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( Riaz Shahina ),박수진 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
In this study branched polyethyleneimine (b-PEI)-assisted exfoliation of MoS2 nanosheets (MoS2--PEI) was carried out. These non-covalently functionalized MoS2-PEI nanosheets were employed as toughening agents for epoxy composites. The contents of MoS2-PEI nanosheets were maintained at weight fractions lower than 0.16 wt%. The epoxy composites exhibited a 67% increase in fracture toughness (KIC) and a corresponding 101% increase in fracture energy (GIC) at nanosheets loadings as small as 0.06wt.% (MP-6), KIC shows linear relationship with the surface free energy (SFE) and is highest at 81 mJ m-2 for the MP-6 composite. However, the SFE values of the MP-9 and MP-16 composites decreased to 67.20 mJ/㎡ and 70.25 mJ m<sup>-2</sup>. Furthermore, the thermal stability of the epoxy composites improved significantly. The optimum MoS2-PEI nanosheet loading was observed to be 0.06wt.%, beyond which a gradual decrease in the thermal stability was observed.
Amino functionalized graphene oxide-epoxy composites: Initiated by thermal latent catalysts
( Riaz Shahina ),박수진 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Curing of epoxy by homopolymerization provide advantages and broadens the field of application of these polymeric materials. Cationic initiators, which remain inactive under normal environmental conditions and became active by external stimulations such as heating and photoirradiation, had been synthesized and their importance has been recognized in organic and polymer synthesis. Commercially available diglycidyl ether of bisphenol A (DGEBA) was used as base resin and the thermally latent catalyst, N-benzylepyrizinium hexafluoroantimonate (N-BPH) was synthesized by using the reported method. The cationic system shows excellent latent curing which was not affected by adding filler. The cure kinetics was determined by DSC measurements. An improve in the thermal and mechanical properties of composites was observed by increment of filler contents.
An overview of TiO2-based photocatalytic membrane reactors for water and wastewater treatments
Shahina Riaz,박수진 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.84 No.-
Photocatalytic membrane reactors (PMRs), which coupled photocatalysts (PCs) with the membraneseparation process has gained huge interest for the purification of water and wastewater treatments. Titanium dioxide (TiO2) is the most commonly used material used for the preparation of photocatalyticmembrane reactors owing to its exceptional properties such as low cost, less toxicity, and high chemicalstability as well as high surface to volume ratio and quantum confinement effect. Because of the largesurface area of TiO2 nano powder, it proved ample active sites for the reactions and enhance the catalyticactivity. This review provides details on recent developments on TiO2-based photocatalytic membranereactors (T-PMRs) used for water purification and wastewater treatments and in pharmaceuticals basedon the types of membranes, fabrication methods, characterization, operational parameters influencingphotocatalytic process, and applications of membranes in disinfection and in the removal of pollutants. Moreover, a short description of heterogeneous/homogeneous photocatalysis and configurations anddesigns of PMRs is also given. By applying the optimum operating parameters and new engineeringapproach on PMRs, the efficiency of T-PMRs for water purification and wastewater treatments can beenhanced. The future research and perspectives for water purification and waste water treatments usingT-PMRs were also suggested.
Shahina Riaz,박수진 한국고분자학회 2020 Macromolecular Research Vol.28 No.12
We present a two-dimensional tungsten disulfide (WS2)-based material as a reinforcement additive to produce thermally stable, mechanically strong, and light-weight epoxy (EP) composites. An aqueous melamine solution was used to exfoliate the bulk WS2 into nanosheets while simultaneously functionalizing them to obtain melamine-functionalized WS2 (N-WS2) nanosheets. These non-covalently functionalized N-WS2 nanosheets were used as toughening agents for epoxy composites. The contents of the N-WS2 nanosheets were maintained at below 1wt%. The effect of functionalization on the interfacial properties of EP composites was investigated in terms of the interfacial interactions between the EP and the nanosheets. The results demonstrated that the surface free energy of EP composites increased significantly after the incorporation of N-WS2 nanosheets into the EP matrix and further increased with the increased loading of N-WS2 nanosheets up to a maximal value of 54.38 mJ·m-2 for the composite containing 0.18wt% N-WS2 nanosheets, suggesting a stronger interfacial interaction between the EP and N-WS2 nanosheets. A gradual decrease in the surface free energy of the EP composites was observed at higher loadings, which might be attributed to the aggregation of N-WS2 nanosheets within the matrix or excessive bonding of the sheets with one another rather than with the EP matrix due to their larger Van der Waals forces and their large surface area. The mechanical properties of the EP composites were analyzed and demonstrated 55%, 101%, 44%, and 15% improvements in the fracture toughness, fracture energy, flexural strength, and flexural modulus, respectively, for the composite containing 0.18 wt% N-WS2 nanosheets. Moreover, the composites displayed increased glass transition temperatures and better thermal stabilities.
Shahina Riaz,Soo Jin Park 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.105 No.-
To make quantum dot sensitized solar cells (QDSCs) competitive, a power conversion efficiency (PCE)comparable to other developing solar cells is required. Significant attention has been paid to undopedor nitrogen (N) doped carbon quantum dots (N-CQDs) for use as sensitizers or light harvesters in solarcells. However, to our knowledge, the nitrogen and sulfur (S) co-doped CQDs (N, S-CQDs) have never beenused as the absorbing layer alone. In the present work, we synthesize nitrogen and sulfur co-doped carbonquantum dots (N, S-CQDs) from a single precursor thioacetamide (TA), via a hydrothermal method. The as-prepared N, S-CQDs were employed as a ‘‘green” photoactive layer in TiO2 film, as photoanode. Thesolar cell delivered an open-circuit voltage (Voc) of 0.43 V, short-circuit current (Jsc) of 0.61 mA/cm 2, fillfactor (FF) of 52 %, and PCE of 1.36%; highest among all the carbon-based QDSCs. Moreover, Device-NSshowed more stability over 48 h compared to Device-C and Device-N. Undeniably, the achieved PCE isnot satisfactory; however, the upgraded device fabrication and structural design may improve PCE andcurrent densities while sustaining the high open-circuit voltage. This study demonstrated the potentialapplication of N, S-CQDs for low-cost, ‘‘green” quantum dot solar cell applications.