CHARACTERIZATION OF SOME CLAY SAMPLES FOR CERAMIC TILES OBTAIN FROM SOME TOWN IN SOUTHEAST, NIGERIA.
K.B.OKEOMA1
C.A.MADU1
S.O.AJAYI1
O.K.ECHEDU1
U.S.MBAMARA1
C.M.UGBAJA1✉EmailAjayidare2634@gmail.com
1Department of PhysicsFederal University of TechnologyOwerriNigeria
1K. B. OKEOMA,1C. A. MADU, 1S.O. AJAYI, 1O. K. ECHEDU, 1U. S. MBAMARA & 1C. M. UGBAJA
1Department of Physics, Federal University of Technology, Owerri, Nigeria
(Ajayidare2634@gmail.com)Corresponding Author
ABSTRACT
Majority of the available natural resources such as clay in Nigeria have not been receiving sufficient attention. Hence, there is need for investigation into the possible exploitation of these resources. This study characterised four (A-D) different clay samples obtained from two locations Isuochi in Abia and Ihube in Imo State of Nigeria to establish their suitability as raw material for ceramic tiles fabrication. The clay samples were analysed based on B.S 1377:1975, I.S. 1498–1970 and ASTM standards to obtain their elemental, mineralogical composition, physical and refractory properties, such as chemical composition, linear shrinkage, plasticity index, total porosity, bulk density. The results revealed that the clays belong to Alumino-Silicate Refractories through chemical analysis, since the major constituents of the clay samples (more than 75%) were Alumina (Al2O3) and silica (SiO2). All samples exhibited low CaO levels and the SiO₂/Al₂O₃ ratios indicative of kaolinitic composition. Mineralogical results showed that the main mineral present in the clays were quartz, feldspars, kaolinite and muscovite/illite.The results for linear shrinkage, Plasticity index, total porosity and Bulk density are between the range of (8.16–10.44%); (10.28–15.64%); (33.98–55.15%); (1.12–1.32 g/cm3) respectively. The clay properties meet the required standards for fireclay refractory materials, and this could replace imported clays / ceramics in refractory applications, such as in production of earthenwares, tiles. If these clays are carefully exploited, it will assist in addressing the problem of unemployment in the country, and over dependence on foreign goods.
KEYWORDS:
Clay
Characterization
Fabrication
Refractory
Ceramic
A
A
1.0 Introduction
The majority of the available natural resources in Nigeria have not been receiving sufficient attention despite the harsh economic environment created by over dependence on oil sector [1]. If these resources are harvested and adequately utilized, they could significantly contribute to the country's economic growth. Industrialization has been identified as an effective means to enhance a country's economic status [2, 3]. One such resource is clayey deposits which are abundant in many parts of Nigeria. The clay materials are very sensitive to water. This sensitivity makes them difficult to handle but also a subject of extensive scientific studies. These deposits are composed of kaolinite, iron-rich illite, and quartz in varying proportions. They have been widely used as the main components of raw materials in the fabrication of diversified ceramic products [4]. The use of local clay resources offers an alternative to expensive imported materials and can help reduce the foreign currency deficit. The properties of clays that interest the ceramic industry include their plasticity, which facilitates shaping, as well as their chemical and mineralogical composition, thermal properties, color, and mechanical strength after firing [5]. If adequately utilized, these resources could significantly contribute to Nigeria's economic growth. Pure clays do not occur naturally; they contain mixtures of different clays and associated minerals [6]. Currently, many ceramic tiles are manufactured from mixtures of mineral raw materials, primarily composed of clays along with quartz, feldspar, and carbonates. During the fabrication process, these raw minerals are mixed in varying proportions, considering the influence of each component on the properties of the final products [7]. According to the World Resources Institute, the development of clay resources has ripple effects on national economies, with increased consumption correlating with population growth. Exploiting these resources promotes employment growth, scientific innovation, and economic development [8]. Industrialization of clay materials has been identified as an effective means to enhance a country's economic status [9]. Their applications depend heavily on their structure, composition, physicochemical characteristics, and their abundance, combined with their relatively low cost [10]. The use of clay in tile production is influenced by both technological needs and aesthetic factors, such as color after firing and the material's behavior during manufacturing. A study by Ochen [11] investigated the use of locally sourced raw materials in Uganda for producing porcelain tiles. They experimented with different proportions of materials: 40%–60% clay, 30%–40% feldspar, and 10%–30% sand, fired at temperatures between 1050 and 1250°C. Porcelain tiles are known for their high flexural strength, typically greater than 35 MPa, and low water absorption, less than 0.5%. The study found that the best tile properties were achieved at 1200°C with a mixture of 30%–40% kaolin, 30%–40% feldspar, 20% ball clay, and 10% sand, resulting in a flexural strength of 33 MPa and water absorption of 0.08%. Another study the sintering behavior of diatomite powder bodies, revealing that high-porosity, high-compressive-strength diatomite monoliths can be formed at 1000°C. However, above 1200°C, a melt phase forms, eliminating the intrinsic pores of the diatomite and increasing its density. Microstructural analyses indicated that impurities in diatomite, such as Na2O, K2O, Al2O3, CaO, and MgO, promote the formation of low-temperature eutectics, resulting in a melt phase in the silica-rich grains [12]. Thus, determining the mineralogical, chemical, granulometric, and rheological characteristics of clays is essential to assess their potential for industrial applications [13, 14]. The objective of this study is to assess the properties of the abundant clay minerals found in the municipality of Isuochi in Abia and Ihube in Imo State of Nigeria. This evaluation will encompass the physical properties, plasticity, mineralogy, chemical compositions, morphology and thermal properties of these clay minerals. The goal is to determine their suitability as raw materials for the production of ceramic industrial products. Utilizing these local resources will provide a cost-effective alternative to imported materials, potentially encouraging investment in the expansion or establishment of new ceramic manufacturing industries in the region. This, in turn, could generate more employment opportunities in businesses directly and indirectly associated with the ceramic industry, fostering a more sustainable community.
