope. The purities of vitrinite and inertinite are more than 90% and 80%, respectively, while the purity of liptinite is nearly 70%. The initial pyrolysis temperature of liptinite is about 385°C, and those of the other macerals are all about 410°C. The maximum pyrolysis temperatures are between 470–480°C for all macerals studied. The maximum weight loss rate and the total weight loss rate decrease in the order of liptinite, vitrinite, semi-vitrinite and inertinite. The softening temperature of the liptinite (including sapropelic groundmass) is 350–370°C, while that of vitrinite is about 410–420°C as shown by the in-situ pyrolysis in a heating stage microscope. The pyrolysis process of vitrinite goes through the stages of edge shrinking, pore formation, surface softening, the formation of liquid phase, and solidification. Only slight morphological changes are observed in semi-vitrinite, while no changes are observed in inertinite. The active components in Huangling coal are vitrinite and liptinite, and the liptinite can promote the softening and melting characteristics of the adjacent vitrinite.

Insights into the role of calcium during coal gasification in the presence of silicon and aluminum

Clarifying the effect of other inert minerals on the catalytic performance of Ca in coal gasification is critical and meaningful to understand the deactivation mechanism of catalyst. In this work, four coal samples, demineralized coal (Dem-coal), coal loaded Ca (Ca + Dem-coal), coal containing Si and Al ((Si, Al)-coal), and coal loaded Ca, Si, and Al (Ca+(Si, Al)-coal), were prepared to analyze the impact of interactions on gasification reactivity. The gasification activity of coal samples with CO2 agent at 900 °C was evaluated via thermal gravimetric analyzer (TGA). An in-situ heating stage microscope was applied to record the change of morphology of coal particles in the whole process. Besides, Factsage thermodynamic calculations were combined with in-situ X-ray diffraction (XRD) results to investigate the evolution of minerals including Ca, Si, and Al. The results indicate that Ca presenting in the form of CaO exhibits excellent catalytic performance. Si and Al existing in the form of SiO2 crystals and amorphous structure respectively, hinder the process severely. Noticeably, the interactions of Si, Al, and Ca has a catalytic effect on coal gasification, though the gasification reactivity of Ca+(Si, Al)-coal is a bit lower than that of Ca + Dem-coal. In-situ XRD results confirmed the formation of CaSiO3, Ca2SiO4, and Ca2Al2SiO7, suggesting that these Ca complexes are catalytically active, but the catalytic performance of them is inferior to that of CaO. The evidence proved powerfully that it is not the reactions among Ca, Si, and Al which caused the deactivation of Ca catalyst.

Fluorescence and Micro-FTIR characteristics of typical liptinite at low temperature thermal conversion

The subgroups and contents of liptinite have significant influence on yields of tar and gas in pyrolysis.The heating stage microscope, fluorescence analysis and Micro-FTIR were used to study the characteristics of typical liptinite at low temperature thermal conversion. The results showed that the relative fluorescent intensities decreased and the maximum fluorescence wavelength increased as the pyrolysis temperature increase. The fluorescence characteristics of resinite and suberinite began to change at 240 ℃, and remarkable changed at 280−320 ℃. The fluorescence characteristics of sporinite, cutinite, and bituminite A began to change at 280 ℃, and remarkable changed at 320−360 ℃. The fluorescence characteristic of alginite began to change at 280 ℃, and lasting changed till 400 ℃. The fluorescence characteristic of bituminite B changed at 320−360 ℃. The absorption peak of aliphatic compound in alginite was strongest, and the peaks of bituminite, resinite, cutinite, and sporinite decreased in turn. The aliphatic compounds and oxygen-containing groups of liptinite group decreased and the content of aromatic hydrocarbon relatively increased as the temperature increase. The aromatization degree of liptinite group was low and basically remain unchanged at low temperature thermal conversion. The hydrogen-rich degrees and the change of aliphatic chains of liptinite group confirmed well with the fluorescence characteristics.

In-situ investigation of melting characteristics of waste selective catalytic reduction catalysts during harmless melting treatment

Selective catalytic reduction (SCR) catalyst waste is a hazardous solid waste that seriously threatens the environment and public health. In this study, a thermal melting technology is proposed for the treatment of waste SCR catalysts. The melting characteristics and mineral phase transformation of waste SCR catalysts blended with three different groups of additives were explored by heating stage microscopy, thermogravimetric analysis/differential scanning calorimetry (TG/DSC) analysis, thermodynamic simulation, and X-ray diffraction (XRD) analysis; heavy metal leaching toxicity was tested by inductively coupled plasma-atomic emission spectrometry (ICP-AES) analysis. The results indicated that the melting point of waste SCR catalysts can be effectively reduced with proper additives. The additive formula of 39.00% Fe2O3 (in weight), 6.50% CaO, 3.30% SiO2, and 1.20% Al2O3 achieves the optimal fluxing behavior, significantly decreasing the initial melting temperature from 1223 °C to 1169 °C. Furthermore, the whole heating process of waste SCR catalysts can be divided into three stages: the solid reaction stage, the sintering stage, and the primary melting stage. The leaching concentrations of V, As, Pb, and Se are significantly reduced, from 10.64, 1.054, 0.195, and 0.347 mg/L to 0.178, 0.025, 0.048, and 0.003 mg/L, respectively, much lower than the standard limits after melting treatment, showing the strong immobilization capacity of optimal additives for heavy metals in waste SCR catalysts. The results demonstrate the feasibility of harmless melting treatments for waste SCR catalysts with relatively low energy consumption, providing theoretical support for a novel method of disposing of hazardous waste SCR catalysts.

