1. Introduction
Improvement and the development of the materials regarding their properties and specially the industrial applications have always been the great interest of scientists, engineers, and researchers. Search of the most efficient and economical materials is still being done even after the development of the advanced materials. Ceramics is one of the classes which is nonmetallic and inorganic materials and is indispensable in our daily life. Furthermore, engineered ceramics have received substantial focus because of their applications [1–3].
Spinel structure materials are represented by the general formula AB2X4 where A and B are the divalent and trivalent cations while X is typically chalcogens that have extensive applications nowadays due to their properties. Magnesium aluminate is a spinel structure ceramic material that has several advantages, including thermal stability at higher temperatures, lack of sensitivity to chemicals, insensitivity to heat, and an adsorptive surface [4, 5].
Magnesium aluminate spinel (MgAl2O4) is a well-established refractory material that has received significant attention over the years due to its unique properties. These properties include a good thermal conductivity, low thermal expansion coefficient at elevated temperatures, high melting point (2105°C), chemical inertness, and good chemical and mechanical strength. As a result of these advantageous characteristics, MgAl2O4 is suitable for application in various refractory applications [6, 7]. The manufacturing of high-quality MgAl2O4 powder is an important step in the application of MgAl2O4 spinel. The conventional approach for creating MgAl2O4 is a solid-state reaction of Al2O3 and MgO at around 1500°C. This technique is simple to implement and ideal for large-scale manufacturing [8], but the reaction temperature is quite high, and the end product lacks the requisite purity and particle size. In addition to the conventional method of synthesis of spinel MgAl2O4, molten salt synthesis is also used. In recent years, the molten salt synthesis (MSS) approach has received a lot of interest. In this process, the reaction medium is low melting salts, which allow reactants to combine in an atomic scale liquid fraction [9]. The MSS liquid/solid system enables more homogeneous mixing and diffusion of input materials than the conventional solid-state synthesis technique, resulting in a significant reduction of temperature and reaction time [10]. Safaei-Naeini et al. [11] employed the molten-salt approach to successfully produce MgAl2O4 nanoparticles at 850°C by heating various MgO- and Al2O3-containing precursors in KCl in stoichiometric proportions, nanosized spinel powders were created. Fazli et al. [12] used a molten-salt method to create nanocrystalline MgAl2O4 spinel. Nano alumina, magnesia, and lithium chloride were used as starting materials. The ideal sintering procedure for best outcomes was discovered as 850°C sintering temperature with a 3h soaking period. The optimal salt-to-oxide ratio has been stated to be 5:1. Zhang et al. [13] have described a molten synthesis process for Mg-Al spinel. The initial precursors were high-purity alumina and magnesia, and the solvent was KCl, which was utilized to investigate how varied salt concentrations influenced the shape. Zhang et al. [14] used molten-salt synthesis to create a MgAl2O4 (MA) spinel layer on a Ti3AlC2 substrate in a different study.
Magnesium aluminate spinel’s have been observed to possess a range of favorable features, making them highly utilized as refractory materials and structural materials in metallurgical applications [15]. Magnesium aluminate spinel, characterized by its diverse stoichiometric compositions, finds extensive utilization across a range of applications depending upon the specific environmental conditions of the intended application area. The primary utilization domains of magnesium aluminate spinel as refractory materials include cement rotary kilns, steel-teeming ladles [16–18], and the regenerators checker work element of glass tank furnaces [19, 20]. Spinel magnesium aluminate has been produced by numerous researchers, who have also suggested its potential application in the metallurgical industry [21]. Despite the existence of several refractory applications, there is a noticeable absence of literature regarding the crucible development of MgAl2O4 as it possesses highly desirable features that are essential for an efficient crucible, such as a high melting point, chemical inertness, high thermal stability, good chemical, and mechanical strength. Therefore, some efforts have been carried out in this paper to demonstrate the preparation of crucibles from Magnesium aluminate nanoparticles (MgAl2O4). Firstly, the synthesis of MgAl2O4 was conducted by using the molten salt method in different salt-to-oxide ratios. The resulting samples were characterized using SEM, XRD and Ceramography was also performed to investigate the surface of ceramic samples. Finally, a variety of crucibles were fabricated utilizing both pure MgAl2O4 and a combination of Al2O3.
