Refractory Research Articles

Compressive loading and response time behavior of concrete containing refractory brick coarse aggregates

This research aimed to determine compressive stress and response time of using refractory brick waste as alternative natural coarse aggregates combined with blended cement in manufacturing sustainable concrete. The experiment was conducted by adding 15–50% aggregates volume of refractory bricks coarse aggregate (RBCA) to concrete mix in order to determine the suitability as coarse aggregates. The results showed that the slump values for the combination of standard concrete (SC) with all RBCA satisfied the design value of ± 20 cm and this showed easy handling and workability of the fresh concrete produced. Moreover, the peak stress and toughness were reduced as RBCA increased from 15 to 50% at both w/c of 0.52 and 0.49. The relationship between compressive stress and response time also showed that the travel time at the elastic, peak, and ultimate stages decreased as RBCA increased from 15 to 50% at both w/c. It was concluded that concrete mix with 50% RBCA did not meet the required criteria at w/c of 0.49 but those with 15–50% RBCA satisfied the minimum requirements at w/c of 0.52.

Pengukuran Efisiensi Proses Produksi Castable Guna Mengidentifikasi Wasting Time di PT Benteng Api Technic

PT Benteng Api Technic was founded in 1997 and produces refractory bricks, refractory cement and various refractory materials. Refractory cement or castable currently still uses a pre-order system before the production process is carried out. During observations for seven days with 38 observations, there were activities that were felt to be less efficient, then the value stream mapping method was carried out to streamline waste. The result is a defect when the production process is finished, there is a repetition of the production process because it does not pass the feasibility test, processing because a lot of leftover material falls in the bagging section and the material is no longer used. Waiting is the average part of weighing materials/products of 1.54 seconds (waiting for the material composition recipe and weighing platform trouble/error). Material mixing section with an average/product of 1.82 seconds (waiting for machine repairs due to leaking air duct). Total production lead time is 3396 seconds. Once the waste is identified, the next step is to eliminate the activity by testing data adequacy and testing data uniformity. The results of the analysis of the castable production process contained 2 analyses, the first analysis by reducing activity time with an average total time of 3285 seconds/44 cement and the second analysis by reducing and eliminating the cement weighing activity in the bagging section with a total time of 2873 seconds/44 cement

Mechanism of solute hardening and dislocation debris-mediated ductilization in Nb-Si alloy

Niobium (Nb) is sensitive to even minute quantities of silicon (Si) solutes, which are known to induce pronounced hardening. However, the underlying mechanism for hardening remains elusive since the effect of Si solutes on dislocation behavior is unclear. Here, using tensile testing, in-situ microscopy and nanomechanical testing, the behavior of dislocations in dilute Nb-Si alloys, containing from 0 at.% to 0.8 at.% Si, is investigated. We show that the hardness, strength and strain hardening rate increase from two to four times, while the uniform elongation in tension only reduces 50 % as the Si content increases. Dislocations evolve from complex entangled patterns in Nb to parallel long-straight screw dislocation-dominated structures in Nb-Si alloys. In-situ indentation reveals that the origins of the marked hardening in Nb-Si alloy are the reduction of dislocation mobility and cross-slip propensity. Large densities of dislocation debris-superjogs and loops introduced throughout the sample during warm rolling and annealing are found to provide active internal dislocation sources, which explain the minimal ductility loss seen in these Nb-Si alloys. These findings can help guide the alloy design of high-performance refractory materials for extreme temperature applications.

Materials design for hypersonics.

Hypersonic vehicles must withstand extreme conditions during flights that exceed five times the speed of sound. These systems have the potential to facilitate rapid access to space, bolster defense capabilities, and create a new paradigm for transcontinental earth-to-earth travel. However, extreme aerothermal environments create significant challenges for vehicle materials and structures. This work addresses the critical need to develop resilient refractory alloys, composites, and ceramics. We will highlight key design principles for critical vehicle areas such as primary structures, thermal protection, and propulsion systems; the role of theory and computation; and strategies for advancing laboratory-scale materials tomanufacturable flight-ready components.

Extraction of Valuable Components in the Process of Recycling of Technogenic Materials of Alumina Production

In the process of recycling man-made resource-saving additives into alumina raw materials, waste fireclay refractory bricks used for lining rotating furnaces and other thermal units were tested. A sufficiently high level of aluminum oxide extraction from fireclay lining has been experimentally confirmed. It has been established that when more than 95 000 tons of stored refractory fireclay brick waste is involved in the technological process, savings on a natural raw material resource are achieved: about 56 700 tons of nepheline ore.

