Search Results (81)

This study investigates the thermally induced phase transformation of Ni-exchanged LTA zeolite as a dual-purpose method for nickel immobilization and the synthesis of stable ceramic pigments. The process describes a cost-effective and sustainable alternative to conventional pigment production, aligning with circular economy principles. Upon thermal treatment at temperatures ranging between 900 °C and 1300 °C, Ni-exchanged LTA zeolite undergoes a transformation to NiAl₂O₄ spinel, confirmed by XRPD, FTIR, and thermal analysis. Initially, NiO is formed, but as the temperature increases, it dissolves and transforms into NiAl₂O₄. Colorimetric studies revealed intensified blue pigmentation with increasing temperature, correlating with crystallite growth and structural evolution. SEM analysis showed morphological changes from cubic particles to sintered agglomerates, enhancing pigment stability and hardness. The Ni-LTA sample calcined at 1300 °C showed the highest hue angle, which was consistent with the formation of over 99 wt.% of the nickel aluminate crystalline phase at this temperature. The results demonstrate that Ni-LTA zeolite can be effectively transformed into durable greenish-blue pigments suitable for application in porcelain. This transformation is especially evident at 1300 °C, where a spinel phase (NiAlSi₂O₄) forms, with colorimetric values: L = 58.94, a* = –16.08, and b* = –15.90. Full article

Twelve sherds of blue-and-white Chinese porcelains recovered from archaeological excavations in the Santana Convent (Ming and Qing Dynasties) in Lisbon were studied using several non-invasive spectroscopies, namely micro-Raman, X-ray Fluorescence (XRF), Ground State Diffuse Reflectance (GSDR), and stereomicroscopy. The use of the X-ray diffraction technique (XRD) allowed us to complete the mineralogical characterization of the ceramic bodies and glazes of the porcelains. The sample selection ranges from the 16th to the 18th centuries. The micro-Raman spectra clearly showed two types of glazes, alkaline glaze and calcium-based glaze. The GSDR absorption spectra of the blue glazes point to the use of different cobalt pigments, but a strong dependence on the glaze type does not seem to exist. The kilns where the porcelains were produced also play an important role. Both the GSDR absorption and the micro-Raman spectroscopies allow us to differentiate the Iranian blue pigment from the Chinese pigment. A direct and simple correlation between the use of Iranian blue pigment, mixtures of Iranian and Chinese pigments, or simply Chinese pigments and the stylistic dating of each sample was established. Furthermore, several important spectroscopic characterizations could be achieved in this study. Full article

Recently, the development of nanoparticle pigments has attracted interest in chemical preparation due to their potential functional properties, such as phosphate-based pigments. The present research focuses on the feasibility of synthesising the BaCr₂(P₂O₇)₂ pigment under hydrothermal conditions. The effect of the microstructural features of ceramic pigments (the crystalline structure, morphology, and particle size) on their optical properties (colour and reflectance) was also studied. The BaCr₂(P₂O₇)₂ compound was prepared in different fluid media, including water and NaOH solutions (0.5–1.0 M), at several reaction temperatures (170–240 °C) and intervals (6–48 h). The single-phase BaCr₂(P₂O₇)₂ did not crystallise without by-products (BaCr₂O₁₀, BaCr₂(PO₇)₂) in water and the alkaline solutions, even at 240 °C for 48 h; in these fluids, the ionic Cr³⁺ species oxidised to Cr⁶⁺. In contrast, the BaCr₂(P₂O₇)₂ single-phase crystallisation was favoured by adding urea as a reductant agent (25.0–300.0 mmol). Monodispersed BaCr₂(P₂O₇)₂ fine particles with a mean size of 44.0 nm were synthesised at a low temperature of 170 °C for 6 h with 0.5 M NaOH solution in the presence of 50.0 mmol urea. The phosphate pigment particle grew to approximately 62.0 nm by increasing the treatment temperature to 240 °C. A secondary dissolution–recrystallisation achieved after 24 h triggered a change in the particle morphology coupled with the incrementation of the concentration of NaOH in the solution. The pyrophosphate BaCr₂(P₂O₇)₂ pigments prepared in this study belong to the green colour spectral space according to the CIELab coordinates measurement, and exhibit 67.5% high near-infrared (NIR) solar reflectance. Full article

