Open Porosity Research Articles

Effect of Mechanically Activated Nepheline-Syenite Additive on the Physical-Mechanical Properties and Frost Resistance of Ceramic Materials Composed of Illite Clay and Mineral Wool Waste.

This study investigates the coupling effect of mechanically activated nepheline-syenite (NS) and mineral wool melt waste (MWMW) on the physical-mechanical properties of a ceramic body. The results indicate that an optimal amount (10-20%) of NS additive promotes the formation of the smallest pore size from 0.001 to 0.01 µm, as well as improves physical, mechanical, and durability properties of the ceramic samples with MWMW, when fired at temperatures between 1000 and 1080 °C. As the NS content increases, the composition becomes more alkaline, leading to enhanced vitrification and the formation of a glass phase during firing. This reduces open porosity, modifies pore size distribution, and enhances compressive strength and frost resistance. An NS content of 15% produces the best results, increasing the smallest pore fraction and yielding favourable properties, such as reduced open porosity, water absorption and density, increased compressive strength, and does not affect the linear shrinkage. The frost resistance test demonstrates that the coupling effect of NS additive and MWMW improves the samples' resistance to freeze-thaw cycles, with the best performance observed at 15% NS content. The study also highlights the usefulness of structural parameters and ultrasound testing for assessing and predicting the frost resistance of ceramic samples.

Influence of recycled display glass e-waste on ternary dune sand mortar engineering properties

The present study explores the feasibility of using recycled materials from display glass electronic waste (DGE-waste) in the production of cementitious mortars as a granular corrector for dune sand and as a cementitious addition. The effects of the DGE-waste replacement ratio (5–20% with 5% steps by weight of three types of dune sand from three different regions) on the engineering properties of reinforced cementitious composite were experimentally investigated to assess the performance of dune sand mortar. The results show that the incorporation of DGE-waste in dune sand mortar can increase the mechanical strengths (flexural and compressive) by up to 35% and 43%, respectively, and improve the dynamic modulus of elasticity by at most 12% as compared with the control mortar, as well as decrease open porosity by up to 28%, which reduces micro-cracks and voids. When cement is replaced with 15% recycled DGE-waste, the mechanical strength and dynamic modulus of elasticity, as well as open porosity and absorption, are decreased by 4–7% and 17–20%, respectively. Considering the environmental impact and engineering properties, the optimal percentage of DGE-waste incorporation is 15% for cement replacement and 20% for dune sand replacement.

High temperature oxidation behavior of porous MoAlB ceramic from 800 °C to 1100 °C in air

MoAlB possesses the characteristics of both metals and ceramic materials, which has attracted extensive attention due to its excellent high-temperature oxidation resistance. For this reason, porous MoAlB is considered applicable to the practice of filtration under harsh environment. In this study, the high-temperature oxidation behavior of porous MoAlB ceramics is systematically studied at the temperatures ranging from 800 to 1100 °C. According to the results, the porous MoAlB exhibits good oxidation resistance at a maximum temperature of 1000 °C. The oxidation kinetics of porous MoAlB can be divided into three stages, and the estimated activation energies of the three stages are 253.83 kJ·mol−1, 367.48 kJ·mol−1 and 317.84 kJ·mol−1, respectively. In the stable stage at 1000 °C, the quadratic mass gain per unit area shows linearity over time, and the oxidation rate of porous MoAlB reaches 37.31 mg2·cm−4·h−1. As revealed by the analysis of the composition and microstructure of oxide layers, the main components of the oxide layer include MoO3, MoO2, Al2O3, B2O3. With the extension of oxidation time, the content of Al2O3 in the oxide films increases. The average pore size, permeability and open pore porosity of porous MoAlB show a trend of first decreasing and then tending to be stable. In addition, a discussion is conducted on the high-temperature oxidation mechanism of porous MoAlB.

Synergized Tricomponent All-Inorganics Solid Electrolyte for Highly Stable Solid-State Li-Ion Batteries.

