Nano-textured Copper Oxide Nanofibers for Efficient Air Cooling.

Ever decreasing of microelectronics devices is challenged by overheating and demands an increase in heat removal rate. Herein, we fabricated highly efficient heat-removal coatings comprised of copper oxide-plated polymer nanofiber layers (thorny devil nanofibers) with high surface-to-volume ratio, which facilitate heat removal from the underlying hot surfaces. The electroplating time and voltage were optimized to form fiber layers with maximal heat removal rate. The copper oxide nanofibers with the thorny devil morphology yielded a superior cooling rate compared to the pure copper nanofibers with the smooth surface morphology. This superior cooling performance is attributed to the enhanced surface area of the thorny devil nanofibers. These nanofibers were characterized with scanning electron microscopy, X-ray diffraction, atomic force microscopy, and a thermographic camera

Isobaric Vapor–Liquid Equilibrium for Acetone + Methanol + Phosphate Ionic Liquids

Isobaric vapor–liquid equilibrium (VLE) at atmospheric pressure (101.3 kPa) for the binary systems of acetone + methanol, acetone + phosphate ionic liquids (ILs), and methanol + phosphate ILs, and for the ternary system of acetone + methanol + phosphate ILs are measured using a circulation VLE still. The phosphate ILs include 1,3-dimethylimidazolium 1,3-dimethylimidazolium dimethylphosphate ([MMIM]­[DMP]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM]­[DEP]), and 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM]­[DBP]). The addition of these phosphate ILs to the azeotropic acetone + methanol system results in a salting-out effect on acetone and makes the azeotropic point disappear. The relative volatility α₁₂ of acetone over methanol increases with increasing molar fraction of ILs. The equilibrium data were well fitted by the electrolyte nonrandom two-liquid model (e-NRTL). Compared with some reported ILs previously such as pyridinium hexafluorophosphate, imidazolium trifluoromethane sulfonate and imidazolium dicyanamide, such imidazolium phosphate ILs are fluorine-free, are prepared more simply with lower cost, and make the azeotropic point disappear at less added amount of ILs. This work shows that such phosphate ILs are a class of potential solvents to separate azeotropic acetone + methanol system

Polyacrylonitrile nanofibers with added zeolitic imidazolate frameworks (ZIF-7) to enhance mechanical and thermal stability

Zeolitic imidazolate framework 7/polyacrylonitrile (ZIF-7/PAN) nanofiber mat of high porosity and surface area can be used as a flexible fibrous filtration membrane that is subjected to various modes of mechanical loading resulting in stresses and strains. Therefore, the stress-strain relation of ZIF-7/PAN nanofiber mats in the elastic and plastic regimes of deformation is of significant importance for numerous practical applications, including hydrogen storage, carbon dioxide capture, and molecular sensing. Here, we demonstrated the fabrication of ZIF-7/PAN nanofiber mats via electrospinning and report their mechanical properties measured in tensile tests covering the elastic and plastic domains. The effect of the mat fabrication temperature on the mechanical properties is elucidated. We showed the superior mechanical strength and thermal stability of the compound ZIF-7/PAN nanofiber mats in comparison with that of pure PAN nanofiber mats. Material characterization including scanning electron microscope, energy-dispersive X-ray spectroscopy, tensile tests, differential scanning calorimetry, and Fourier transform infrared spectroscopy revealed the enhanced chemical bonds of the ZIF-7/PAN complex

Desulfurization of Fuel Oil: Conductor-like Screening Model for Real Solvents Study on Capacity of Ionic Liquids for Thiophene and Dibenzothiophene

To screen and use ionic liquids (ILs) as environmental-friendly extractive solvents in removing aromatic sulfur compounds (S-compounds) from fuel oils, the knowledge of their capacity for S-compounds (or solubility of S-compounds in ILs) is very important. In this work, the capacities of 1860 potential ILs (30 anions, 62 cations) for two representative S-compounds of thiophene (TS) and dibenzothiophene (DBT) are calculated using conductor-like screening model for real solvents (COSMO-RS). The influences of cation family, cation alkyl chain length, cation symmetry, anion nature, anion alkyl chain length, and functional group on the capacity are extensively discussed and are understood from microlevel view with σ-profile, σ-moments, and COSMO-RS energies. It is observed that the capacity is very dependent on cation and anion structure characteristics and is in a very wide range (e.g., 10^–3∼10¹ for TS, 10^–3∼10² for DBT); the van der Waals (vdW) and hydrogen-bonding (HB) energies have significant effects on the capacity. Increasing the nonpolarity and vdW energies of cation or alkyl chain on anion, or the polarity and HB energies of anion, can favor the capacity. This work is valuable to rationally select or design the ILs for desulfurization of fuel oils