2.0 MATERIALS AND METHODS
2.1 Material
Four (4) clay samples (A-D) were collected randomly from two locations Isuochi in Abia and Ihube in Imo State of Nigeria, namely: Sample A, Sample B from Isuochi, Sample C and Sample D from Ihube were prepared for X-ray diffraction (XRD), X-ray Fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), in accordance to the standard procedure. The analyses were carried out to investigate the mineralogical composition, relative proportions of the constituent compounds, the morphology and the phase identification of the four prepared samples from the clay deposits.
2.2 Methology (Experimental Analysis)
2.2.1 Chemical Composition
Representative samples of the selected clay materials were analysed to determine their chemical constituents using Atomic Absorption Spectrophotometer (AAS) in line with the recommendation of Chestie [15]. The X-ray fluorescence (XRF) or Atomic Absorption Spectrophotometer (AAS) can be used for this purpose. In this study X-ray fluorescence (XRF) were used to determine the chemical constituents of the clay samples as presented in Table 2.
2.2.2 Atterberg Limit (Consistency Tests)
In carrying out refractory clay materials’ liquid limit, plastic limit and plastic index were determined.
2.2.2.1 Liquid Limit
100g of each of the samples was made to pass through 425 µm sieve and mixed thoroughly with distilled water in evaporating dish to form a uniform paste. A portion of the paste was placed in the cup of the liquid limit device (Plate 1a). The mix was levelled to have a maximum depth of 1cm (see Plate Ib). The grooving tool was drawn through the sample along the symmetrical axis of the cup by holding the tool perpendicular to the cup as shown in Plate Ic below. The handle of the device was then rotated and the numbers of blows were counted till the two parts of the clay particle came into contact at the bottom of the groove. In the case where some clays slide on the surface of the cup instead of flowing, the results were discarded and then repeated. The operations were repeated five times in accordance with BS 1377: part 2:1990 guideline [16]. Five readings were obtained in the range of 25 blows. The liquid limit was determined using required Atterberg Table and by plotting the graph on semi-logarithmic graph between the numbers of blow.
(a)
(b) (c)
Plate I: Determination of a Clay Sample Liquid Limit
2.2.2.2 Plastic Limit
Each of the samples weighing 15g was made to pass through 425 µm sieve and mixed thoroughly with distilled water until the clay mass became plastic to be easily moulded into a ball with fingers. The portion of the ball was taken and rolled with the palm (hand) on a glass plate to form clay mass of thread of uniform of 3mm throughout its length. The clay was re-moulded again into a ball repeatedly until the thread started to crumble at the diameter of 3mm. The crumbled thread was kept in desiccators for water content determination. A portion of the plastic clay was weighed, sieved through a set of sieve and then fired at 1150C for 30 minutes. It was then kept in desiccators for 15 minutes and re-weighed. The difference was calculated and result was recorded. The test was repeated with two more times. The average plastic limit was then taken as average of the three water content values.
2.2.2.3 Plasticity Index
The plasticity index was calculated using equation (iii) given below .
Plasticity Index,
(1)
The specimens (cones) were prepared from each of the selected clay samples. Each clay sample was thoroughly mixed water to attain adequate clay plastic, which was moulded into cone shape and dried to a temperature of 900oC. The specimens were arranged around a refractory plaque to test for the refractoriness of clay samples. The plaque containing the test cones with some standard cones whose melting points were slightly above/or below that of expected test cones were placed in a furnace. The furnace temperature was raised at the rate of 100oC per minute until the test cone bent over and levelled with the base of the disc. The final temperatures were then recorded at the end of the experiment.