Formation of green strength in hydraulically bonded refractory castables at room temperature

A sufficient green strength of refractory castables is necessary to avoid damage during demoulding and heating up of refractory linings and prefabricated parts. However, there is a lack of knowledge on the mechanisms underlying the build-up of green strength in refractory castables. This work focuses on how green strength is formed within the matrix of PCE-dispersed and CA cement bonded refractory castables during their setting.Setting was monitored using several measuring methods, such as sonic velocity, amount of hydrate phases formed from CA cement, ζ-potential (stability resp. coagulation of the matrix suspension), porosity, and specific surface area and was linked to the corresponding increase of green strength of refractory castables during setting.Considered by time after adding water, the first stiffening of the refractory castables is related to the collapse of the rheological system of their matrix suspension (coagulation), resulting in a very low increase in green strength (apparent hardening). This stiffening occurs early if Ca-precipitates are formed together with molecules of the dispersing agent (Ca-PCE, PCE with short side chains) or if the amount of pore water is being reduced below a critical value (rheologically stable matrix due to dispersion of hydrate phases by PCE with long side chains). The major increase in green strength occurs when a significant amount of CA cement reacts to hydrate phases and, correspondingly, water is being bonded. This main increase in green strength may occur directly after stiffening (if CA cement is being hydrated quickly) or several hours after stiffening (if the hydration of CA cement is retarded).Regarding the green strength, the predominant factor influencing the build-up of green strength in refractory castables is the reduction of free water in the pores due to its bond in hydrate phases (reduction of a lubricating, interparticle water film). Minor influences are the reduction in porosity (volume expansion by hydration of CA cement), the increase in the specific surface area (hydrate phases are finer than the initial CA cement particles), and the entanglement of plate-like hydrate phases.

Durability assessment of concrete containing recycled coarse refractory brick aggregate

Durability assessment of concrete containing recycled coarse refractory brick aggregate

Thermochemical interactions between yttria‐stabilized zirconia and molten lunar regolith simulants

AbstractOxygen produced through in‐situ resource utilization (ISRU) is critical to maintaining a permanent human presence on the lunar surface. Molten regolith electrolysis and carbothermal reduction are two promising ISRU techniques for generating oxygen directly from lunar regolith, which is primarily a mixture of oxide minerals; however, both processes require operating temperatures of 1600°C to melt lunar regolith and dissociate the molten oxides. These conditions limit the use of many oxide refractory materials, such as Al2O3 and MgO, due to rapid degradation resulting from reactions between the refractory materials and molten lunar regolith. Yttria‐stabilized zirconia (YSZ) is shown here to be a promising refractory oxide to provide containment of molten regolith while demonstrating limited reactivity. This work focuses on corrosion studies of YSZ powders and dense YSZ crucibles in contact with molten lunar maria and highlands regolith simulants at 1600°C. The interactions between YSZ and molten regolith were characterized using scanning electron microscopy/energy dispersive spectroscopy, X‐ray diffraction, and electron backscatter diffraction. A FactSage thermochemical model was created for comparison with the experimental results. These combined analyses suggest that lunar maria regolith will degrade the YSZ faster than the lunar highlands regolith due to the lower viscosity of the maria regolith. The feasibility of long‐term molten regolith containment with YSZ is discussed based on the YSZ powder and crucible results.

Whisker Bond: From Findings to Concept in Refractories

Ceramic bonds are conventionally formed during the<sup> </sup>burning of<sup> </sup>refractory bricks and by using pre-fabricated blocks or monolithic lining, which is characterized as the coalescence of the particles by liquid sintering. However, the whisker bond was discovered with the outstanding performance of unburnt periclase–spinel–Al bricks while substituting magnesia–chrome bricks in the chromium-free campaign of refractory lining of RH degassers. Thanks to the prominent effect of the whisker bond, such a refractory material demonstrates ultrahigh hot strength, high resistance to slag penetration, and thermomechanical stress. Investigations reveal the initial melting of metal Al at the melting point of 660°C, aluminum liquid rims around the cavities formed before ~800°C, gaseous AlN yielded and distributed throughout<sup> </sup>the matrix with increasing temperature, gaseous Mg reduced from ~1000°C, and MgAlON whiskers eventually formed in the matrix. Microstructure observations show a dense interwoven whiskers bonded matrix in most residual parts of the used periclase–spinel–Al bricks. The whisker network in the matrix is made up of<sup> </sup>straight columns<sup> </sup>of 1–5 µm in diameter and 20–40 µm in length, which is different from birdnesting, nano-size curly whiskers observed in the past. The findings suggest a whisker-bond concept in terms of the bond mode of the whisker network and the process of the vapor-solid forming mechanism.

