The main application background and overview of barium metaborate
Barium metaborate is also known as barium borate. White powder. Molecular weight 349.07. Dissolved in water. Functional pigments. It can enhance the anti-mildew, anti-rust, fire-proof and anti-powder properties of the coating. It is prepared by adding barium sulfide and borax aqueous solution into an autoclave, adding a small amount of sodium silicate, and heating at 125 to 140°C. At present, according to data from different manufacturers, the particle size of barium metaborate products generally fluctuates between 0.35 and 35 μm, with an average particle size of about 8 μm and an effective particle size of only 3 μm. Existing barium metaborate has the characteristics of moisture absorption and agglomeration. , high water solubility, poor compatibility in various resins and poor fastness in paint films, etc., it must be modified with amorphous hydrated silica. At present, the existing method for preparing barium metaborate is to mix and melt barium salts (barium sulfide, barium hydroxide, barium carbonate, barium nitrate) and borate (boric acid, borax, etc.), or use its aqueous solution to perform a precipitation reaction. have to.
The main specific preparation methods are: 1) Borax barium sulfide method: roast the mixture of barite and coal powder, and extract it with hot water in the extractor to obtain the barium sulfide material liquid, which is then mixed with borax aqueous solution and sodium silicate aqueous solution Measure each of the three materials into the reactor. After the three materials are added, seal the reactor, raise the temperature to 110±5℃, stir and react for 2 hours, then cool to 70~80℃, and the precipitate is centrifuged, washed, dried and pulverized. , to prepare barium metaborate finished product. Disadvantages of this process: complex process flow, high equipment requirements, harsh reaction conditions, high energy consumption, and environmental pollution. 2) Weimin from the Fujian Institute of Material Structure, Chinese Academy of Sciences, used barium hydroxide, boric acid and hydrogen peroxide as raw materials and used a liquid phase synthesis method to prepare barium metaborate powder. This process requires centrifugal separation and reduced pressure drying, and is not suitable for large-scale production. 3) Zhou Youfu and others from the Fujian Institute of Material Structure, Chinese Academy of Sciences, used inorganic salts and boric acid aqueous solutions as raw materials, organic amines as precipitants, precipitated, filtered, dried, and calcined between 650 and 850°C to obtain barium metaborate powder. This process is also a liquid-phase synthesis, but it requires the addition of a precipitant, suction filtration, washing and other processes, and it cannot convert all raw materials into products, which can easily cause environmental pollution.
Main applications of barium metaborate
Barium metaborate is a white functional pigment. It has anti-rust, anti-mildew, anti-pollution, anti-powdering, anti-discoloration, flame-retardant and other functions in coatings. It is a multi-functional non-toxic anti-rust. Pigments, used in the manufacture of primers and topcoats for anti-rust coatings. Barium metaborate can also be used in ceramics, paper, rubber and plastics industries. Barium metaborate exists in two polytypes: high-temperature phase (α-BaB2O4) and low-temperature phase (β-BaB2O4). Low-temperature phase barium metaborate single crystal (β-BaB2O4) is a nonlinear optical crystal with comprehensive excellent properties of cesium carbonate. It has a wide light transmission band (190nm~3500nm) and phase matching range (409.6nm~3500nm). It has a large Nonlinear optical coefficients, high optical damage resistance threshold, wide temperature band and superior optical uniformity provide practical possibilities for various nonlinear optical applications. At present, low-temperature phase barium metaborate single crystal (β-BaB2O4) is mainly used in: (1) generation of 2, 3, 4 and 5 harmonics of Nd: YAG and Nd: YLF lasers; (2) multiplication of dye lasers The occurrence of frequency, triple frequency and frequency mixing; (3) The generation of 2, 3, 4 and 5 harmonics of titanium sapphire and alexandrite lasers; (4) Can be used in the research and development of a variety of advanced laser technologies such as all-solid-state , wide-band coordinated laser, ultra-short pulse laser, and DUV laser; (5) Optical parametric amplification (OPA) and optical parametric oscillation (OPO), etc. For example, preparing a low-temperature phase barium metaborate single crystal film includes the following specific steps: placing a Li2CO3 and Al2O3 mixed block with pores in a platinum crucible; placing or suspending a double-sided polished α-BBO wafer on a platinum wire , plus a crucible cover covered with Li2CO3 and Al2O3 mixed powder and a thermocouple, the top of the crucible is sealed with a platinum cover, and placed in a resistance furnace; the resistance furnace is heated to 700~1000℃, kept at a constant temperature for 2~100 hours, and Li2O diffuses Into the α-BBO wafer, a solid-state reaction occurs with the α-BBO wafer, so that the surface layer of the α-BBO wafer undergoes a phase change to form a β-BBO single crystal thin film. This method can grow a β-BBO single crystal film of required micron size on an α-BBO substrate, which not only saves materials, but also enables mass production, which is of great significance to the development of laser technology and integrated optics.
Main Application Preparation of Barium Metaborate
Method 1: A method for preparing barium metaborate nanopowder, the steps of which are:
A. Weigh barium hydroxide and boric acid with a molar ratio of 1:2, mix evenly at room temperature, grind until it changes from solid to wet, then from wet to viscous, and then continue Grind for 1h;
B. The product obtained in the previous step is dried in an air atmosphere and room temperature to obtain the product Ba[B(OH)4]2. Compare it with the JCPDS standard card to show that its crystal form is consistent with the JCPDS standard card 48- 0941 matches.
Method 2: Use barium hydroxide to react with boric acid and hydrogen peroxide. The product is aged, washed, separated, dried and roasted to obtain nanoscale β-BaB2O4 powder. The reaction formula is:
The specific preparation steps are as follows:
(1) Heat and dissolve a quantitative amount of Ba(OH)2·8H2O.�Quantitative amount of distilled water, the preparation concentration is 0.3mol/L-0.5mol/L, dissolve it and filter it while it is hot;
(2) Heat and dissolve a certain amount of H3BO3 in a certain amount of distilled water. The prepared concentration is 0.7mol/L-1.0mol/L. Cool slightly. Then add an appropriate amount of 30% hydrogen peroxide aqueous solution, H3BO3: 30% H2O2 =1mol:250ml-500ml;
(3) Spray (2) into the fully stirred (1), the reaction temperature is 30℃-60℃, the PH of the reaction system=6-12, H3BO3:Ba(OH)·8H2O＝2:1-1.10(mol);
(4) After the reaction is completed, let it stand for 30 minutes to 62 hours, then centrifuge and wash multiple times with distilled water or absolute ethanol;
(5) Dry under reduced pressure at 100-120℃ and then sinter at 500℃-600℃ for 0.5-3h.