Garnet-type oxide Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO) features superior ionic conductivity and good stability toward lithium (Li) metal, but requires high-temperature sintering (≈1200°C) that induces high fabrication cost, poor mechanical processability, and high interface resistance. Here, a novel high-performance tricomponent composite solid electrolyte (CSE) comprising LLZTO-4LiBH4 /xLi3 BN2 H8 is reported, which is prepared by ball milling the LLZTO-4LiBH4 mixture followed by hand milling with Li3 BN2 H8 . Green pellets fabricated by heating the cold-pressed CSE powders at 120°C offer ultrafast room-temperature ionic conductivity (≈1.73×10-3 Scm-1 at 30°C) and ultrahigh Li-ion transference number (≈0.9999), which enable the Li|Li symmetrical cells to cycle over 1600h at 30°C with only 30mV of overpotential. Moreover, the Li|CSE|TiS2 full cells deliver 201mAhg-1 of capacity with long cyclability. These outstanding performances are due to the low open porosity in the electrolyte pellets as well as the high intrinsic ionic conductivity and easy deformability of Li3 BN2 H8 .

Improved corrosion resistance of cathodic arc evaporated Al0.7Cr0.3−xVxN coatings in NaCl-rich media

The corrosion resistance of cathodic arc evaporated Al0.7Cr0.3−xVxN coatings with a vanadium content up to 22.3 at% has been electrochemically tested in a 0.1 M NaCl-solution. Significant improvement in the open porosity and corrosion rate was observed for coatings with higher V-contents, due to a denser and more refined coating morphology. Further reduction in the open porosity rate was achieved through an annealing step in air at 700 °C. Here, the formation of an AlVO4 top-oxide and underlying oxygen-rich V-depletion zone provides additional sealing of the coating surface, whilst reducing the corrosion current density to a final 1.59 × 10−9 A/cm2.

Optimization of the PEO process for in-situ synthesis of SiO2 and hydroxyapatite on Mg alloy and assessment of biodegradation and bioactivity

In the current study, a MgO-based bioactive coating consisting of silicon dioxide (SiO2) and hydroxyapatite (HA) was fabricated on the surface of AZ31 magnesium alloy through the plasma electrolytic oxidation (PEO) method. To achieve the goal, the process conditions were optimized in an electrolyte containing 5 g/L Na3PO4.12H2O, 15 g/L Na2SiO3.9H2O, and 10 g/L C3H7O6CaP with a pH of 12.5 and an electrical conductivity of 30 mS.cm−1. Thereafter, silicon dioxide and hydroxyapatite were simultaneously synthesized in-situ over the PEO process for 10min at an operating voltage of 370 V. The percentage of surficial open porosity of the relevant PEO layer was estimated to be approximately 10.30 % using the ImageJ software. Furthermore, in-vitro corrosion and bioactivity assessments of PEO layer were conducted in the simulated body fluid (SBF) at 37 °C with immersion intervals of up to 10 days. The results of electrochemical impedance spectroscopy (EIS) indicated that the PEO coating containing both SiO2 and HA maintained its protective performance against corrosion over the entire 7 days of immersion in the SBF, whereas the corrosion resistance of the PEO layer with only the synthesized SiO2 experienced a significant decline after 3 days of immersion. Assessment of in-vitro bioactivity over 10 days of immersion in the SBF revealed that the sample with synthesized SiO2 and hydroxyapatite in its PEO layer exhibited a higher potential for hydroxyapatite deposition on the surface compared to SiO2-containing PEO coating.

THE EFFECT OF THE TYPE AND CONTENT OF CARBONATES ON THE CHARACTERISTICS OF POROSITY OF CERAMIC MEMBRANES

The main issue considered in the work is the creation of a matrix for ceramic membranes, which would be distinguished by low cost and high porosity. In order to reduce the cost of ceramic membranes, a widespread approach was chosen, which is powerfully used by many researchers, namely the use of natural minerals - kaolin and saponite - as the main components of the matrix. Carbonates were used as pore generating agents to achieve the required porosity value. Three series of ceramic membranes (CM) differing in chemical composition were synthesized in the work: KP1, KP2, and KP3 series. The main composition of CM includes: kaolin, saponite, sodium silicate and carbonates. The effect of the type and amount of carbonates (CaCO3, NH4HCO3, (NH4)2CO3) as pore generating agents on the formation of the porous structure of the samples was studied. The type and content of carbonates varied in different samples from 8 wt% up to 40 wt%. The dry pressing method using pressure equivalent to 8 tons and 15 tons was used to form ceramic membranes. The main parameters by which the properties of ceramic membranes were evaluated: water absorption, total and open porosity. Standard methods were used to determine these parameters for synthesized samples. The chemical composition of the dry mixture of the ceramic membrane, for which the porosity is the maximum in the series of manufactured samples, was established. It was established that the addition of calcium carbonate components to the dry mixture increases the porosity of ceramic membranes and water absorption. The chemical composition of a ceramic membrane sample with the best indicators of total and open porosity in the KP2 series is given. The chemical and phase composition of samples of the KP2 series, as well as their structural and adsorption characteristics, were investigated by X-ray fluorescence and diffraction methods of analysis and low-temperature nitrogen adsorption-desorption. The effect of the addition of silicon carbide on the characteristics of the porosity of the samples was determined.