Porous silica gel powders, doped with gold nanoparticles (AuNPs), were obtained by heating silica gels containing 1-dodecanethiol and tetrachloroauric acid at temperatures of 450 °C, 700 °C and 900 °C, and characterized using X-ray diffraction, TEM/EDS studies, UV/Vis reflectance spectroscopy and DTA/TG investigations. The color and microstructure of the obtained samples with a composition SiO₂:AuNPs (about 0.03% Au) depend on the heating temperature. The UV/Vis reflection spectra of the samples are explained using Mie’s theory. The thermal stability of the obtained samples, as well as the processes occurring in the sol–gel matrix upon heating, were monitored by DTA/TG. The textural properties of the obtained materials were described based on adsorption–desorption isotherms. The obtained nanocomposites are promising pigments for ceramic glazes, similar to the Purple of Cassius. The textural properties of certain samples, S_BET = 200–350 m²/g, a mean pore diameter (D_AV) of approximately 10 nm and a specific pore volume (V_t) between 0.5 and 0.8 cm³/g, make them promising candidates for catalytic applications, comparable to aerogel-like materials. Full article

Recent archaeological sites dating to the late 19th and early 20th centuries have rarely been studied to date. Among the 500 “glassy” beads excavated from Dohouan (Côte d’Ivoire), elemental analyses reveal that fewer than half contain abnormally high alumina contents, associated with a soda–potash–lime flux (three compositional groups). The remaining beads are typical lead-based glass. The Raman spectra of the alumina-rich beads are quite complex due to their glass–ceramic nature, combining features similar to the vitreous phase of porcelain glaze with the presence of various crystalline phases (quartz, wollastonite, calcium phosphate, calcite). Organic residues are also observed. Colors are primarily produced by transition metal ions, although some specific pigments have also been identified. These characteristics suggest that the alumina-rich beads were manufactured by pressing followed by sintering, as described in patents by Richard Prosser (1840, UK) and Jean Félix Bapterosse (1844, France). A comparison is made with beads from scrap piles at the site of the former Bapterosse factory in Briare, France. This process represents one of the earliest examples of replacing traditional glassmaking with a ceramic process to enhance productivity and reduce costs. Full article

This manuscript addresses an application study by employing a mathematical model of a thermoelastic plate weakened by multi-curved holes under the effect of stress forces in the presence of heat conduction. When the initial heat flow is directed to the plate system, complex variable procedures are used to compute the basic Goursat functions, taking into account the time-dependent variables through conformal mapping, which transfers the domain to the exterior of a unit circle. The problem reduces to a general form of a contact problem in two dimensions, which is called an integrodifferential equation of the second type with the Cauchy kernel. Additionally, different hole shapes are generated using Maple 2023. Computational simulations are performed to determine the normal and shear stress components in the presence and absence of heat effects at various times. Furthermore, numerical calculations of Goursat functions are carried out and graphically displayed for some specific materials. This investigation provides valuable information about industries, such as those regarding ceramic tile, glass, rubber, paint, ceramic pigment, and metal alloys. Full article

This study investigates the application of terahertz frequency-modulated continuous-wave (FMCW) imaging for the non-destructive inspection of a historical enamel plate, using both reflection and transmission modes. A 300 GHz FMCW radar system was employed to capture high-resolution images of the plate’s internal and surface structures. Through optimized data acquisition and processing, the system successfully revealed subsurface features such as fractures, as well as surface-level textural variations linked to the decorative glazes. Although pigment differentiation remains a challenge, contrast variations observed in THz images suggest correlations with material composition. The results highlight the potential of FMCW terahertz imaging as a compact, rapid, and non-contact diagnostic tool for cultural heritage analysis. Its practicality and adaptability make it particularly suitable for in situ inspections in museums or restoration contexts. Full article

CuCrO₂ (mcconnellite) was synthesized using both the solid-state method and microwave dielectric firing. It was characterized as a novel black ceramic pigment for use in various industrial glazes. For the first time, the application of mcconnellite (CuCrO₂) and its coloured glazes as selective solar absorbers (SSA) for integral ceramic solar collectors has been reported. The addition of quartz or anatase as colour modifiers was investigated to prevent the bluing of the pigment in Zn-containing glazes, a phenomenon associated with the exsolution of copper. Furthermore, doping with lanthanide oxides was explored to address two key challenges: controlling the formation of pinhole defects in porcelain glazes, which are linked to the destabilization of Cu⁺, and adjusting the IR cut-off wavelength to improve its performance as SSA. Full article

