Effect of MgO on the Properties of Alumina-Graphite Based Refractory Including 20 wt% Non-Stabilized ZrO2

Chemical Properties ◽

Cold Isostatic Pressing ◽

Modulus Of Rupture ◽

Coarse Grained ◽

Linear Change ◽

Abstract In this study the effect of magnesium oxide in the range of 0 to 10 wt. % on the mechanical properties, corrosion rate, preventing carbon bond oxidation and microstructure of alumina-graphite (coarse-grained) refractory bodies including 20 wt. % of non-stabilized zirconia is investigated. The refractories were fabricated by mixing raw materials, where phenolic resin in the form of liquid was used as binder, and then granulation, cold isostatic pressing and firing at 1400 °C for 8 hours in a reducing atmosphere. Mechanical, physical and chemical properties of the fabricated refractories were evaluated by determining cold compressive strength, modulus of rupture and thermal shock resistance, bulk density, molten shock resistance, permeant linear change, oxidation and corrosion resistance. The results showed that in the presence of MgO, the zirconia grain size increases and it results in a decrease in bulk density that leads in more slag penetration and decreasing corrosion resistance. It has also revealed that addition of MgO to the base refractory leads to decreasing in cold crushing strength, modulus of rupture, and thermal shock resistance. It has been also proved that it causes an expansion during sintering process and results in positive permeant linear change.

Thermal Fatigue Behavior of Ladle Purging Plug

10.4028/www.scientific.net/amr.105-106.158 ◽

2010 ◽

Vol 105-106 ◽

pp. 158-161

Author(s):

Hui Zhang ◽

Yan Ruo Hong ◽

Hong Xia Li ◽

Yang Bin

Keyword(s):

Thermal Shock ◽

Thermal Fatigue ◽

Fatigue Behavior ◽

Modulus Of Rupture ◽

Coarse Grained ◽

Fine Grained ◽

Shock Resistance ◽

Thermal Fatigue Behavior ◽

Fracture Damage

The thermal fatigue behavior of alumina-magnesia based and alumina-chromia based purging plug materials are comparatively studied. By comparing thermal shock parameters, the changes of elastic modulus and hot modulus of rupture after thermal shock cycles, we come to a conclusion that microcracks emerge in the alumina-magnesia based material, which hinder the crack growth during thermal shock cycles. The fine-grained and network structure of alumina-magnesia based material are also helpful to improve thermal shock resistance. However, cracks are difficult to form in the alumina-chromia based material but it tends to fracture damage quickly once the cracks nucleation due to coarse-grained structure of alumina-chromia based material.

Effect of Sintering Temperatures on the Sintering Performance and Thermal Shock Resistance of MgO-Al2O3-Fe2O3 Composite

10.4028/www.scientific.net/amr.194-196.1755 ◽

2011 ◽

Vol 194-196 ◽

pp. 1755-1758

Author(s):

Jing Long Bu ◽

Yan Qing Cai ◽

Li Xue Yu ◽

Zhi Fa Wang ◽

Rong Lin Wang

Keyword(s):

Bulk Density ◽

Thermal Shock ◽

Rotary Kiln ◽

Ferric Oxide ◽

Potential Application ◽

Bending Strength ◽

Raw Materials ◽

Linear Change ◽

The composites in the MgO-Al2O3-Fe2O3 system were prepared using high pure magnesia and alumina as raw materials and ferric oxide powder as additive. The effect of sintering temperatures on the sintering performance and thermal shock resistance of the composites was studied. The results showed that both the apparent porosity and linear change ratio of the samples decreased with the increase of sintering temperatures, and their bulk density and bending strength increased accordingly. The sample sintered at 1550°C exhibits excellent thermal shock resistance. The XRD and SEM results indicated that the crystal phase of the samples remained the same, but their microstructure became denser as the sintering temperatures increased from 1500°C to 1600°C. As a result, the composites could be sintered at about 1550°C, which has a potential application in cement rotary kiln linings.

Influence of an addition amount of a new type of alumina on the properties of ramming mullite-corundum mixes and samples from them

Scientific research on refractories and technical ceramics ◽

10.35857/2663-3566.120.06 ◽

2020 ◽

Vol 120 ◽

pp. 66-82

Author(s):

V. V. Primachenko ◽

I. G. Shulik ◽

I. V. Khonchik ◽

T. G. Tishina

Keyword(s):

