Preparation and Properties of MgO-MgAl2O4-FeAl2O4 Bricks in Cement Kiln

2011 ◽  
Vol 250-253 ◽  
pp. 554-560 ◽  
Author(s):  
Shu Long Ma ◽  
Yong Li ◽  
Jia Lin Sun ◽  
Yue Li ◽  
Wen Bin Xia

Sintered magnesia with different particle sizes, fused MgAl2O4and FeAl2O4were used as the raw materials. FeAl2O4is added in MgO-MgAl2O4bricks at different ratios to gradually replace MgAl2O4. After the raw materials were molded and sintered at the tunnel furnace with the temperature 1 530°C for 10 hours, the MgO-MgAl2O4-FeAl2O4bricks could be made. After the analysis of the phase composition, microstructure and routine performance of the specimens, the influence by adding FeAl2O4to the samples on the properties such as thermal shock resistance, adhesion strength of kiln crust are discussed as the key point. The result shows that the addition of FeAl2O4has no evidently influence on the apparent porosity and volume density. The cold compressive strength of the samples reduces gradually with the addition of FeAl2O4, and it decreases obviously when the amount of FeAl2O4is more than 8%. When the addition of FeAl2O4is 5% FeAl2O4in the MgO-MgAl2O4-FeAl2O4bricks, MgAl2O4and FeAl2O4can combine each other’s advantages. The thermal shock resistance not only decreased obviously but the adhesion strength to kiln crust is increased.

2020 ◽  
Vol 94 (2) ◽  
pp. 414-453
Author(s):  
Małgorzata Daszkiewicz ◽  
Piotr Łuczkiewicz ◽  
Jörg Kleemann ◽  
Aneta Kuzioła

AbstractThe necropolis at Malbork-Wielbark was excavated from 1927 to 1936 and 2008 to 2019. This burial ground is the eponymous site of the Wielbark culture. To date, over 2000 burials, both inhumation and cremation (pit and urn graves), have been recorded at this site, attesting to its continuous use from the Early Pre-Roman Iron Age (phase A1) to the early Migration Period (phase D1), with particular emphasis on the Roman Period. The cemetery site partially overlies and damages an earlier Iron Age settlement of the Pomeranian culture.Laboratory analyses were carried out on 113 pottery sherds. The series of samples chosen for analysis reflected, as far as was possible, all relative chronological phases and vessel shapes. The pottery was analysed using a step by step strategy built on the results of MGR-analysis (i. e. the classification of samples based on their matrix type) and on a macroscopic assessment of clastic material. In addition, an estimation of chemical composition by portable energy-dispersive X-ray fluorescence (pXRF) was available for each sample. After they had been classified, samples were selected for chemical analysis by wavelength-dispersive X-ray fluorescence (WD-XRF), estimation of physical ceramic properties (open porosity, water absorption and apparent density), Kilb-Hennike analysis (K-H analysis), thin-section studies using a polarising microscope, a study of surface phenomena by RTI (Reflectance Transformation Imaging), thermal analysis (TG-DTG-DTA), X-ray diffraction analysis and functional properties analysis (water permeability and thermal shock resistance), as well as experimental estimation of magnetic properties.The results of MGR-analysis carried out on ceramic samples taken from 113 potsherds revealed that all of the pottery was made from various non-calcareous clays with fine-grained iron compounds homogeneously distributed in the matrix. It was decided not to carry on determining/using MGR-groups, as nearly every sherd represents a different MGR-group. This means that these vessels were made during different production cycles. The differences in thermal behaviour between samples were attributed only to matrix-type groups. It can be concluded that 85 % of the total sherds were made from plastic raw materials of the same provenance, and that the same matrix-type groups occurred in all chronological phases. The percentage of vessels made of particular raw materials indicates a significant difference in the preferences of Pomeranian Culture potters and those of Pre-Roman Iron Age, Early Roman Period and those of the Late Roman Period, when one type of raw material disappears from use. This last period is also characterized by an increase in the number of vessels fired in a reducing atmosphere. Standardization is also evident in vessel-wall thickness, which falls within a narrow range of values, on the other hand combined with a large variety in grain sizes up to very large ones and with a wide range of open porosity values, which in turn points to a lack of care in the preparation of the ceramic body. Vessels that may have been non-local origin are noted in all chronological phases. Analysis of functional properties (water permeability and thermal shock resistance) revealed that the pottery deposited in graves included fully functional wares, such as cooking pots, as well as vessels intended solely as grave goods.More than a few samples evidence the use of a slow-rotating potter’s wheel, and it is also possible that a template was used for forming vessel rims. However, there are very few examples of truly technologically advanced vessels. The technology is generally tailored to the desired type or form of vessel.


