Firing Temperature Range Research Articles

Influences of SiO2, Al2O3, CaO and MgO in phase transformation of sintered kaolin-ground granulated blast furnace slag geopolymer

Kaolin has an excellent structure formed via a wide range of firing temperature. The correlation between the mineralogy and reactivity of individual elements is extremely complex in a sintered geopolymer material. The main objective of this work is to elucidate the influence of the chemical composition of the raw materials used post-sintering on the kaolin-ground granulated blast furnace slag (GGBS) geopolymer. The samples were cured at room temperature for 5 days before being sintered. The ratio of solid-to-liquid were 1:1, 1.5:1, and 2:1. The addition of the GGBS to the kaolin geopolymer slurry did not only hasten the hardening process during geopolymerization, the presence of SiO2, Al2O3, CaO, and MgO in GGBS had accelerated the formation of nepheline, gehlenite, akermanite, and albite phase after sintering based on the result from x-ray diffraction and fourier-transform infrared spectroscopy On top of the phase transformation, a high ratio of solid-to-liquid (SL 2) had improved the pore distribution from irregular size to well defined formation and increased the densification of the sintered materials. Elemental distribution from micro-XRF investigation prove the high concentration of Ca in localized area and uniformly distribution of Si aligned with the phase of akermanite in SL 2. The main chemical composition of kaolin and GGBS which are SiO2, Al2O3, CaO and MgO had contributed in phase transformation of sintered kaolin-GGBS geopolymer.

Identification of vessel use and explanation of change in production techniques from the Old to the Middle Kingdom: Organic residue analysis, fabric and thermal characterization of pot sherds from Qubbet el‐Hawa, Aswan, Egypt

For the first time, residue‐analysis results of a red‐rim bowl discovered at Qubbet el‐Hawa in Aswan, Egypt, are discussed alongside the thermal characterization of unpublished pottery bowls of the Old and Middle Kingdoms from the same site. Scanning electron microscopy with energy‐dispersive X‐ray spectrometry (SEM‐EDX) and X‐ray diffraction (XRD) analysis were performed to provide fabric description of the bowls. The results show the presence of 4‐heptenoic and 4‐decenoic acids. The Old Kingdom bowl showed a firing temperature range of 800–850°C, while the Middle Kingdom example was fired to higher temperatures. This is a suggested explanation of the decrease in the use of red coating as a surface treatment after the Old Kingdom.

Egyptian Cretaceous clay deposits: Insights on Mineralogy, Geochemistry, and Industrial uses

Development of products which can be produced from a country’s natural resources is very important as far as the industrialization of a nation and saving foreign exchange is concerned. The recent vast expansion of the ceramic industry in Egypt results in an excessively high consumption rate of Aswan clays, so the current study aims to explore other potential materials for application in the vitrified clay pipes industry. Based on the abundance of ceramic raw materials in Egypt and the demand for vitrified clay pipes, it is pertinent to develop and manufacture vitrified clay pipes by exploiting the locally available raw materials in other localities. This research thus concerns the characterization of some clay materials of the Cretaceous. Three economic clay formations were selected for the study: (1) the Malha Formation at Abu Darag and Zafarana, North Eastern Desert; (2) Naqb El Sillim Formation at the Bahariya Oasis, North Western Desert; and (3) Abu Aggag Formation at Aswan, South Eastern Desert. The clayey formations were investigated to assess their potential in the manufacture of vitrified clay pipes. Based on the obtained results of mechanical, chemical, and technical characteristics, the Naqb El Sillim Formation has the best results in a wide range of firing temperatures (1140–1180 °C) compared with the required limits of the international standards for clay pipes application. On the other hand, the Malha and Abu Aggag formations needed some additives to satisfy the standard limits of clay pipes application so, the granite wastes were selected and added by 20% to these samples, then fired at 1180 °C. The experimental results obtained from the studied samples indeed revealed the viability of manufacturing vitrified clay pipes from the raw materials.