2. Materials and methods
2.1. Supporting chemicals and equipment used in synthesis
Following are the chemicals and equipment used in the synthesis of Magnesium aluminate nanoparticles.
2.1.1. Chemicals.
High-quality reagents of lab grade were supplied by the laboratory. Magnesium Oxide Powder (MgO), and Aluminum Oxide Powder (Al2O3) were the raw materials used to prepare Magnesium Aluminate (MgAl2O4) nanoparticles. Potassium chloride (KCl) was used as the solvent.
2.2. Different methodologies used for preparing MgAl2O4 nanoparticles
As illustrated in Fig 1, two different samples were employed in the case of MgAl2O4. The process approach of Sample A was derived from the author’s own trial-and-error method. Sample A is a mixture of equimass quantities. In this method, precursors were prepared using a ratio of 15:1 (i.e., 15 g of KCl with 1g of MgO and an Al2O3 mixture). MgO and Al2O3 were then mixed together in equal amounts using ethanol as the solvent. In sample B, an equimolar mixture of MgO and Al2O3 is prepared in ethanol [13]. All methods remained consistent with Sample A, with the exception of an additional step involving the mixing of MgO and Al2O3 using a mortar and pestle for Sample B. The primary distinction between Sample A and Sample B lies in the composition of the mixtures, specifically the utilization of equimass and equimolar quantities, respectively.
[Figure omitted. See PDF.]
The Experimentation Section provides a comprehensive discussion of the steps involved in each sample preparation.
2.3. Experimentation
A brief experimentation plan of the complete setup is shown in Fig 2.
[Figure omitted. See PDF.]
2.3.1. Preparation of Sample A.
Magnetic stirrer was calibrated after placing the petri dish on the weight machine. 6g of fine Al2O3 powder was weighted and placed in a beaker. 6 g of MgO powder was weighted and placed with Al2O3 powder in the same beaker. 15ml of ethanol was added to the mixture with the help of a pipet. Then the beaker was placed on a magnetic stirrer for half an hour to mix the sample completely. After one hour, the powder settled at the bottom and excess ethanol drained out. The wet sample was placed in a ball milling machine for 3 hours. The sample was collected in the beaker and placed in a drying oven at 80°C for 4 hours after ball milling. The dried sample was then mixed with KCl powder. 30 g of KCl powder was mixed with 2g of dried sample (i.e. 15:1) and then placed in the ball milling machine for 1 hour.
After preheating the graphite crucible with its lid at 1150°C for 4 hours along with furnace cooling, the resulting sample was then placed in the preheated graphite crucible and tightly packed with its lid. The crucible was placed in a furnace for calcination at 1150°C for 4 hours. The sample was furnace cooled and ready for examination after calcination.
2.3.2. Preparation of Sample B.
1 M solutions of both MgO and Al2O3 were prepared by mixing 1 g of MgO powder in 25 ml of ethanol and 2.5g of Al2O3 powder in 25 ml of ethanol. Table 1 shows the details of Sample B solution preparation.
[Figure omitted. See PDF.]
The two solutions are then put in a beaker. The beaker was placed on a magnetic stirrer for half an hour in order to mix the solution completely. The beaker was covered with aluminum foil and placed in a fume hood for 22 hours. The powder settled down at the bottom and excess ethanol drained out. The wet sample was placed in a ball milling machine for 3 hours. After ball milling, the sample was collected into the beaker and placed in a drying oven at 80°C for 4 hours. 120 g of KCl powder is mixed with 4g of dried sample (i.e., 30:1) and placed in a ball milling machine for 1 hour. Then again, milled in a mortar pestle for 15 min. The resulting sample was then placed in a preheated graphite crucible and tightly packed with its lid. The crucible was placed in a furnace for calcination at 1150°C for 4 hours. The sample was furnace cooled and ready for examination after calcination.
2.4. Characterization
Characterization is an organized examination or formal evaluation exercise. It involves the measurements, tests, and gauges applied to certain characteristics regarding an object or activity. Table 2 shows the equipment used to characterize different characteristics of Magnesium aluminate nanoparticles.