Role of SiO2 in tailoring stability and nonlinear optical behaviour of gold nanoparticles in glass

In the present work, a new approach is introduced to mitigate the loss of gold nanoparticles while preparing the glass through the traditional melt-quench technique. The role of refractory material i.e. SiO2 in loss reduction is studied by comparing the results obtained for bismuth borate (40Bi2O3:60B2O3) and borosilicate (40Bi2O3:40B2O3:20SiO2) glasses containing gold nanoparticles of different sizes (10 nm, 40 nm and 100 nm). The particle density and thermal stability obtained from FESEM and DTA, respectively, increase considerably with the presence of SiO2 as one of the components of glass composition. The nonlinear optical behaviour of both systems in non-resonant regions has been obtained using the Z-scan technique. In addition, the suitability of the prepared glasses for optical limiting and switching applications has been analysed.

Experiments Using Different Types of Waste to Manufacture Ceramic Materials: Examples on a Laboratory Scale

Reusing waste as raw materials to produce other materials can entail a decrease in production costs and in the abusive use of natural resources. Furthermore, it can even improve the properties of the end product or material. In this sense, a review of the most relevant literature published in recent decades shows that numerous solutions have been proposed or implemented, such as its use to produce construction materials, catalysts, pigments, pozzolana, refractory materials, glass-ceramic products, etc. Our research group has verified the viability of using different types of waste as secondary raw materials to obtain several types of ceramic, glassy and glassceramic materials, as well as frits. This article highlights several types of industrial waste that have both non-toxic (Li, Ca and Mn) and highly toxic (Cr VI) differentiating elements that can be used in sintering and vitrification industrial processes to immobilise them or render them inert. We studied the compositions and characterised the various materials obtained, conducting toxicity and leaching tests on waste/materials designed with high amounts of chromium. A suggestion for future lines of research has been proposed.

Criterial dependencies of the movement of the melt refractory material in the bath of an ore thermal furnace under electromagnetic influence

In this work, for the first time, criterion dependencies of the speed of movement of the melt in the bath of an ore-thermal furnace during electric arc melting of oxide refractory materials under external electromagnetic influence were obtained. The initial quantitative characteristics for generalization in the form of the dependence of the speed in the zone of intense movement of the melt on the currents in the electrodes and the electromagnetic device were taken on the electrolyte and mercury physical models of an ore-smelting furnace with an electromagnetic device. Physical modeling was carried out while maintaining the invariance of the derived similarity criteria: the electrovortex flow parameter πμ and the external magnetic field parameter πl. In order to extend the experimental results obtained to a whole group of similar phenomena, the dependences of the dimensionless speed of melt movement (Reynolds criterion) on the dimensionless parameters of the external magnetic field and electric vortex flow were obtained and constructed. Since for all similar processes the similarity criteria retain the same values, then the criterion dependencies for them will be the same, and the results obtained can be extended to all similar cases.

Experimental study on the radiation-induced destruction of organic compounds on the surface of the Moon

Volatile organic molecules and a complex organic refractory material were detected on the Moon and on lunar samples. The Moon’s surface is exposed to a continuous flux of solar UV photons and fast ions, e.g. galactic cosmic rays (GCRs), solar wind (SW), and solar energetic particles (SEPs), that modify the physical and chemical properties of surface materials, thus challenging the survival of organic compounds. With this in mind, the aim of this work is to estimate the lifetime of organic compounds on the Moon’s surface under processing by energetic particles. We performed laboratory experiments to measure the destruction cross section of selected organic compounds, namely methane (CH4), formamide (NH2CHO), and an organic refractory residue, under simulated Moon conditions. Volatile species were deposited at low temperature (17 - 18 K) and irradiated with energetic ions (200 keV) in an ultra-high vacuum chamber. The organic refractory residue was produced after warming up of a CO:CH4 ice mixture irradiated with 200 keV H+ at 18 K. All the samples were analyzed in situ by infrared transmission spectroscopy. We found that destruction cross sections are strongly affected (up to one order of magnitude) by the dilution of a given organic in an inert matrix. Among the selected samples, organic refractory residues are the most resistant to radiation. We estimated the lifetime of organic compounds on the surface of the Moon by calculating the dose rate due to GCRs and SEPs at the Moon’s orbit and by using the experimental cross section values. Taking into account impact gardening, we also estimated the fraction of surviving organic material as a function of depth. Our results are compatible with the detection of CH4 in the LCROSS eject plume originating from layers deeper than about 0.7 m at the Moon’s South Pole and with the identification of complex organic material in lunar samples collected by Apollo 17 mission.

