Identification characteristics of brucite

t is characterized by 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 (OH) - structure, Mg2 is packed in the octahedral space one layer apart. Each mg is surrounded by 6 Oh, and there are 3 mg on each side of each oh. The structure of Mg (0001) is weakly lamellar. Mg Oh is not octahedral, but flattened along the c-axis. The thickness of Mg Oh film changes from 0.247 nm to 0.211 nm. The structural characteristics of brucite make it have plate-like crystal, low hardness and ‖ {0001} cleavage.


The complex trigonometric polyhedral crystal is d3d-3m (l33l33pc). The crystals are plate-shaped or leaf like. The common simplexes are: parallel double-sided C {0001}, hexagonal column m {1120}, rhombohedron R {1011}, Q {0113} or {2021}. The crystals are usually plate-shaped, fine scaly, round and irregular granular aggregates; sometimes parallel fibrous aggregates are found, which are called brucite. There is structural distortion in the wurtzite. It is white and grayish white, green, yellow or maroon when mixed with Fe and Mn; the fresh surface and fracture glass luster; the cleavage surface is pearly luster; the brucite is silk luster; transparent. The cleavage {0001} is very complete. The hardness is 2.5. The thin piece is flexible and flexible. The relative density was 2.3 ~ 2.6. It is thermoelectric. The whiteness of massive brucite can reach 95%.


Under polarizing microscope: abnormal interference color is reddish brown instead of normal primary yellow or orange. Under the influence of stress, ductility can be positive or negative. However, it can show biaxial crystal, 2V ? 25 ℃. The refractive index ne is 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 elastic modulus is 13800 MPa, and it has a certain brittleness. Vickers hardness is 50.4 ~ 260.5, and has obvious anisotropy. It is easy to grind into fine powder. The theoretical relative density is 2.39.


Electromagnetic properties: the mass resistivity of brucite is 8.82 ? 106 Ω? g / cm2, the volume resistivity is 5.9 ? 106 Ω? cm, the surface resistivity is 3.6 ~ 4.5 ? 106 Ω, showing anisotropy; the resistivity increases when heating. The dielectric constant is 4.7 ~ 5.4 (1MHz); the dielectric constant increases with obvious directivity at low frequency (50 Hz) and intermediate frequency; the tangent value of dielectric loss angle 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 is a non-magnetic mineral; the specific magnetization coefficient increases with heating, but there is a trough 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 0.46 w / m · K, and the loose fiber is 0.131-0.213 w / m · K (bulk density 0.47 g / cm3). The thermal expansion of brucite is 16.7 * 10-7 / ℃ in longitudinal direction and 8.8 * 10-7 / ℃ in transverse direction, and the thermal expansion behavior is basically linear. It also has the properties of flame retardant, 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 rates in oxalic acid, citric acid, acetic acid, mixed acid and Al (OH) 3 solutions. 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 waterproof protective layer.


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


Spherical type: it is formed by hydration of periclase and occurs in the form of nodules, with the diameter ranging from several millimeters to more than 20cm. The nodules are cemented by cryptocrystalline brucite and a small amount of calcite and serpentine. The ore quality is good.


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


Fiber type: it occurs in serpentine in vein shape, and the content of brucite is generally 1-9%. The intercalated minerals 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: magnesium and MgO extracted from brucite, the content of MgO in the ore is high, the impurities are less; the decomposition temperature is low; the volatile matter produced during heating is non-toxic and harmless, so mg and MgO can be extracted from brucite.


Reburning magnesia: mainly used to produce magnesia refractories. Magnesia carbon brick and magnesium chromium brick are widely used in modern iron and steel industry. The amount of this kind of MgO has exceeded 1 / 2 of its output. The re fired magnesia prepared 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: the United States, Russia, Canada, Britain and other countries use chemical methods to extract light magnesium oxide from low-grade brucite rocks