Tzen-Chin Lee

The utilization of thin film transistor liquid crystal display waste glass as a pozzolanic material.

This investigation elucidates the pozzolanic behavior of waste glass blended cement (WGBC) paste used in thin film transistor liquid crystal displays (TFT-LCD). X-ray diffraction (XRD) results demonstrate that the TFT-LCD waste glass was entirely non-crystalline. The leaching concentrations of the clay and TFT-LCD waste glass all met the current regulatory thresholds of the Taiwan EPA. The pozzolanic strength activity indices of TFT-LCD waste glass at 28 days and 56 days were 89% and 92%, respectively. Accordingly, this material can be regarded as a good pozzolanic material. The amount of TFT-LCD waste glass that is mixed into WGBC pastes affects the strength of the pastes. The strength of the paste clearly declined as the amount of TFT-LCD waste glass increased. XRD patterns indicated that the major difference was the presence of hydrates of calcium silicate (CSH, 2 theta=32.1 degrees), aluminate and aluminosilicate, which was present in WGBC pastes. Portland cement may have increased the alkalinity of the solution and induced the decomposition of the glass phase network. WGBC pastes that contained 40% TFT-LCD waste glass have markedly lower gel/space ratios and exhibit less degree of hydration than ordinary Portland cement (OPC) pastes. The most satisfactory characteristics of the strength were observed when the mixing ratio of the TFT-LCD waste glass was 10%.

Recovery of hazardous semiconductor-industry sludge as a useful resource.

Sludge, a solid waste recovered from wastewater of semiconductor-industries composes of agglomerates of nano-particles like SiO(2) and CaF(2). This sludge deflocculates in acidic and alkaline aqueous solutions into nano-particles smaller than 100 nm. Thus, this sludge is potentially hazardous to water resources when improperly dumped. It can cause considerable air-pollution when fed into rotary-kilns as a raw material for cement production. In this study, dried and pulverized sludge was used to replace 5-20 wt.% Portland cement in cement mortar. The compressive strength of the modified mortar was higher than that of plain cement mortar after curing for 3 days and more. In particular, the strength of mortar with 10 wt.% substitution improved by 25-35% after curing for 7-90 days. TCLP studies reveal no detectable release of heavy metals. Preliminary studies showed that nano-particles deflocculated from the sludge, when cured for up to 3 days retain in the modified mortar their nano-size, which become large-sized hydration compounds that contribute to the final mortar strength. Semiconductor sludge can thus be utilized as a useful resource to replace portion of cement in cement mortar, thereby avoiding their potential hazard on the environment.

Elucidating the hydration properties of paste containing thin film transistor liquid crystal display waste glass.

This study discusses the thin film transistor liquid crystal display (TFT-LCD) waste glass-blended cement (WGBC) pastes. It presents their compressive strength, their products of hydration and solid silicates changes. The samples were subjected to Fourier transformation infrared spectroscopy, differential thermal and thermo-gravimetric analysis and (29)Si magnetic angle spinning/nuclear magnetic resonance. The experimental XRD results demonstrated the speciation of the TFT-LCD waste glass, and that the major component was SiO(2). At 40% substitution of TFT-LCD waste glass, at 28 days and 56 days, the compressive strength was 35% and 30% lower, respectively, than that of the Portland cement paste. The intensity of the Ca(OH)(2) band at 3,710 cm(-1) in the 56-day hydrated products of the WGBC pastes that contain TFT-LCD waste glass exhibit comparatively weak peaks suggesting that much Ca(OH)(2) during hydration was consumed. Later, the CSH contents of the WGBC pastes increased, revealing that liberated Ca(OH)(2) was consumed in pozzolanic reactions.