Fired Clay Research Articles

NOTES ON BRONZE POLE-TOPS WITH A GRIFFIN FROM SCYTHIAN ALEKSANDROPOL BARROW

The article proposes a scheme and algorithm for the manufacture of four bronze pole-tops from the Scythian Royal Alexandropol burial mound dated to the second half of the 4th century BC, which can serve as a basis for understanding the manufacturing process or the ancient repair of the similar Scythian replicated products.
 There is both a general idea of the manufacture of such bronze pole-tops by casting (according to a wax model or in detachable forms), and private judgments about the nature of castings, the correction of defects and the repair of pole-tops and their parts. But at the same time, specific details of the production process by different researchers (S. V. Polin, B. N. Mozolevsky, A. I. Melyukova, L. I. Babenko, A. R. Kantorovich, V. R. Erlikh, etc.) are assumed different, showing a very colorful picture.
 The process of making bronze pole-tops which were similar in composition, but different in the elaboration and decoration, most likely consisted of the following successive steps: creating a stencil of wax models of griffins in a rectangular frame; revision and decoration by hand of some individual parts on the surface of these wax figures (wings, paws, etc.), giving individuality to each object; attachment and molding of wax plugs; closure of the wax model by the clay mold, its drying and firing (?); casting in metal; destruction of clay mold; machining the surface of the casting.
 The pole-tops are casted from lead-tin bronze (copper is the base, tin is 9—12 %, lead is 2—3 %, traces of arsenic, iron and nickel). The pole-top (no. Dn 1853 1/6) differs by one feature. On the side edges of the nozzle are high dark triangles with clear boundaries, made by lead-tin plating. On the other objects such ornamentation (?) is not visible.
 Thus, the considered pole-tops were made using a single stencil and cast according to a single technical scheme.

Effective Ecological and Cheap Heating of Dwelling Spaces

The sustainability of human civilization depends largely on green energy management. This work represents one way to achieve this goal. The work is devoted to converting microwave radiation to heat. The article analyses different ways of heating residential and utility areas. Materials suitable for converting microwave radiation to heat from ceramic composites, concretes, fire clays, and bauxite with water glass are enclosed. For all materials we have measured DTA/TG (Differential Thermal Analysis/Thermogravimetric Analysis) curves, XRD (X-Ray Diffraction) patterns, chemical composition of samples, the specific heat capacity cp [J/kg.K], thermal conductivity k [W/m.K] and diffusivity α [m2/s-1]. The cooling curves of these materials after microwave heating are characterized in detail. The paper also presents a description and construction of a microwave reactor together with the parameters of the living space heating.

Influence of process parameters of firing clay materials on phase composition and structure of ceramics

The article describes the influence of the technological impact the firing process has on ceramics structure. The process of forming a ceramic crock is described, which is represented by crystalline phase and glass phase. The dependences of the end product properties on the phases constituting its structure are described. Using X-ray phase analysis and electron microscopy, the authors studied ceramics produced from three types of clay materials with different content of clay minerals (kaolinite and montmorillonite). The change in the phase composition of the ceramic crock depending on the firing temperature is described. A conclusion was made on the fact that the structure is mainly glass phase with crystalline impurity inclusions. A necessity has been revealed for producing ordered structure for mullite.

Enhancement of a Process Flowsheet for Recovering and Concentrating Critical Materials from Bituminous Coal Sources