Low water absorption and pyroplastic deformation of alumina‐strengthened porcelain with petalite and Gairome clay

AbstractThe pyroplastic deformation (PD) of porcelain is a key issue for reducing production loss. In this study, material design to realize both a low water absorption (WA) and low PD in alumina‐strengthened porcelain, which have a trade‐off relationship, was proposed. In this porcelain material design, a rigid microstructure composed of entangled needle‐like mullite crystals is formed by the addition of Gairome clay, which has the positive effect of suppressing PD but negatively affects densification. This was balanced by the controlling the amount and viscosity of the liquid phase in the porcelain fired at elevated temperatures with optimized quantities of added petalite and Gairome clay to obtain a low WA and low PD. As a result, a WA below 0.5% and PD index below 1.5 × 10−6 mm−1 in a wide firing temperature range from 1194 to 1384°C were obtained for porcelain containing Amakusa clay at 37.8 mass%, Gairome clay at 17.0 mass%, petalite at 13.7 mass%, and alumina at 31.5 mass%.

Декоративни разкъсани керамични глазури, базирани на циркониев силикат с температура на изпичане 980°C – 1050°C

Тhe research article concerns the creation of decorative ceramic glazes with a specific surface vision and firing temperature range between 980оС – 1050оС. The glazes which are subject of this study have a specific texture, characterized by the assembling of the glaze into segments of different shapes and sizes, resulting in stripping of the lower layer (ceramic body or engobe). The purpose of the study is: (1) To create fragmented glazes using micronized zirconium silicate, which can be applied in the temperature range 980°C - 1050°C, suitable for red baked ceramics and chalk faience; The glazes thus created should have a clear texture and the ability to be tinted in different colors. This is а topic of present interest, as there are no glazes for ceramics with a similar structure developed on the basis of zirconium silicate for red baked ceramics and chalk faience so far. The emphasis is put entirely on decorative glazes, which are a combination of technical parameters and artistic techniques, the totality of which influences their specific look.

Sintering Behavior of Highly Porous Ceramic Materials Based on the Al2O3–MgO System

We have studied the sintering of ceramic samples based on magnesium oxide, alumina, and magnesium aluminate spinel in order to assess the conceptual feasibility of producing ceramic foam materials in the Al2O3–MgO system and examined the effect of sintering aids on the sintering process. The range of firing temperatures has been found that ensures the preparation of materials with an open cellular pore structure: the optimal temperatures are from 1600 to 1700°C. The porosity of the synthesized materials is up to 85% and their compressive strength reaches 1.4 MPa.

Impact of firing temperature on insulating properties of Low Temperature Co-fired Ceramics

Abstract In this paper, results of investigation on the impact of firing temperature on insulating properties of Low Temperature Cofired Ceramics are presented. Dissipation factor, volume resistivity and breakdown electric field intensity were determined for firing peak temperature in the range from 800 °C to 900 °C. The tests were performed for two commercial LTCC materials: 951 Green Tape (DuPont, USA) and SK47 (Keko, Slovenia). The results showed that the firing temperature had a significant effect on the dielectric loss factor, volume resistivity and lifetime at applied high voltage. No clear tendency was observed for dielectric strength in the analyzed firing temperature range.

Early Bronze Age Plain Simple Wares of Tilbeshar (Turkey): Archaeometric Characterization

The present study reports the results obtained through an archaeometric investigation on representative Early Bronze Age plain simple wares of Tilbeshar which is located almost 32 km southeast of Gaziantep (Turkey). The samples were characterized by XRD (X-ray diffraction), thin section (optical microscopy), FTIR (Fourier Transformed Infrared Spectroscopy), TG-DTA (Thermogravimetric Differential Thermal Analysis) and SEM/EDX (scanning electron microcopy/energy dispersive X-ray spectroscopy). The chemical composition of the samples showed that the potsherds possessed high amount of CaO indicating use of calcareous clays. Proving this data XRD, TG-DTA and FTIR analyses revealed the presence of calcite, as well. Considering the mineral/phase contents of the samples, the firing temperature of the potsherds was found to change in the range of 700-900 o C. The appearance of neo-formations for most of the samples suggested a firing temperature range of 800-900 o C for such potsherds. SEM images of the samples showed that there was a very low partial vitrification for some of the samples, while it was not observed for the others. This observation approved the firing temperature ranges of the samples. Petrography results suggested that the main rock type for the potsherds was basalt (igneous rock) and the raw materials likely originated from mafic rocks. Taking into account the whole data and the geological formation of the region, it was predicted that the potsherds likely belonged to a local production.