Physical and mechanical properties of Ignimbrite from Arucas, Canary Islands

This research is a contribution to the mineralogical and physical–mechanical characterisation of the ignimbrites from Arucas (Gran Canaria Island), used as building stones under the commercial names of "Piedra de Arucas Lomo Tomás de León" and "Piedra de Arucas Rosa Silva". This stone has been used for more than five hundred years and is part of the local architectural heritage, but has also been exported to other regions of the world. To perform this characterisation, a chemical analysis was carried out using X-ray fluorescence (XRF), mineralogical and petrographic properties were obtained using polarised optical microscopy (POM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Several physical properties were determined, namely: apparent density (AP), open porosity (OP), water absorption at atmospheric pressure (WA), water absorption by capillarity (WAC), ultrasound velocity (PWV) and colour. Mechanical properties were obtained through compressive strength (UCS), bending strength (BS), point load (PLT), indirect tensile (BTS) and energy at break (IR) tests. To evaluate the durability, the samples were subjected to salt crystallisation cycles (CS), SO2 action (AS) and salt spray (SS) and the abrasion resistance (AR) was determined. The results obtained show that, although both samples share the same lithology and belong to the same geological formation (Salic Formation, trachytic-phonolitic), they show very different properties. Porosity stands out as the property with the higher difference among the two studied varieties. Therefore, the application of these ignimbrites should be done accordingly, avoiding environmental conditions that promotes the wettability and/or the salt crystallisation.

Physico-Mechanical and Microstructure Characteristics of Porous Mullite Ceramics

Porous mullite ceramics were prepared from mixtures of Egyptian kaolinite-clay and calcined α-alumina powder. The effects of two methods of compaction as well as two types of binder were investigated. The influence of sintering temperature on the physical properties, crystalline phase, compressive strength and microstructure was studied. Mullite bodies processed by uniaxial pressing utilizing 15wt. % water at 1500°C for 2h exhibited the highest compressive strength of 150 MPa and bulk density of 2.1 g/cm3, as well as, an open porosity of 35%. In the present study, the only stoichiometric mullite was achieved by the crystallization of metakaolin. The mullite crystallizing out from the liquid phase was rich in silica, as determined by EDS, while that resulting from alumina grains was rich in alumina. The microstructure showed that primary mullite appeared at 1200°C, beside the unreacted alumina particles. On the other hand, at 1400°C alumina particles started to react with the glassy phase to form parallel laminates of mullite.

The Role of High Carbon Additives on Physical–Mechanical Characteristics and Microstructure of Cement-Based Composites

Traditional supplementary cementitious materials (SCMs) have been proven to reduce the negative impact of Portland cement production on the environment. However, the availability of SCMs becomes limited due to their extensive usage. For this reason, our work aimed to investigate the effect of partial substitution of ordinary Portland cement (OPC) with two different types of carbon-rich waste powders—biochar (BC) and coal dust (CD), dosed separately up to 10 wt.% of OPC, on the physical, microstructural and mechanical properties of hardened specimens. Obtained data pointed out that replacing OPC with small amounts of BC and CD (not exceeding 5.0 wt.% and 2.5% wt.%, respectively) initiated an increment in mechanical strengths due to a decrease in total open porosity and enhanced formation of hydration products of such composites compared with the reference. Overall, both examined alternatives, if added in appropriate amounts, have the perspective to be effectively applied in cement manufacturing and concrete production, and thus to importantly contribute to the long-term sustainability of the construction industry in view of energy savings, reduced releasing of the greenhouse gasses and mitigating of global climate changes.

