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Transformation kinetics of mullite formation in kaolin–Al2O3 ceramics was studied by x-ray diffraction, transmission electron microscopy, and energy dispersion spectrometry. The mullitization process of kaolin–Al2O3 ceramics is described by two stages; one is the primary mullite transformation at 1273 to 1573 K, and the other is the secondary mullite formation at 1573 to 1873 K. The activation energy of 1164.6 kJ mol-1 obtained for the secondary mullite formation is lower than 1356.9 kJ mol-1 for the primary mullite transformation by the general form of the Johnson–Mehl–Avrami equation. The lower value of growth morphology parameter strongly supports that in the secondary mullite formation the added alumina is dissolved into glassy phase and the mullite is then precipitated.

In this paper, an adaptive controller is proposed to balance a rotary inverted pendulum with time-varying uncertainties. The goal of the control is to bring the pendulum close to the upright position regardless of the various uncertainties and disturbances. Its underactuated dynamics is first decoupled by Olfati's transformation into a cascade form, and then an adaptive controller is designed to deal with the uncertainties in the new space. Based on the Lyapunov-like theory, the closed loop stability and boundedness of all internal signals can be proved. The simulation results show that the proposed scheme is capable of giving good performance, as desired.

GaAs is grown by metal-organic vapor-phase epitaxy on a 55 nm round-hole patterned Si substrate with SiO2 as a mask. The threading dislocations, which are stacked on the lowest energy facet plane, move along the SiO2 walls, reducing the number of dislocations. The etching pit density of GaAs on the 55 nm round-hole patterned Si substrate is about 3.3 × 105 cm−2. Compared with the full width at half maximum measurement from x-ray diffraction and photoluminescence spectra of GaAs on a planar Si(001) substrate, those of GaAs on the 55 nm round-hole patterned Si substrate are reduced by 39.6 and 31.4%, respectively. The improvement in material quality is verified by transmission electron microscopy, field-emission scanning electron microscopy, Hall measurements, Raman spectroscopy, photoluminescence, and x-ray diffraction studies.

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Secondary mullite has been formed in 60 wt% kaolin-40 wt% Al 2 O 3 ceramics by solution-precipitation in the glassy phase in contact with Al 2 O 3 particle, showing a plate-like morphology, at temperatures above 1673 K. The lattice constant modification of secondary mullite has been determined: the lattice parameters of orthorhombic structure of a, b, and c axes decrease from 8. 653, 8.770, and 3.167 Å to 7.958, 8.064, and 2.926 Å, respectively. The Al 2 O 3 content in the secondary mullite crystals increases from 59.69 to 70.41 wt% when the grain width increases from 15 to 40 nm. Both the formation of secondary mullite and its grain growth are intimately related to the presence of the glassy phase originated from impurity (K 2 O) in the kaolin. Their locations as well as their chemical composition of mullite grains, Al 2 O 3 grains, and glassy phase are provided by the meticulous experiments using high-resolution transmission electron microscopy, selected-area electron diffraction, and energy dispersive spectroscopy techniques.

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