This paper presents the results of archaeometric research on the white and red materials used to decorate some ceramic vessels belonging to the Boian culture, the Vidra and Spanţov phases from the 5th millennium BC, discovered at Hârşova-Tell, on the right bank of the Danube, Romania. Digital microscopy, wavelength-dispersive X-ray fluorescence spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used to identify the morphology, the crystalline phases, chemical formula, and percentage content of each crystalline phase in the white decoration materials and what type of pigment was used to prepare the red paint. The results obtained reveal that the white decorating material in the pottery is mostly made of calcite. It was added after the pottery was fired. Sometimes, powders from burnt bones were also used. The red pigment is hematite. The work contributes to the completion of a puzzle related to the artistic vision of the members of the Boian communities in decorating ceramics with culture-specific motifs, preserving the pattern, and adapting to the local natural resources. Full article

In the present case study, the manufacturing technology for glazed pottery was investigated, with particular focus on the great variety of colours and glaze recipes used in Western Anatolia and East Asia and observed in finds from rescue excavation sites in Greece. An assemblage of 40 ceramic fragments dating from the Late Byzantine and Islamic to the Ottoman/Venetian periods was examined for their decoration, surface treatment, and production technology. The peculiarities of the colour recipes applied on the glazed pottery of different assumed origins of production were investigated, focusing on glaze technology and employing colourants. This was achieved by the use of an analytical workflow that considered the compositional details of pigments, slip coatings, and glazes. The chemical evaluation was carried out utilising X-Ray Fluorescence Spectroscopy (pXRF) and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS). Raman Spectroscopy provided information about the compositional variation, and the microscopic examination via Optical Microscopy (OM) and Scanning Electron Microscopy (SEM-EDS) yielded information about the sample stratigraphy of the examined ceramic sections. Through a wide range of colour and glaze recipes, this study of glazed ceramics was able to define and express the essential elements of each pottery workshop’s perception of colour. Full article

The earliest archaeological evidence of wine came from ceramic vessels of the Transcaucasian ‘Shulaveri-Shomutepe’ or ‘Aratashen-Shulaveri-Shomutepe culture’ (SSC/AShSh: c. 6000–5200 BC). Western European ‘Bell Beaker culture’ (BB: c. 2500–2000 BC) is characterized by bell-shaped pottery vessels but has so far not been found with residues consistent with wine. Knowing that wild grapes populated both habitats, the absence of wine during the Bell Beaker period remains to be explained. The main goal of this work was to investigate whether the shape of the vessels could influence the performance of spontaneous fermentation, specifically regarding the production of volatile acidity. Crushed grapes or juices from various grape cultivars were fermented in two types of vessels: (i) borosilicate glass beakers (4–5 L) to imitate bell beakers and (ii) Erlenmeyer flasks (5 L) to imitate SSC/AShSh vessels. Fermentations occurred spontaneously, and the wines were analyzed for their conventional physical–chemical parameters (e.g., ethanol content, total acidity, volatile acidity, pH), chromatic characteristics (e.g., wine color intensity, wine hue), and volatile composition by gas-chromatography-flame ionization detection (GC-FID). At the end of fermentation, the yeast species were identified by molecular methods. In addition, wine yields and phenolic composition (e.g., total phenols, anthocyanins, total pigments) were determined for wild grapes in comparison with six red varieties Vitis vinifera L. subsp. sativa (Vinhão, Marufo, Branjo, Melhorio, Castelão and Tempranillo Tinto), chosen as a function of their genetic relatedness with the wild counterpart. Wines produced from V. sylvestris grapes showed higher total acidity and color intensity when compared to the cultivated varieties. Saccharomyces cerevisiae dominated at the end of all spontaneous fermentations in all types of vessels and conditions. Wines fermented in Erlenmeyers showed ethanol concentrations as high as 14.30% (v/v), while the highest ethanol level was 12.30% (v/v) in beakers. Volatile acidity increased to a maximum of 4.33 g/L (acetic acid) in Erlenmeyers and 8.89 g/L in beakers. Therefore, the shape of the vessels influenced the performance of fermentation, probably due to the different exposures to air, leading to vinegary ferments more frequently in open mouths than in conical-shaped flasks. These results provide a hypothesis based on fermentation performance for the absence of wine produced in the Iberian Peninsula until the arrival of Phoenician settlers. Full article