2013 ◽  
Vol 315 ◽  
pp. 477-481 ◽  
Author(s):  
I.A. Rafukka ◽  
B. Onyekpe ◽  
Y. Tijjani

The physical properties of some materials used by local foundries were investigated with a view to assessing their suitability for use as low heat duty refractory bricks. The samples were collected from Malamai village, Gezawa Local Government, Kano state; they are Gezawa clay and Burji (Clay). The samples were crushed, ground, sieved and the chemical compositions were determined. The clay samples were treated separately as well as blended with Gezawa clay in different proportions and molded in to bricks. The bricks were dried and fired to 1100. Test for refractoriness, thermal shock resistance, linear shrinkage; bulk density, porosity and compressive strength were carried out on each of the specimen. Burji blended with 50% to 90% Gezawa clay gave improved thermal shock resistance with a refractoriness of 1300 and hence could be used for non ferrous melting cupolas.


2008 ◽  
Vol 368-372 ◽  
pp. 1152-1154
Author(s):  
Hua Zhi Gu ◽  
Hou Zhi Wang ◽  
Mei Jie Zhang ◽  
Ao Huang ◽  
Wen Jie Zhang

The temperature distribution of the permeable brick was modeled using CFX software. The influence of magnesia and corundum on thermal shock resistance of non-cement bonded alumina-based permeable brick was investigated. The results indicated that, in the gas blow process, the high temperature regions near the working face of the brick gradually expanded with the increase of the gas flow rate. Therefore the inner part of the brick had the complex and large change of thermal stress. Further experiments demonstrated that thermal shock resistance of alumina-magnesia based castable refractory was better than that of alumina-chrome based castable refractory. With the increase of magnesia amount, the alumina-magnesia based castable refractory had more cycles of heating and water-cooling. When different kinds of corundum were added in the raw materials, the sample with tabular corundum showed the best thermal shock resistance, the one with white fused corundum performed worse and the one with fused dense corundum performed worst.


2012 ◽  
Vol 509 ◽  
pp. 240-244
Author(s):  
Li Ying Tang ◽  
Xi Cheng ◽  
Ping Lu ◽  
Fang Yue

Abstract: Cordierite–alumina ceramics were prepared with the raw materials of cordierite and α-alumina powder, and TiO2,CuO and MgO were added as composite additives. The effect of MgO/ CuO ratios on the microstructure, thermal conductivity and thermal shock resistance of cordierite–alumina ceramics were researched by X-ray diffraction, scanning electron microscopy and laser flash analyzer; the bulk density and the porosity of cordierite – alumina ceramics were measured. The results show that with increasing of MgO/CuO ratios, the bulk density and thermal conductivity increase firstly and then decrease, and have a minimum with 0.4wt% MgO and 0.667 MgO/CuO; and the porosity of ceramics decreases firstly and then increases and has a maximum with 0.4wt% MgO and 0.667 MgO/CuO;There are little changes in the size of the grain of the ceramics, and a small amount of magnesium aluminate spinel precipitate; the thermal shock resistance performance of the ceramics is developed with the increasing of MgO/CuO ratios.


2009 ◽  
Vol 79-82 ◽  
pp. 1983-1986 ◽  
Author(s):  
Xiao Li Ji ◽  
Fei Xu ◽  
Hai Ya Chen

Prepared silicon carbide(SiC) ceramic foams combined with mullite whiskers which synthesized by in-situ reaction. Studied on the influence of temperature on the synthesis of mullite whisker, and the influence of mullite content on the compressive strength, thermal shock resistance of SiC ceramic foams. The results indicate that the performance of mullite whiskers synthesized at 1400°Cwere best, when mullite content was 25%, SiC ceramic foams could reach the maximum compressive strength for 1.75MP, the most thermal shock resistance for14 times.


2021 ◽  
Vol 325 ◽  
pp. 174-180
Author(s):  
Martin Nguyen ◽  
Radomír Sokolář

This article examines the utilization of fly ash in comparison with alumina as raw materials and sources of aluminium oxide for synthesis of forsterite-spinel refractory ceramics. Raw materials were milled, mixed in different ratios into two sets of mixtures and sintered at 1500°C for 2 hours. Sintered samples were characterized by X-ray diffraction analysis and scanning electron microscopy. Samples were also subjected to determination of porosity, water absorption and bulk density. Thermal and thermomechanical properties were determined by thermal analyses, refractoriness, refractoriness under load, thermal shock resistance and thermal dilatometric analysis with determination of thermal expansion coefficient. Mixtures with 10 wt.% and 20 wt.% of fly ash had the most promising results compared to alumina mixtures. Thermal shock resistance and modulus of rupture were improving with increasing content of aluminium oxide in the mixture.


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