The Long-Term Efficiency and Compatibility of Hydrophobic Treatments in Protecting Vulnerable Sandstone at Arbroath Abbey (Scotland)

The application of hydrophobic treatments as a means of protecting vulnerable stone heritage has been a topic of research for decades. The findings of previous research have shown that there are a number of factors that influence the efficiency of a treatment and that sometimes, if used incorrectly, such treatments can even accelerate stone weathering and decay. In this study, we revisit a hydrophobic treatment test area at Arbroath Abbey where the product was applied over 40 years ago, thus providing a rare opportunity to investigate the long-term efficiency of hydrophobic treatments. As well as assessing the condition of the treated area in situ by means of moisture analyses, lab-based accelerated salt weathering experiments are conducted to better understand the impact of silane-based treatments on sandstone durability. Moreover, the petrography and petrophysical properties of weathered sandstone (open porosity, capillary absorption, and vapour diffusion) before and after treatment are also characterised to provide a better understanding of how stone properties may influence the compatibility of the treatment. The field-based results show that the treated area has maintained a degree of hydrophobicity since its application over 40 years ago. Both field-based and lab-based analyses suggest that silane-based treatments can be used successfully in protecting sandstone when applied correctly, both in reducing the rate of decay and functioning over long periods of time. However, sandstone heterogeneity may mean that some individual stones are less compatible with the hydrophobic treatment tested than others. Further field-based analyses (including methods such as XRF and in situ vp) of the treated area is required in order to determine the state of conservation more accurately. These results highlight the complexity in selecting a suitable hydrophobic treatment, especially at built sites where the mineralogy and petrophysical properties of the stone may vary between blocks. However, such treatments may still be important to consider as many climates, including Scotland’s, are becoming progressively wetter, increasing the vulnerability of stone heritage to moisture ingress, accelerated decay, and eventual ruin.

Mechanical and dielectric properties of Si3N4-SiO2 ceramics prepared by digital light processing based 3D printing and oxidation sintering

Si3N4-SiO2 ceramics are considered as the preferred high-performance wave-transmitting material in the aerospace field. However, traditional fabrication methods for Si3N4-SiO2 ceramics have the disadvantages of high cost and complicated fabrication process. In this paper, Si3N4-SiO2 ceramics with excellent mechanical and dielectric properties were fabricated by digital light processing-based 3D printing combined with oxidation sintering. Firstly, the curing thickness and viscosity of slurries with different solid loadings for vat photopolymerization-based 3D printing were studied. Then, the effects of the sintering temperature on the linear shrinkage, phase composition, microstructure, flexural strength, and dielectric properties of Si3N4-SiO2 ceramics, and the influences of solid loading on them were explored. The curing thickness and viscosity of the slurry with a solid loading of 55 vol% were 30 μm and ∼1.5 Pa‧s, respectively. The open porosity and the flexural strength of Si3N4-SiO2 ceramic with a solid loading of 55 vol% were 4.3 ± 0.61% and 76 ± 5.6 MPa, respectively. In the electromagnetic wave band of 8–18 GHz, the dielectric constant of Si3N4-SiO2 ceramics was within the range of less than 4, and the dielectric loss remained below 0.09. The method of digital light processing-based 3D printing combined with oxidation sintering can be further extended in the preparation of Si3N4-based structure-function integrated ceramics.

Ceramic Foams with Controlled Geometries Through 3D‐Printed Sacrificial Templates

Powder‐based 3D printing was combined with sacrificial templating to realize highly porous yttria‐stabilized ZrO2 (YSZ) ceramic foam objects with well‐defined geometries. The porous sacrificial template is 3D printed using poly(methyl methacrylate) powder. Various methods are evaluated to optimize ceramic slurry infiltration into the 3D‐printed template and subsequent burn‐out. The optimized method yields ceramic foam objects with an open porosity of >66% and replicates the geometry of the 3D‐printed template with high fidelity.

Rapid performance optimization strategy of MK-FA-GBFS based geopolymer foam heavy-metal adsorbent

Geopolymer foams (GPFs) are promising materials for heavy-metal-containing wastewater treatment. However, because of the diversity of precursors and the complex application environments, it is challenging to balance the processing and application performances. Herein, a “simplex-centroid” mixture design method was explored to optimize the performances and establish relationships between the precursors, microstructure, and molecular structure. Further, according to the design performance and rheological limitations of the foaming system, an optimal component was selected to fabricate a GPF using chemical foaming. The fabricated GPF exhibited a high compressive strength (0.86 MPa) and high open porosity (∼86%) with uniform pores with diameters of 0.1–1.2 mm. Pb2+, Cu2+, and Ni2+ static adsorption capacities of 112.8, 64.9, and 40.2 mg/g, respectively, were achieved. The combination of simplex-centroid method and chemical foaming is effective for optimizing the processing and application performances of GPF, and could be beneficial for future large-scale manufacturing of GPFs for water-treatment applications.