Reduction of samarium in air fired samples of barium tetraborate

The reduction of samarium in air fired samples of barium tetraborate has been identified for the first time by divalent samarium emission spectroscopy. The samarium(II) fluorescence is significantly quenched at ambient temperatures, but is apparent upon cooling of the sample to 77 K. Formation of the divalent samarium in the system is limited to short firing times and a small range of firing temperatures from 825 to 900 °C. The formation of a more luminescent pentaborate impurity phase is often seen in the barium tetraborate system, even with stoichiometric preparation of the barium tetraborate.

Effect of Firing Regime on the Structure and Properties of Highly Porous Ceramic Materials Based on Alumina-Magnesia Spinel

Results are provided for a study of sintering spinel porous ceramics using aluminum and magnesium oxides as starting components without sintering additives. It is shown that the optimum firing temperature range in order to prepare materials with an open-cellular porous structure is 1700 – 1730°C. It is established that preliminary heat treatment of oxides significantly affects material mechanical characteristics of. Materials are obtained with an interconnected porosity of up to 85% and compressive strength of up to 10 MPa.

Rapid thermal processing of cost‐effective contacts for silicon solar cells

AbstractThis paper reports on the investigation of rapid thermal processing (RTP) of contacting the Al‐BSF solar cell with Ag, Cu, and Ni in conjunction with aerosol printing technique. The study showed a liftoff and delamination, respectively, for the bi and tri stack layers of Ag frit/Ni and Ag frit/Ni/Cu fired above 790°C peak firing temperature. The 770°C peak firing temperature gave excellent electrical performance for both bi and tri stack layer contacts, which is not favorable to forming thick back surface field (BSF) required for high open circuit voltage (VOC). This suggests that the bilayer and trilayer contacts involving Ag frit are limited to low peak firing temperature, but Ni frit, on the other hand, showed a wider firing temperature range. This is supported by low reverse saturation current density (J02) of 1.1 × 10−11 A/cm2 and high shunt resistance (RSH) of 5750 Ω·cm2 for the Ni frit fired at 800°C peak firing temperature. More so, the adhesion of Ni Frit to silicon is better than Ag counterpart as evidenced in the SEM micrograph. Thus, by adopting RTP Ni/Cu contacts, the cost of metallization of solar cell can be dropped from 35% of total processing cost to only 5% to 6%, which is approximately 30% drop in the total cost of processing.

Prediction of minimum achievable NOx levels for fuel-staged combustors

While lean-premixed (LPM) combustors are used widely in combined cycle power plants, their NOx emissions rise drastically at the high firing temperatures required for increased combined cycle efficiencies, e.g., >60 ppm at 1975 K, the target for 65% thermal efficiency. The axially staged combustor architecture is a promising approach to increase temperature without a thermal NOx penalty. A chemical reactor network model in a design optimization framework is used to investigate the minimum theoretical NOx achievable by a high-pressure, staged combustor under CO emission constraints, as well as the corresponding optimum configuration, e.g., fuel splits and post-secondary injection residence times. Under ideal conditions, minimum NOx favors the most fuel-lean main burner that can autoignite the secondary stage, and the shortest secondary stage residence time that allows sufficient oxidation to achieve the CO constraint. Compared to the theoretical minimum emissions of standard LPM approaches, the staged combustor architecture is capable of achieving dramatically lower NOx levels, e.g., ∼1 ppm corrected to 15% excess oxygen at 1975 K, with greater relative NOx reductions as firing temperature increases. In fact, the minimum NOx levels are relatively insensitive to combustor firing temperature and overall residence time. As an added advantage, the main LPM burner can be optimized for a single operating condition. The results also demonstrate that the low NOx entitlement levels achievable for single-point designs are also valid for a fixed architecture, staged combustor required to operate over a range of firing temperatures.

