In this studymagnesia spinel refractory brick, the effect of adding different amounts of stoichiometric magnesia alumina spinel to magnesia brick was investigated. For this purpose, magnesia-alumina spinel was synthesized at a temperature of 1400 C and then it was added in the range of 15-35% by weight to the magnesia refractory brick composition. Then, the optimal firing temperature for this magnesia-spinel refractory was determined using phase analysis and condensation studies. After that, the final refractory products were examined in terms of density, percentage of apparent porosity, cold compressive strength (S.C.C.), (RUL) and the residual cold flexural strength after thermal shock. The results showed that the magnesia brick sample It contains 25% by weight of spinel with optimal composition in terms of properties. For a century, the synthesis of magnesia-alumina spinel and the production of spinel refractories have been known, but the volume expansion of 5-7% during the process of forming spinel from its primary oxides, magnesia and alumina, does not allow the material to condense during heating and firing. Therefore, a two-stage thermal program is used to synthesize spinel with high density, the first stage is to complete the spinel formation process and the second stage is to densify the spinel. Although the use of two-stage thermal program will not be suitable from the economic point of view Magnesia chromite refractories with properties similar to magnesia spinel bricks have a lower price and are more economical. In fact, the use of chromite is done in order to improve the shock resistance quality of magnesia bricks. Cr in the oxidizing atmosphere of rotary cement kilns under +3, however, materials containing chromium are known to be dangerous because Cr is transformed (relationship 1 and 2). On the one hand, the environment and the very good physical and chemical properties of magnesia alumina spinel on the other hand caused the desire to replace chromite magnesia bricks with spinel magnesia bricks. Today, the use of magnesium aluminate as an alternative phase in magnesia-based refractories is considered. The main application environments of magnesia-spinel refractories are in the firing and transfer area of the cement rotary kiln and alumina-spinel castables in the side walls and bottoms of steel pans [1, 2, 3, 6} Relationship 1 2Cr2O3 + 3O2 + 4Na2O → 4Na2Cr2O4 Relationship 2 2Cr2O3 + 3O2 + 4K2O → 4K2CrO4 +3 Stoichiometric magnesia alumina spinel with the chemical formula MgAl2O4 is formed through the penetration of Al and Mg2+ ions. The weight ratio for the synthesis of stoichiometric spinel is 28.33% magnesia and 71.67% alumina. o The melting temperature of magnesia alumina spinel is around 2135 C. 
is spinel stronger than garnet
Spinel is a stone with a hardness of 8-7.5 on the Mohs scale and a chemical composition of MgAl2O4, which can grow with octahedron forms or cubic, isometric, eight-level, twelve-level and twin crystals. Spinel stone can be found in three geological conditions: ) in the form of crystals in limestone or dolomitic limestone related to metamorphism, gneiss or serpentine 2) Shapeless grains in original igneous rocks 3) water-worn pebbles in sedimentary deposits Community Verified icon Spinel is available in a variety of colors from red to garlic green to black and matte, even blue, although in the past it was basically known as red spinel. Its yellow type is Rubicelle, its pure red type is Balas Ruby, bright orange to red orange (Flame Spinel), brown types (Piconite), dark green to black in which the presence of iron is evident (Hercynite). Spinel), dark green to blackish, which is a little lighter than the Hercynite sample (Pleonaste Spinel). Its blue or purple-blue variety known as Gahno-Spinel was found in 1937 and has a large amount of zinc. Among the rare phenomena in this stone, we can mention the changing color, the Chetoyansi and Trapich phenomenon, the asterism or star (in the form of four and six arms). Spinel is actually the name of a group of metal oxide minerals that cause them to have the same crystallization structure. This mineral can include a set of different mineral compounds with the general formula of XY2O4, which can be replaced by elements such as Fe+2, Zn, Mn+2, Ni, Co, Cu, Mg, and instead of Y Elements such as Fe+3, Cr, V+3, Ti+4, G e, or Sb Al can be replaced and create a new mineral. 
refractory brick cost
The price of Chamoti brick depends on factors that are different and cannot always set a fixed price for it. In general, the factors that cause the variation in the price range of Chamouti brick are: Chosen color (for example: Chamouti firebrick has a darker color and its price is higher.) brick feature; the size of the work; The city of the project And… With more than a quarter of a century of experience, Ajarnema Mihrab has tried to provide standard products with excellent quality and can compete with domestic similar types. The products of Mihrab brick industry are compatible with various styles of architecture and interior design. The high variety of products allows designers to design the architecture and the interior and exterior of the building based on the diverse tastes of customers. With more than a quarter of a century of experience, Ajarnema Mihrab has tried to provide standard products with excellent quality and can compete with domestic similar types. 
The products of Mihrab brick industry are compatible with various styles of architecture and interior design. The high variety of products allows designers to design the architecture and the interior and exterior of the building based on the diverse tastes of customers. At Mihrab firebrick industries, we produce firebricks for the exterior and interior of the building in different colors (English, chamotte, oyster white, black and brown) and different designs, with the support of our experts and high experience. The three most used synthetic spinel compounds in the market are non-stoichiometric, and the percentage of alumina and magnesia in them is shown in Table 1. Spinel 66 MR is used to produce magnesia spinel products, and spinel 76 AR and AR 90 are used to produce alumina spinel products. The chemical composition of stoichiometric magnesia alumina spinel, spinel 66 MR, 76 AR and 90 AR is shown in Al2O3-MgO phase diagram (Fig. 2