Recovery of rare earth elements (REE) from coal-related resources has recently received significant interest due to supply concerns and their key roles in critical industries and defense-related technologies. An integrated flowsheet consisting of sorting, crushing/grinding, physical separation, acid leaching, solvent extraction, and selective precipitation was designed to achieve continuous production of rare earth products from various coal-related resources such as coarse refuse and acid mine drainage. A pilot plant was constructed that enabled continuous testing of the circuitry on a range of different coal-based feedstocks. Despite achieving significant success in producing high-grade rare earth oxide products, low REE recovery values and high operational costs necessitated a re-evaluation of the process flowsheet. This article describes the circuitry improvements that were based on both laboratory and pilot plant test results. Roasting as a pre-leach treatment was found to significantly improve the leaching rate and overall REE recovery values. After roasting West Kentucky No. 13 and Fire Clay coal refuse materials at 600 °C, REE recovery increased by 60 and 40 absolute percentage points, respectively. Rare earth concentration in the pregnant leachate solution (PLS) was increased to around 700 ppm prior to solvent extraction using a staged precipitation method. REEs in the precipitate were re-dissolved, purified, and extracted from the PLS using solvent extraction and selective precipitation to values of around 80%. As a result of the improvements, chemical consumption in the acid leaching and solvent extraction processes was significantly reduced. A techno-economical assessment of the improved flowsheet indicated significant commercialization potential.

Clay source and firing temperatures of Roman ceramics: A case study from Plovdiv, Bulgaria

AbstractDuring urgent archaeological excavations in the city of Plovdiv (South Bulgaria), a Roman pottery workshop was found, including several dome kilns, ceramic sherds, and a large clay deposit incorporating yellow and gray clay layers. A set of the ceramic specimens (kitchenwares and tablewares) and raw clay samples were investigated using a portable device for X‐ray fluorescence and laboratory equipment for magnetic measurements, aiming to provide specific information about the origin and firing technology of the pottery. Despite significant difference in calcium content between local raw clay and pottery samples, we conclude that local natural clay sources were used and the initial stages of production involved clay purification, although we cannot rule out the procurement of more distant clay sources. Magnetic susceptibility testing allowed for determination of the maximum firing temperatures, showing that the pottery were fired predominantly at 780°C, with some samples being fired at temperatures up to 860°C. Magnetic analyses show that kitchenwares were fired under more uniform conditions than the tablewares, which undoubtedly reflected in the quality of the vessels produced.

Enhanced leachability of rare earth elements from calcined products of bituminous coals

The modes of occurrence associated with rare earth elements (REEs) in bituminous coal sources were evaluated along with their potential recovery by calcination treatment at 600 ℃ followed by sequential extraction. The coal samples were collected from three different resources, i.e., Fire Clay, West Kentucky No. 13, and Illinois No. 6 seams. Sequential extraction tests indicated that the majority of REEs in the calcined samples occurred as metal oxides especially for the West Kentucky No. 13 calcined material (54% of total REEs), which is distinct from untreated coal and combustion byproducts from pulverized coal boilers reported in literature. In addition, heavy REEs were more likely associated with easily dissolvable forms (i.e., ion-exchangeable, carbonates, and metal oxides). The calcined samples were leached under weak acidic conditions with and without adding ammonium sulfate to recover REEs. About 13%, 24%, and 20% of the REEs were extracted from the Fire Clay, West Kentucky No. 13, and Illinois No. 6 materials, respectively, by leaching at pH 4.0. The addition of 1 M ammonium sulfate further increased the recovery values to 18%, 45%, and 32%, respectively. In addition, about 64% of HREEs were extracted from the West Kentucky No. 13 calcined material under this condition. As such, a significant portion of the REEs can be easily extracted from the samples obtained by calcining the coals at 600 ℃.

Secular and catastrophic processes reflected in sediments of the Suchedniów water reservoir, Holy Cross Mountains (Poland)

Abstract The Suchedniów water reservoir is located in the central section of the River Kamionka in the northern part of the Holy Cross Mountains of central Poland. This area once belonged to the Old Polish Industrial District that, during the Middle Ages, was very intensively developed by iron metallurgy. Many forges and mills along the rivers used water power, which led to the construction of an anthropogenic, small-scale water retention system. At the beginning of the twentieth century many of these reservoirs were drained after the collapse of metallurgical activities. The present-day reservoir was built in 1974 and drained in 2017. Research into the drained basin has documented various forms and sediments, some of which record present-day depositional processes (fire proof clay layer, inland fan delta), while others represent the historical period (lacustrine sediments of older reservoirs). Traces of catastrophic events have been preserved as well; an assemblage of megaripples marks the sudden drainage caused by a dam break in 1974.