2.2.3 Bulk Density
Fresh two (2) pairs of each sample of the clay bricks were selected to determine the bulk density of the clay samples. The samples were dried for 24 hours in air and later in oven at 110oC for 24 hours. The samples were kept in desiccators. The dried weights of the samples were also measured nearest to 0.001g using analytical balance. The weighed samples were transferred into separate beakers and soaked with water. They were heated for 30 minutes to release the trapped air the samples. The samples were cooled and the weight of each sample was taken. Each sample was suspended in water in the beaker and the suspended weight was measured. The bulk density of the clay samples was determined using the relationship below
2
2.2.4 Linear Shrinkage
The specimens were rolled in rods of 12cm and marked along a line to maintain the same position after heat treatment. The specimens were dried in still air for 24 hours and later fired at temperature of 110oC in oven for 6 hours, allowed to cool at room temperature and transferred into desiccators. The dried lengths of the specimens were recorded and their linear shrinkage values of the specimens were determined using the relationship below.
% (3)
2.2.5 X-ray Fluorescence (XRF) Spectroscopy Analysis
Quantitative analysis of the major minerals within the samples was done by X-ray Fluorescence Spectroscopy using a Magi X Pro XRF Spectrometer. For this purpose, a mass of 8g of each of the powdered clay samples was mixed with 2g of Herzog organic binder. The organic binder contained 90% cellulose and 10% wax. The mix was further ground and homogenized using a mill. The homogenized samples were placed in an aluminum cup and hydraulically pressed into pellets under very high pressure of 20 tones for 60 seconds. This was done to ensure sample integrity under the vacuum and a consistent surface to receive the X-rays.
2.2.6 Fourier-Transform Infrared Spectroscopy (FTIR)
FTIR is a technique used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas [17]. The term Fourier transform infrared spectroscopy originates from the fact that a Fourier transform (a mathematical process) is required to convert the raw data into the actual spectrum. FTIR spectroscopy provides insights into the chemical structure of clay minerals by detecting vibrational modes of molecular bonds, particularly those involving hydroxyl groups, silicates, and water. It is particularly useful in identifying functional groups, such as OH-, Si–O, Al–O–Si, and CO₃²⁻, which help distinguish between similar minerals that may be indistinguishable by XRD alone [18].
2.2.7 X-ray Diffraction (XRD)
X-ray diffraction (XRD) is a versatile non- destructive analytical technique used to analyze physical properties such as phase composition, crystal structure and orientation of powder, solid and liquid samples. Many materials are made up of tiny crystallites. X-ray diffraction is now a common technique for the study of crystal structures and atomic spacing. X − ray diffraction is based on constructive interference of monochromatic X − rays and a crystalline sample. These X − rays are generated by a cathode ray tube, filtered to produce monochromatic radiation, collimated to concentrate, and directed toward the sample. XRD is a fundamental technique for identifying the crystalline phases present in clay minerals.
2.2.8 Thermogravimetric Analysis (TGA)
Thermogravimetric analysis or thermal gravimetric analysis (TGA) is a method of thermal analysis in which the mass of a sample is measured over time as the temperature changes. This measurement provides information about physical phenomena, such as phase transitions, absorption, adsorption and desorption; as well as chemical phenomena including chemisorption, thermal decomposition, and solid-gas reactions (e.g., oxidation or reduction) [19]. Thermogravimetric analysis is a method of thermal analysis in which changes in physical and chemical properties of materials are measured as a function of increasing temperature or as a function of time. TGA assesses the thermal stability and composition of clay materials by measuring weight changes as a function of temperature. It reveals moisture content, dehydroxylation temperatures of clay minerals (e.g., kaolinite dehydroxylates around 450–600°C), and the decomposition of any carbonates or organic matter [20]. This data is vital in ceramic processing, where thermal transformations directly impact sintering behavior and dimensional stability.
2.2.9 Scanning Electron Microscopy (SEM) Analysis
Morphological, quantitative and qualitative analyses of the clay samples were carried out using SEM model JEOL 840. The SEM studies for the mineral analysis of representative samples were conducted in two stages. All the samples were carbon coated in order to make the minerals surface conductive. In the first stage, which was aimed at examining the minerals morphology and identifying their mode of occurrence, crushed carbon coated minerals were examined directly with scanning electron microscopy without polishing. The second stage of the microscopic study was aimed at identifying the mineral phases present within the samples. Qualitative chemical analysis of minerals was carried out on the clay samples to produce Backscattered images (BSI). The Quantitative analysis was carried out using the EDX analysis.
3.0 RESULTS AND DISCUSSION
3.1 Physical Properties of the Clay Samples
The study investigated the Atterberg limits (liquid limit, plastic limit, and plasticity index) of powders from four samples after passing them through a 425-micron sieve are as presented on Table 1 and Fig. 1. The results were as follows: The Atterberg limits of sample A shows a liquid limit of 26.73% and a plastic limit of 16.45%, which resulted in a plasticity index of 10.28%. The Atterberg limits of the sample B shows a liquid limit of 33.59% and a plastic limit of 19.64%, which resulted in a plasticity index of 13.95%. The Atterberg limits of the sample C shows a liquid limit of 39.21% and a plastic limit of 25.94%, which resulted in a plasticity index of 13.27%. The Atterberg limits of the sample D shows a liquid limit of 38.80% and a plastic limit of 23.16%, which resulted in a plasticity index of 15.64%. Based on the plasticity index values, all samples are classified as medium plasticity clays since they fall between 10% and 20%. According to Danish [21] and Vieira [22], clays must have a plasticity index greater than 10% to be suitable for brick production via an extrusion process. All four samples meet this requirement. The distinct Atterberg limit values for the samples are likely due to the varying populations of fine particle sizes, especially those with diameters less than 2 microns, which significantly impact clay mineral flexibility [23]. Additionally, the amount and type of clay minerals and the type of absorbed cations also influence the Atterberg limit values [24]
Fig. 1
The firing-related properties samples (A–D), highlighting differences in plasticity, shrinkage, bulk density, and porosity.