Thermal Shock ◽

Chemical Properties ◽

Size Composition ◽

Synthesis Process ◽

Crushing Strength ◽

Cold Crushing Strength ◽

Shock Resistance ◽

Spherical Alumina ◽

Addition Amount

Effect investigation of an addition amount of spherical alumina on the properties of ramming mullite-corundum mixes of the MMK-90 (on a binder of an aqueous solution of orthophosphoric acid) and MMKPBF (with a MgO addition on a borophosphate binder) brands, as well as samples from them, have been carried out. As a result of the carried out studies, it was found that the use of an optimal amount (4 %) of spherical alumina in the composition of ramming mullite-corundum mixes provides an increase in by 30 % in the cold crushing strength of samples made from them, fired at a temperature of 1580 °C, while maintaining at sufficiently high level indicators of their thermal shock resistance and slag resistance. The indicated alumina use in the composition of the MMK-90 mix during high-temperature firing of samples leads to an intensification of the mullite synthesis process. In fired samples from the MMKPBF mix, the spherical alumina forms a dense intergrowth of "felt-like" structure, which reinforces the structure, increasing the strength and thermal shock resistance of the samples. Indicators of physical and chemical properties of ramming mullite-corundum mixes of improved composition and samples made from them (for MMK-90 and MMKPBF mixes, respectively): chemical composition, wt. %: Al2O3 — not less than 90.0 and 85.0; SiO2 — within 3.2-5.0 and no more than 2.5; Fe2O3 — no more than 1.0 and 0.6; P2O5 — in the range of 2.5-3.5 and 0.5-1.0; grain size composition, mm — 3-0; cold crushing strength after firing at a temperature of 1580 °С — 110 and 70 N/mm2; thermal shock resistance — > 20 thermal cycles 950 °С — water. Ramming mullite-corundum mixes of improved composition are recommended for use in various heating units with high specific mechanical loads on the lining.

Utilization of Fly Ash in the Synthesis of Refractory Forsterite-Spinel Ceramics

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.321.131 ◽

2021 ◽

Vol 321 ◽

pp. 131-140

Author(s):

Martin Nguyen ◽

Radomír Sokolař

Keyword(s):

Thermal Expansion ◽

Fly Ash ◽

Thermal Shock ◽

Power Plants ◽

Linear Thermal Expansion ◽

Aluminium Oxide ◽

Raw Material ◽

Modulus Of Rupture ◽

Forsterite refractory ceramics is utilized in the metallurgical and cement industries as a lining of metallurgical furnaces and rotary kilns for its high refractoriness up to 1850°C and refractoriness under load above 1600°C. Another significant property of forsterite is its coefficient of linear thermal expansion utilized in the electrotechnical industry for ceramic-metal joints. Addition of aluminium oxide into the raw material mixture results in creation of magnesium-alumina spinel (MgO·Al2O3) which improves sintering, thermal shock resistance and mechanical properties in comparison with pure forsterite ceramics. Inexpensive source of aluminium oxide is fly ash. Utilization of fly ash, secondary energetic product of coal-burning power plants, is important for the environment and sustainable development. This paper evaluated properties of fly ash-based forsterite-spinel ceramics in comparison with alumina-based forsterite-spinel ceramics. Forsterite-spinel ceramics was synthesized from olivine, calcined magnesite and fly ash/alumina powders. XRD analysis was used to determine mineralogical composition, thermal analyses were used to determine the behaviour during firing and scanning electron microscopy to determine the morphology of crystal phases. Refractoriness of pyrometric cones, refractoriness under load, thermal shock resistance, coefficient of linear thermal expansion, water absorption, porosity and modulus of rupture were also determined on fired test samples.

Viability of Some Kano-Nigerian Clays for Refractory Applications

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.315.477 ◽

2013 ◽

Vol 315 ◽

pp. 477-481 ◽

Cited By ~ 2

Author(s):

I.A. Rafukka ◽

B. Onyekpe ◽

Y. Tijjani

Keyword(s):

Compressive Strength ◽

Physical Properties ◽

Bulk Density ◽

Thermal Shock ◽

Linear Shrinkage ◽

Chemical Compositions ◽

Shock Resistance ◽

Materials Used ◽

Refractory Bricks

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.

Effect of MgO/CuO on the Microstructure and Thermal Properties of Cordierite–Alumina Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.509.240 ◽

2012 ◽

Vol 509 ◽

pp. 240-244

Author(s):

Li Ying Tang ◽

Xi Cheng ◽

Ping Lu ◽

Fang Yue

Keyword(s):

Thermal Conductivity ◽

Bulk Density ◽

Thermal Shock ◽

Raw Materials ◽

Laser Flash ◽

Alumina Powder ◽

Alumina Ceramics ◽

Conductivity Increase ◽

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.

