Kung Linliu - Academia.edu (original) (raw)

Papers by Kung Linliu

Macromolecules, Dec 1, 1992

Synchrotron small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) were ... more Synchrotron small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to investigate the structure of a few series of segmented polyurethanes with different hard-segment flexibilities. The segmented polyurethanes based on 1,6-hexamethylenediisocyanat.e (HDI) and 1,4butanediol (BD) as the hard segment showed a folded-chain conformation. The phase structure was found to be insensitive to the increasing hard-segment content and thermal treatment. Phase separation was very fast in these systems as the hard-segment mobility was relatively high and the system viscosity was low. DSC results showed a soft-segment glass transition temperature which was only about 5 O C above that of the pure soft segment, indicating that theseparation between soft and hard segments was nearly complete. The segmented polyurethanes based on 4,4'-methylenebis(pheny1 isocyanate) (MDI) and 4,4'-diaminodiphenyl ether (DDE) probably did not exist in the folded-chain conformation. DSC results showed a soft-segment glass transition temperature which was about 15 OC above that of the pure soft segment. Both systems showed very strong interactions among the hard segments. Results were discussed based on the viscosity-mobility-interaction argument. In addition, a long-time controversy about the dependence of Tgc upon the chemical structure of the soft and hard segments and the soft-and hard-segment lengths could be explained by the viscositymobility-interaction argument. The present study once again suggested the importance of kinetic effects in formulating a better understanding of the structure-property relationships of segmented polyurethanes.

Physical Review Letters, 1992

Coexistence curves of polystyrene PS(Mw=3.7×104 g/mole, Mw/Mn<1.06) and poly(2-chlorostyre... more Coexistence curves of polystyrene PS(Mw=3.7×104 g/mole, Mw/Mn<1.06) and poly(2-chlorostyrene) P2CIS(Mw=2.33×105 g/mole, Mw/Mn~=1.19) in the presence of 22.6 wt % of di-n-butylphthalate (DBP) and of PS (Mw=3.7×104 g/mole, Mw/Mn<1.06)/ P2CIS(Mw=11.2×104 g/mole, Mw/Mn~=1.09) were determined by using a combination of a novel centrifugal method and synchrotron small-angle x-ray scattering. The coexistence curves could be fitted to yield a beta value of ~0.33

Journal of Polymer Science Part B: Polymer Physics, 1993

Small-angle light-scattering (SALS) , polarized light microscopy (PLM) , differential scanning ca... more Small-angle light-scattering (SALS) , polarized light microscopy (PLM) , differential scanning calorimetry (DSC), and small-angle x-ray scattering (SAXS) were used to study morphological changes in segmented polyurethanes with 4,4'-diphenylmethane &isocyanate (MDI) and 1,4-butanediol (B D) as the hard segment. It was found, for the first time, that spherulites could form from the melt by quenching the polyurethanes in the melt state to annealing temperatures between 120°C and Th, the highest annealing temperature for spherulite formation. Th ranged from 14OoC to ca. 170°C and depended upon the hardand soft-segment compatibility. Within the range 120°C to Th, the radius of the spherulite increased with increasing hard-segment content at each fixed annealing temperature. Annealing at 135-140°C gave rise to the largest spherulites. SAXS was used to investigate the phase-separated structures corresponding to the spherulite formation. The interdomain spacing increased with increasing hard-segment content and with increasing annealing temperature. The degree of phase separation first increased with increasing annealing temperature from room temperatures (ca. 25"C), reached a maximum at ca. 107"C, and then decreased with further increase in the annealing temperature. On the basis of these observations, the mechanisms of phase separation, crystallization, and spherulite formation are discussed.