Using the calculation method for low-melting clay assessment

Low-melting polymineral clays are widely used in building ceramics production. The properties of ceramic products depend on many factors. The paper describes properties of low-melting clay from Belebey deposit, Bashkiria. Using mathematical statistics methods, researchers make statistical analysis of grain size composition of clay raw material on Belebey brick factory and also analyze amount of sand additives and mixing moisture content. The study of general and technological properties of clay raw materials, and materials obtained from this raw material, was carried out in accordance with existing regulations using chemical, differential-thermal and non-standard methods. According to chemical analysis, non-standard assessment of clay raw materials was carried out by means of computer program "Assessment", developed at the Department of Building Materials Production and Engineering Structures. The method of calculating quantity and composition of melted material, formed in ceramic masses during firing, using known diagrams of aluminosilicate systems state is used. The assessment made it possible to determine maximum firing temperature and firing range and additives improving clinker formation. The studies show that calculation indicators are consistent with experimental data. They can be used for quick assessment of raw materials properties when changing its composition, and in adjustment of technological parameters of production.

Reconstructing the Firing and Pigment Processing Technologies of Corinthian Polychrome Ceramics, 8-6th Centuries B.C.E

ABSTRACTDecorative, polychrome ceramics from Corinth, Greece, produced during the 8th-6th centuries B.C.E. were luxury goods widely traded throughout Greece and the Mediterranean. Corinthian pottery is the first 5-color polychrome ceramic technology, having slip-glazes in distinctive white, black, red, yellow, and purple colors, and in a variety of surface finishes from glossy, to semi-matte, to matte. The firing temperature range, 925-1075°C, was determined experimentally to be to be higher than previously reported, similar to the Corinthian amphorae and other ceramic products. This firing range is higher than that of the better known, more prestigious Athenian Black-figure and Red-figure ceramics. In this study three examples of Corinthian and one example of Athenian Black-figure ceramics from the Marie Farnsworth collection at the University of Arizona were tested and compared to thirteen clays from Corinth. Analytical techniques included Fourier-transform infrared spectroscopy (FTIR), scanning-electron microscopy with energy-dispersive spectroscopy (SEM-EDS), micro-Raman spectroscopy, and wavelength-dispersive electron microprobe (EPMA with BSE-SEM).Artisans in Corinthian workshops experimented to change the colors of the slips by varying the type and amount of iron-rich raw material, as well as the composition of the clay used as a binder and the amount of flux used as a sintering aid to promote glass formation. Corinthian artisans developed not only different recipes to produce the various colors, but also they were able to control raw-material particle size and composition to produce variations in surface luster (matte, semi-matte and glossy). This research suggests that Corinthian polychrome-slip technology was based on careful control of particle processing, of compositional control of raw materials and their admixtures, and of firing temperature. The behavior or practice of adding different ratios of pigments and glass-forming fluxes to form various optical effects implies a detailed knowledge of what happens when these are heated and fired. This is a process of experimentation focused on developing a distinctive craft practice, which produced a distinctive and highly valued material. The Corinthians developed a more complex, easily recognizable, and culturally distinctive ceramic technology that was intentionally established as a cultural brand, and probably as a luxury brand of high socio-economic value. This research deepens our understanding of the complex pigment processing and firing technologies employed in the production of Corinthian ceramics.