Depositional setting for Eocene seat earths and related facies of the Gippsland Basin, Australia

The origin of seat earths (i.e. underclays, seat rocks, fire clays) has been investigated using sedimentological, palynological and mineralogical analysis of clastic-coal successions from the Eocene Traralgon Formation of the Gippsland Basin, Australia. The seat earths of the Latrobe Group are massive, a light grey to white colour, contain abundant slickensided fracture surfaces and isolated organic matter, and mineralogically consist of abundant kaolinite and lesser amounts of 2 M illite. From palynological evidence, the seat earths have paleoenvironments that grade from a fire-prone heath-fern meadow marsh (i.e. Gleicheniaceae and Epacridaceae dominant), to fire-tolerant shrubs and small trees (i.e. Cyatheaceae, Schizaeaceae and Proteaceae dominant) that fringe raised peatland rainforests. The palynological data also indicate a non-marine origin for the kaolinitic mudstones. The non-marine seat earths were deposited over a foundation of intertidal sediments (containing lenticular, wavy and flaser bedding, tidal rhythmites, extensive burrowing and a diverse assemblage of marine-influenced dinoflagellates). The upward increase in kaolinite, slickensides and rootlets within the seat earth indicates this clay was kaolinitized by pedogenic processes (i.e. weathering by organically derived humic/fulvic acids) prior to and throughout peat formation. The presence of well-preserved and abundant spore-pollen in the kaolinitic mudstones also suggests that the seat earths were deposited in an acidic and relatively reducing setting. The stratigraphic transition from tidal siltstone, to mudstone (seat earth) to coal in ascending order is interpreted as a shallowing-upwards succession. The seat earths of the Gippsland Basin were therefore deposited as a precursor non-marine facies (mostly meadow-marsh) grading into an ombrogenous coal facies, thereby explaining the intimate association between coals and seat earths globally.

Activity calculation and phase transformation predication for heavy metals with slag activity calculation model during using electroplating sludge in production of bricks

Electroplating sludge is usually regarded as the hazardous waste because of the considerable amount of heavy metals. The vitrification process or firing clay bricks mixing of electroplating sludge is an alternative way to disposal it. The reaction behaviors of heavy metals in electroplating sludge at high temperature are closely associated with the leachability of heavy metals from fired products. In this work, an available thermodynamic model, slag activity calculation model, was used to examine the reaction behaviors and predicate the phase transformation of heavy metals under different conditions. CaO would preferably combine with SiO2 and form CaSiO3 at 1100–1500 K. Most of Cr, Zn and Cu would exist in a form of oxides and spinel phases. Cr would be preferably incorporated into ZnO·Cr2O3 and CaO·Cr2O3 rather than CuO·Cr2O3 except metal oxide; Zn would be preferably incorporated into ZnO·Cr2O3 and ZnO·Fe2O3 rather than 2ZuO·SiO2 and ZnO·Al2O3; Cu would be preferably incorporated into CuO·Al2O3 and CuO·Fe2O3 rather than CuO·Cr2O3. Elevating the basicity facilitated Zn to transform into ZnO·Al2O3, ZnO·Fe2O3 and CuO·Fe2O3, while hindered Zn and Cu being incorporating into 2ZnO·SiO2 and CuO·Cr2O3. Increasing the amount of Fe2O3 in system suppressed the formation of heavy metal oxides (i.e. Cr2O3, ZnO and CuO) and spinel species containing Cr, while promoted the formation of spinel species containing Fe, especially for ZnO·Fe2O3 and CuO·Fe2O3. This work can provide some useful information for reaction behaviors and phase transformation of heavy metals during heating solid waste containing heavy metals.

THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THE EFFICIENCY OF THE USE OF HEAT-ACCUMULATING MATERIAL FOR HEAT SUPPLY SYSTEMS

As a result of research, the conditions for the effective use of the volume of heat accumulator based on solid materials were determined. In the course of research, various schemes of the device of tubular heating elements for charging the channel elements of the heat accumulator were considered. Fire clay was used as a heat-accumulating material, capable of operating in a wide temperature range (up to 600 °С). Mathematical modeling of temperature change in the process of discharge over the cross section of the heat-accumulating unit has been carried out. Mathematical modeling was carried out using an application package that allows to obtain the temperature distribution over the cross section of the heat accumulator at key points of its work. The obtained simulation results were tested on an experimental setup consisting of four heat-accumulating units during the charging process and during the discharge of the heat accumulator. According to the research results, the most effective layout of the heating elements was determined, which allows to make the most of the volume of the heat-accumulating material. The dependencies to determine the exponent and the averaging coefficient of the heat flux are also found, which allow a more rational use of the volume of the accumulating nozzle. The research results can be used to reconstruct decentralized heat supply systems for both residential buildings and public buildings. This will significantly align the schedule of electricity consumption during the day and reduce the consumption of hydrocarbon fuels.

Acid Leaching of Rare Earth Elements from Coal and Coal Ash: Implications for Using Fluidized Bed Combustion To Assist in the Recovery of Critical Materials

High-temperature pretreatment of coal-based mineral matter in an oxidizing environment significantly enhances the leaching characteristics of rare earth elements (REEs). A research study has found that the temperatures used in fluidized bed combustion (FBC) of coal to produce electricity are near optimum for pretreating the associated mineral matter prior to leaching to maximize the recovery of critical materials. Tests were performed on representative samples collected from preparation plants treating West Kentucky No. 13, Illinois No. 6, and Fire Clay coal seam sources as well as fly ash and bed ash samples from two FBC power plants. Acid leaching tests using 1.2 M HCl at 75 °C were performed on both the coal and the FBC ash samples. Prior to leaching, the coal samples were pretreated at temperatures of 600, 750, and 900 °C in an oxidizing environment to study the effect on leaching characteristics. The results showed that pretreatment at 600 °C for 2 h resulted in a significant increase in REE recovery from a range of 20–40 to ∼80% for all coal sources. The leaching kinetics is characterized by a quick release of rare earth elements within the first few minutes of the process. For the West Kentucky No. 13 coal source, ∼75% of the REEs were leached in the first 15 min from the 1.4–1.8 specific gravity (SG) fraction that was calcined at 600 °C. Additionally, the leaching kinetics of the major contaminant, that is, Fe, was much lower than that of the REEs, which significantly benefits the efficiency of leaching and the downstream upgrading processes. REE leaching characteristics of the FBC ash samples were similar to those of the calcined coals. Mineralogy characterization showed that the degree of crystallinity for both the calcined coal and FBC samples was similar to the original associated mineral matter, which provided evidence for the advantage of using the FBC byproducts as REE feedstocks over pulverized coal boilers that utilize temperatures greater than 1200 °C. These findings were used to develop a conceptual flowsheet that incorporates FBC technology and its typical combustion environment to enhance the feasibility of recovering critical materials from coal-based sources.

Effect of the ceramic membrane properties on the microbial fuel cell power output and catholyte generation

Ceramic membranes for MFCs offer a low cost alternative to the expensive ion exchange membranes, whilst promoting catholyte accumulation. However, their physicochemical properties need to be optimised, in order to increase the power output and the catholyte quality from MFCs. Two compositions of fine fire clay (FFC) cured under three firing cycles were manufactured, analysed and tested as ion-exchange and structural material for MFCs. The samples were characterised by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The power and catholyte generated from the ceramic MFCs with different FFC types was also evaluated. The results show a direct correlation between the ohmic resistance, the MFC power generation and the water absorption of the ceramics, giving a maximum power of 1 mW from the MFC with the most absorptive FFC (16.37% water absorbance). A slightly more alkaline catholyte was synthesised from the MFCs with higher water absorption FFC.

