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Eduard Penner,Ismail Caylak,Rolf Mahnken 한국섬유공학회 2023 Fibers and polymers Vol.24 No.1
Composite materials, such as fiber reinforced polymers, become increasingly important due to their excellent mechanicaland lightweight properties. In this respect, this paper reports the characterization of a unidirectional carbon fiber reinforcedpolymer composite material. Particularly, the mechanical behavior of the overall composite and of the individual constituentsof the composite is investigated. To this end, tensile and shear tests are performed for the composite. As a result, statistics forfive transversely isotropic material parameters can be established for the composite. For the description of the mechanicalproperties of the constituents, tensile tests for the carbon fiber as well as for the polymer matrix are carried out. In addition,the volume fraction of fibers in the matrix is determined experimentally using an ashing technique and Archimedes’ principle. For the Young’s modulus of the fiber, the Young’s modulus and transverse contraction of the matrix, as well as the volumefraction of the constituents, statistics can be concluded. The resulting mechanical properties on both scales are useful forthe application and validation of different material models and homogenization methods. Finally, in order to validate theobtained properties in the future, inhomogeneous tests were performed, once a flat plate with a hole and a flat plate withsemicircular notches.
Investigating the Cold Plasma Surface Modification of Kaolin- and Attapulgite-Bound Zeolite A
Mahboobeh Ejtemaei,Sepehr Sadighi,Mehdi Rashidzadeh,Sirous Khorram,Jan O. Back,Simon Penner,Michael F. Noisternig,Dariush Salari,Aligholi Niaei 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.106 No.-
Hydrophilic zeolites with low catalytic activity are considered as suitable adsorbents for drying gasstreams containing olefinic compounds. In this contribution, the surface treatment of kaolin and attapulgite/zeolite A extrudates is investigated using argon glow discharge plasma. The zeolite is synthesizedfrom kaolin using the hydrothermal method. Surface and bulk characterization is performed using X-raydiffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, Fourier-transform infrared (FTIR)spectroscopy, temperature-programmed-desorption (TPD) of NH3 and X-ray photoelectron spectroscopy(XPS) techniques. Plasma treatment increases surface area and pore volume, but it decreasesthe weak acidic site density of the extrudates. The obtained results show that attapulgite/zeolite extrudatesare more affected by plasma treatment than kaolin/zeolite extrudates. The catalytic activity ofuntreated and plasma-treated extrudates are compared with respect to coke formation resulting from1-butene and 1,3-butadiene. The plasma-treated sample is more resistant to coke formation (35%decrease compared to untreated one). The potassium contents of extrudates decreased as a result of sputteringloosely bound potassium cations on the crystal surface by argon ions, which led to a decrease inwater sorption capacity (by 15% of the initial sorption capacity).
Koo, Won-Tae,Jang, Ji-Soo,Qiao, Shaopeng,Hwang, Wontae,Jha, Gaurav,Penner, Reginald M.,Kim, Il-Doo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.23
<P>Here, we propose heterogeneous nucleation-assisted hierarchical growth of metal-organic frameworks (MOFs) for efficient particulate matter (PM) removal. The assembly of two-dimensional (2D) Zn-based zeolite imidazole frameworks (2D-ZIF-L) in deionized water over a period of time produced hierarchical ZIF-L (H-ZIF-L) on hydrophilic substrates. During the assembly, the second nucleation and growth of ZIF-L occurred on the surface of the first ZIF-L, leading to the formation of flowerlike H-ZIF-L on the substrate. The flowerlike H-ZIF-L was easily synthesized on various substrates, namely, glass, polyurethane three-dimensional foam, nylon microfibers, and nonwoven fabrics. We demonstrated H-ZIF-L-assembled polypropylene microfibers as a washable membrane filter with highly efficient PM removal property (92.5 ± 0.8% for PM<SUB>2.5</SUB> and 99.5 ± 0.2% for PM<SUB>10</SUB>), low pressure drop (10.5 Pa at 25 L min<SUP>-1</SUP>), long-term stability, and superior recyclability. These outstanding particle filtering properties are mainly attributed to the unique structure of the 2D-shaped H-ZIF-L, which is tightly anchored on individual fibers comprising the membrane.</P> [FIG OMISSION]</BR>