Sample | Liquid limit (%) | Plastic limit (%) | Plasticity index (%) | Linear Shrinkage (%) | Bulk Density(g/cm3) | Total Porosity(%) |
|---|---|---|---|---|---|---|
A | 26.73 | 16.45 | 10.28 | 8.16 | 1.23 | 38.67 |
B | 33.59 | 19.64 | 13.95 | 9.57 | 1.32 | 33.98 |
C | 39.21 | 25.94 | 13.27 | 10.03 | 1.12 | 55.15 |
D | 38.80 | 23.16 | 15.64 | 10.44 | 1.24 | 50.23 |
Plasticity Index and Liquid Limit of the Samples on the Plasticity Chart | Extrusion Prognostic through Atterberg limits of samples studied |
Figure 2: Classification of the clay samples on Casagrande Plasticity Chart
Figure 2, provide valuable insight into the classification and workability of the samples based on their Atterberg limits, particularly focusing on the plasticity index, liquid limit, and plastic limit. Figure 1a displays the data plotted on the Casagrande plasticity chart, a widely used tool for classifying fine-grained soils. The chart includes two standard reference lines (the A-line and the U-line). The A-line serves as a boundary between clays and silts. Above the line plot is clay and below is silts. The U-line represents the upper boundary for natural soils. A vertical line is also drawn at a liquid limit of 50, distinguishing between low-plasticity and high-plasticity soils (Casagrande) [28]. The plotted data points, shown as colored triangles, fall mostly near or slightly above the A-line and to the left of the LL = 50 line. This suggests that the sample A,B and D are predominantly low to medium plasticity clays or clayey silts. It is only sample C that fall just below the A-line may be more silty in nature, but overall, the group can be classified as inorganic clays (CL) or silty clays (ML) according to the Unified Soil Classification System (ASTM ) [29]. Figure 1b further explores the properties of the samples by examining their extrusion behavior, based on their plasticity index and plastic limit. The plotted points, represented by colored dots, fall within or close to the optimal plasticity conditions for extrusion. The majority of the samples lie within these boundaries, suggesting favorable workability characteristics for extrusion processes. A few points fall near the borders, indicating that minor adjustments in water content or processing conditions might be necessary for ideal performance. Together, these figures reveal that the soil samples are predominantly low to medium plasticity clays with good potential for extrusion and workability. This makes them suitable for use in civil engineering or material applications such as compressed earth blocks, adobe production, ceramic manufacturing, or soil-based construction, depending on additional factors like shrinkage, drying behavior, and mechanical strength.
3.2 Geochemistry of the Clay Samples
The chemical composition of the major elements in the clay samples, expressed as percentages of oxides, reveals several important points. Silica (SiO₂) and alumina (Al₂O₃) are the most abundant oxides, with silica ranging from 46.11% to 70.32% and alumina from 24.47% to 33.69%. Notably, sample D has a particularly low silica content of 46.11%. Iron oxide (Fe₂O₃) content is high in samples B, C, and D, but very low in sample A. The alumina content places these samples within the Alumino-Silicate Refractories category, consistent with the work of Hassan [30] and Hassan and Adewara [31]. This classification is further supported by Atanda et al. (2012)[1], who noted that fireclay typically contains 24–32% Al₂O₃ and 50–60% SiO₂. Other oxides such as K₂O, CaO, P₂O₅, MgO, and MnO are present in low to trace amounts, with MgO being entirely absent in all samples. The low levels or absence of MgO, MnO, CaO, and P₂O₅ may result from their high mobility and significant leaching during kaolinitization, as suggested by Njoya [32]. The presence of accessory minerals could explain the low or zero levels of P₂O₅, MgO, and MnO, although these minerals were not identified by XRD. According to Pialy [33], other advanced methods might be needed for their determination. The ratio of SiO₂/Al₂O₃ is greater than 1, indicating an abundance of silica, which is characteristic of kaolinitic clays, according to Kwopnang [34]. Ratios around 2 suggest a mixture of kaolinite and mica or illite, as stated by Pialy [33]. High silica/alumina ratios further indicate the presence of kaolinite, confirmed by XRD analysis. The Fe₂O₃/Al₂O₃ ratio is less than 1 in all samples, indicating the presence of iron-based compounds. Low Fe₂O₃/Al₂O₃ ratios suggest the presence of iron oxides and hydroxides, such as hematite, goethite, and ferrihydrite, as noted by Bomeni [35]. Lastly, the presence of titanium oxide (TiO₂) in variable proportions is attributed to anatase, as suggested by Pialy [33]. According to ASTM [36], a material is classified as a natural pozzolanic material or silicate glass material if its combined content of SiO₂, Fe₂O₃, and Al₂O₃ is greater than 70%, and its CaO content is less than 10%. Our analysis of clay samples revealed that Sample A has a combined SiO₂, Fe₂O₃, and Al₂O₃ content of 96.44%, Sample B has 94.12%, Sample C has 92.78%, and Sample D has 78.19%, with all samples having a CaO content below 10%. These findings confirm that all four samples meet the ASTM criteria, making them excellent candidates for glass production. The high content of SiO₂, Fe₂O₃, and Al₂O₃ in these samples ensure their suitability as natural pozzolanic materials, which are crucial for manufacturing quality glass. Therefore, Samples A, B, C, and D are highly suitable for glass production.