Nano-Scale Rare Earth Distribution in Fly Ash Derived from the Combustion of the Fire Clay Coal, Kentucky

Fly ash from the combustion of eastern Kentucky Fire Clay coal in a southeastern United States pulverized-coal power plant was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). TEM combined with elemental analysis via energy dispersive X-ray spectroscopy (EDS) showed that rare earth elements (REE; specifically, La, Ce, Nd, Pr, and Sm) were distributed within glassy particles. In certain cases, the REE were accompanied by phosphorous, suggesting a monazite or similar mineral form. However, the electron diffraction patterns of apparent phosphate minerals were not definitive, and P-lean regions of the glass consisted of amorphous phases. Therefore, the distribution of the REE in the fly ash seemed to be in the form of TEM-visible nano-scale crystalline minerals, with additional distributions corresponding to overlapping ultra-fine minerals and even true atomic dispersion within the fly ash glass.

Usage of fired wall tile wastes into fireclay sanitaryware products

In the last decade, using the waste products generated in ceramic manufacturing has been one of the important issues. Reusing the waste products is not only an environmental responsibility but also a cost reduction issue. In this study, the possibility of using fired wall tile wastes as a raw material for sanitaryware fire clay compositions was investigated. Four sanitaryware fire clay compositions were prepared by adding fired wall tile waste (FWW) into the standard fireclay composition under industrial conditions at Canakkale Kalebodur Seramik San. A. S. The results showed that addition of FWW increased the strength and decreased the water absorption and thermal expansion coefficient of the fireclay products. The thermal expansion coefficient of the products can be controlled with the addition of FWW. High-temperature deformation decreased with the addition of FWW into the fireclay composition. It can be concluded that FWW can be used in the fireclay production compositions as a raw material.

Mineralogical transformation and microstructure of the alluvials clays

Mineralogical transformations and microstructures during the firing alluvial clays from Monoun plain were studied. The firing of clays was carried out in the temperature range from 800 to 1150?C. Minerals transformation was investigated by X-ray diffraction, polarize stereomicroscopy and scanning electron microscopy (SEM). In the raw materials, typical assemblages with quartz, kaolinite, goethite, anatase, hematite, gibbsite and feldspar were observed. Many neoformed mineral phases were identified with the reaction products including mullite, cristobalite, spinel, amorphous phase which occurred in the high temperature (1050-1150?C) in the fired bricks. The quartz phenocrist with some microlites oxides embedded in few mesostasis glass have been illustrated at 950?C by stereomicroscopy analysis. At 1150?C, the vitreous matrix has embedded phenocrist of quartz and other relic minerals. The best temperature for fired alluvial clay brick was discovered between 1050-1150?C.

The study of thermal conductivity of asbestos cardboard and fire clay powder to assess the possibility of their application in prefabricated structures of cylindrical housings of pressure vessels

Abstract The problem of protecting various elements of process equipment (pressure vessels, reactors, etc.) from critical heating has always been always relevant. The use of thermal insulation materials characterized by low thermal conductivity, high modulus of elasticity and the ability to maintain its aggregate state after a long repeated exposure to pressure and temperature is one of the main ways to address the issue. This work describes the methodology and results of the study of thermal insulation materials (fire clay powder (FCP) and asbestos) and the dependence of their thermal conductivity on the pressure applied to them. The results of the study of thermal insulation materials of different thicknesses demonstrated that a significant effect of reducing the harmful thermal effects on the main load-bearing elements of the process equipment is achieved with a sufficiently small thickness of the embedded layer of the material (up to 10 mm). Likewise, the work describes the progress and results of experimental studies of the combined cylindrical wall with built-in wall heating elements and a layer of thermal insulation material. Coefficients of thermal conductivity of thermal insulation materials (fire clay powder and asbestos) have been determined. The practical possibility of effective protection against overheating of the bearing cylindrical wall of the pressure vessel body has been proved. The use of the thermal insulation layer results in the possibility of increasing the temperature and pressure of the process space of pressure vessels and reactors without changing the size of the bearing part of the wall in comparison with existing similar structures.