Controllable preparation and thermal properties of SiC spherical high temperature shape-stable composite phase change materials based on gel-casting

The development of high-temperature composite phase change materials (CPCMs) suitable for mass-production and high-performance is still a very urgent problem in the efficient utilization of renewable energy. In this study, a SiC spherical high-temperature CPCMs based on aqueous gel-casting suitable for batch molding using commercially available silicone molds is proposed. The porosity of the porous SiC framework can be adjusted by changing the content of starch granules in the slurry. The sample containing 20 wt% starch has relatively high open porosity and thermal conductivity, which is considered to be close to the optimal formulation of CPCMs. This formula possesses a high thermal conductivity of 10.2 W·m−1·k−1 benefiting from the continuous thermal transport channels consisting of the uniformly distributed large spherical pores and interconnected small pores. Meanwhile, the thermal storage density of the CPCMs reaches 395.21 J·g−1 in the temperature range of 550 ℃ and 750 ℃ since up to 89.06% of the pores are filled with molten salts. At the same time, the CPCMs exhibit excellent cycle stability in 100 thermal cycles. In particular, these CPCMs can be easily integrated into thermal energy storage (TES) system. Based on the rapid heat storage simulation of the C-D model, the packed-bed latent thermal energy storage system containing spherical CPCMs will have a more uniform temperature distribution and a 26.7% reduction in charging time compared with the traditional packed-bed system. This work provides a new reference for the design of spherical CPCMs in TES systems.

Experimental and numerical analysis of the hygric performance of earthen buildings after façade hydrophobization treatment

Earth is used extensively for buildings worldwide, as its thermal properties contribute to a favorable indoor thermal environment. However, earthen materials are sensitive to moisture ingress, which can result in structural damage and undesirable indoor humidity conditions. Through hydrophobization treatment, the capillarity of earth can be significantly reduced while hygroscopicity remains largely unchanged, thereby possibly improving the hygric performance of earthen buildings. In the present study, experiments and simulations were conducted to investigate the effect of hydrophobization on earthen materials and buildings. The experimental results show that the bulk density, open porosity, and pore-size distribution of rammed earth changed by only a few percent after hydrophobization treatment. The thermal properties (thermal conductivity, specific heat capacity, solar reflectivity and longwave emissivity) and hygroscopic properties (sorption isotherm and water vapor permeability) also showed limited changes (<20 % in most cases). In contrast, capillarity, represented by the capillary absorption coefficient, was reduced by over 80 %. Numerical simulations further showed that relative humidity and moisture content at the exterior and middle positions of earthen walls strongly decreased after hydrophobization treatment. The largest moisture flux discrepancy between untreated and treated walls was 652.1 g/(h·m2). Furthermore, the parametric analysis indicated that façade treatment dominated the hygric state of the exterior and middle positions of earthen walls, while ventilation was most important at the wall interior and in the indoor space. Therefore, combining façade hydrophobization treatment and ventilation is recommended to improve the performance of earthen walls and maintain a favorable indoor environment.

3D hierarchical porous structures printed from a silica-nickel composite paste

Material extrusion of paste as one of the 3D printing techniques is commonly used in additive manufacturing industry. It allows to efficiently obtain structures of complex geometry at a relatively low cost. Ceramics are among the materials eagerly printed with this technique, especially as a support material. Hence, the combination of silica as base material and nickel as catalyst seems to be a highly promising system in processes such as CO2 methanation or hydrogenation processes.The key aspects that should be taken into consideration when designing a new material are the proper material composition, its microstructure, as well as the final properties. From the point of view of the above-mentioned applications, material should have high open porosity. Appropriate micro- and macroporosity enable the optimal flow of liquid and gaseous reagents through the material, ensuring high efficiency of the processes carried out. It is also crucial to select the appropriate catalytic material, hence the use of nickel as a catalytically active metal was proposed for the research.This article demonstrates the development, preparation and characterization of silica-nickel porous structures obtained via material extrusion. The nanosilica-Ni paste with 75 wt% of Ni powder particles was prepared with stirring and degassing for homogenous consistency. 3D printed scaffolds have undergone heat treatment to remove the organic binders and partially sintered to achieve a relevant mechanical strength. The analysis of the paste was performed using the detailed thermal analysis, XRD analysis and Raman spectroscopy for a determination of the optimal thermal processing conditions. In addition, the characterization of the final materials was carried out to confirm the effectiveness of the procedures developed. Application of the reductive atmosphere (mixture of N2+H2) during heat treatment prevented nickel particles from oxidation, as well as strongly eliminated the microstructure defects such as cracking and material shrinkage. The results demonstrate the perspective application of material extrusion as a printing technique of highly porous materials with well-preserved pre-designed 3D geometry.

