Effect Of Firing Temperature Research Articles

Influence of firing temperature and duration on the hardness of dental zirconia for optimum selection of sintering conditions

In order to optimize the properties of dental zirconia, the sintering process involves firing zirconia to elevated temperatures for an extended time that can take several hours. The aim of this study is to investigate the effect of firing temperature and firing duration on the hardness of dental zirconia to indicate the optimum sintering conditions. Thirty-six zirconia specimens in shape of bars were randomly assigned to nine groups. The zirconia specimen groups were sintered using a sintering furnace with different firing temperatures (900°C, 1200°C, and 1800°C) and firing durations (6, 9, and 12 h). A total of 108 hardness measurements were conducted for all specimens (12 hardness readings per group). For each of the specimen groups, micro Vickers hardness test was performed using a load of 1 Kgf (9.807 N) and the Vickers hardness number was computed. Statistical analysis using Kruskal-Wallis test was conducted to examine the significant differences on Vickers hardness number HV among the specimen groups according to the firing parameters with 0.005 p-value used as an indicator. Results suggest that there is an association between the increase in the hardness number and the increase in firing duration at a given firing temperature. The results also indicate that there is an association between the increase in the hardness number and increase in firing temperature at a given firing duration. The greatest rate of hardness increase with time is associated with groups of firing temperature 1200°C. The highest rate of hardness increase with temperature happened during the first 6 h of sintering process. On the other hand, there is no significant increase in the hardness number when increasing the firing temperature beyond 1200°C.

Preparation of SiC coated graphite flake with much improved performance via a molten salt shielded method

AbstractOxide‐based castables have been used in high‐temperature furnace linings, especially for steel and iron processing, however, the poor thermal shock resistance and corrosion resistance limited the further enhancement of their service life. Carbon possesses excellent performances including low wettability to slag, low thermal expansion coefficient, which can greatly improve thermal shock resistance and slag resistance of oxide‐based castables. However, it has poor water‐wettability and oxidation resistance, which limited its application in the castables. Many efforts have been attempted to improve water‐wettability of graphite flake used for carbon‐containing castables, but it is still a huge challenge. In this work, a facile method for fabricating silicon carbide (SiC) coated graphite flakes has been firstly proposed by using graphite flake and silicon powder as the precursors via a molten salt shielded synthesis technique in air atmosphere, KCl was chosen to be a salt encapsulation providing a liquid reaction medium and a shield against oxidation of air. Effects of firing temperature, holding time, and molar ratio of Si and graphite flake on the formation of SiC coatings were investigated. The results show that the as‐prepared SiC coated graphite powders were loose and non‐agglomerated, and the coatings with ∼5 μm in thickness were crack‐free and firmly grown on the surface of graphite flake, composed of SiC nanosized particles. Compared to uncoated graphite flake, the SiC coated graphite possessed significantly improved water‐wettability, dispersibility, and oxidation resistance, making it to be a prime carbon form for fabricating carbon‐containing castables.

Effect of Firing Temperature on some Mechanical Properties of Osun State Ceramic Tiles

The work evaluates the effect of firing temperature on the mechanical properties of ceramic tiles. This was with the view to determine the optimum processing condition for Osun State ceramic tiles. Ceramic raw materials collected from Osun State were batched using clay-feldspar-silica sand blending ratio of 5:4:1, 5:3:2, 5:2:3, 5:1:4, 6:3:1, 6:2:2, 6:1:3, 7:2:1, 7:1:2 and 8:1:1 by weight; and homogeneously mixed. Three replica samples were moulded by the method of dry forming, fired at 1200, 1300 and 1400 oC and subjected to breaking and flexural strength tests using the Universal Testing Machine while the hardness test was carried out on a Moh’s scale. The results showed that breaking strength, flexural strength and Moh’s hardness fell within the range 199.43 to 325 N, 11.97 to 19.50 N/mm2 and 2.5 to 4 MH respectively, while Figures revealed that samples with 60% clay, 10% feldspar and 30% silica sand fired at 1320 oC will process the best mechanical properties. In conclusion, ceramic raw materials collected from Osun State are viable for ceramic tile production.

