Polygonal Single‐Crystal Aluminum Borate Microtubes

Abstract

In this paper we report the synthesis of polygonal single‐crystal aluminum borate microtubes by the direct calcination of alumina and boron nitride powders in air. The diameters of the obtained tubes vary between 1 and 15 μm; and the lengths are in the range of tens to hundreds of micrometers. The cross‐sections of the microtubes are in the shapes of rectangular, hexagonal, and quasi‐circle. A new solid–liquid–solid growth mechanism was proposed to account for the formation of microtubes instead of whiskers.

Microstructure and interface characterization of a cast Mg2B2O5 whisker reinforced AZ91D magnesium alloy composite

“…However, there are some drawbacks for SiC whisker-reinforced magnesium matrix composite, e.g., the higher cost of SiC whiskers [3]. Recently, metal borate compounds including aluminum borate (Al 18 B 4 O 33 and Al 4 B 2 O 9 ) [4][5][6] and magnesium borates (Mg 3 B 2 O 6 [7] and Mg 2 B 2 O 5 ) nanowires/nanotubes [8][9][10][11][12][13][14][15] have been synthesized successfully. These metal borates have good mechanical properties, such as high Young's modulus and strength, good chemical inertness, and low thermal expansion coefficient [8,13].…”

Fabrication of β-Si3N4 whiskers by microwave sintering using ZrO2–Y2O3–Al2O3 as liquid phase

“…The formation of platelike whiskers shown in Fig. The variable whisker diameter was due to the fact that the adjacent small liquid droplets tended to aggregate together and larger liquid droplets with various sizes were generated [13]. Figure 3c shows the rodlike whiskers with a variable diameter of 0.2 -1.7 lm.…”

Nanostructures from Zirconium Diboride and Alumina Ceramics

“…Rectangular single‐crystal mullite tubes have been synthesized by a lengthy solid–vapor process 24 and aluminum borate nanotubes have been grown using molten salt flux synthesis, high‐temperature sintering, and CVD 25,26 . These nanosized hollow whiskers can be used for microfluidic transfer, optical resonance cavities, or waveguides 7 . Combining microwave and arc heating, we have established that under the appropriate conditions ZrB 2 reacts with alumina initiating the growth of mullite‐like rectangular nanotubes.…”

“…A similar refractory oxide is aluminum borate, which as Al 18 B 4 O 33 remains stable until ∼1950°C 6 . Aluminum borates offer high elastic modulus and tensile strength 7 . Both mullite and aluminum borates are well‐suited for high‐temperature structural applications 7,8 .…”

“…Aluminum borates offer high elastic modulus and tensile strength 7 . Both mullite and aluminum borates are well‐suited for high‐temperature structural applications 7,8 . These properties encourage the use of aluminum borate whiskers for metal matrix reinforcement in applications such as automotive engines 9,10 .…”