Polyvinyl alcohol (PVA)/CNT composite membranes were prepared without adding cross-linkers; herein, carboxylated CNTs served as alternative cross-linkers. A molecular simulation confirmed the cross-linking capability between CNTs and PVA chains, which led to the prediction that the cross-linked PVA/CNT complex would be stable in water. To realize the simulated outcome, the multiwalled CNTs were activated and functionalized via sonication methods and subsequent acid treatment. The PVA/CNT composite membranes, including the CNTs treated by probe sonication, exhibited sufficient stability against dissolution in water at 80 °C when the CNT loading reached 1.5 wt %, thus substantiating the proposed idea. The composite membranes exhibited a high separation performance for green recycling of 1-methyl-2-pyrrolidone (NMP) during manufacturing of lithium-ion batteries (LIBs). Long-term operations using membranes with 1.5 wt % CNTs also exhibited a steady combination of total flux and water/NMP selectivity of approximately 0.06 kg/m2·h and 3500, respectively. Thus, the membranes developed here and the corresponding NMP dehydration performance could contribute to increasing the sustainability of the LIB manufacturing industry.

Three-dimensional NAND flash memory featuring dozens of vertically stacked memory cells is the state-of-the-art technology for most storage platforms. To fabricate threedimensional (3D) NAND memory, lateral etching of the Si 3 N 4 layer over SiO 2 is an essential step that is conducted through a wet etching process using a phosphoric acid-based etchant. Silylphosphate or highly selective nitride serves as an etching solution additive to control the SiO 2 layer dissolution rate. However, silylphosphate is prepared with an expensive monomeric silica precursor and at high reaction temperatures and generates environmentally harmful byproduct gases, such as HCl, HF, and CH 3 OH. This study demonstrates that silyl-phosphate can be prepared using low-cost polymeric silica under a mild reaction temperature by changing the characteristic acidity of phosphoric acid. The possibility of tuning the phosphoric acid acidity was first studied by molecular dynamics simulations, and phosphoric acids with stronger acidity were prepared by the evaporation of water from H 3 PO 4 (85%). The concentrated phosphoric acid enabled a fast reaction of polymeric silica and phosphate at a low reaction temperature (80 °C). The obtained silyl-phosphate lowered the SiO 2 layer dissolution rate, thereby yielding a Si 3 N 4 /SiO 2 layer etching ratio of up to 940. The proposed method offers an environmentally friendly production process for special chemicals used in 3D NAND flash memory fabrication. KEYWORDS: 3D NAND, concentrated H 3 PO 4 , fumed silica, Si 3 N 4 layer, SiO 2 layer, wet etching

Pervaporation is a green process that consumes low energy and does not require solvents for separation. In this work, interfacial engineering of poly(vinyl alcohol) (PVA)/carbon nanotube (CNT) electrospun fibers was attempted to fabricate dense membranes for pervaporation. Ethanol and water were used as nonsolvent and solvent, respectively, to alter the nanoscopic configuration of the fibers through interfacial solvent interactions. PVA and PVA/CNT mats with micron-sized pores (>100 μm) were prepared by optimizing electrospinning conditions. The mats were compacted via immersion in ethanol. They exhibited asymmetric close-packed top and bottom layers and porous intermediate layers. Further consolidation was achieved using water to fuse the fibers. The mats with more than 1.5 wt % CNT loading were stable against water owing to the cross-linking between CNTs and PVA. Because of the uniform dispersion of CNTs into the PVA matrix, the PVA/CNT dense films exhibited higher water/ethanol selectivity and water flux than those exhibited by similar films prepared by solution-casting. Thus, simple interfacial engineering of electrospun mats presented in this work successfully generates high-performance PVA/CNT membranes. A high alcohol dehydration performance and time-efficient membrane fabrication are achieved.