The recycling of clay waste from construction debris highly depends on the chemical and mineralogical composition of the waste. Clays and clay minerals are known to be among marginal construction waste, representing an interesting opportunity and platform to produce other low-cost and low-carbon materials due to their possibilities for functional material design, such as adsorbents, drug delivery, catalysts and photocatalysts, and nanocomposites. The present review analyzes a wide variety of mechanisms for encapsulating organic and inorganic species between the layers of clay minerals. Through the compilation of advances in acid activation, exchange of inorganic cations, intercalation, and pillarization, new applications for clay materials are generated, paving the way to a nanometric world with functional, magnetic, adsorption, and catalytic capabilities. New trends are consolidated in the reuse of recycled clays in infrastructure projects, such as hydraulic concrete, water purification, soil fertility, pigments and paints, food packaging and storage, and ceramic appliances. It is concluded that clay waste is suitable to reuse in many industrial products and construction materials, enabling a reduction in the consumption of raw materials. Full article

In this paper, based on our previous expertise on ceramic artifacts, several archaeometric methods applied to some samples collected from the Dudești archaeological site (Oltenia region, Romania) are reported for the first time in the literature. The chemical composition, and microstructural and morphological characterization of these samples offer important conclusions about the processing conditions. Some specific techniques such as X-ray diffraction (XRD), wavelength-dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), stereomicroscopy, environmental scanning electron microscopy (ESEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy provide compositional information about composition and the decay processes. Additionally, the Brunauer–Emmett–Teller (BET) method helps to estimate pore sizes and specific surface areas. A thermogravimetric analysis (TGA/TDG) was used to establish details regarding the production technology and also the raw materials source used to make the ceramics. The obtained results indicated that the ceramics are based on a paste of muscovite and feldspar, with high plasticity, together with quartz and hematite/goethite and calcite, the latter in very low concentrations. According to the obtained results, we could assume that clays from the investigated samples had a low concentration of calcium. Gypsum is present as paste in a very low concentration, identified by the presence of a sulphate group in WDXRF. In the same context, iron oxides have a significant impact on the firing atmosphere of iron-rich clay, resulting in blackening under reducing conditions and a reddish coloration under oxidative conditions. The use of hematite and gypsum as pigments further contributes to the color variations in the pottery. The consistent firing temperature range of 200–600 °C in Dudești pottery implies a standardized production process, the variation in color being dependent on the specific reducing/oxidative regime conditions (reducing atmosphere followed by rapid oxidation). This relationship between clay composition and local sources suggests a connection to Neolithic pottery production in the region and their color depending on the reducing/oxidative regime conditions. Full article

Transition metal complexes have historically played a pivotal role in creating vibrant pigments utilized across artistic mediums such as ceramics, paintings, and glass mosaics. Despite their extensive historical use, our understanding of the mechanisms governing transition metal complex behavior has predominantly emerged in recent times, leaving numerous aspects of this process ripe for exploration. These complexes exhibit striking color variations under diverse conditions when employed in pigment formulations. This review utilizes a bottom-up scientific approach, spanning from microscopic to macroscopic scales, to unravel the molecular origins of the colors generated by transition metal complexes in pigments and ceramic glazes. Advanced spectroscopy techniques and computational chemistry play pivotal roles in this endeavor, highlighting the significance of understanding and utilizing analytical data effectively, with careful consideration of each technique’s specific application. Furthermore, this review investigates the influence of processing conditions on color variations, providing valuable insights for artists and manufacturers aiming to enhance the precision and quality of their creations while mitigating environmental impact. Full article

Egyptian Faience, a revolutionary innovation in ancient ceramics, was used for crafting various objects, including amulets, vessels, ornaments, and funerary figurines, like shabtis. Despite extensive research, many aspects of ancient shabti production technology, chemistry and mineralogy remain relatively understudied from the 21st to the 22nd Dynasty, belonging to a recovered 19th-century private collection. The fragments’ origin is tentatively identified in the middle Nile valley in the Luxor area. Our study focused on a modest yet compositionally interesting small collection of shabti fragments to provide information on the glaze’s components and shabti’s core. We found that the core is a quartz and K-feldspars silt blended with an organic component made of plastic resins and vegetable fibres soaked with natron. The studied shabti figurines, after being modelled, dried, and covered with coloured glaze, were subjected to a firing process. Sodium metasilicate and sulphate compounds formed upon contact of the glaze with the silica matrix, forming a shell that holds together the fragile inner matrix. The pigments dissolved in the sodic glaze glass, produced by quartz, K-feldspars, and natron frit, are mainly manganese (Mn) and copper (Cu) compounds. The ratio Cu₂O/CaO > 5 produces a blue colour; if <5, the glaze is green. In some cases, Mg and As may have been added to produce a darker brown and an intense blue, respectively. Reaction minerals provided information on the high-temperature firing process that rapidly vitrified the glaze. These data index minerals for the firing temperature of a sodic glaze, reaching up to a maximum of 1050 °C. Full article