Effect of M-ZrO2 on Sintering Behavior and Thermal Shock Resistance of Dense Cr2O3 Material

10.4028/www.scientific.net/amr.199-200.1928 ◽

2011 ◽

Vol 199-200 ◽

pp. 1928-1931 ◽

Cited By ~ 2

Author(s):

Hong Ji Yin ◽

Tao Zhang ◽

Ai Jun Wu ◽

Jin Xiang Wang

Keyword(s):

Polyvinyl Alcohol ◽

Oxygen Partial Pressure ◽

Thermal Shock ◽

Room Temperature ◽

Cold Isostatic Pressing ◽

Sintering Behavior ◽

Quenching Effect ◽

Material Sample ◽

The samples were prepared using Cr2O3 micropowder, TiO2 micropowder and m-ZrO2 micropowder as main starting material, polyvinyl alcohol as binder, by a series of processes such as pulping, spraying granulation, machine moulding and cold isostatic pressing, and sintering at 1 500°С for 3 h in nitrogen protected atmosphere furnace (oxygen partial pressure was 10 Pa). Then thermal shock resistance of the samples was tested by wind quenching. Effect of m-ZrO2 (2%-5% in mass) on sintering behavior and thermal shock resistance of Cr2O3 material was investigated. The results show that m-ZrO2 can accelerate the sintering of Cr2O3 material, but excess 2 wt% m-ZrO2 doesn’t work; m-ZrO2 can obviously improve thermal shock resistance of Cr2O3 material, sample containing 3 wt% m-ZrO2 has 34 wind quenching cycles from 1 150°С to room temperature, and sample without m-ZrO2 only has 11 cycles.

EVALUATION AND CHARACTERIZATION OF GAKEM AND ABOUCHICHE CLAY SAMPLES IN BEKWARRA LGA OF CROSS RIVER STATE FOR USE AS REFRACTORY MATERIALS

Nigerian Journal of Technology ◽

10.4314/njt.v36i3.26 ◽

2017 ◽

Vol 36 (3) ◽

pp. 844-848

Author(s):

FA Ovat ◽

DE Ewa ◽

EA Egbe

Keyword(s):

Bulk Density ◽

Thermal Shock ◽

Linear Shrinkage ◽

Apparent Porosity ◽

Refractory Materials ◽

Crushing Strength ◽

Cold Crushing Strength ◽

The characterization of some clay as refractory materials for furnace lining has become relevant to find solutions to the cost involved in the purchase and importation of these refractory materials. This work investigated the refractory properties of clay samples for their suitability for use in the industries. Clay samples were collected from Gakem and Abouchiche areas and analysed for physical and chemical properties to determine the suitability of the clays as refractory materials. The results showed cold crushing strength (21.46MN/m2), thermal shock resistance (27 cycles), bulk density (3.52g/cm3), linear shrinkage(3.80%), apparent porosity (28.84%) and permeability (80%) for Gakem; and cold cold crushing strength (18.40MN/m2), thermal shock resistance (25 cycles), bulk density(2.81g/cm3), linear shrinkage (3.70%), apparent porosity (25.86%) and permeability (77%) for Abouchiche respectively. The chemical compositions of these clay samples were also investigated. The results showed that the samples fall under Aluminosilicate type of clay because of their high values of Aluminium Oxide and Silicon Oxide. Tests showed that clay from these areas can be used to produce refractory materials that can withstand a furnace temperature of about 1600Â°C.Â http://dx.doi.org/10.4314/njt.v36i3.26

Thermal and Thermomechanical Properties of Refractory Forsterite-Spinel Ceramics

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.325.174 ◽

2021 ◽

Vol 325 ◽

pp. 174-180

Author(s):

Martin Nguyen ◽

Radomír Sokolář

Keyword(s):

Fly Ash ◽

Thermal Shock ◽

Raw Materials ◽

Thermal Analyses ◽

Aluminium Oxide ◽

Thermomechanical Properties ◽

Modulus Of Rupture ◽

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.

Influence of Additives on Performance of Silicon Carbide Refractory

10.4028/www.scientific.net/amr.538-541.2277 ◽

2012 ◽

Vol 538-541 ◽

pp. 2277-2280

Author(s):

You Fu Guo ◽

Ming Yue Zheng ◽

Jing Long Bu ◽

Yue Jun Chen ◽

Li Xue Yu ◽

...

Keyword(s):

Silicon Carbide ◽

Thermal Expansion ◽

Bulk Density ◽

Thermal Shock ◽

Silica Fume ◽

Bending Strength ◽

Carbide Refractory ◽

Shock Resistance ◽

Silicon Carbide Refractory

Silicon carbide with diffierent granularity was used as raw material, quartz, silica fume, aluminum powder or alumina was used as additive with dosages of 1% (in mass, similarly hereinafter), 3% and 5%. Silicon carbide refractory material was prepared in oxidizing atmosphere at 1400 °C for 3 h. Performence of samples were researched by measurements of apparent porosity, bulk density, bending strength at room temperature, thermal shock resistance and thermal expansion rate, and analyzed by SEM. The results showed that samples added silica fume have low thermal expansion rate and apparent porosity, high bending strength and bulk density, good thermal shock resistance, compact texture as well. It can be deduced that 5% silica fume plays the excellent role to improve integrated performance of silicon carbide refractory material.