ZnO sintering aid effect on proton conductivity of BaCe0.6Zr0.3Y0.1O3-δ electrolyte for hydrogen sensors

Proton-conducting solid-state electrolytes, including perovskite-type materials, hold promise for hydrogen sensor development. These sensors leverage the proton conductivity of such materials to detect hydrogen gas presence. However, achieving both high density for gas tightness and good protonic conductivity in these refractory materials can be challenging.In this study, we propose the preparation of dense pellets of BaCe0.6Zr0.3Y0.1O3-δ using ZnO as a sintering aid (BCZY-Zn). These pellets were extensively characterized using X-ray diffraction and electrochemical impedance spectroscopy and compared with pellets sintered without sintering aid (BCZY). Subsequently, BCZY-Zn electrolyte was utilized to fabricate amperometric sensors for hydrogen monitoring. Finally, amperometric measurements were conducted at 500 °C while maintaining a voltage of 150 mV between electrodes. The sensors' performance was evaluated for hydrogen partial pressures ranging from 12 to 100 Pa within an argon atmosphere. Additionally, response and recovery times were calculated.

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO2

We present observations obtained with the Near Infrared Spectrograph on JWST of the five Jupiter Trojans that will be visited by the Lucy spacecraft—the Patroclus–Menoetius binary, Eurybates, Orus, Leucus, and Polymele. The measured 1.7–5.3 μm reflectance spectra, which provide increased wavelength coverage, spatial resolution, and signal-to-noise ratio over previous ground-based spectroscopy, reveal several distinct absorption features. We detect a broad OH band centered at 3 μm that is most prominent on the less-red objects Eurybates, Patroclus–Menoetius, and Polymele. An additional absorption feature at 3.3–3.6 μm, indicative of aliphatic organics, is systematically deeper on the red objects Orus and Leucus. The collisional fragment Eurybates is unique in displaying an absorption band at 4.25 μm that we attribute to bound or trapped CO2. Comparisons with other solar system small bodies reveal broad similarities in the 2.7–3.6 μm bands with analogous features on Centaurs, Kuiper Belt objects (KBOs), and the active asteroid 238P. In the context of recent solar system evolution models, which posit that the Trojans initially formed in the outer solar system, the significant attenuation of the 2.7–3.6 μm absorption features on Trojans relative to KBOs may be the result of secondary thermal processing of the Trojans’ surfaces at the higher temperatures of the Jupiter region. The CO2 band manifested on the surface of Eurybates suggests that CO2 may be a major constituent in the bulk composition of Trojans, but resides in the subsurface or deeper interior and is largely obscured by refractory material that formed from the thermophysical processes that were activated during their inward migration.

Precise density measurements of refractory metals over 3000 K: Revisiting UV imaging technique at ultrahigh temperatures

Precise density and thermal expansion measurements of refractory materials are extremely challenging due to the chemical reactions and thermal gradients at ultrahigh temperatures. The UV image technique has been successfully applied to the density measurements at high temperatures above 3000 K. However, intense radiation from the sample can blur the edge of the sample image, leading to uncertain measurements. In this study, we investigate the influence of the contrast between the UV background light and sample radiation (B–S) on density measurements. We find that lower B–S contrast can significantly affect the calibration factor that converts image pixels to real size, resulting in underestimated density with scattering and overestimated thermal expansion coefficients at ultrahigh temperatures. This result underscores the necessity of adequate B–S contrast to ensure the precision of density measurements using UV imaging methods for refractory materials beyond 3000 K. By considering the critical minimum value of the B–S contrast, we successfully measure the densities and thermal expansion coefficients of four refractory metal liquids (tungsten, rhenium, osmium, and tantalum) with the improved UV technique, which are crucial for high-temperature industries. This work will be valuable for other imaging methods measuring the thermophysical properties at ultrahigh temperatures.