Neda Kalantari,Maged F. Bekheet,Parastoo Delir Kheyrollahi Nezhad,Jan O. Back,Ali Farzi,Simon Penner,Nagihan Delibas,Sabine Schwarz,Johannes Bernardi,Dariush Salari,Aligholi Niaei 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.111 No.-
We introduced chromium and boron into the hierarchical structure of ZSM-5 by following an incipientwet impregnation and hydrothermal synthesis approach to enhance the performance of the catalystsin the methanol-to-propylene process. Crystal structure, preferred orientation, and crystal symmetry ofsynthesized zeolites were discussed using Rietveld refinement and revealed that all synthesized zeolitescrystallized in a monoclinic structure, whereas the boron-incorporated sample exhibited an orthorhombicsymmetry. Large-scale defect-free single-crystalline structures of hierarchical zeolite created by CTABand F127 mesoporogens are confirmed by electron microscopy and magic angle spinning nuclear magneticresonance (MAS NMR). The formation of surface metal oxides and extra-framework metal oxidescaused changes in the electronic structure of the components as visible in Si 2p and O 1s spectra. The predominantpresence of OH groups and the higher Cr (VI) /Cr (III) ratio account for the better performanceof impregnated chromium-ZSM-5 especially in the production of light olefins. The introduction of boronby impregnation further preserved the preferred growth orientation, hierarchical structure with highcrystallinity and caused surface acidity changes in favor of increasing propylene selectivity to 67% witha propylene/ethylene ratio of close to 8.
Accelerating Palladium Nanowire H<sub>2</sub> Sensors Using Engineered Nanofiltration
Koo, Won-Tae,Qiao, Shaopeng,Ogata, Alana F.,Jha, Gaurav,Jang, Ji-Soo,Chen, Vivian T.,Kim, Il-Doo,Penner, Reginald M. American Chemical Society 2017 ACS NANO Vol.11 No.9
<P>The oxygen, O-2, in air interferes with the detection of H-2 by palladium (Pd)-based 11, sensors, including Pd nanowires (NWs), depressing the sensitivity and retarding the response/recovery speed in air relative to N-2 or Ar. Here, we describe the preparation of H-2 sensors in which a nanofiltration layer consisting of a Zn metal organic framework (MOF) is assembled onto Pd NWs. Polyhedron particles of Zn-based zeolite imidazole framework (ZIF-8) were synthesized on lithographically patterned Pd NWs, leading to the creation of ZIF-8/Pd NW bilayered H-2 sensors. The ZIF8 filter has many micropores (0.34 nm for gas diffusion) which allows for the predominant penetration of hydrogen molecules with a kinetic diameter of 0.289 nm, whereas relatively larger gas molecules including oxygen (0.345 nm) and nitrogen (0.364 nm) in air are effectively screened, resulting in superior hydrogen sensing properties. Very importantly, the Pd NWs filtered by ZIF-8 membrane (Pd NW5@ZIF-8) reduced the H-2 response amplitude slightly (Delta R/R-o = 3.5% to 1% of H-2 versus 5.9% for Pd NWs) and showed 20-fold faster recovery (7 s to 1% of H-2) and response (10 s to 1% of H-2) speed compared to that of pristine Pd NWs (164 s for response and 229 s for recovery to 1% of H-2). These outstanding results, which are mainly attributed to the molecular sieving and acceleration effect of ZIF-8 covered on Pd NWs, rank highest in H-2 sensing speed among room -temperature Pd-based H-2 sensors.</P>
Chandran, Girija Thesma,Jha, Gaurav,Qiao, Shaopeng,Le Thai, Mya,Dutta, Rajen,Ogata, Alana F.,Jang, Ji-Soo,Kim, Il-Doo,Penner, Reginald M. American Chemical Society 2017 Langmuir Vol.33 No.37