Clay Samples | SiO2 | Al2O3 | TiO2 | Fe2O3 | CaO | MgO | MnO | K2O | P2O5 | SO3 | SiO2/ Al2O3 | Fe2O3/ Al2O3 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
A | 70.32 | 25.16 | 2.02 | 0.96 | 0.16 | 0.00 | 0.05 | 0.02 | 0.18 | 0.14 | 2.79 | 0.04 |
B | 50.40 | 24.66 | 2.92 | 19.06 | 0.10 | 0.00 | 0.04 | 1.35 | 0.14 | 0.30 | 2.04 | 0.77 |
C | 50.62 | 33.69 | 4.50 | 8.47 | 0.17 | 0.00 | 0.03 | 0.95 | 0.00 | 0.24 | 1.50 | 0.25 |
D | 46.12 | 24.47 | 3.22 | 7.61 | 0.20 | 0.00 | 0.10 | 2.80 | 0.00 | 14.23 | 1.88 | 0.31 |
3.3 FTIR Spectroscopy
The FTIR spectra of the samples are shown in Fig. 3a-3d, recorded in the range of 4000–400 cm− 1. Figure 3a-3d shows the FT1R spectra of (a) Sample A (b) Sample B (c) Sample C (d) Sample D. Samples A to D, are clay samples. Among the clay samples, A – D, the following infrared bands/peaks were observed. Peaks 3690, 3894 and 3653 cm− 1 for inner-surface hydroxyl groups stretching, 3623 cm− 1 for inner hydroxyl group stretching, 1636 cm− 1 for hydroxyl deformation of water, 2017 and 2013 cm− 1 for N = C = S stretching (isothiocyanate), 1741 and 1737 cm− 1 for carbonyls of aldehydes [37, 38]). The other bands include; 1115 cm− 1 for Si-O stretching, 1029, 1028, 1006, 1003 and 999 cm− 1 for in-plane Si-O stretching, 910 cm− 1 for OH deformation of inner hydroxyl group, 790, 799, 753, 686, and 678 cm− 1 for Si-O. [38–40]. A summary of the common peaks from the infrared spectra is shown in Table 3.
 Figure 3a: The FTIR spectra for Sample A |  |
|---|---|
 Figure 3c: The FTIR spectra for Sample C |  Figure 3d: The FTIR spectra for Sample D |
A B C D Assignments (Wavenumber, cm− 1) |
|---|
3690 3690 3694 3694 OH stretching of inner-surface hydroxyl group 3653 - 3653 3653 OH stretching of inner-surface hydroxyl group - 3623 - - OH stretching of inner hydroxyl groups 2017 2017 2013 2013 Isothiocyanate stretching 1741 1737 - - Carbonyl stretching - - 1636 1636 OH deformation of water 1115 1115 1115 1115 Longitudinal Si-O stretching 1029 - 1029 1028 Si-O stretching in-plane 1006 1003 1003 999 Si-O stretching in-plane 910 910 910 910 OH deformation of inner hydroxyl group 790 790 799 799 Si-O 753 753 753 753 Perpendicular mode Si-O 686 686 678 686 Perpendicular mode Si-O |
| - Not identified |
| From Fig. 3, it could be observed that there are some clay minerals that were found in the samples A - D. The possible minerals present are shown in Table 4. The clay mineral, kaolinite was present in them in the following associated bands; 3690, 3675, 3649, 3653, 1741, 1029, 790, 686, 3623, 1737, 3694, 1636, and 678 cm− 1. The observed peaks of kaolinite agreed with that reported by Jozanikohan and Aborghooei,[41]. Quartz was indicated with these observed absorption vibrations; 1115, 1305, 999, 1029, 1006, 790, 753, 686, 1003, 799 and 678 cm− 1. Between the absorption band region of 800 and 600 cm− 1, the peaks observed were attributed to feldspar, and they are; 790, 753, 686, 799, and 678 cm− 1. The mineral illite has these associated peaks in the samples; 1029, 910, 3623, 1028 and 3649 cm− 1. The presence of the mineral saucite is characteristic with these peaks; 1029, 910, 3623, and 3649 cm− 1. The assignments of the bands/peaks are in line with those in earlier reported works [18, 20, 37, 39, 41–43] |
.