The Relationship Between Structural Features and Local Mechanical Properties of a Fine-Grained Matrix in Refractory Ceramic Materials. SiO2 Ceramics Case Study

The Relationship Between Structural Features and Local Mechanical Properties of a Fine-Grained Matrix in Refractory Ceramic Materials. SiO2 Ceramics Case Study

Mineralogical, geochemical and physical properties assessment of clay deposits in Umuoke Obowo Southeastern Nigeria for industrial applications

This study assessed the suitability of clay deposits from Umuoke, Obowo in southeastern Nigeria as local raw materials for industrial applications. Ten samples were collected from different mining pits across the locality. X-ray fluorescence, X-ray diffraction and physical property tests characterized the clays based on geochemical composition, mineralogy and key attributes. The clays showed high silica (56.41%) and alumina (32.82%) contents typical of aluminosilicate clays. Iron oxide levels were moderately elevated (3.34% Fe2O3). Clay minerals kaolinite (18.9-37.0%) and illite (0.5-4.15%) occurred predominantly alongside non-clay minerals like quartz, feldspars and metal oxides. The clays exhibited high plasticity (avg. plasticity index 26.61%) enabling easy moulding and shaping. Porosity averaged 21.33% appropriate for refractories. Firing shrinkage (6.5-19.2%) and density (1.54-1.76 g/cm3) were in acceptable ranges. Strength post-firing reached the 15 N/mm2 minimum standard. Estimated refractoriness was 1680.22°C. Overall, the Umuoke clays demonstrate favourable chemistry, mineralogy and physical properties for refractories and structural ceramics applications pending some processing adjustments. Locally exploiting these deposits can promote import substitution, rural industrialization and sustainable development in Nigeria. Further pilot testing can optimize formulations and processes for targeted ceramic products. Comprehensive nationwide clay deposit prospecting is also recommended. The clays are suitable for refractory bricks, ceramic tableware, architectural ceramics, wall tiles, pottery items.

Simulation of the Service Environment and Selection of the Refractory Lining for a Heat Recovery Coke Oven.

A heat recovery coke oven (HRCO) is one of important approaches to achieving a carbon peak and carbon neutrality in China. However, the steady operation of an HRCO is significantly influenced by the internal working conditions and the quality of lining refractories. In this work, a comprehensive study of the internal working conditions of an HRCO was carried out. The results suggest that the partition wall (PW) between the carbonization and combustion chambers is the most vulnerable area, with the corresponding traditional silica bricks inadequate for the service requirements. A reference based on a comparison of the average thermal stress and high-temperature compressive strength is offered for evaluating and selecting silica bricks for the PW. New optimized silica bricks within the reference are verified to be more applicable to the actual working conditions of an HRCO than the traditional silica bricks. As such, this work provides valuable guidance for the optimization and selection of silica bricks for the PW in an HRCO.

SYNTHESIS OF ALUMINA FROM KAOLIN FOUND IN AJEBO, OGUN STATE, NIGERIA

This study proposes the utilization of kaolin as an alternate resource for alumina production due to the decreasing availability of bauxite ores in Nigeria. This project covers the procedures and operations required to produce a high surface area γ-alumina using kaolin, a refractory material. The kaolin used in this study was sourced from Ajebo in Ogun State, Nigeria. The mineral processing of kaolin was the initial step involving removing inherent impurities from the clay. Subsequently, calcination was performed to eliminate crystallised water and impurities and activate the kaolin's limited alumina content. This activation process facilitated the subsequent acid-leaching reactions. At 90oC, 5M HCl acid was used to leach meta-kaolin, which was then filtered. The filtrate was mixed with 5M NaOH at 900oC and was transformed into sodium aluminate. This reaction also facilitated the removal of magnesium and iron hydroxides. Subsequently, HCl was introduced to adjust the pH of the solution. The resulting aluminium hydroxide was then calcinated at temperatures of 700oC and 900oC for 2 hours each to produce γ-alumina. Ultimately, the calcined material was cooled to ambient temperature inside the furnace. The produced γ-alumina was further characterised using X-ray Fluorescence (XRF), Fourier Transform Infrared spectrometer (FTIR), and Scanning Electron Microscopy (SEM).