Progress and major BARRIERS of nanocatalyst development in direct methanol fuel cell: A review

Direct methanol fuel cells (DMFC), among the most suited and prospective alternatives for portable electronics, have lately been treated with nanotechnology. DMFCs may be able to remedy the energy security issue by having low operating temperatures, high conversion efficiencies, and minimal emission levels. Though, slow reaction kinetics are a significant restriction of DMFC, lowering efficiency and energy output. Nowadays, research is more focused on fundamental studies that are studying the factors that can improve the capacity and activity of catalysts. In DMFC, among the most widely explored catalysts are platinum and ruthenium which are enhanced in nature by the presence of supporting materials such as nanocarbons and metal oxides. As a result, this research sheds light on nanocatalyst development for DMFCs based on Platinum noble metal. To summarize, this research focuses on the structure of nanocatalysts, as well as support materials for nanocatalysts that can be 3D, 2D, 1D, or 0D. The support material described is made up of CNT, CNF, and CNW, which are the most extensively used because they improve the performance of catalysts in DMFCs. In addition, cost estimations for fuel cell technology are emphasized to show the technology's status and requirements. Finally, challenges to nanocatalyst development have been recognized, as well as future prospects, as recommendations for more innovative future research.     

Evaluation of hydrodynamic behavior of the perforated gas distributor of industrial gas phase polymerization reactor using CFD-PBM coupled model

A 2D computational fluid dynamics (Eulerian–Eulerian) multiphase flow model coupled with a population balance model (CFD-PBM) was implemented to investigate the fluidization structure in terms of entrance region in an industrial-scale gas phase fluidized bed reactor. The simulation results were compared with the industrial data, and good agreement was observed. Two cases including perforated distributor and complete sparger were applied to examine the flow structure through the bed. The parametric sensitivity analysis of time step, number of node, drag coefficient, and specularity coefficient was carried out. It was found that the results were more sensitive to the drag model. The results showed that the entrance configuration has significant effect on the flow structure. While the dead zones are created in both corners of the distributors, the perforated distributor generates more startup bubbles, heterogeneous flow field, and better gas–solid interaction above the entrance region due to jet formation.     

Damage tolerance in additively manufactured ceramic architected materials

Technical ceramics exhibit exceptional high-temperature properties, but unfortunately their extreme crack sensitivity and high melting point make it challenging to manufacture geometrically complex structures with sufficient strength and toughness. Emerging additive manufacturing technologies enable the fabrication of large-scale complex-shape artifacts with architected internal topology; when such topology can be arranged at the microscale, the defect population can be controlled, thus improving the strength of the material. Here, ceramic micro-architected materials are fabricated using direct ink writing (DIW) of an alumina nanoparticle-loaded ink, followed by sintering. After characterizing the rheology of the ink and extracting optimal processing parameters, the microstructure of the sintered structures is investigated to assess composition, density, grain size and defect population. Mechanical experiments reveal that woodpile architected materials with relative densities of 0.38–0.73 exhibit higher strength and damage tolerance than fully dense ceramics printed under identical conditions, an intriguing feature that can be attributed to topological toughening.     

Constructing developable surfaces by wrapping cones and cylinders

We model developable surfaces by wrapping a planar figure around cones and cylinders. Complicated developables can be constructed by successive mappings using cones and cylinders of different sizes and shapes. We also propose an intuitive control mechanism, which allows a user to select an arbitrary point on the planar figure and move it to a new position. Numerical techniques are then used to find a cone or cylinder that produces the required mapping. Several examples demonstrate the effectiveness of our technique.     

Nanostructured titanium nitride for highly sensitive localized surface plasmon resonance biosensing

Titanium nitride (TiN) as an alternative plasmonic ceramic material with superb properties including high hardness, outstanding corrosion resistance and excellent biocompatibility, has exhibited great potential for optical biochemical sensing applications. By sputtering about 35 nm–50 nm TiN on glass (f-TiN), the surface was found to provide sensing capability toward NaCl solution through the phenomenon of surface plasmon resonance. When the TiN film of about 27 nm–50 nm in thickness was sputtered onto a roughened glass surface (R–TiN), the sensing capability was improved. This was further improved when holes at nanoscale were created in the TiN film of about 19 nm–27 nm in thickness (NH–TiN). The roughened surface and nanohole patterns provided confinement of surface plasmons and significantly improved the sensitivity toward the local refractive index changes. In detail, the calculated refractive index resolution (RIR) of the optimal NH–TiN sensors for NaCl was found to be 9.5 × 10⁻⁸ refractive index unit (RIU), which had outperformed the f-TiN and R–TiN sensors. For biosensing, the optimized NH–TiN sensor was found to be capable to detect both small and large biomolecules, i.e. biotin (molecular weight of 244.3 g/mol) and human IgG (160,000 g/mol), in a label-free manner. Especially, the NH–TiN sensor significantly improved sensitivity in detecting small molecules due to the localized plasmonic confinement of electromagnetic field. Combining with the excellent mechanical and durability properties of TiN, the proposed NH–TiN can be a strong candidate for plasmonic biosensing applications.     

Metalorganic chemical vapor deposition of silver thin films for future interconnects by direct liquid injection system

Deposition of Ag films by direct liquid injection-metal organic chemical vapor deposition (DLI-MOCVD) was chosen because this preparation method allows precise control of precursor flow and prevents early decomposition of the precursor as compared to the bubbler-delivery. Silver(I)-2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionato-triethylphosphine [Ag(fod)(PEt₃)] as the precursor for Ag CVD was studied, which is liquid at 30 °C. Ag films were grown on different substrates of SiO₂/Si and TiN/Si. Argon and nitrogen/hydrogen carrier gas was used in a cold wall reactor at a pressure of 50–500 Pa with deposition temperature ranging between 220 °C and 350 °C. Ag films deposited on a TiN/Si diffusion barrier layer have favorable properties over films deposited on SiO₂/Si substrate. At lower temperature (220 °C), film growth is essentially reaction-limited on SiO₂ substrate. Significant dependence of the surface morphology on the deposition conditions exists in our experiments. According to XPS analysis pure Ag films are deposited by DLI-MOCVD at 250 °C by using argon as carrier gas.     

甲磺酸铜催化合成草酸二异戊酯

制备了甲磺酸铜催化剂,对其结构进行了IR和热重分析,并用于催化草酸和异戊醇的酯化反应。结果表明,甲磺酸铜具有催化活性高、稳定,易分离,重复使用性能优良,对环境友好的特点。最佳酯化工艺条件为:n(异戊醇):n(草酸)=2．8:1,w(甲磺酸铜)=0．3％,以过量的异戊醇为带水剂,回流反应2．0 h,酯化率可达到96．8％。