Combined effects of bayer process bauxite waste (red mud) and agricultural waste on technological properties of fired clay bricks

The sustainability of raw materials used in great amounts in the production of building materials used in the construction industry is of great importance. This research investigates the utilization of bayer process bauxite waste and agricultural residues as alternative additive materials for clay replacement to produce eco-friendly porous ceramic bricks. The use of organic and inorganic additives in brick production reduces the consumption of natural clay reserves and the weight of the brick. In addition, these additives have been used as pore formers in brick production to increase thermal performance and waste remediation in ceramic structures for environmental beneficial. Considering these issues, two different types of waste and their combinations were evaluated in brick production in the study. Hazelnut shells (HS) (from 2.5 wt% to 10 wt%), which is an agricultural waste, were used as pore former during firing of brick. On the other hand, this study is related to the evaluation of red mud waste (RM) (from 5 wt% to 30 wt%), which is released in large quantities at the result of Bayer process in the aluminum metallurgy and threatens environmental health, as an alternative raw material in the production of clay bricks. The compacted samples were fired at 900 °C and 1000 °C for 2 h to investigate the effects of firing temperature. Bulk density, water absorption, apparent porosity were determined by Archimedes method. Thermal conductivity and compressive strength of the samples were measured by a thermal conductivity analyzer with a modified transient plane source, and the mechanical test method, respectively. Also, the microstructural and leaching analysis of produced samples was performed. This research have confirmed that the potential use of these wastes decreases the bulk density and mechanical strength and increases the porosity, which leads to higher thermal insulation . The results indicated that samples produced with addition of 10% HS-30% RM exhibited the lowest thermal conductivity values (0.45 W/mK) and the acceptable compressive strength (9 MPa). Also, the effective thermal conductivity coefficient of the perforated brick model designed from this sample is found as 0.112 W/mK in ANSYS Fluent 19.1 Software. Furthermore, the brick samples with a high amount of waste materials show values of leaching toxicity much lower than the specified limits of the Environmental Protection Agency (EPA). The microstructures are also supporting the porosity ratios of brick samples. Based on the results, the combination of waste materials considered for making brick samples in this study can be used as additives in lightweight eco-friendly brick production to reduce waste landfill and recycle waste. • An agricultural residue is evaluated as a pore maker in brick production. • Red mud exhibits partially a flux effect with increasing firing temperature. • Addition of wastes increases porosity and lightweight bricks are produced. • Thermal conductivity of a perforated brick model designed from obtained results is simulated. • Leaching analysis is revealed that the fired bricks are eco-friendly.

Longleaf pine seedling growth and survival: Effects of season and intensity of simulated prescribed burning

Restoration of longleaf pine (Pinus palustris Mill.) forests is an important land management goal in the southern United States. To achieve this goal, longleaf pine is increasingly being planted across its range. Fire is an important ecological factor that has historically shaped and sustained longleaf pine forests. However, we have limited information on how fire impacts longleaf pine seedlings in newly established plantations. We conducted this study in Northwest Florida to examine the effects of fire intensity (low intensity ((LI), ∼100 °C), medium intensity ((MI), ∼300 °C), high intensity ((HI), ∼500 °C), and an untreated control) on survival, growth (root collar diameter (RCD) and height), physiological processes (net assimilation (A), stomatal conductance (gsw), and intrinsic water use efficiency (iWUE)), and biomass allocation of longleaf pine seedlings over a period of six months after fire was applied in four seasons (summer, fall, winter, spring). Within a given season, the survival of seedlings did not significantly differ at different fire intensities, except in the summer (α = 0.05). For the summer application, survival was lower (18%) in the HI treatment compared to the MI (98%), LI (93%), and control (93%) (p = 0.003). RCD growth was significantly affected by fire intensity treatment only for the summer application. For the summer application, RCD growth six months after treatment (MAT) was highest (7.3 mm) in the control compared to the LI (2.7 mm), MI (2.7 mm), and HI (2.0 mm) (p = 0.021). The height growth of seedlings did not significantly differ at different fire intensities, though their values were greater at 6 months compared to 3 months. The effect of fire temperature on percent biomass allocation was only significant for the fall foliage (p = 0.004). Neither root, stem, nor total shoot percent biomass significantly differed for any other season. Largely, A, gsw, and iWUE were not significantly affected by fire temperature. iWUE did differ for MAT (p = 0.003), however, no pattern could be discerned. Overall, our observations suggest that longleaf pine seedlings are highly resistant and resilient to fire intensity in different seasons, with some vulnerability to high-intensity summer fires which can adversely affect their survival and growth. Summer burning is still a viable option for seedling survival provided conditions on the ground favor low/medium intensity fire.