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3. Results and discussion
3.1. Result of Sample A
Laser Particle Size Analyzer was used to obtain the average particle size. Fig 3 depicts the resultant sample A. The graph in Fig 4 shows that the particle size was 6 μm and was not considered in the nano range (<100 nm). This is the case of mixing the quantities of magnesium oxide and aluminum oxide in equimass quantities rather than equimolar quantities, as stated in [13].
[Figure omitted. See PDF.]
[Figure omitted. See PDF.]
3.2. Results of Sample B
The sample obtained after performing the experiment as shown in Fig 5 was then characterized using different techniques to find out different characteristic properties.
[Figure omitted. See PDF.]
3.2.1. XRD.
Powder diffraction (XRD) is a method employed to determine the preferred orientation, crystallite size (grain size), and crystallographic structure of solid samples that are either polycrystalline or powdered. The sample needs to be homogenized, finely ground, and its average bulk composition is necessary for XRD. Magnesium aluminate spinel was examined. The parameters used in XRD for the analysis of magnesium aluminate are at ambient pressure. XRD equipment (X’pert Pro PW 3040/60, Philips, USA) using copper as the radiation source: voltage = 40 kV, current = 30 mA, no filter used, monochromator = Cu PRS (30 m). XRD detected the compounds present in the prepared sample i.e., MgAl2O4 as shown in Fig 6. An effect of the finite crystallite sizes is seen as a broadening of the peaks in an X-ray diffraction. Graph in Fig 6 representing the powder XRD patterns of prepared MgAl2O4 obtained after heat treatment of KCl precursor at 1150°C. The peaks ranging from 66° to 67° clearly show the presence of MgAl2O4 particles.
[Figure omitted. See PDF.]
3.2.1.1. Calculation of particle size from Scherrer equation. Table 3 shows the particle size calculation of Sample B.Where,
β is the line broadening at half the maximum intensity (FWHM), after subtracting the instrumental line broadening, in radians.
λ is the X-ray wavelength,
K is a dimensionless shape factor, with a value close to unity. The shape factor has a typical value of about 0.9,
D the mean size of the ordered (crystalline) domains, which may be smaller or equal to the grain size,
θ is the Bragg angle (in degrees).
[Figure omitted. See PDF.]
3.2.2. Thermal analysis.
The differential scanning calorimeter (DSC) is a powerful apparatus used in the area of thermal analysis. The thermal analysis approach involves the quantification of the difference in heat energy required to increase the temperature of a specimen in comparison to a reference material. The difference is assessed as a function of temperature. DSC curve in Fig 7 shows that at 600°C, 0.05 W/g heat flows into the material and the TGA curve shows only 3.5% weight loss at 600°C. These results made MgAl2O4 more prominent for its thermal insulation application. The first hump in the curve around 100°C indicates the evaporation of moisture content. The second Hump in the curve between 250°C to 450°C showed the removal of KCl content from the sample, leaving behind pure MgAl2O4.
[Figure omitted. See PDF.]
3.2.3 Scanning electron microscopy analysis.
The scanning electron microscope (SEM) is a variant of the electron microscope that utilizes a high-energy electron beam to scan and generate images of a sample in a raster scan pattern. JEOL Ltd. Scanning electron microscopy (SEM) is used to obtain micrographs, which confirm the presence of nanoparticles. The SEM micrograph shown in Fig 8(A) is 20,000X (particle size is in the range of 120 nm to 143 nm), but the SEM micrograph in Fig 8(B) is 30,000X (particle size is in the range of 86.7 nm to 99.1 nm), which is under nanometric scale, demonstrating the presence of irregularly shaped and sized particles. In some regions, the cohesiveness of the particles has increased, resulting in the formation of agglomerated places within the sample. Thus, it is believed that some particles within the sample are used as condensation nucleation sites around which smaller particles condense, resulting in agglomeration. Sintering of MgAl2O4 materials is challenging due to their distinct chemical stability and high melting point. The sintering properties of MgAl2O4 are influenced by the uniformity, size, and agglomeration of the particles. The irregularity and non-uniformity of the particles are attributed to the elevated calcination temperature [22–24]. Particles were agglomerated in Fig 8(A)–8(C) of SEM which was due to the high calcination temperature (i.e., 1150°C). Therefore, particles diffused into one another and connected through a physical bond. This problem can be controlled by minimizing the calcination temperature to 800°C, which is also the melting temperature of KCl. The ratio of mixed powder to solvent was also high enough that it also produced residues in sufficient quantity, and it resulted in the agglomeration of particles. If that ratio was minimized to 1:3 (i.e., mixed powder to KCl) instead of 1:30, the problem was eliminated completely.