Morphological changes and ash fusibility of coal, rice straw and their mixture during CO2 gasification

The gasification behavior of single particle of coal, rice straw, and coal-rice straw mixture were investigated by in-situ heating stage microscope, X-ray diffraction, and scanning electron microscopy. The gasification process of coal particle can be divided into three stages consisting of swelling stage, shrinkage stage, and ash fusion stage, while the swelling stage is not observed for the gasification of rice straw particle. The presence of rice straw particle facilitates the shrinkage of coal particle during the co-gasification process due to the migration and catalytic effect of alkaline components which are abundant in biomass. Further, it was found that the average melting temperature of particles is close to the deformation temperature (DT) of ash sample, implying that the DT may reflect the melting properties of particles in a real gasifier. Finally, the ash fusion mechanisms were explored. It was identified that the formation of high-melting points mullite, quartz and anorthite are responsible for the high ash fusion temperatures of coal (with flow temperature over 1500 °C). The addition of 20 wt% rice straw (with flow temperature of 1133 °C) to coal improves the formation of lower-melting points minerals containing alkaline and alkaline-earth elements, and sulphur in the mixture that facilitates the ash fusion process and induces the slag formation. Thus, the flow temperature of the mixture decreases to 1369 °C. The ash fusion behavior of coal follows the “softening-melting” mechanism, while this behavior of rice straw shows a typical “melting-dissolution” mechanism. The ash fusion behavior of coal-rice straw mixture reveals both mechanisms; however, the “melting-dissolution” mechanism seems to be more characteristic for this mixture.

Mica (KMg3AlSi3O10F2) based glass-ceramic composite sealant with thermal stability for SOFC application

In this work, pre-synthesized fluorophlogopite mica (KMg3AlSi3O10F2) crystalline powder was added into potassium-magnesium boro-alumino-silicate (K2O–MgO–B2O3–Al2O3–SiO2) glass powder to synthesize glass-ceramic composite (GCC) sealant for solid oxide fuel cell (SOFC) application. The basic purpose was to report the influence of KMg3AlSi3O10F2 on microstructure, thermal expansion and volume shrinkage behavior of GCCs in terms of their SOFC sealing ability. The predominant crystalline phase was also identified as fluorophlogopite mica (KMg3AlSi3O10F2) by X-ray diffraction in the GCCs heat-treated at 900 °C (for 2 h) followed by 800 °C (for 10 h). Higher thermal expansion (10.65–10.81 × 10−6/K at 50–800 °C) compatible with SOFC components (metallic electrode/interconnect, ceramic electrolyte) was realized for 5–10 wt % mica containing GCC. However, it was found decreased linearly with adding further KMg3AlSi3O10F2 content (20–40 wt%) in the composites. GCC with 5 wt % of mica was stable under thermal cycling testing and no significant degradation was observed in thermal expansion till 10 cycles. Field emission scanning electron microscopy revealed the spherical shaped nanocrystallites morphology of those GCCs and that was ascribed for their compact bonding with SOFC components. Heating stage microscopy (HSM) ensured the lower softening temperature (752 ± 7 °C) for 5 wt % mica containing GCC which furthermore showed 11–13% volume shrinkage (to ensure the self-healing) in SOFC operating temperature. In a summary, the above factors confirmed the suitability of 5 wt % mica (KMg3AlSi3O10F2) containing K2O–MgO–B2O3–Al2O3–SiO2 system (GCC) for SOFC sealant application.

Investigation into the flow behavior of high-temperature ash and low-temperature ash of high calcium coal

The flow behavior of high-temperature ash (HTA) and low-temperature ash (LTA) of high calcium coal in the heating process was investigated systematically. By means of the heating stage microscope, the behavioral changes of samples were studied visually. The composition and mineral matters transformations of HTA and LTA samples were analyzed by X-ray fluorescence and X-ray diffraction. The results show that the original composition of HTA sample is different from that of LTA sample. In addition, the HTA and LTA samples experience the shrinkage, fusion and spreading processes in succession. However, the volume change of HTA sample is different from that of LTA sample. The volume of LTA sample shows a slow change at the temperature lower than 800 °C, while the volume of HTA sample is unchanged. In the temperature range of 800°C–1100 °C, the remarkable shrinkage of HTA and LTA samples are demonstrated. The formation of srebrodolskite and gehlenite attributes to this volume change. Moreover, the sharp shrinkage of HTA and LTA samples is indicated at 1100°C–1300 °C. This is caused by the formation of eutectics. Because of the diverse content and species of mineral matters in LTA sample, the volume change of LTA sample is more remarkable than that of HTA sample. The maximal shrinkages of LTA and HTA sample are 57% and 53%, respectively.