Aluminum borate whiskers

Aluminum borate whiskers are applied widely because of their excellent performances and relatively low cost. Below are their main performance advantages. 

Higher elasticity modulus than SiC and SijN4 whiskers 

Higher tensile strength than potassium titanate whiskers 

Good heat resistance, similar to that of potassium titanate whiskers 

Color Shape Density (glcm ) Diameter (pm) Length (pm) Tensile Strength (GPa) Elasticity Modulus (GPa) Moh s Scale of Hardness Melting Point (°C) 

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Aluminum borate whiskers are produced commercially by an external flux method. Chlorides, sulfates, or carbonates of alkali metals are added to alumina and boric oxide (or boric acid) and the mixture is heated to 800°C-1000°C to produce aluminum borate whisker (length 10-30 pm and diameter 0.5-1.0 pm). It has a melting point of 1440°C, a very low coefficient of thermal expansion, and an excellent chemical resistance toward acids. The aluminum borate whisker was reported to be effective in improving not only the thermal degradation but also the glass transition temperature of epoxy76... 

Both hydrated and anhydrous metal borates have numerous industrial uses. Some of the major uses of hydrated metal borates are the manufacture of glasses, ceramics, and industrial fluids, and as micronutrient fertilizers, fire retardants, and biostats. Anhydrous borates find use as heterogeneous catalysts, scintillation hosts, and in the fabrication of optoelectronic devices. Anhydrous aluminum borates are used as additives in oxide ceramics to promote the formation of desirable phases. Also, aluminum borate whiskers are used as reinforcing additives in composite materials. Specific nses of sodium, calcium, zinc, and barium borates are discussed in sections below. 

When aluminum borate whiskers were incorporated in SAN/PA-6 blends, the whisker, due to acid/based interaction had a better affinity to PA-6 than to SAN and for this reason they ended up in residence in the polyamide phase. A similar principle was used to obtain a conductive blend by compounding PA, PP and carbon black. Carbon black has a better affinity to polyamide and thus it prefers to reside in the polyamide phase or in the interphase formed between two immiscible polymers. Even when carbon black is added initially to polypropylene, it still transfers to the polyamide phase. This migration and preferential location of carbon black is not only an interesting scientific principle but it also has important practical implications. For the purpose of conductivity, a certain threshold concentration of carbon black is required to enable percolation and this threshold concentration is substantially lower if the carbon black settles in only one phase. This phase be-... 

Typical fillers glass fiber, PTFE, aluminum borate whiskers... 

It is not only the blend morphology which is affected by filler presence filler orientation might be affected by its surface treatment, as was observed in the works on PC/ABS blends containing aluminum borate whisker. When the whisker surface was treated with epoxy silane, its reaction to flow in injection and compression molding processes changed, resulting in a different orientation even though all other parameters of process and composition were the same. ... 

Shikoku Chemical Corp. aluminum borate whiskers 19... 

I.E.Gonenli and GL.Messing, Texturing of Mullite by Templated Grain Growth with Aluminum Borate Whiskers, / Ear. Cer. Soc.. 21, 2495-2501 (2001). 

X. Zhang, X. Zhang, B. Zhu, K. Lin, J. Chang, Mechanical and thermal properties of denture reinforced with silanized aluminum borate whiskers. Dent. Mater. J. 31 (6) (2012) 903-908. 

Gonenli IE, Messing GL (2001) Texturing of mullite by templated grain growth with aluminum borate whiskers. J Eur Ceram Soc 21 2495-2501... 

Table 3.4 Physical and Chemical Properties of Aluminum Borate Whiskers...

Based on these excellent performances, aluminum borate whiskers are used not only for thermal insulation material, heat-resistant material, and corrosion-resistant material but also for reinforcing agents in thermoplastic resin, thermosetting resin, ceramics, cement, and metal, and are used mainly to reinforce light metal alloy, ceramic material, resin matrix composite, coatings, and so on. 

At present, Chinese researchers have considerable knowledge and experience in the synthesis of aluminum borate whiskers, reinforcing and toughening composites, and industrialization. Before long, aluminum borate whiskers will be used widely in reinforced metal matrixes (aluminum base, magnesium base), ceramic matrix, plastic, glass, fiber, and coatings. ... 

The low cost of raw materials, simple manufacturing technique, low facility demand, and easy operation process make the cost of magnesium borate whiskers much lower. Thus, magnesium borate whiskers are a kind of new cost-effective reinforcing agent with potentially wide applications after aluminum borate whiskers, and can be used in aluminum, magnesium, and their alloys and in engineering plastics. ... 

Figure 3.18 shows infrared spectroscopic information of aluminum borate whiskers before and after being modified with sodium stearate. As shown in Figure 3.18, when aluminum borate whiskers are modified, the infrared adsorption peaks at 2918 cm" (asymmetrical stretching vibration of C-H bond in CHj) and 2851 cm" (symmetrical stretching vibration... 

Figure 3.18 Infrared spectrum of aluminum borate whiskers before and after modification, (a) Unmodified and (b) modified.

Wenyun Zhang, Yanbo Yuan, Qinghua Chen et al. Influence of nano-silica content on flexural properties of the aluminum borate whisker and silica filler composites resins. West China Journal of Stomatology, 29(4) 195-199, 2011. 

In recent years, there has been a breakthrough in the manufacturing cost of potassium titanate whiskers, aluminum borate whiskers, and so forth. Meanwhile, inexpensive and high-quality inorganic whiskers such as calcium carbonate, calcium sulfate, and magnesium are successfully synthesized, which makes inorganic whiskers a new type of filling modification material of polymer materials. This field has become a research hotspot all over the world and reveals broad application and market prospects. 

Shi et al. 5 also discovered that the wear resistance of PTFE improved about 300 times that of the pure PTFE after adding potassium titanate whiskers. Hu and Liang added aluminum borate whiskers and calcium sulfate whiskers respectively to bismaleimide resin and found that the wearability of both materials improved. When the content of aluminum borate whiskers was 8%, the wear rate of the material declined from 4.39 X 10" mmVCN irO to 1.42 x 10 mmV(N-m). When the content of calcium sulfate whiskers was 10%, the wear rate of the material declined from 2.89 x 10" mmy(N-m) to 1.28 x 10" mmVCN-m). Thus it can be seen that the high hardness of inorganic whiskers determines their broad application prospects in the field of polymer wear-resistant materials. 

Xiaolan Hu, Guozheng Liang. Friction and wear properties of aluminum borate whiskers modified bismaleimide resin. Acta Materiae Compositae Sinica, 21(6) 21-26, 2004. 

To characterize further the mode of action of sodium stearate molecules and the surface of the whiskers, we apply the same approach to the aluminum borate whiskers. Infrared spectra of aluminum borate whiskers before and after modification are shown in Figure 5.11. 

As shown in Figure 5.11, absorption peaks of 2918 cm" and 2851 cm" on the spectra of the modified aluminum borate whiskers significantly increase. The absorption peak at 2850 cm" is characteristic of the C-H bond symmetric stretching... 

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