[Figure omitted. See PDF.]
(a) SEM image at 20,000X (b) SEM image at 30,000 X (c) SEM image at 15,000 X.
Table 4 provides a concise overview of the synthesis and characterization of magnesium aluminate nanoparticles.
[Figure omitted. See PDF.]
4. Making of crucibles
In the making of the crucible, the binder was the major component which allows the particle to bind compactly. PVA is mostly used as a binder for making the crucibles of ceramics. Table 5 shows the steps of preparing crucibles. PVA solution was made by taking PVA as a solute and water as a solvent. 5 gm of PVA powder was mixed in 100 ml of water and the mixture was stirred until all the solute particles were dissolved.
[Figure omitted. See PDF.]
4.1 Making of crucibles from 100% MgAl2O4
4.1.1 First attempt.
1g of PVA was added to 20 g of MgAl2O4 powder. The powder was then put in a mortar and pestle and mixed vigorously in order to achieve a homogenous composition. After cleaning the die and punch, oil was applied in order to avoid friction. Then the sample was placed in a die. Die and punch was placed on a hydraulic press of 10 tons. A pressure of 6 tons was applied for 5 min. The pressure was then released; the die and punch were removed from the pressing machine. The crucible was then removed from the still-attached die to the punch. The crucible was removed from the punch very carefully.
Result: The powder was not compressed, and it was shattered because of the low content of PVA.
4.1.2 Second attempt.
1.5g of PVA is added to 20 g of MgAl2O4 powder. The powder was then put in a mortar and pestle and mixed vigorously in order to achieve the homogenous composition. After cleaning the die and punch, oil was applied in order to avoid friction. Then the sample was placed in a die. Die and punch were placed on a hydraulic press of 10 tons. Pressure of 6 tons was applied for 5 min. Pressure was then released; die and punch were removed from the pressing machine. The crucible was then removed from the still-attached die to the punch. The crucible was removed from the punch very carefully.
Result: The compressed powder did not get the required shape when it was detached from the punch because of the low content of PVA.
4.1.3 Third attempt.
2 g of PVA is added to 20 g of MgAl2O4 powder. The powder was then put in a mortar and pestle and mixed vigorously to achieve the homogenous composition. After cleaning the die and punch, oil was applied to avoid friction. Then the sample was placed in a die. Die and punch were placed on a hydraulic press of 10 tons. Pressure of 6 tons was applied for 5 min. Pressure was then released; die and punch were removed from the pressing machine. The crucible was then removed from the still-attached die to the punch. The crucible as demonstrated in Fig 9(A)–9(C) was removed from the punch very carefully.
[Figure omitted. See PDF.]
(a) Crucible attached to the punch (b) Front view of 100% MgAl2O4 unsintered crucible (c) Top view of 100% MgAl2O4 unsintered crucible.
4.2 Making of crucibles from 100% Al2O3
2 g of PVA is added to 20 g of Al2O3 powder. The powder was then put in a mortar and pestle and mixed vigorously in order to achieve the homogenous composition. After cleaning the die and punch, oil was applied in order to avoid friction. Then the sample was placed in a die. Die and punch were placed on a hydraulic press of 10 tons. Pressure of 6 tons was applied for 5 min. The pressing machine’s die and punch were removed. The crucible was then removed from the still-attached die to the punch. The crucible as illustrated in Fig 10 was removed from the punch very carefully.
[Figure omitted. See PDF.]