Sample Assignment of minerals (bands in cm− 1) |
|---|
A Kaolinite (3690, 3653, 1741, 1029, 790 and 686), quartz (1115, 1029, 1006, 790, 753, 686), feldspar (790, 753 and 686), illite (1029 and 910), saucite (1029 and 910) B Kaolinite (3690, 3623, 1737, 790 and 686), quartz (1115, 1003, 790, 753 and 686), feldspar (790, 753 and 686), illite (3623 and 910), saucite (3623 and 910) C Kaolinite (3694, 3653, 3623, 1636 and 678), quartz (1115, 1029, 1003, 799, 753 and 678), feldspar (799, 753 and 678), illite (3623, 1028 and 910), saucite (3623 and 910) D Kaolinite (3694, 3653, 3623, 1636 and 678), quartz (1115, 1029, 1003, 799, 753 and 678), feldspar (799, 753 and 686), illite (3623, 1028 and 910), saucite (3623 and 910) |
3.4 Scanning Electron Microscopy (SEM)
 Figure 4a: Typical SEM/EDS Micrographs for sample A showing the Morphology of the Clay and its Chemical Composition |
 Figure 4b: Typical SEM/EDS Micrographs for sample B showing the Morphology of the Clay and its Chemical Composition | ||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 Figure 4c: Typical SEM/EDS Micrographs for sample C showing the Morphology of the Clay and its Chemical Composition |
 Figure 4d: Typical SEM/EDS Micrographs for sample D showing the Morphology of the Clay and its Chemical Composition |
Figure 4 are the results of the SEM/EDS analysis for all four samples, which show the SEM micrographs of the relative sizes of the clay particles at 500X magnification, chemical composition at both general surface and the spectra depicting the peaks of the elements present. Table 5, shows the EDS analysis for elemental chemical composition. The analysis shows the actual percentage of the various elements contained in the clay samples. The EDS analysis revealed very reasonable similarity in the results with the XRF and FTIR. The EDS chemical
Clay Samples | O | Si | Al | N | C | Ti | S | Fe | K | Cl | Na |
|---|---|---|---|---|---|---|---|---|---|---|---|
A | 63.44 | 12.38 | 14.52 | - | 3.67 | 6.00 | - | - | - | - | - |
B | 53.12 | 21.93 | 15.66 | - | 0.68 | - | 3.15 | 3.93 | - | - | - |
C | 51.49 | 18.87 | 19.54 | 6.31 | 0.64 | - | - | 3.16 | - | - | - |
D | 41.42 | 6.01 | 5.27 | - | 12.12 | - | - | - | 16.71 | 6.91 | 11.56 |
| - Not identified | |||||||||||
analysis of the clay samples as shows in Table 5 reveals notable differences in elemental composition, reflecting their diverse mineralogical origins. Sample A is dominated by oxygen (63.44%), aluminum (14.52%), and silicon (12.38%), with moderate carbon (3.67%) and titanium (6.00%), suggesting it is a typical aluminosilicate clay possibly rich in kaolinite or halloysite. Sample B has a higher silicon content (21.93%) and significant amounts of aluminum (15.66%), sulfur (3.15%), and iron (3.93%), indicating possible presence of iron sulfide minerals such as pyrite. Sample C contains the highest aluminum (19.54%) and notable nitrogen (6.31%) and iron (3.16%), possibly from organic matter or nitrogen-containing minerals. Sample D is unique, with low aluminosilicate content and high levels of potassium (16.71%), chlorine (6.91%), sodium (11.56%), and carbon (12.12%), pointing to the presence of feldspar or saline contamination.
3.5 X-ray diffraction (XRD) analysis
The X-ray diffraction (XRD) analysis provided a quantitative insight into the mineralogical composition of four clay samples (A–D), as shown in Figs. 5a–5d and Table 6, highlighting both shared and unique constituents. Sample A was predominantly composed of quartz (62%) and orthoclase/alkali feldspars (21%), with a notable presence of dickite (17.8%), a polymorph of kaolinite. The minor presence of muscovite/illite (0.3%) suggests minimal layered silicate contribution. Quartz and feldspar dominance, coupled with low illitic content, indicates limited plasticity but high thermal stability, often favorable in refractory materials [44, 45]. Sample B exhibited a more varied mineralogy, containing quartz (49%), feldspars (15%), muscovite/illite (9.1%), and secondary phases like anhydrite (6.5%) and osumilite (15%). The presence of these additional phases implies a more thermally or chemically altered clay, potentially of volcanic or hydrothermal origin [46, 47]. The high-temperature phases such as osumilite suggest high-temperature alteration environments or pyroclastic deposition. Sample C was distinct for its high kaolinite content (32%), coupled with quartz (53%) and low feldspar content (4%). This mineral profile suggests a relatively unaltered, sedimentary-derived kaolinitic clay, which is typically favorable for ceramic and refractory applications due to its purity, whiteness upon firing, and low shrinkage [48, 49]). Sample D contained a significant amount of clinochlore (18%), a chlorite group mineral, along with orthoclase/alkali feldspar (27%), quartz (44%), and muscovite/illite (11%). This composition indicates a metamorphic influence, as chlorite and muscovite often form under greenschist to low-grade metamorphic conditions [50]. Their presence suggests that this sample may have higher thermal resistance and structural rigidity due to the inherited layered silicate framework and iron-magnesium content in chlorites. Therefore, Samples A and C are more silica-rich and potentially suitable for ceramic formulations, particularly due to their higher quartz and kaolinite contents. Sample B shows a complex mineral assemblage indicating mixed or altered geological origins, while Sample D’s high chlorite and illite content suggests a different structural evolution and potentially improved thermal resistance. Figure 6 presents a bar chart illustrating the mineralogical composition percentages of all four samples as determined by X-ray diffraction (XRD) analysis.
