ABSTRACT
Many crucial components inside electronic devices are made from non-renewable, non-biodegradable, and potentially toxic materials, leading to environmental damage. Finding alternative green dielectric materials is mandatory to align with global sustainable goals. Carboxymethyl cellulose (CMC) is a bio-polymer derived from cellulose and has outstanding properties. Herein, citric acid, dextrin, and CMC based hydrogels are prepared, which are biocompatible and biodegradable and exhibit rubber-like mechanical properties, with Young modulus values of 0.89 MPa. Hence, thin film CMC-based hydrogel is explored as a suitable green high-k dielectric candidate for operation at low voltages, demonstrating a high dielectric constant of up to 78. These fabricated transistors reveal stable high capacitance (2090 nF cm-2) for ≈±3 V operation. Using a polyelectrolyte-type approach and poly-(2-vinyl anthracene) (PVAn) surface modification, this study demonstrates a thin dielectric layer (d ≈30 nm) with a small voltage threshold (Vth ≈-0.8 V), moderate transconductance (gm ≈65 nS), and high ON-OFF ratio (≈105). Furthermore, the dielectric layer exhibits stable performance under bias stress of ± 3.5 V and 100 cycles of switching tests. The modified CMC-based hydrogel demonstrates desirable performance as a green dielectric for low-voltage operation, further highlighting its biocompatibility.
ABSTRACT
Renewable energy sources are prospective solutions for addressing future energy needs arising from the ever-increasing population and dwindling petroleum reserves. Biobutanol is one of the most efficient biofuels for use as a mixture with motor vehicle fuels. Biobutanol is produced from the acetone-butanol-ethanol (ABE) fermentation process and is separated into the pure components via multicomponent distillation. Mathematical modelling of the continuous multicomponent distillation of ABE was carried herein out using an equilibrium-based model with the modified Hang-Wanke method in MATLAB R2020a programming language and compared with the simulation results using Aspen Plus V9. The variables of this study were the feed stage, number of trays, reflux ratio to butanol purity, butanol recovery, and energy load of the reboiler and condenser. Based on the simulation results, the operating conditions in columns 1 and 2 were recommended based on the butanol purity, recovery, and reboiler load; the recommended operating conditions for column 1 are as follows-feed stage: 4, reflux ratio: 4, number of trays: 20 trays, with a column efficiency of 55.43%. The recommended operating conditions for column 2 are as follows-feed stage: 2, reflux ratio: 0.4, number of trays: up to 10, with a column efficiency of 54.94%.
ABSTRACT
Surface nanopatterns of dual ring-banded spherulites in poly(nonamethylene terephthalate) (PNT) were investigated using polarized optical microscopy (POM) and atomic force microscopy (AFM). The surface morphology differs between narrow-spaced single ring bands versus widely spaced double ring bands in spherulites, labeled Type-1 and Type-2, respectively. Ridge and valley consist of two discrete species ranging from nano- to micrometer-sized crystals shaped and oriented differently. Ridges of Type-1 and Type-2 spherulites apparently differ in shapes of the crystal plates. AFM height profile analysis reveals that the ridge of Type-2 ring-banded spherulite is higher than that of Type-1 spherulites. The crystal packing on the ridges and valley of these two types of ring-banded was further compared using high-magnification AFM phase imaging. There exists a transition zone in going from the ridge and valley regions in the Type-2 ring-banded spherulites crystallized at Tc = 75-85 °C; the crystals on the transition zone change gradually in sizes and orientation from those in the ridge to valley. By contrast, Type-1 ring-banded spherulite does not have this kind of transition zone, meaning that crystals in the ridges abruptly submerge into valley in Type-1 ring-banded spherulites. Details of packing of nanosize crystals in forming ridge and valleys of these two ring band types are discussed.
ABSTRACT
The single-crystal morphology of poly(L-lactic acid) (PLLA) in blending with poly(butylene adipate) (PBA) in PLLA/PBA blends was for the first time reported in melt crystallization. At crystallization temperature (T(c)) = 110 °C, by adding 30 wt % PBA into PLLA, the lamellae exhibit six-stalk dendrites with single-crystal packing. Phase separation and crystallization took place simultaneously at T(c) = 110 °C in PLLA/PBA (70/30) blend, leading to discrete PBA domains and continuous PLLA domains. For PLLA/PBA (70/30) blend, all PBA were rejected from the growth front of PLLA crystals, expelled, and crystallized at ambient temperature as ring-banded PBA spherulites inside the discrete domains only, resulting in a favorable environment for formation of PLLA single crystals in the continuous domain. Atomic force microscopy (AFM) observation on individual crystallites reveals that lozenge-shaped single crystals were packed with a clockwise spiral pattern, stacked in 1-3 layers, and these lozenge-shaped crystals are aligned six hexasected directions into hexastalk dendrites with occasional side branches that are also aligned at 60° to main branches. The monolamellar thickness of lozenge-shaped single crystals was measured to be about 13-34 nm, and the dimension is about 0.8-3 µm along the short axis and 1.6-5 µm along the long axis. Typically, three layers of single crystals are stacked one on another; the lozenge crystals on the bottom layer are about twice as large as those on the top layer, forming a pyramid shape in the depth direction. Formation mechanisms of single crystals in melt-crystallized PLLA/PBA blend from 700 nm film thickness are discussed in correlation with exact phase separation at 30 wt % PBA.
ABSTRACT
Top-surface and three-dimensional views of Type-1 and Type-2 of ring-banded spherulites in poly(nonamethylene terephthalate) (PNT) in thicker bulk crystallized on a nucleating potassium bromide (KBr) substrate were examined using various microscopy techniques: scanning electron microscopy (SEM), polarized-optical microscopy (POM), and atomic-force microscopy (AFM). In PNT crystallized at higher crystallization temperature (T(c)) with heterogeneous nucleating substrate, typically two types of ring-banded spherulites are present that differ significantly in patterns and ring spacings: Type-1 Type-2 (single- and double-ring-banded spherulites). Three-dimensional view on fractured spherulites in bulk PNT samples reveals that the single-ring-banded spherulite (Type-1) tends to be well-rounded spheres as they are nucleated homogeneously from bulk; the double-ring-banded spherulite (Type-2) is concentric hemisphere or truncated sphere shells owing to be nucleated from bottom. With confined thickness of films, the 3-D hemispheres in PNT may become truncated into multi-shell annular cones or arcs when thickness or growth is restricted. Based on the top-surface vs. interior views of banded lamellar assembly, origins and inner structures of dual types of ring bands in PNT were examined in greater details.