4.3 Making of crucibles from MgAl2O4 and Al2O3 in different ratios
4.3.1 Experiment A.
16g of Al2O3 and 4g of MgAl2O4 were placed in a mortar pestle along with 2g addition of PVA and mixed homogeneously. After cleaning the die and punch, oil was applied in order to avoid friction. Then the sample was placed in a die. Die and punch were placed on a hydraulic press of 10 tons. Pressure of 6 tons was applied for 5 min. Pressure was then released; die and punch were removed from the pressing machine. The crucible was then removed from the still-attached die to the punch. The crucible as shown in Fig 11(A) was removed from the punch very carefully.
[Figure omitted. See PDF.]
(a) Unsintered crucible of Experiment A (b) Unsintered crucible of Experiment B.
4.3.2 Experiment B.
14g of Al2O3 and 6g of MgAl2O4 are placed in a mortar pestle along with 2g addition of PVA and mixed homogeneously. After cleaning the die and punch, oil was applied in order to avoid friction. Then the sample was placed in a die. Die and punch were placed on a hydraulic press of 10 tons. Pressure of 6 tons was applied for 5 min. Pressure was then released; die and punch were removed from the pressing machine. The crucible was then removed from the still-attached die to the punch. The crucible as shown in Fig 11(B) was removed from the punch very carefully.
A summary of different compositions used in Experiment A and Experiment B is shown in Table 6.
[Figure omitted. See PDF.]
All four unsintered crucibles are depicted in Fig 12.
[Figure omitted. See PDF.]
Unsintered crucibles (A) 100% MgAl2O4 (B) 80% Al2O3 and 20% MgAl2O4 (C) 70% Al2O3 and 30% MgAl2O4 (D) 100% Al2O3.
4.4 Sintering of crucibles
Sintering of all four crucibles (i.e., 100% MgAl2O4, 80% Al2O3 and 20% MgAl2O4, 70% Al2O3 and 30% MgAl2O4, 100% Al2O3) were conducted at 1100°C for 2 hours along with 30 min holding at 400°C and 30 min holding at 700°C. The resulting crucible was then furnace cooled as shown in Fig 13. Three crucibles were successfully sintered without any damage, however the sintering process for 100% MgAl2O4 did not yield satisfactory results. Hence, a comprehensive examination into the phenomenon of cracking is carried out.
[Figure omitted. See PDF.]
Sintered crucibles (A) 100% MgAl2O4 (B) 80% Al2O3 and 20% MgAl2O4 (C) 70% Al2O3 and 30% MgAl2O4 (D) 100% Al2O3.
4.5 Making of tablets to carry out the investigation of sintering of 100% MgAl2O4
Tablets of 100% MgAl2O4 were made to study the effects of sintering and densification of particles as the crucibles made in the experiment did not seem to be sintered at the described conditions.
4.5.1 Preparation of tablets.
1g of PVA was added to 10g of the sample and mixed vigorously till complete homogenization. Then the powder was divided into three equal quantities. Three tablets were made for the confirmation of tests. The tablets were made with a 1cm diameter die and punch. A pressure of 5000 psi was applied to compact the powder. The densities of tablets were calculated after compaction by measuring the height and diameter of the tablets with a vernier caliper. The green tablets were sintered at 1150°C for 2 hours, followed by 30 minutes at 300°C and 30 minutes at 700°C. The densities of tablets were calculated after sintering by using the same procedure as mentioned above. Stereographic images were also taken before and after the sintering of tablets.
For Ceramography, samples were hot mounted. Grinding of samples was done using 400 grit size of silicon carbide paper for 2 min, followed by grinding on 600 grit size paper for 2 min and finally on 1000 grit size paper for 2 min. The samples were washed and polished using coarse alumina powder (i.e., 1μm) for 2 min, followed by polishing using fine alumina powder (i.e., 0.5 μm). The samples were washed once more before being etched for 10 minutes with concentrated Aqua regia and hot blowing for 3 minutes. The samples were then taken to the Olympus Multicolor Microscope and images were taken at 400 X.
4.5.2 Density of tablets.
The density of any material can be affected by two parameters (i.e., mass and volume). During sintering, both parameters may be affected. Loss of PVA and moisture content results in weight loss, and shrinkage of geometry results in volume decreases. However, a marginal change in density was observed due to both of the above-mentioned reasons. Table 7 shows the density of tables before and after sintering.
[Figure omitted. See PDF.]