Gravity-Driven Hybrid Membrane for Oleophobic–Superhydrophilic Oil–Water Separation and Water Purification by Graphene

We prepared a simple, low-cost membrane suitable for gravity-driven oil–water separation and water purification. Composite membranes with selective wettability were fabricated from a mixture of aqueous poly­(diallyldimethylammonium chloride) solution, sodium perfluorooctanoate, and silica nanoparticles. Simply dip-coating a stainless steel mesh using this mixture produced the oil–water separator. The contact angles (CAs) of hexadecane and water on the prepared composite membranes were 95 ± 2° and 0°, respectively, showing the oleophobicity and superhydrophilicity of the membrane. In addition, a graphene plug was stacked below the membrane to remove water-soluble organics by adsorption. As a result, this multifunctional device not only separates hexadecane from water, but also purifies water by the permeation of the separated water through the graphene plug. Here, methylene blue (MB) was removed as a demonstration. Membranes were characterized by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy to elucidate the origin of their selective wettability

Gravity-Driven Hybrid Membrane for Oleophobic–Superhydrophilic Oil–Water Separation and Water Purification by Graphene

We prepared a simple, low-cost membrane suitable for gravity-driven oil–water separation and water purification. Composite membranes with selective wettability were fabricated from a mixture of aqueous poly­(diallyldimethylammonium chloride) solution, sodium perfluorooctanoate, and silica nanoparticles. Simply dip-coating a stainless steel mesh using this mixture produced the oil–water separator. The contact angles (CAs) of hexadecane and water on the prepared composite membranes were 95 ± 2° and 0°, respectively, showing the oleophobicity and superhydrophilicity of the membrane. In addition, a graphene plug was stacked below the membrane to remove water-soluble organics by adsorption. As a result, this multifunctional device not only separates hexadecane from water, but also purifies water by the permeation of the separated water through the graphene plug. Here, methylene blue (MB) was removed as a demonstration. Membranes were characterized by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy to elucidate the origin of their selective wettability

Supersonically sprayed thermal barrier layers using clay micro-particles.

Several clay minerals were supersonically sprayed onto flexible substrates to form highly thermally and electrically insulating materials which could be wrapped onto protected surfaces. Among these clay minerals, montmorillonite (Mt) revealed the best thermal insulating properties

Self-Junctioned Copper Nanofiber Transparent Flexible Conducting Film via Electrospinning and Electroplating.

Self-junctioned copper nanofiber transparent flexible films are produced using electrospinning and electroplating processes that provide high performances of T = 97% and Rs = 0.42 Ω sq−1 by eliminating junction resistance at wire intersections. The film remains conductive after being stretched by up to 770% (films with T = 76%) and after 1000 cycles of bending to a 5 mm radius

Breakup Process of Cylindrical Viscous Liquid Specimens after a Strong Explosion in the Core

Basic understanding and theoretical description of the expansion and breakup of cylindrical specimens of Newtonian viscous liquid after an explosion of an explosive material in the core are aimed in this work along with the experimental investigation of the discovered phenomena. The unperturbed motion is considered first, and then supplemented by the perturbation growth pattern in the linear approximation. It is shown that a special non-trivial case of the Rayleigh-Taylor instability sets in being triggered by the gas pressure differential between the inner and outer surfaces of the specimens. The spectrum of the growing perturbation waves is established, as well as the growth rate found, and the debris sizes evaluated. An experimental study is undertaken and both the numerical and analytical solutions developed are compared with the experimental data. A good agreement between the theory and experiment is revealed. It is shown that the debris size λ, the parameter most important practically, scales with the explosion energy E as λ ∼ E −1/2 . Another practically important parameter, the number of fingers N measured in the experiments was within 6%-9% from the values predicted numerically. Moreover, N in the experiments and numerical predictions followed the scaling law predicted theoretically, N ∼ m 1/2 e, with me being the explosive mass

Efficient heat removal via thorny devil nanofiber, silver nanowire, and graphene nanotextured surfaces.

Several types of nano-textured surfaces were studied with the goal to enhance heat removal rate in a cooling device (a heat sink) with water flow-through. The nano-textured surfaces where heat removal to flowing water took place included: (i) electrospun copper-plated thorny-devil nanofibers deposited on the copper substrate, (ii) graphene oxide flakes sprayed on the copper substrate, and (iii) silver nanowires spin-coated on a separate copper substrate. Their cooling performance was monitored by measuring the difference between the outlet and inlet temperature of water flowing through the heat sink and the temperature of the nano-textured copper substrate in the heat sink. The effect of the macroscopic vortex generator (wires) on cooling of the heat sink surface was less than that of the nano-textured surfaces, which revealed that the latter provide a much larger interfacial area, rather than an extra flow mixing, to enhance heat transfer rate. Of the nano-textured surfaces the most significant cooling enhancement was achieved with silver nanowires