Mineral Phase | Sample A (%) | Sample B (%) | Sample C (%) | Sample D (%) |
|---|---|---|---|---|
Quartz | 62 | 49 | 53 | 44 |
Orthoclase/Albite | 21 | 15 | 4 | 27 |
Anhydrite | - | 6.5 | - | - |
Osumilite | - | 15 | - | - |
Muscovite/Illite | 0.3 | 9.1 | 0.7 | 11 |
Clinochlore | - | 5.9 | - | 18 |
Kaolinite | - | - | 32 | - |
Dickite | 17.8 | - | - | - |
| - Not identified | ||||
The overall comparison of the clay samples, as presented in Table 7, highlights the primary mineral constituents, dominant characteristics, and their potential applications.
Sample | Main Minerals | Dominant Feature | Likely Use/Application |
|---|---|---|---|
A | Quartz, Dickite, Feldspar | High silica with kaolin group (Dickite) | Refractory, ceramic filler [48] |
B | Quartz, Osumilite, Illite, Clinochlore | Complex mix, moderate fluxing minerals | Thermally active clay, possibly ceramic [44] |
C | Quartz, Kaolinite | High kaolinite content | Metakaolin, pozzolan, cement additive [54, 55] |
D | Feldspar, Illite, Clinochlore | High fluxing & plastic minerals | Ceramic, structural clay products [56, 57] |
Fig. 5a
X-ray diffraction pattern of Sample A
Fig. 5b
X-ray diffraction pattern of Sample B
Fig. 5c
X-ray diffraction pattern of Sample C
Fig. 5d
X-ray diffraction pattern of Sample D
Fig. 6
This bar chart compares the percentage composition of identified minerals in Clay Samples
3.6 Thermal Analysis of clay samples
The thermalgravimetric analysis (TGA) of Samples A through D reveals distinct weight loss patterns as the temperature increases, reflecting differences in moisture content, organic/inorganic composition, and thermal stability as show in Fig. 7. The data was analyzed across three key temperature intervals: 30–150°C (representing moisture loss), 150–500°C (decomposition of organics and dehydroxylation of clays), and above 500°C (residual weight indicating thermally stable inorganics). These zones correspond to well-established thermal behaviors in clay minerals [51, 52]). In the initial temperature range of 30–150°C, which accounts for the evaporation of free and bound water, Sample C exhibited the highest weight loss of approximately 10%. This suggests that it holds the greatest moisture content, potentially due to higher surface area or more hygroscopic clay minerals such as smectites [45]). In contrast, Sample D showed the lowest moisture loss at about 6%, indicating a comparatively lower water content and perhaps a denser or more compact clay structure with fewer surface-bound water molecules. In the mid-temperature range of 150–500°C, which includes the degradation of organic matter, loss of structural hydroxyl groups, and possible decomposition of carbonates, all four samples experienced significant weight loss. Samples A and C showed the greatest loss in this range, each around 68%, indicating a high proportion of organic matter and reactive clay minerals that undergo substantial breakdown. Sample B displayed a slightly lower loss at 61%, while Sample D showed a moderate loss of about 62%, suggesting it contains somewhat less degradable material than Samples A and C. Above 500°C, the weight loss plateaued, and the remaining mass largely represents stable inorganic residues such as silicates and oxides [53]. Here, Sample D retained the most mass—about 32% of its original weight—demonstrating superior thermal stability and a greater proportion of refractory mineral content. Conversely, Sample C had the least residue, around 22%, reinforcing the observation that it contains the most thermally labile material. Therefore, Sample C appears to be the most volatile, with the highest moisture content and overall weight loss, suggesting it is rich in organics and less thermally stable minerals. Sample D, on the other hand, is the most thermally resilient, with minimal moisture loss and the highest final residue, indicating a composition dominated by stable inorganic components. Samples A and B fall in between, with Sample A more similar to Sample C in terms of organic loss, and Sample B resembling Sample D with its moderate moisture content and higher residue. Table 8 indicate the correlation between the bulk density, linear shrinkage and the thermogravimetric analysis of the clay samples
Sample | Linear Shrinkage (%) | Bulk Density (g/cm³) | Moisture Loss (30–150°C) | Mid-Temp Loss (150–500°C) | Residue > 500°C | Interpretation |
|---|---|---|---|---|---|---|
A | 8.16 | 1.23 | Moderate (~ 7–8%) | High (~ 68%) | ~ 24% | Medium shrinkage, high organic/clay content [44, 48] |
B | 9.57 | 1.32 | Moderate (~ 7%) | Lower (~ 61%) | ~ 28% | Highest density, moderate shrinkage, more stable [56, 57] |
C | 10.03 | 1.12 | Highest (~ 10%) | High (~ 68%) | ~ 22% | Most volatile, most shrinkage, least stable [54, 55] |
D | 10.44 | 1.24 | Lowest (~ 6%) | Moderate (~ 62%) | ~ 32% | Densest residue, lowest volatility, highest thermal stability [48] |