4.5.3 Stereo micrographs.
Stereographic images were taken at 15X of tablets as shown in Fig 14. Before sintering, the blackish area on the surface of the sample indicated the oil content which was applied during compression of the tablet. Moreover, the metal particle inclusions were embedded on the sample from the die which can be seen as tiny sharp black spots. In addition, the tablets’ edges were damaged during their removal from the die.
[Figure omitted. See PDF.]
After sintering, the surface of the sample appeared to be clearer and brighter due to the removal of oil content. The particles were well densified and compacted and other inclusions like black spots were also minimized due to the sintering as shown in Fig 15.
[Figure omitted. See PDF.]
4.5.4 Ceramography.
Images of the surfaces of sintered tablets were taken by using a metallurgical microscope at 400X as demonstrated in Fig 16.
[Figure omitted. See PDF.]
The surfaces were found to be dull and clear. It has a compact and dense structure and was unaffected by the etchant used. White spots on the surface were due to the alumina which was embedded on the surface during polishing. Sintering was achieved at 1150°C, which could be seen from the micrographs. Compactness can be enhanced by increasing the sintering temperature and the holding time.
4.5.5 Hardness of sintered sample.
Hardness was taken by Rockwell hardness tester. Steel ball indenter applied 100 kg of force for a dual time of 10 seconds. These indents were taken close to each other. Stereographic images showed that very less damage occurred on the surface. During testing, a crack developed in the mounting area, but the sample remained intact, and the hardness of the sample was estimated to be above the measuring scale. Ball penetrated less than 1mm into the surface which can be seen in the images as illustrated in Fig 17.
[Figure omitted. See PDF.]
5. Conclusion
The molten salt technique was employed in order to obtain nanoparticles of MgAl2O4. Potassium chloride (KCl) was employed as the solvent in the experiment. The laser particle analyzer was utilized to characterize Sample A, revealing that the average particle size measured 6 μm, exceeding the nano range. It is evident that the primary cause for the significant particle size was the equimass proportion of magnesium oxide and aluminum oxide, as opposed to equimolar ratios. Consequently, a sample denoted as B has been meticulously created by combining equal molar amounts of magnesium oxide (MgO) and aluminum oxide (Al2O3) in an ethanol solvent. The confirmation of MgAl2O4 nanoparticles derived from Sample B was achieved by the analysis of X-ray diffraction (XRD) findings. The observed peaks within the range of 66° to 67° provide unambiguous evidence of the existence of MgAl2O4 particles. The determination of the smallest and average crystallite size of the sample was achieved by applying the Scherrer formula. The resulting measurement revealed a value of 15.3 nm and 46.7 nm respectively. The scanning electron microscope (SEM) images also presented evidence of an average particle size of 91.2 nm. The differential scanning calorimetry (DSC) analysis reveals that at a temperature of 600°C, the material experiences a heat flow of 0.05 W/g. Additionally, the thermogravimetric analysis (TGA) curve demonstrates a weight loss of only 3% at 600°C. This characteristic is particularly significant when considering the material’s potential application in thermal insulation. Ultimately, crucibles were fabricated with a combination of MgAl2O4 and high-purity alumina. Additionally, these substances were combined in varying proportions to create diverse compositions of crucibles. Sintering of all four crucibles (i.e., 100% MgAl2O4, 80% Al2O3 and 20% MgAl2O4, 70% Al2O3 and 30% MgAl2O4, and 100% Al2O3) was conducted at 1100°C. However, cracks appeared on the crucible composed of 100% magnesium aluminate during the sintering process. Therefore, a comprehensive examination of the phenomenon of cracking is carried out at 1150°C by making the samples in the form of small tablets of damaged crucible. The tablets undergo ceramography and hardness testing in order to examine the reason for crack development. The results revealed that the absence of cracks on the surfaces of all three tablets shows that a minimum temperature of 1150°C was necessary for the sintering process of MgAl2O4. Future studies should examine the investigation of incorporating MgAl2O4 into Al2O3 crucibles, which would enhance the characteristics of the material, including its strength at elevated temperatures and thermal insulating properties. The enhancement of the mechanical properties of a magnesium aluminate crucible would also be achieved by the utilization of elevated sintering temperatures and extended furnace holding times. The rate at which the furnace generates heat also has an impact on the sintering process. By utilizing the lowest heating rate, it is possible to enhance the strength of the crucible as well.