Composition, Processing and Properties of Composite Ceramic Sickle Blades from Mesopotamia

ABSTRACTCeramic tools were made in lowland Mesopotamia from about 4500 to 2750 B.C.E. At first hammers, adzes, axes and sickles were made. By about 3300-3100 B.C.E., only sickles were made. We reverse engineered the technology to show that local, salty montmorillonite clay and quartz sand were formed into a composite blade and handle from a biconical coil and fired to 1120-1170°C based on analysis of refiring tests. At 1200°C the montmorillonite clay transforms to glass, so the firing range was right on the edge of slumping the ceramic into a useless mass. To prevent plastic deformation of the clay about 25-33 vol% of quartz sand was added. The extensive glassy matrix phase enabled the best blades to be resharpened by pressure flaking. The compositions, phase assemblage, firing temperature range, material limits on processing, and properties have been characterized for 15 sickle samples from Nippur using Xeroradiography, SEM-EDS, EPMA, and analysis of refiring tests. Strength and hardness tests and toughness calculations were conducted on replicate test tiles made using clay from Pit M at Nippur, Iraq, and sand.Based on finds of small groups of well-fused sickles that were overfired and melted together and our experiments that demonstrated the difficulty of controlling peak temperature range and firing time for the somewhat variable raw material, the sickles probably were fired in small groups, of perhaps 10-15, in small arched, tunnel kilns that achieved high temperatures by facing somewhat predictable oncoming wind flows that provided natural draft. No evidence of workshops has been located, but, based on the archaeological finds at Nippur and our analyses, we propose that sickle-making may have been practiced as a local, seasonal, popular technology with tools being made by farmers or part-time specialists who fired in small, temporary tunnel kilns in fields or near settlements during the dependable seasonal winds. This research investigated the sickles as a well-engineered, but risk-prone ceramic manufacture that fulfilled an important a societal need, agricultural success. The technological choices of craftsmen were narrowed by raw material constraints, risk-taking, practice and workmanship to achieve desired properties and performance characteristics.

Pozzolanic reactivity of pure calcined clays

Eight reference clay samples, 4 kaolinitic, 3 smectitic and 1 illitic clay, were purified and thermally treated in order to determine their pozzolanic reactivity in cementitious materials. The clays were calcined in a fixed-bed electrical furnace at temperatures ranging between 500°C and 900°C. Both raw and calcined clays were characterized by ICP-OES, XRD and BET techniques. Their pozzolanic reactivity was evaluated with clay-lime pastes after 3, 7, 14, 28, 56 and 90days using thermogravimetry (TGA). The results indicate that all kaolinitic clays are highly reactive at a broad range of firing temperatures (500–900°C). The degree of ordering of the raw kaolinite influences the optimal activation temperature and the rate of the calcined clay-lime reaction. The smectitic clays possess a clear optimal calcination temperature of 800°C. Ca-rich smectites are proven to be somewhat more reactive than Na-rich smectites. However, even at 800°C, its reactivity is significantly smaller compared to kaolinite. Hectorite and illite calcined at an optimal temperature of 800 and 900°C, respectively, exhibit poor pozzolanic reactivity.

Probing firing-induced changes in non-carbonate clay through 55Mn EPR techniques

Non-carbonate clay samples, fired in steps of 50°C between 600°C and 1000°C, were examined through electron paramagnetic resonance (EPR) techniques (X- and Q-Band pulsed- and cw-EPR). X-band pulsed EPR and Q-Band pulsed- and cw-EPR techniques were able to spot 55Mn(II) signals out of the large iron background in the full range of firing temperatures, allowing one to follow the phase transformations through the evolution of the manganese signal. Q-Band pulsed EPR turned out to be particularly suitable to detect even small amounts of this ion in calcite, while the 55Mn hyperfine coupling constant, determined through Q-Band cw-EPR, could be used to detect transitions to the glassy phase.