Table 8 indicate that the Sample C, characterized by its low bulk density and high linear shrinkage, exhibited the highest total weight loss during thermogravimetric analysis, along with the lowest final residue. This behavior suggests that it is the least thermally stable sample, likely due to a higher concentration of organic matter and less compact, more hygroscopic clay minerals such as smectite [45, 51]. In contrast, Sample D, although it also displayed high shrinkage, had a moderate bulk density and experienced the lowest initial moisture loss and the highest residue after 500°C. These characteristics point to the presence of dense, thermally stable minerals such as feldspars and oxides. Sample B, which had the highest bulk density, showed greater thermal stability than Sample A, evidenced by its lower mid-temperature weight loss and higher final residue. This indicates a more compact structure with fewer thermally degradable components [47]. Overall, the thermal behavior of the clay samples closely aligns with their physical properties, supporting established correlations between bulk density, shrinkage, and thermal stability in clays [44].
Fig. 7a
TGA/DTA for Sample A
Fig. 7b
TGA/DTA for Sample B
Fig. 7c
TGA/DTA for Sample C
Fig. 7d
TGA/DTA for Sample D
Conclusion:
The investigation of four clay samples from Isuochi in Abia State and Ihube in Imo State, Nigeria, reveals that these natural resources possess significant potential for ceramic and refractory applications. Chemical analysis shows that all samples are rich in silica (SiO₂), alumina (Al₂O₃), and iron oxide (Fe₂O₃), with low calcium oxide (CaO) content—meeting ASTM C618-14 standards and suggesting a kaolinitic nature favorable for ceramic processing. The Atterberg limits place the clays in the medium plasticity range (10.28%–15.64%), confirming their suitability for extrusion-based brick manufacturing. Linear shrinkage values (8.16%–10.44%) fall within acceptable limits for alumino-silicate refractories, indicating good firing behavior and minimal risk of cracking or warping. Mineralogical analysis via XRD shows varied compositions, with Sample A being rich in quartz and feldspar suggesting good refractory potential. Sample B, with complex mineral phases such as anhydrite and osumilite, may be the result of geological alteration. Sample C, with high kaolinite content, is most suitable for ceramic tile fabrication due to its purity and plasticity. Sample D, containing chlorite and muscovite, suggests a metamorphic origin and offers excellent thermal resistance, making it ideal for high-temperature applications. Thermal analysis (TGA) supports these findings by revealing moisture and organic content variability across samples. Sample D demonstrated the greatest thermal stability with the lowest moisture loss, while Sample C had the highest total weight loss, indicating higher organic and volatile content. The FTIR analysis confirms the presence of key clay minerals such as kaolinite, quartz, feldspar, illite, and saucite in Samples A to D. Characteristic absorption bands for each mineral closely match those reported in previous studies, validating their identification. The overlapping peaks suggest mineral intergrowth or associations within the clay matrix, indicating a complex mineralogical composition suitable for various industrial applications depending on thermal and structural stability. The EDS analysis highlights significant elemental variation across the clay samples, indicating diverse mineralogical compositions. Sample A suggests aluminosilicate dominance, likely kaolinite-rich. Sample B shows high silicon and iron-sulfur content, implying possible pyrite presence. Sample C is enriched in aluminum and nitrogen, pointing to organic or nitrogen-bearing minerals. Sample D stands out with high levels of potassium, chlorine, and sodium, suggesting feldspathic or saline influence. These differences reflect distinct geological origins and potential for varied industrial applications.
Funding Declaration: There is no funding for this research
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Clinical trial registrationNot applicable.
Consent to Publish
Declaration:Not Applicable
Ethics And Consent to Participate Declaration:Not Applicable
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Data Availability
All data generated and/or analysed during this study are included in this published article.
A
Author Contribution
S.O. Ajayi and C.M. Ugbaja contributed equally to this work. They jointly collected and prepared samples for analysis. S.O. Ajayi drafted the manuscript under Dr. K.B. Okeoma's supervision. The manuscript was then reviewed and edited by Prof. Mrs. C.A. Madu, Dr. K.B. Okeoma, Dr. O.B. Echendu, and Dr. U.S. Mbamara. All authors approved the final version.
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