<P>The influence of hexamethylenetetraamine (HMTA) on the morphology of delta-MnO2 and its properties for electrical energy storage are investigated-specifically for ultrathick delta-MnO2 layers in the micron scale. Planar arrays of gold@delta MnO2, core@shell nanowires, were prepared by electrodeposition with and without the HMTA and their electrochemical properties were evaluated. HMTA alters the MnO2 in three ways: First, it creates a more open morphology for the MnO2 coating, characterized by 'petals' with a thickness of 6 to 9 nm, rather than much thinner delta-MnO2 sheets seen in the absence of HMTA. Second, the electronic conductivity of the delta-MnO2 is increased by an order of magnitude. Third, (delta-MnO2 prepared in HMTA shows a (001) interlayer spacing that is expanded by approximate to 30% possibly accelerating Li transport. The net effect of 'HTMA doping' is to dramatically improve high rate performance, culminating in an increase in the specific capacity for the thickest MnO2 shells examined here by a factor of 15 at 100 mV/s.</P>
Hollow Pd–Ag Composite Nanowires for Fast Responding and Transparent Hydrogen Sensors
Jang, Ji-Soo,Qiao, Shaopeng,Choi, Seon-Jin,Jha, Gaurav,Ogata, Alana F.,Koo, Won-Tae,Kim, Dong-Ha,Kim, Il-Doo,Penner, Reginald M. American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.45
<P>Pd based alloy materials with hollow nanostructures are ideal hydrogen (H-2) sensor building blocks because of their double-H-2 sensing active sites (interior and exterior side of hollow Pd alloy) and fast response. In this work, for the first time, we report a simple fabrication process for preparing hollow Pd-Ag alloy nanowires (Pd@Ag HNWs) by using the electrodeposition of lithographically patterned silver nanowires (NWs), followed by galvanic replacement reaction (GRR) to form palladium. By controlling the GRR time of aligned Ag NWs within an aqueous Pd(2+)containing solution, the compositional transition and morphological evolution from Ag NWs to Pd@Ag HNWs simultaneously occurred, and the relative atomic ratio between Pd and Ag was controlled. Interestingly, a GRR. duration of 17 h transformed Ag NWs into Pd@Ag HNWs that showed enhanced H-2 response and faster sensing response time, reduced 2.5-fold, as compared with Ag NWs subjected to a shorter GRR period of 10 h. Furthermore, Pd@Ag HNWs patterned on the colorless and flexible polyimide (cPI) substrate showed highly reversible H-2 sensing characteristics. To further demonstrate the potential use of Pd@Ag HNWs as sensing layers for all-transparent, wearable H-2 sensing devices, we patterned the Au NWs perpendicular to Pd@Ag HNWs to form a heterogeneous grid-type metallic NW electrode which showed reversible H-2 sensing properties in both bent and flat states.</P>
Ogata, Alana F.,Song, Seok-Won,Cho, Su-Ho,Koo, Won-Tae,Jang, Ji-Soo,Jeong, Yong Jin,Kim, Min-Hyeok,Cheong, Jun Young,Penner, Reginald M.,Kim, Il-Doo American Chemical Society 2018 ANALYTICAL CHEMISTRY - Vol.90 No.15
<P>A new type of chemiresistor, the impedance-transduced chemiresistor (ITCR), is described for the rapid analysis of glucose. The ITCR exploits porous, high surface area, fluorine-doped carbon nanofibers prepared by electrospinning of fluorinated polymer nanofibers followed by pyrolysis. These nanofibers are functionalized with a boronic acid receptor and stabilized by Nafion to form the ITCR channel for glucose detection. The recognition and binding of glucose by the ITCR is detected by measuring its electrical impedance at a single frequency. The analysis frequency is selected by measuring the signal-to-noise (<I>S</I>/<I>N</I>) for glucose detection across 5 orders of magnitude, evaluating both the imaginary and real components of the complex impedance. On the basis of this analysis, an optimal frequency of 13 kHz is selected for glucose detection, yielding an <I>S</I>/<I>N</I> ratio of 60-100 for [glucose] = 5 mM using the change in the total impedance, Δ<I>Z</I>. The resulting ITCR glucose sensor shows a rapid analysis time (<8 s), low coefficient of variation for a series of sensors (<10%), an analysis range of 50 μM to 5 mM, and excellent specificity versus fructose, ascorbic acid, and uric acid. These metrics for the ITCR are obtained using a sample size as small as 5 μL.</P> [FIG OMISSION]</BR>