Polymer, 1998

Small-angle X-ray scattering and differential scanning calorimetry were used to study the morphol... more Small-angle X-ray scattering and differential scanning calorimetry were used to study the morphology in segmented polyester-based polyurethanes with 4,4′-methylene bis(phenyl isocyanate) and butanediol as hard segment. The polyesters with various mole ratios of -CH3 side chain were synthesized from adipic acid and glycols which were mixtures of various mole ratios of hexanediol and 1,2-propanediol. The effect of -CH3 side-chain content

Journal of Micromechanics and Microengineering, 2009

Employing methods of computational fluid dynamics, we investigated the physical phenomena and flu... more Employing methods of computational fluid dynamics, we investigated the physical phenomena and fluid dynamics of a microfluid during ejection of a droplet with a designed system of a nozzle plate connected to a flat-plate piezoelectric material. A comparison between experimental measurements and numerical simulations was devised to validate the theoretical model. The volume-of-fluid piecewise linear-interface construction (VOF-PLIC) interface-capturing method was adapted to represent the fluid domain and to track the evolution of its free boundaries whereas the continuous surface force (CSF) mode was chosen to model the interfacial physics. The results show that the curvature of the flow channel affects the velocity, period before disintegration, volume of the droplet and number of satellite drops. Increasing the diameter of the orifice increases the volume and decreases the velocity of the droplet. Increasing the amplitude or frequency of the nozzle plate raises the input energy, so increasing the velocity, decreasing the volume and hastening the disintegration of the droplet, but an increased amplitude or frequency increases the number of satellite drops. At the hydrophobic boundary, the velocity increases, the droplet volume decreases and the period before disintegration is abbreviated because of the decreased adhesive force between the fluid and the boundary surface.

Journal of Micro/Nanolithography, MEMS, and MOEMS, 2010

Numerical calculations are performed to investigate the effect of the component of a single trans... more Numerical calculations are performed to investigate the effect of the component of a single transducer pulse on the ejection of a drop for a drop-on-demand ink-jet printhead with a piezoelectric actuator. The flow field is governed by continuity and Navier-Stokes equations. A volume-of-fluid method with a piecewise-linear interface construction is used to track the complicated topological variation of the liquid-gas interface. The computer code is validated with experimental results present in the literature. The volume of the primary drop is closely related to the maximum displacement D f of chamber wall induced by the piezoelectric actuator in the forward stoke; the velocity of the primary drop depends on the ratio of D f to the time period of the forward stoke ⌬ f. Moreover, the fact that the formation of the primary drop depends weakly on the conditions of the backward stroke is considered. A decreased interval between forward and backward strokes might serve to suppress the formation of satellite drops owing to reducing the liquid thread length l b at pinching off to a value less than the upper limit l b *. The breaking up of the freely flying liquid thread from nozzle outlet has two modes-multiple breaking up and end pinching-and depends on the thread length at pinching off.

Journal of Applied Polymer Science, 1996

Polyurethanes were synthesized from polyester and butanediol with three different diisocyanates, ... more Polyurethanes were synthesized from polyester and butanediol with three different diisocyanates, ie, 4,4´-diphenylmethane diisocyanate (MDI), m-xylene diisocyanate (XDI), and 2,4-toluene diiscynate (TDI). The effect of chemical structures of diisocyate compounds on ...

Review of Scientific Instruments, 1994

A centrifuge ball viscometer was developed for fluids with a wide viscosity range. The viscosity ... more A centrifuge ball viscometer was developed for fluids with a wide viscosity range. The viscosity &amp;eegr; could be obtained from an empirically derived relationship ac=b(&amp;eegr;V∞)c, where ac is the applied acceleration, b and c are empirically determined parameters, and V∞ is the terminal velocity. The key features of this viscometer are as follows. (1) A wide range of viscosities can

A dual polysilicon gate structure is required to increase the circuit speed and the packing densi... more A dual polysilicon gate structure is required to increase the circuit speed and the packing density, as well as the low-power operation as the design rule of CMOS scales down to sub- 0.25micrometers . In order to get the superior device performance of 0.18micrometers logic device, we need to do the gate implantation prior to polysilicon etch. The critical dimensions (CD) different between NMOS and PMOS during polysilicon gate etching needs to be reduced for matching the design drive current of NMOS and PMOS. In this work, the pressure, the bias power, the total flow of CF4 and Cl2 and the N2 flow are used for the investigation of 0.18micrometers device during the dual gate etch. After optimizing all etch parameters, the CD offset is small between NMOS and PMOS. The vertical profile, the small bias, and CD micro-loading are obtained using in-situ BARC and polysilicon etching. The result of pitting free, stringers free and notching free after dual polysilicon etching is achieved, and the remaining thickness of deep UV photoresist at shoulder is about 800-880A. From this study, both good performance device and the process controllability are obtained with in-situ bottom anti- reflective coating and dual polysilicon gate etching.