Determination of the Firing Temperature and Optimum Ratio of Valorizing Rice Husk Ash, Clear Glass Cullet and Ranong Clay for Developing Ecological Wall Tiles

The purposes of this study were to investigate the effect of firing temperature and utilizing residue materials on the physical properties and microstructure of the ecological wall tiles. Rice husk ash (RHA), clear glass cullet (CGC), and Ranong clay (RNC) were utilized. Eleven formulations were constructed and divided into two groups with different contents of RHA, at 10% and 20%. After molding by uniaxial pressing at 10 MPa, the tested specimens were fired at temperatures of 950 and 1050ºC, with heating rate of 100ºC/h, and soaked for 1 h. The bending strength of specimens fired at 1050ºC were enhanced by up to 205% compared with specimens fired at 950ºC. Formula B1, fired at 1050oC was optimal for further commercial production. It utilized 20 wt% RHA, 50 wt% CGC, and 30 wt% RNC which met the criteria of the Thai Industrial Standard (TIS) 2508-2555 type BIII. Moreover, the microstructure of specimens was characterized by scanning electron microscopy (SEM). It revealed that a glassy phase had developed in the high bending strength specimens under the influence of high firing temperature and CGC content. In addition, RHA residue material promoted a greyish color in ceramic bodies. Finally, it can be concluded that the valorization of RHA, CGC, and RNC in the development of ecological wall tiles with white-greyish texture was feasible.

Correction to: Effect of firing temperature on self-cleaning and photocatalytic performance of clay-based bricks under visible light irradiation

Correction to: Effect of firing temperature on self-cleaning and photocatalytic performance of clay-based bricks under visible light irradiation

Effect of firing temperature on self-cleaning and photocatalytic performance of clay-based bricks under visible light irradiation

Effect of firing temperature on self-cleaning and photocatalytic performance of clay-based bricks under visible light irradiation

Effect of particle size distribution on the evolution of porous, microstructural, and dimensional characteristics during sinter-crystallisation of a glass-ceramic glaze

Glass-ceramic test pieces, obtained from three different particle size distributions of a frit, were fired at temperatures between 800°C and 1200°C. Evolution of porous characteristics of the test pieces with firing temperature enabled the mechanisms responsible for the microstructural changes and the temperature range in which each mechanism predominated to be identified. Induced anorthoclase and diopside crystallisation porosity was observed to increase, after which it decreased at high temperatures by solution–reprecipitation of these phases, until a minimum was reached. The process caused crystal size, mean pore size, and pore size distribution uniformity to rise. Models were developed that appropriately describe the combined effect of firing temperature and glaze particle mean volume diameter on open porosity, linear shrinkage, mean pore size, and pore size distribution uniformity. Effect of glaze particle size distribution on pore size distribution, in the solution-reprecipitation stage, was perfectly described by mean pore size at solution-reprecipitation onset.

Effect of Fire Temperature and Exposure Time on High-Strength Steel Bolts Microstructure and Residual Mechanical Properties.

In this study, the influence of different fire conditions on tempered 32CrB3 steel bolts of Grade 8.8 was investigated. In this research different temperatures, heating time, and cooling methods were correlated with the microstructure, hardness, and residual strength of the bolts. Chosen parameters of heat treatments correspond to simulated natural fire conditions that may occur in public facilities. Heat treated and unheated samples cut out from a series of tested bolts were subjected to microstructural tests using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), XRD phase analysis, and the quantitative analysis of the microstructure. The results of the microstructure tests were compared with the results of strength tests, including hardness and the ultimate residual tensile strength of the material (UTS) in the initial state and after the heat treatments. Results of the investigations revealed considerable microstructural changes in the bolt material as a result of exposing it to different fire conditions and cooling methods. A conducted comparative analysis also showed a significant effect of all such factors as the temperature level of the simulated fire, its duration, and the fire-fighting method on the mechanical properties of the bolts.

Potential use of Kraft pulp mill and flat glass cutting wastes in red ceramic products

This study assessed the incorporation of green liquor dregs, an inorganic solid waste from Kraft pulp mill, and flat glass cutting waste (FGCW) into red ceramic formulations. Since in Brazil sanitary landfills are still the main destination of industrial wastes such as those used in this research, a survey was conducted to identify the number of landfills in the region of origin of each waste and the amount of waste that could have this destination avoided. The effects of firing temperature and simultaneous incorporation of both industrial wastes were analyzed to optimize heat treatment and waste content in the formulation to manufacture red ceramic products. The influence of green liquor dregs and FGCW incorporation into clayey mass was evaluated varying waste content between 0 and 50 wt%. The specimens were prepared by uniaxial pressing, fired at 850 and 950 °C, and had their physical-mechanical properties and mineralogical and microstructural characteristics analyzed. The best results were obtained for the formulation with 10 wt% green liquor dregs and 30 wt% FGCW fired at 950 °C. This result highlights the potential of using green liquor dregs, a waste difficult to be recycled due to its chemical composition, associated with FGCW, which acts as a fluxing agent in ceramic formulations.

