Identification characteristics of brucite

It is characterized by its morphology, low hardness and (0001) complete cleavage. In the ternary system, A0 = 0.313nm, C0 = 0.474nm; Z = 1. Brucite structure is one of the important layered structures. In the structure, (OH) - is close packed in six directions. Mg2 is filled in the octahedral space separated by the stacking layer. Each mg is surrounded by six Oh's, and each Oh side has three mg's. The [Mg (OH) 6] octahedron ∧ {0001} is connected to form a layer in a common arris way, and the interlayer is maintained by a very weak hydrogen oxygen bond, forming a layered structure. Mg oh was not octahedral, but flattened along the c-axis. The thickness of Mg Oh changed from 0.247nm to 0.211nm. Due to its structural characteristics, brucite has plate-like crystal shape, low hardness and ∧ {0001} extremely complete cleavage.


Complex triangular hemihedral crystals, d3d-3m (l33l33pc). The crystals are plate or leaf like. Common simplex: parallel double-sided C {0001}, hexagonal column m {1120}, rhombohedron R {1011}, Q {0113}, or {2021}. The crystals are usually plate-shaped, fine scale-shaped, round and irregular granular aggregates; sometimes there are parallel fibrous aggregates, which are called brucite. There is structural distortion in brucite. White, gray white, green, yellow or maroon when Fe and Mn are mixed; fresh surface and fracture glass luster, cleavage surface pearl luster, brucite silk luster; transparent. The cleavage {0001} is very complete. The hardness is 2.5. The thin pieces are flexible and flexible. The relative density is 2.3 ~ 2.6. Thermoelectricity. The whiteness of massive brucite can reach 95%.


Polariscope: abnormal interference color red brown instead of normal primary yellow or orange. Under the influence of stress, ductility can be positive or negative. One axis crystal (), but two axis crystal, 2V ? 25 ℃. The refractive index ne = 1.5705 ~ 1.5861, no = 1.5612 ~ 1.570, and the difference between NE and no decreases after heating.


Mechanical properties: the tensile strength of brucite is 902mpa, which belongs to medium strength fiber material. The modulus of elasticity is 13800mpa, which has certain brittleness. The Vickers hardness is 50.4 ~ 260.5, and it has obvious anisotropy. Easy to grind into fine powder. The theoretical relative density is 2.39.


Electro magnetic properties: the mass resistivity of brucite is 8.82 ? 106 Ω J G / cm2, the volume resistivity is 5.9 ? 106 Ω J cm, the surface resistivity is 3.6 ~ 4.5 ? 106 Ω, the resistivity is anisotropic; the resistivity increases when heating. The dielectric constant is 4.7 ~ 5.4 (1MHz); at low frequency (50Hz) and medium frequency, the dielectric constant increases with obvious directionality; the dielectric loss tangent is 0.105. The dielectric constant and dielectric loss tangent increased by 54% and 2.7 times respectively. The specific magnetization coefficient of brucite is 9.815-15.779 ? 10-6cm3 / g, which belongs to non-magnetic mineral. Heating makes the specific magnetization coefficient increase, but there is a low near 300 ℃, 500 ℃ and 600 ℃. When the temperature is higher than 700 ℃, it shows medium strong magnetism.


Thermal properties: the reliable use temperature of brucite is 400 ℃. The thermal conductivity of brucite is 0.46w/m · K, and that of loose fiber is 0.131 ~ 0.213w/m · K (bulk density 0.47g / cm3). The thermal expansion of brucite is 16.7 * 10-7 / ℃ in the longitudinal direction and 8.8 * 10-7 / ℃ in the transverse direction, and the thermal expansion behavior is basically linear. Brucite also has the properties of flame retardant, resistance to open fire and high temperature flame. The decomposition temperature of brucite is 450 ℃.


Chemical properties: brucite is the best alkali resistant natural inorganic fiber. However, it can be completely dissolved in strong acid, and can be dissolved at different speeds in oxalic acid, citric acid, acetic acid, mixed acid and Al (OH) 3 solution. In humid or rainy climate, brucite is easy to be eroded by CO2 and H2O in the atmosphere, so the surface of brucite products needs to have a waterproof protective layer.


Surface properties: the diameter of monobrucite fiber measured by TEM is 0.54 ~ 0.86 μ m, the thinnest is 0.086 μ M. The electromotive potential of brucite can reach 36.3 MV. The pH value of the zero potential point is 12.5. Brucite fiber has good splitting and dispersibility, and long fiber. After mechanical beating or chemical dispersion, beating degree can be improved obviously, and wet spinning and papermaking can be carried out. It is formed by hydrolysis of soluble magnesium compounds in strong alkaline solution, and is the secondary change product of alkaline solution acting on magnesium silicate. The deposit is mainly related to serpentine and also occurs in contact metamorphic magnesite limestone, coexisting with calcite, tremolite, serpentine and phlogopite. Sometimes it occurs in dolomitic limestone and is associated with calcite, hydromagnesite and periclase. Brucite ore can be divided into three main types: spherical type, massive type and fiber type


Globular type: it is formed by hydration of periclase, and it is nodular, with a diameter from several millimeters to more than 20cm. The nodule is cemented by cryptocrystalline brucite and a small amount of calcite and serpentine. The quality of ore is good.


Massive type: it is the product of hydrothermal alteration of magnesium rich rocks. The ore is a massive aggregate of crystalline grains, coexisting with serpentine, calcite, magnesite and so on. The content of brucite is about 30-40%.


Fiber type: it occurs in serpentinite in vein shape, and the content of brucite is generally 1-9%. The minerals of inclusion are serpentine and magnetite. The purity of brucite is very high. Brucite is mainly used in the following industrial fields:


Extraction of Mg and MgO raw materials: extracting mg and MgO from brucite, the content of MgO in the ore is high, the impurities are few; the decomposition temperature is low; the volatile produced during heating is non-toxic and harmless, so mg and MgO and other products can be extracted from brucite.


Re fired magnesia: mainly used to produce magnesia refractories. In modern iron and steel industry, magnesia carbon brick and magnesia chrome brick are widely used. This kind of MgO consumption has exceeded 1 / 2 of its output. The re fired magnesia made from brucite has the advantages of high density (> 3.55 g / cm3), high refractoriness (> 2800 ℃), high chemical inertness and high thermal shock stability.


Light magnesium oxide: light magnesium oxide is extracted from low-grade brucite by chemical methods in the United States, Russia, Canada, Britain and other countries