Citation: Khan SA, Mohd Zain Z, Siddiqui Z, Khan W, Aabid A, Baig M, et al. (2024) Development of Magnesium Aluminate (MgAl2O4) Nanoparticles for refractory crucible application. PLoS ONE 19(1): e0296793. https://doi.org/10.1371/journal.pone.0296793
About the Authors:
Shaheer Ahmed Khan
Roles: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Validation, Writing – original draft, Writing – review & editing
E-mail: [email protected]
Affiliations: Department of Engineering Sciences, Pakistan Navy Engineering College (PNEC), National University of Sciences and Technology (NUST), Karachi, Pakistan, Department of Materials Engineering, NED University of Engineering and Technology, Karachi, Pakistan
ORICD: https://orcid.org/0000-0002-7302-0884
Zakaria Mohd Zain
Roles: Funding acquisition, Project administration, Resources, Supervision
Affiliation: Department of Manufacturing & Materials Engineering, International Islamic University Malaysia (IIUM), Kuala Lumpur, Malaysia
Ziauddin Siddiqui
Roles: Conceptualization, Formal analysis, Methodology, Supervision, Visualization, Writing – review & editing
Affiliation: Department of Engineering Sciences, Pakistan Navy Engineering College (PNEC), National University of Sciences and Technology (NUST), Karachi, Pakistan
Wajahat Khan
Roles: Formal analysis, Methodology, Software, Visualization, Writing – review & editing
Affiliation: Department of Engineering Sciences, Pakistan Navy Engineering College (PNEC), National University of Sciences and Technology (NUST), Karachi, Pakistan
Abdul Aabid
Roles: Funding acquisition, Project administration, Resources, Writing – review & editing
Affiliation: Department of Engineering Management, College of Engineering, Prince Sultan University, Riyadh, Saudi Arabia
ORICD: https://orcid.org/0000-0002-4355-9803
Muneer Baig
Roles: Project administration, Supervision, Writing – review & editing
Affiliation: Department of Engineering Management, College of Engineering, Prince Sultan University, Riyadh, Saudi Arabia
Mohammad Abdul Malik
Roles: Resources, Writing – review & editing
Affiliation: Department of Engineering Management, College of Engineering, Prince Sultan University, Riyadh, Saudi Arabia
ORICD: https://orcid.org/0000-0002-3888-5911
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Abstract
Ceramics are the oxides of metals and nonmetals with excellent compressive strength. Ceramics usually exhibit inert behavior at high temperatures. Magnesium aluminate (MgAl2O4), a member of the ceramic family, possesses a high working temperature up to 2000°C, low thermal conductivity, high strength even at elevated temperatures, and good corrosion resistance. Moreover, Magnesium Aluminate Nanoparticles (MANPs) can be used in the making of refractory crucible applications. This study focuses on the thermal behavior of Magnesium Aluminate Nanoparticles (MANPs) and their application in the making of refractory crucibles. The molten salt method is used to obtain MANPs. The presence of MANPs is seen by XRD peaks ranging from 66° to 67°. The determination of the smallest crystallite size of the sample is achieved by utilizing the Scherrer formula and is found to be 15.3 nm. The SEM micrographs provided further information, indicating an average particle size of 91.2 nm. At 600°C, DSC curves show that only 0.05 W/g heat flows into the material, and the TGA curve shows only 3% weight loss, which is prominent for thermal insulation applications. To investigate the thermal properties, crucibles of pure MANPs and the different compositions of MANPs and pure alumina are prepared. During the sintering, cracks appear on the crucible of pure magnesium aluminate. To explore the reason for crack development, tablets of MgAl2O4 are made and sintered at 1150°C. Ceramography shows the crack-free surfaces of all the tablets. Results confirm the thermal stability of MANPs at high temperatures and their suitability for melting crucible applications.
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Details
; Zakaria Mohd Zain; Siddiqui, Ziauddin; Khan, Wajahat; Aabid, Abdul
; Baig, Muneer; Mohammad Abdul Malik