Effect of the firing process on the critical current density of YBa2Cu3O7-x films derived from the sol-gel method

The firing process plays a crucial role on the microstructures of sol-derived YBa2Cu3O7-x (YBCO) films; thus, it affects the critical current density, Jc, of the films. In this paper, the effect of the oxygen partial pressure–temperature (PO2–T) combination during the firing process on the microstructure and Jc of an YBCO film derived from a low-fluorine sol-gel method was investigated. The results indicate that the optimal PO2–T combination for a high-Jc YBCO film is different from that derived from an in-situ deposition reported previously. When the optimal PO2–T combination is adopted, the resulting YBCO films exhibit good biaxial texture characteristics and dense surfaces over the entire firing temperature range of 700–775 °C. In addition, the YBCO films exhibit a Jc of above 2 MA/cm2, even though they are fired at 700 °C. Moreover, Jc is near 10 MA/cm2 for the YBCO film fired at 775 °C.

The feasibility of vitrifying a sandstone enclosure in the British Iron Age

Iron Age structures with evidence for having been subjected to high temperatures have been identified throughout Europe. The thermal conditions that must have yielded such evidence of alteration remain enigmatic, especially for the case of high-silica, quartz-rich building materials such as sandstones. Here, we conduct an experimental investigation of thermal treatment using the Wincobank Iron Age hill fort site in Sheffield, South Yorkshire (U.K.) as a test case. We have selected samples of the unaltered protolithic sandstone from which the fort was constructed as starting material as well as material from the vitrified wall core. An experimental suite of thermally treated protolith samples has been analysed using a combined approach involving X-ray diffraction and thermal analysis (simultaneous differential scanning calorimetry with thermogravimetric analysis). Comparison between our experimental products and the variably vitrified samples found in the wall of the Wincobank hill fort helps to constrain firing temperatures and timescales. For mineralogical markers, we employ the high-temperature conversion of quartz to cristobalite and the melting of feldspar to compare the relative abundance of these phases before and after thermal treatment. We find that the Iron Age wall samples have mineralogical abundances most consistent with a minimum firing temperature range <1100–1250°C and a firing timescale of >10h. These first quantitative constraints for a fort constructed of sandstone are consistent with those found for forts constructed of granitic material. Finally, we explore the reasons for thermal disequilibrium during firing and invoke this mechanism to explain the differential vitrification found at some Iron Age stone-built enclosures.

Avaliação da atividade pozolânica dos resíduos de cerâmica vermelha produzidos nos principais polos ceramistas do Estado de S. Paulo

&lt;p&gt;Com intuito de se obter vantagens técnicas, econômicas e ambientais, vem se acentuando o interesse da indústria do cimento para adições minerais em substituição parcial ao clínquer no cimento Portland. Uma das adições minerais mais comuns e que vem ganhando espaço no mercado brasileiro corresponde à argila calcinada, que agrega basicamente as características de pozolanicidade aos seus produtos compostos. Um material com propriedades potencialmente similares às argilas calcinadas e ainda não aproveitado como pozolana no país refere-se aos resíduos da indústria de cerâmica vermelha (RCV). Este trabalho buscou aprofundar o conhecimento sobre as propriedades cimentícias dos RCV, focalizando-se as propriedades pozolânicas de oito amostras coletadas em cerâmicas representativas de quatro dos principais polos paulistas, e suas relações com as composições das matérias-primas utilizadas (massas cerâmicas) e com a temperatura de queima. Os resíduos cerâmicos, após moagem controlada, mostraram-se adequados para a utilização como aditivo pozolânico para o cimento Portland. As amostras ensaiadas apresentaram um consumo médio de 500 mg de Ca(OH)&lt;sub&gt;2&lt;/sub&gt;/grama de amostra no Ensaio Chapelle, suplantando em 14,7% o valor mínimo normatizado. A máxima reatividade verificada situa-se na faixa de temperatura de queima entre 700 °C e 800 °C. Esse intervalo de maior reatividade corresponde aos patamares de queima usuais praticados nas empresas de cerâmica vermelha, o que corrobora com o potencial de aproveitamento de seus resíduos como adição mineral, fazendo com que o RCV possa constituir uma nova fonte de material pozolânico para o setor cimenteiro no país.&lt;/p&gt;