Manufacturing, Physical and Chemical Characterization of Fire Clay Brick Value Added with Cow Dung Ash

Aim of this study was to introduce an eco-friendly, low cost and durable clay bricks with partial substitution of Cow Dung Ash (CDA). Five types of clay brick, consist CDA percentages 0, 5 10, 15 and 20% to the total weight of mixture, were manufactured by employing traditional method of dimension (18.5×8.5×6.5) cm3. The clay and CDA were well mixed with the addition of sufficient amount of water to form a good workability. Green molded bricks were allowed to dry under sunlight for two days and then fired in the traditional brick kiln. Physical properties of the burned red bricks were then tested and analyzed with Sri Lankan and British Standard Specifications. The average density, water absorption, compressive strength and flexural strength for 10% Cow Dung Ash (CDA) are 1447 kg.m-3, 17%, 150 kg.cm-2 and 0.82 kg.cm-2 respectively. These physical properties were compared with the standard brick purely manufactured from clay. From the results, clay-CDA bricks are obviously superior to the control brick; those are available in the Eastern region markets.

Features of the kinetics of mass transfer processes in the process of firing ceramic materials

In article the technique of definition factors of carrying over weight of substance in the course of roasting ceramic materials which is based on exponent dependences of change mass bodies from time of its heating is offered.
 The process of firing ceramic materials is associated with the transfer of heat and mass of matter. Therefore, for a more complete calculation of the heat treatment mode, it is necessary to know the conditions for the mass transfer in the product being calcined. The aim of the work is to determine the mass transfer coefficients of the substance in the process of firing ceramic materials.
 The mass loss rate of the bound matter or the mass loss per unit time will be directly proportional to the average mass content of the body. On the other hand, the mass loss rate of the bound matter is numerically equal to the slope of the mass content kinetics curve.
 Proposed in the work formulas can be applied when studying the process of mass transfer during firing of samples from different clays, as when firing clay samples of different diameters under the same conditions, they will differ in the mass content (mass loss rate of the bound substance) during heating and their final relative amount (mass content) of the lost mass will be the same.

The investigation of the modified refractory concrete in terms of the clay filler's kind

The properties of the conventional refractory concrete modified by means of the microsilica and the antiflocculant additions including the different kinds of the fire clay filler were investigated in the article. It was established that the refractory concrete with the filler Bos145 (about 44 % of Al2O3) had the smaller open porosity, and both high density and the ultimate compressive strength comparing to these characteristics which the concretes with the fillers Bos125 and Bos135 had (about 26 and 37 % of Al2O3respectively). Also it was found out that independently of the fire clay filler's kind another SiO2-based addition promoted the increase of the concrete's alkaline resistance by the factor of 5 and more. It was shown that this SiO2-based addition is effective at the temperatures up to 1100 °C, as at 1200 °C the chamotter concrete's porosity grew up and the resistance of the material against the alkaline melt decreased considerably.

Ceramic properties of Uşak clay in comparison with Ukrainian clay

ABSTRACTIn this contribution, a new raw material, Uşak clay (Usc), was investigated in order to assess its potential for the ceramic industry by comparing it with a world reference ceramic material, a Ukrainian clay (Ukc). Mineralogical characterization (X-ray diffraction [XRD], scanning electron microscopy [SEM] and Fourier-transform infrared [FTIR] spectroscopy), quantitative chemical analysis (X-ray fluorescence [XRF]) and the thermal properties of Ukc and Usc samples were investigated. Additionally, Atterberg limits, particle-size distribution and cation exchange capacity of both samples were determined. Various technological properties of Ukc and Usc were determined in the temperature range 800–1430°C. The bending and compressive strengths, total linear shrinkage, colour, water absorption and unit-volume mass values were measured. The findings from these analyses show that kaolinite-dominated Ukc and quartz-dominated Usc samples differ from each other not only mineralogically, but also in terms of their chemical, physical and technological properties. The firing colour of Usc was determined as 84% white, and so this can be considered as a light firing clay. In addition, due to its low plasticity, Usc may be utilized to reduce both the plasticity of the ceramic materials and the viscosity in slip-casting applied ceramics. Furthermore, the melting temperature of 1300°C suggests that Usc cannot be classified as refractory. However, this property does suggest an economic value for Usc in terms of developing technological characteristics at lower firing temperatures.