Laboratorial Study of the Combined Effect of SO2 and High-Temperature Ageing on the Physical and Mechanical Properties of Encostinha Marble, a Portuguese Stone

ABSTRACT The effects of SO2, high temperature (600°C) and cooling type (slow and rapid) were investigated in this study as decay factors of a building stone (Encostinha Marble). Changes in colour, gloss, apparent density, open porosity, capillary water absorption and ultrasonic pulse velocity were assessed, complemented with SEM observations and XRD analysis. SO2 did not significantly react with the marble; no neoformed products were identified and only superficial changes were registered. Specimens became darker and duller. The increase in size of pre-existing microcracks and the development of new ones caused by high temperature, with a consequent increase in open porosity, was the main cause of the marked degradation of physical and mechanical properties. The cooling type was also shown to influence the physical and mechanical characteristics of the marble. A more pronounced increase in open porosity and capillary water absorption in specimens cooled by total immersion in tap water was observed. This increase was not in line with the corresponding decrease in ultrasonic parameter values.

Regulation and inhibition of early whitening of calcium aluminate cement/hemihydrate gypsum decorative mortar by polymer emulsion

Whitening of decorative mortar is an important factor hindering its application, which is difficult to mitigate. This paper studied the effect of different polymer emulsions on the early whitening of decorative mortar using calcium aluminate cement (CAC) and hemihydrate gypsum (HH) as cementitious material. The whitening phenomenon and white deposits of CAC/HH decorative mortars were investigated through digital processing of images, optical microscopy (OM), scanning electron microscopy (SEM) and Raman spectroscopy analysis. The results show that the white deposits were mainly ettringite (AFt) and CaCO3, whose quantity and size determined the severity of whitening. The addition of vinyl acetate-ethylene copolymer emulsion (VAE) and poly acrylic ester emulsion (PAE) could inhibit the generation of AFt and reduce the crystal size and amount of CaCO3, thus inhibiting the whitening. In order to reveal the inhibition mechanism of polymer emulsions on the whitening, the effect of polymer emulsions on the cement hydration was studied by hydration heat and X-ray diffraction (XRD), the porosity and capillary water absorption were also tested. It shows that the inhibition of whitening of CAC/HH decorative mortar by polymer emulsions was mainly achieved by reducing the open porosity and capillarity water adsorption, which directly decreased the pathway of the ion transport from the interior to the exterior of the mortar, thereby reducing the generation of the white deposits on the mortar surface and improving the anti-whitening property of CAC/HH decorative mortar.

Evolution of the microstructure of superfine grain graphites under thermal oxidation

Nuclear graphite is used as a moderator and structural material in a number of Gen-IV reactor designs, such as the (Very) High Temperature Reactors. Chronic or acute thermal oxidation affects the mechanical properties of the graphite components and the impact on the structural integrity of the core depends on the evolution of the microstructure during oxidation.This study qualitatively examined the microstructure of four superfine grain graphites using polarised and fluorescent optical microscopy. These graphites had similar physical properties but notable differences in the oxidation rate at 700 °C. Using fluorescent microscopy, it was possible to distinguish between open and closed porosity in graphite, which is useful in understanding the progression of thermal oxidation and penetration depth. Based on the samples in this work, fine open and closed porosity may be linked to increased surface oxidation and relatively high oxidation rate, whereas high penetration depth may be linked to relatively low open porosity consisting mainly of large pores. Fairly large domains of coherent crystallite orientation, perhaps due to the presence of agglomerates, may also indicate lower oxidation rates at 700 °C.This paper demonstrated that fluorescent microscopy combined with image analysis, is a useful tool in understanding the progression of thermal oxidation and the corresponding effect on the microstructure.