Nonglak Meethong

Size-Dependent Lithium Miscibility Gap in Nanoscale Li1 − x FePO4

Olivine compounds have emerged as important and enabling positive electrode materials for high-power, safe, long-life lithium rechargeable batteries. In this work, the miscibility gap in undoped Li 1-x FePO 4 is shown to contract systematically with decreasing particle size in the nanoscale regime and with increasing temperature at a constant particle size. These effects suggest that the miscibility gap completely disappears below a critical size. In the size-dependent regime, the kinetic response of nanoscale olivines should deviate from the simple size-scaling implicit in Fickian diffusion.

Synthesis and characterization of stable and binder-free electrodes of TiO 2 nanofibers for li-ion batteries

An electrospinning technique was used to fabricate TiO2 nanofibers for use as binder-free electrodes for lithium-ion batteries. The as-electrospun nanofibers were calcined at 400-1,000°C and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM and TEM images showed that the fibers have an average diameter of ∼100 nm and are composed of nanocrystallites and grains, which grow in size as the calcination temperature increases. The electrochemical properties of the nanofibers were evaluated using galvanostatic cycling and electrochemical impedance spectroscopy. The TiO2 nanofibers calcined at 400°C showed higher electronic conductivity, higher discharge capacity, and better cycling performance than the nanofibers calcined at 600, 800, and 1,000°C. The TiO2 nanofibers calcined at 400°C delivered an initial reversible capacity of 325mAh ċ g-1 approaching their theoretical value at 0.1 C rate and over 175mAh ċ g-1 at 0.3 C rate with limited capacity fading and Coulombic efficiency between 96 and 100%.

Li 2 MnO 3 domain size and current rate dependence on the electrochemical properties of 0.5Li 2 MnO 3 ·0.5LiCoO 2 cathode material

Layered-layered composite oxides of the form xLi2MnO3·(1−x) LiMO2 (M = Mn, Co, Ni) have received much attention as candidate cathode materials for lithium ion batteries due to their high specific capacity (>250mAh/g) and wide operating voltage range of 2.0–4.8 V. However, the cathode materials of this class generally exhibit large capacity fade upon cycling and poor rate performance caused by structural transformations. Since electrochemical properties of the cathode materials are strongly dependent on their structural characteristics, the roles of these components in 0.5Li2MnO3·0.5LiCoO2 cathode material was the focus of this work. In this work, the influences of Li2MnO3 domain size and current rate on electrochemical properties of 0.5Li2MnO3·0.5LiCoO2 cathodes were studied. Experimental results obtained showed that a large domain size provided higher cycling stability. Furthermore, fast cycling rate was also found to help reduce possible structural changes from layered structure to spinel structure that takes place in continuous cycling.

The Utility of Rice Husk Ash from Biomass Power Plant of Nakhon Ratchasima Province for Synthesis of Nano-Silica for Using Cathode Material of Lithium Ion Battery

The high purity nanosilica materials could preparation from different synthesis route. In this research, rice husk ash was extracted into silica powder, by chemical extraction method. Then, chemical composition analysis with XRF technique. In addition, the extracted silica nanoparticles were analyzed by XRD technique. Physical structure of nanoscale particles by SEM imaging. The results showed that the chemical composition of rice husk ash consists mainly of silica. While, the extracted silica nanoparticles had a high silica content of 99.9999%. In addition, silica extracted with silica nanoparticles was confirmed by XRD at position 2θ ≈ 22° and the crystalline extracts were amorphous to the physical characteristics of the SEM images. In the future, nanosilicon powder may be used to synthesize lithium-ion batteries.

Properties of Dan Kwian, Sukhothai and Ratchaburi Pottery Clays Fired at 700 and 900 °C

Dan Kwian, Sukhothai and Ratchaburi pottery clays are economically important pottery clays. They are well known in the Thai ceramic society for making Dan Kwian pottery, Sawankhalok pottery and Dragon jars, respectively. There have been several studies of these pottery clays. However, few of them used statistics to analyze their results. This work is a comparative study of the compositions and properties of these three pottery clays using statistical software to analyze the results. Results show that the major components of these pottery clays are SiO2 and Al2O3. The Modulus of Rupture (MOR) of each pottery clay fired at 700°C are not significantly different. Sukhothai pottery clay fired at 900°C has a higher MOR and bulk density while its porosity, water absorption and apparent specific gravity are less than those of the Dan Kwian and Ratchaburi pottery clays fired at the same temperature. Additionally, the current study developed regression equations for estimating the properties of all pottery clays under study. Finally, it was found that the L*, a*, b* and reflectance spectra of all pottery clays increased when firing temperature was increased from 700 to 900°C.

Effect of Donor Dope Ions, Compaction Pressures and Sintering Temperatures on PTCR and Dielectric Properties of BaTiO3

Donor doped BaTiO3 is a well known PTCR material. Many PTCR theories have been written but none of them can completely explain the PTCR property. In this work, BaTiO3 samples doped with Sb, La, Nb and Pb ions and compacted under various uniaxial pressures were examined. Results show that Sb and La-doped BaTiO3 have PTCR properties corresponding to Heywang and Jonker models to a greater degree than Nb-doped BaTiO3. Moreover, it was found that La and Nb-doped Ba1-xPbxTiO3 samples sintered at l000-1100°C have good PTCR properties while samples of the same composition sintered at 1150-1200°C have fair to poor PTCR properties. The PTCR properties in these materials do not correspond to Heywang and Jonker models. The resistivity change in these materials at Curie’s point is relatively lower than the resistivity change at other temperatures.