Thermal conductivity of aluminum nitride (AlN) has been calculated by density functional perturbation theory (DFPT) and quasi-harmonic approximation (QHA) combined with Debye theory in the paper. Debye temperature is evaluated respectively from sound velocity and heat capacity. From 300K up to 1000K, the predicted thermal properties in pure crystal AlN based on these two Debye temperatures are compared with each other and the latter shows excellent agreement with Slack’s experimental data. The relative difference based on Debye temperature from heat capacity is within the limits of ±5.5%. This agreement with experiment is due to the Debye temperature derived from capacity contains the temperature effect while describe the three phonon process.

The effects of grain sizes and oxygen impurities on thermal conductivity in aluminum nitride (AlN) ceramics has been calculated by density functional perturbation theory (DFPT) and quasi-harmonic approximation (QHA) combined with Debye theory in the paper. From 300K up to 1000K, the predicted thermal properties are compared with experimental data. The agreements with experiment suggest that the theoretical method used in the paper is an effective approach. From our theoretical study, the reduction of thermal conductivity is greater between grain sizes of 1μm and 5μm, while it’s smaller between 8μm and 10μm. Oxygen defects bring about greater influence on thermal conductivity at low temperature than at high temperature. The influence of the oxygen defect is not as significant as the grain sizes when the oxygen concentrations are less than 0.70 at. %, so it’s more important to increase the grain sizes than reduce the oxygen contents in the preparation process to achieve high thermal conductivity AlN ceramics.

Thermal management is one of the major challenges in the development of high powered LEDs. The effects on thermal conductivity of impurity concentration and thickness are studied in Cu doped AlN (AlN:Cu) phosphor in the paper. Density functional perturbation theory (DFPT) and quasi-harmonic approximation (QHA) combined with Debye model are used in the calculation. The results show that thermal conductivity of AlN:Cu is higher than that of Nd doped ytterbium aluminum garnet (YAG:Nd) from 300K up to 1000K thus the temperature of LEDs can be controlled efficiently. Thermal conductivity increases with the rising of thickness while it decreases with the addition of Cu concentration. The influence of Cu concentration on thermal conductivity depends on temperature. The lower the temperature is, the bigger the influence.

In this paper, the novel Si-MCM-41/SA porous hybrid membrane was prepared by in-corporating inorganic mesoporous material Si-MCM-41 into sodium alginate (SA) matrix, then cross-linking with 5% glutaraldehyde and 1.0 mol/L hydrochloric acid. Using scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and atomic force microscope (AFM), the prepared Si-MCM-41 sample and Si-MCM-41/SA porous hybrid membrane were characterized. The adsorption kinetics of the dibenzothiophene (DBT) by the Si-MCM-41/SA porous hybrid membrane was explored. Meanwhile, the effects of Si-MCM-41 content, porogen addition amount, DBT concentration, solution temperature, toluene concentration and other factors on the adsorption property of the Si-MCM-41/SA porous hybrid membrane were studied. In addition, the selectivity and reusability of the Si-MCM-41/SA porous hybrid membrane were also explored. The results show that the Si-MCM-41/SA porous hybrid membrane has excellent adsorption capacity for DBT, reaching 350.74 mg/g, which is a great improvement over the pure SA membrane. Moreover, among three sulfides of thiophene, 3-methylthiophene and DBT, the Si-MCM-41/SA porous hybrid membrane has the highest adsorption selectivity for DBT. The Si-MCM-41/SA porous hybrid membrane can be reused at least 5 times. Therefore, it can be known that the Si-MCM-41/SA porous hybrid membrane is an ideal adsorption material with practical application prospects.

In this paper, we carry out linear response calculation to determine the phonon density of states and the thermodynamic properties of the wurtzite and zinc-blende AlN by using the norm-conserving pseudo-potential method. The optimized lattice constant is in good agreement with the available experimental data. The internal energies increase almost linearly with temperature and the phonon free energy curves move down with increasing temperature in both structures. The zero value of the lattice vibration free energy appears at temperature 707K in wurtzite and 728K in zinc-blende AlN respectively. The specific heat capacity of the wurtzite AlN is higher than that of the zinc-blende AlN at room temperature owing to the difference of the phonon spectra.