Quantitative Investigation of the Morphologically Corrugated CVD-grown Graphene Monolayer Surface with a Nanoparticle-on-Mirror system

Graphene can be used as a starting material for the synthesis of useful nano-complexes for flexible, transparent electrodes, therapeutic, bio-diagnostics and bio-sensing. In order to apply graphene in the medical field, chemical vapor deposition (CVD) method has been mainly utilized considering its large and near-homogenious carbon constituents. Especially, the less degree of perturbation of graphene monolayer (GM), which is followed by the underneath catalytic Cu surface morphology, is very crucial in terms of providing the suspended GM and relatively fluent lateral carrier mobility with lower sheet resistance value. In this work, we can suggest a surface-Enhanced Raman Spectroscopic (SERS) indicator in a quantitative way on the status of z-directional morphological corrugation of a CVD–grown GM (CVD-GM) by applying a Nanoparticle-on-Mirror (NPoM) system composed of Au nanoparticle (NP) / CVD-GM / Au thin film (TF) plasmonic junction structure. A new (or enhanced) Radial Breathing Like Mode (RBLM) SERS signal around ~150 cm-1 from CVD-GM spaced in NPoM is clearly observed by employing a local z-polarized incident field formed at the Au NP–Au TF plasmonic gap junctions. With this observation, the value of I[out-of-plane, RBLM] / I[in-plane, [2D] at certain domains, it can be suggested as a new optical nano-metrology value to relatively determine between lower z-directional morphological corrugation (or protrusion) status of a CVD-GM spaced in our NPoM system (lower I[RBLM] / I[2D] value) and higher degree of lateral carrier mobility of the CVD-GM associated with lower sheet resistance values as a result of higher blue-shifted Raman in-plane (G, 2D) peak maximum position. Furthermore, we will also expect the bio-sensing performances by utilizing the high specific surface area and ultrahigh flexibility of the CVD-GM in one of the future prospective works such as pressure-strain, strain-to-electricity and chemical-coupled sensor via I[RBLM] / I[2D] values.

Research on the Influence of the AW 5754 Aluminum Alloy State Condition and Sheet Arrangements with AW 6082 Aluminum Alloy on the Forming Process and Strength of the ClinchRivet Joints

Clinching joints with an additional deformable rivet are modifications of the clinching joints. The clinch riveting (CR) joint is formed indirectly by a deformable rivet. The research included an analysis of CR joints’ forming process for aluminum alloy sheets made of AW 6082 in T6 state condition and AW 5754 in three different state conditions: H11, H22 and H24. As a result of forming the joint for various sheet arrangements, the highest value of blocking the upper sheet in the lower sheet (tu) was obtained for the arrangements with two 5754-H24 aluminum alloy sheets. For such a large interlock parameter tu, the greatest thinning of lower sheet (tn) was obtained, which influenced the maximum tensile shear force and the joint failure mechanism. Based on the load-displacement diagrams obtained from the static shear test of lap joints, the total energy of failure and energy to achieve the maximum load capacity were calculated. The highest energy absorption to achieve the maximum load capacity, in the case of the same sheet materials, was obtained for the 5754-H11 aluminum alloy sheets. On the other hand, among the tested combinations, the highest value of energy absorption (for the joint maximum load capacity) was obtained for the sheet arrangement: top sheet AW 6082-T6 and the bottom AW 5754-H24. The highest value of the total energy up to fracture was obtained when the material of the top sheet was AW 6082-T6, and the bottom AW 5754-H22. For each sheet arrangement, a similar analysis of the joint strength parameters, interlock parameters and forming force were made.

Microstructure and Mechanical Properties of Fe-36Ni and 304L Dissimilar Alloy Lap Joints by Pulsed Gas Tungsten Arc Welding

High-quality joining of dissimilar alloys between Fe-36Ni alloy and 304L stainless steel is essential in the manufacturing of LNG tanker. In this study, lap joints of Fe-36Ni and 304L dissimilar alloys were fabricated by a pulsed gas tungsten arc welding (P-GTAW) process. The effects of low-frequency pulse on the appearance, microstructure and mechanical properties of the Fe-36Ni/304L lap joints was investigated. With the increase of frequency, the feature sizes of α (the transition angle of the upper surface of Fe-36Ni to the surface of the weld bead) and R (shortest distance between weld root and weld surface) exhibited downtrend and uptrend, respectively, while La (the maximum weld width of lower sheet) and P (the maximum weld penetration of lower sheet) changed in a smaller range. Fusion zone (FZ) is mainly composed of γ phase and M23C6 during solidification, and M23C6 particles are distributed on the grain boundaries of the cells, which reduced the mechanical properties of joint. The average hardness between 110 HV1 and 136 HV1 is lower than that of the base metals. Fractures of all joints located at the Fe-36Ni side near the weld, and a dimple fracture in all samples indicated a ductile fracture. This study found that the heat input values remain 198.86 J mm−1 and increased pulse frequency can improve the maximum tensile force. The average maximum tensile force of the lap weld is 11.95 kN when pulsed frequency is 15 Hz.

Three-dimensional squeezed flow of aqueous magnetite–graphene oxide hybrid nanofluid: A novel hybridity model with analysis of shape factor effects

In the present article, we intend to study quasi-analytically the unsteady three-dimensional squeezed flow of the magnetite–graphene oxide/water hybrid nanofluid inside a rotating channel with two horizontal and parallel sheets, in which the lower sheet is stationary, stretchable, and permeable, while the upper sheet is moving and impermeable. Our methodology is based on the single-phase Tiwari–Das hybrid nanofluid model considering nanoparticles and base fluid masses instead volume concentration of first and second nanoparticles. The dimensional partial differential equations are altered to a set of nondimensional ordinary differential equations with the help of similarity transformation method, which is then solved numerically using the bvp4c function from MATLAB. The governing similarity parameters are the empirical shape factor of nanoparticles, the suction parameter, the squeezing parameter, the rotation parameter, the Eckert number, and the Prandtl number. Results indicate that when the upper sheet faster moves toward the lower sheet, the profiles trend is opposite in comparison with when the upper sheet faster moves away from the lower one. On the one hand, the drastic thermal conductivity of the graphene oxide is a major reason to achieve maximum heat transfer rate enhancement of our working fluid. Finally, this study may be applicable in biomechanics, flow through arteries, food processing, polymer processing, lubrication, injection modeling, etc.

Novel stretchable thermochromic transparent heaters designed for smart window defroster applications by spray coating silver nanowire

The as-designed heaters proved to be excellent candidates for employment in window defrosters, as they satisfy the essential prerequisites such as lower sheet resistance, high transparency, mechanical robustness and good stability to tensile strain.

Comparative Studies of Transparent Conductive Electrodes Based on Silver Nanowires and Carbon Nanotubes

The effects of reducing the contact resistance of AgNW networks by using TiO2and PEDOT:PSS were compared. The AgNW+PEDOT:PSS TCE was able to give a lower sheet resistance of 30~60Ω/□, while the AgNW+TiO2gave a relatively higher, but still practical value of 85~125Ω/□. Then the AgNW+PEDOT:PSS TCE was further compared with the SWCNT+PEDOT:PSS TCE, and it was found the SWCNT+PEDOT:PSS TCE had a lower conductivity of 70~110Ω/□ but a superior long-term mechanical stability.