A Scanning Electron Microscopy and Energy Diffraction X-Ray Spectroscopy Study to Evaluate the Effect of Firing Temperature at the Ceramic-Noble Metal Alloy Interface in Porcelain Fused to Metal Restorations

Introduction: Porcelain Fused to Metal (PFM) restorations offer aesthetics of ceramics and the strength of metal hence are the gold standards of fixed partial dentures. However, the fracture of porcelain-metal interface still remains a matter of concern. Aim: To study the porcelain-noble metal alloy interface of PFM restorations at different firing temperatures, using Scanning Electron Microscopy (SEM) and Energy Diffraction X-ray Spectroscopy (EDS). Materials and Methods: This in-vitro study was conducted between November 2018 to October 2019 at Prosthodontics Department of Saraswati Dental College and Hospital and King George’s Medical University Lucknow, Uttar Pradesh, India. A total of 75 strips of noble metal alloy were prepared and layered with 1 mm of porcelain on one surface, conforming to American National Standard/American Dental Association Specifications (ANSI/ADA) specification no. 38 for Metal-Ceramic Dental Restorative Systems: 2015. These were randomly divided equally into three groups. Specimens of each group (n=25) were fired at different temperatures that is 850oC, 900oC and 960oC, respectively. Scanning electron microscopy and Energy diffraction X-ray spectroscopy were performed at the noble metal alloy and ceramic interface of all specimens. Data was recorded and statistically analysed using one-way Analysis of Variance (ANOVA) and post-hoc Tukey HSD test. Results: Irregularities/Coarseness (50 μm) was seen on the noble metal alloy surface adjacent to ceramic layer in SEM images at all the three chosen temperatures. The EDS study revealed intermingled zones of partial oxygen depletion at the interface region with formation of intermetallic compound, lead zirconate titanate and complete oxygen depletion zone near metal alloy end of interface. The mean value of Shear Bond Strength (SBS) was 16.31 MPa at 850oC, 24.33 MPa at 900oC and 19.41 MPa at 960oC (p-value <0.05). Conclusion: Difference in properties and location of the intermetallic compound formed at the interface, as well as the location of the oxygen depletion zone could account for the weaker bond formed between noble alloy-porcelain interface compared to base metal-porcelain interface.

Preparation of mullite whisker reinforced SiC membrane supports with high gas permeability

Mullite whisker reinforced porous SiC membrane supports were fabricated by an in situ reaction bonding technique using SiC particles as skeleton materials, fine kaolin and α-Al2O3 powder as bonding agents, activated carbon as pore-forming agent and MoO3 as additive, and pressureless firing at 1350–1520 °C for 2 h in air. The effects of firing temperature and MoO3 addition amount on the properties of membrane support, such as open porosity, bending strength, microstructure and phase composition, thermal shock resistance and air permeability were investigated. The results showed that the morphology of the mullite whiskers and properties of porous SiC membrane supports were greatly influenced by the firing temperature and MoO3 addition amount. The membrane support with 8 wt % MoO3, fired at 1450 °C for 2 h, exhibited outstanding properties, including a bending strength of 24.69 ± 0.86 MPa, an open porosity of 43.30 ± 0.58%, a corresponding strength retention rate of 95.22% after 30 times cyclic thermal shock and Darcian permeability coefficient k1 and non-Darcian permeability coefficients k2 of 6.18 × 10−9 m2 and 1.50 × 10−3 m, respectively.

Studies on the Mechanical and Physical Properties of Hematite Iron Ore Pellets Prepared Under Different Conditions

The global iron-producing industries are trying to use the high alumina content iron ores due to the exiguity of high-grade ores and economic reasons. For this purpose, this present study focuses on the utilization of high alumina hematite iron ores obtained from eastern part of India in pelletization experiments. The effects of firing temperature and time, and binder addition on compressive strength, porosity and XRD analysis of resultant pellets were investigated. The experimental results showed that the amount of Al2O3 in the iron ore pellets did not show a much variation on the compressive strength (< 100 N) and porosity with increase in temperature up to 1373 K, followed by a gradual change in their values with further rise of firing temperature up to 1573 K. The X-ray diffraction patterns of resultant fired hematite iron ore pellets did not show any change in the major phase.

Porous alumina-felsite ceramic composites prepared by direct coagulation casting method: Felsite rock (central-eastern desert, Egypt)

In this work, the direct coagulation casting method was used to shape porous alumina-felsite ceramic composites. The felsite rocks used in this work were extracted from Wadi Atalla area, central-eastern desert, Egypt. Felsite is studied geologically, microscopically, and applied as a source for silica. The effect of felsite raw material additions up to 30 wt% and the effect of firing temperatures on the alumina were also investigated. The zeta potential of the suspended ceramic slurries was studied at different Ammonium Citrate Tribasic (ACT) concentraion and at different wt.% of felsite. Also, the viscosity was measured at different wt.% of felsite. The bulk density, apparent porosity and linear shrinkage were measured as well as the mechanical properties of the fired samples. The phase composition and the microstructural evolution of the fired samples were determined by XRD and SEM, respectively. Felsite additions enhance the physical and mechanical properties of the fired samples. The DCC process yields high-strength porous ceramic bodies and highly reliable ceramic parts. The results showed that the porous ceramic composites can be fired at 1600 °C to achieve apparent porosity of 40% and compressive strength of 35 MPa at 30 wt% of felsite.

English

English

Influence of gallium oxide concentration on the properties of transparent ceramics based on magnesium aluminate spinel

AnnotationThe article deals with the preparation precursor of magnesium aluminate spinel by the method of inverse co-precipitation, as well as the study of effect of firing temperature and the concentration of the gallium oxide addition on the optical and ceramic properties of the products is shown.

Effect of firing temperature on physico-mechanical properties of contemporary clay brick productions in Lalitpur, Nepal

Effect of firing temperature on some physico-mechanical properties of ten brick samples, those were composed by feldspars, quartz, alumina-rich spinel, primary mullite and hematite phases, was investigated in accordance with ASTM standards. The brick samples fired between 700° to 1100° C showed 11-23 % water adsorptivity (WA), 19-37 % apparent porosity (AP) and 1.50-1.65 g/cm3 bulk density (BD) indicate good physical properties. The maximum compressive strength (CS) of the fired-bricks at 950° to 1000° C was found to be between 15.6 and 17.1 MPa. At 700°-1000° C firing temperatures, the CS of these bricks is found to be increased exponentially with decreasing of both WA and AP, however it is found to be increased with increasing the BD. Consequently, it can be said that there is good correlation between mechanical and physical properties of the fired-brick samples up to the firing temperature of 1000° C.&#x0D; Bangladesh J. Sci. Ind. Res.55(1), 43-52, 2020

Detection and characterization of CO gas using LTCC micro-hotplates

In the present work, a tin oxide (SnO2)-based gas sensor has been fabricated on Low Temperature Co-fired Ceramic (LTCC) substrate by screen printing method for detection of the silent killer gas (carbon monoxide). The tin oxide paste has been prepared for deposition on inter-digitated electrodes patterned on LTCC substrate. The developed gas sensor module has been fired at different temperatures (625, 820 and 860°C) and the effect of firing temperature has been studied. The developed sensor is small in size with low power consumption, better sensitivity and repeatability.

Fire cues and germination of invasive and native grasses in the Cerrado

Fire-related cues may enhance seed recruitment in flammable ecosystems and differences in fire-germination responses of invasive vs. native species can drive the invasion process. We evaluated the effects of heat shock and smoke water solution treatment on seed germination of invasive (Melinis minutiflora, Urochloa decumbens, U. brizantha) and native grasses (Axonopus pressus, Aristida setifolia, Gymnopogon foliosus) of the Cerrado. The effect of fire temperature was tested by exposing seeds to heat shock treatments of 60, 100, and 200 °C for one minute, comparing them to untreated seeds. The effect of smoke was tested by soaking seeds for 24-h in an aqueous smoke comparing them to seeds soaked in distilled water. Differences among treatments were evaluated by ANOVA and randomization tests. None of the tested species had germination stimulated by the temperature or smoke. Both species of Urochloa experienced decreased viability with increasing temperature, while seeds of native species and M. minutiflora tolerated heat shock up to 200 °C. The invasive grasses usually germinated faster than the native grasses. Germination time is therefore a crucial trait driving the invasion process, irrespective of fire-related cues. Other seed traits (e.g. dormancy) and higher resprouting capacity may help invasive species to persist in frequently burned savannas.