Surface hydrophobicity: effect of alkyl chain length and network homogeneity

Understanding the nature of hydrophobicity has fundamental importance in environmental applications.Using spherical silica nanoparticles(diameter=369±7 nm)as the model material,the current study investigates the relationship between the alkyl chain network and hydrophobicity.Two alkyl silanes with different chain length(triethoxymethylsilane(C1)vs.trimethoxy(octyl)silane(C8))were utilised separately for the functionalisation of the nanoparticles.Water contact angle and inverse gas chromatography results show that the alkyl chain length is essential for controlling hydrophobicity,as the octyl-functionalised nanoparticles were highly hydrophobic(water contact angle=150.6°±6.6°),whereas the methyl-functionalised nanoparticles were hydrophilic(i.e.,water contact angle=0°,similar to the pristine nanoparticles).The homogeneity of the octyl-chain network also has a significant effect on hydrophobicity,as the water contact angle was reduced significantly from 148.4°±3.5°to 30.5°±1.0°with a methyl-/octyl-silane mixture(ratio=160:40μL·g^–1 nanoparticles).     

A first principles study of key electronic,optical, second and third order nonlinear optical properties of 3-(4-chlorophenyl)-1-(pyridin-3-yl) prop-2-en-1-one: a novel D-$$\pi $$-A type chalcone derivative

In this work we assess the significant electrooptic properties of a novel chalcone derivative 3-(4-chlorophenyl)-1-(pyridin-3-yl) prop-2-en-1-one using a computational approach. The ground-state molecular geometry was optimized, and geometrical parameters and vibrational modes are established and found to be in strong correlation with experimental results. The excitation energy is observed to be 326 nm (3.8 eV), calculated at the TD/B3LYP/6-31G level (stands for time dependent/Becke’s three Lee-Yang-Parr/basis set). Additionally, a unique insight was gained on a number of properties of the molecular levels such as the HOMO-LUMO gap (i.e. \({\sim } 4\,\hbox {eV}\)) and electrostatic potential maps. The potential applications of the 3-(4-chlorophenyl)-1-(pyridin-3-yl)prop-2-en-1-one (CPP) molecule in nonlinear optics are confirmed by second and third harmonic generation studies at five different characteristic wavelengths. The static and dynamic polarizability are found to be many-fold higher than that of urea. The second and third harmonic generation values of the titled molecule are found to be 56 and 158 times higher than standard urea molecule, respectively, computed at same wavelength (i.e. 1064.13 nm). From these studies it is clear that the material possesses superior properties and could be applied in optoelectronic device fabrications.     

Nitrogen-doped multiwalled carbon nanotubes decorated with copper(I) oxide nanoparticles with enhanced capacitive properties

We report on the enhanced capacitive properties of a copper(I) oxide nanoparticle (Cu₂O NP)-decorated multiwalled carbon nanotube (MWCNT) forest with nitrogen (N) doping. A careful in situ solid-state dewetting and plasma doping method was developed that ensured homogeneous decoration and contamination-free Cu₂O NPs with N doping on the nanotube sidewalls. The morphology and structure of the hybrid materials were characterised by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy and X-ray photoemission spectroscopy. The electrochemical performance of the hybrid materials was investigated by cyclic voltammetry and galvanostatic charge/discharge tests in a 0.1 M Na₂SO₄ electrolyte. The electrochemical tests demonstrated that the Cu₂O NP/N-MWCNT electrode exhibits a specific capacitance up to 132.2 F g^?1 at a current density of 2.5 A g^?1, which is 30% higher than that of the pure MWCNT electrode. Furthermore, the electrode could retain the specific capacitance at 85% stability over 1000 cycles. These observations along with the simple assembly method for the hybrid materials suggest that the Cu₂O NP/N-MWCNT could be a promising electrode for supercapacitor applications.     

Enhanced opto-electronic properties of X-doped (X = Al,Ga, and In) CuO thin films for photodetector applications

Recent trends in optoelectronics still need a highly efficient photodetector based on p-type metal oxide semiconductors. This work stands with the improvement in the performance of CuO thin films via doping with different metals into the thin films. The CuO thin films were successfully doped with 1 wt% of X (X?=?Al, Ga, and In) by spray pyrolysis method. The prepared doped CuO thin films were characterized to interpret the structural, morphological, and elemental characteristics using advanced techniques. These doped CuO thin films were subjected to study the photodetection ability by analyzing optoelectronic properties. The doping also tuned the optical and electrical properties. Among the fabricated photodetectors, the Al-doped CuO detector shows a maximum photocurrent. The CuO:Al (1.0%) thin film exhibits a high photocurrent of 2.59 × 10^?6 A, the responsivity of 2.82 × 10^??1 AW^??1, the external quantum efficiency of 66%, and the detectivity of 1.45 × 10¹⁰ Jones. Compared to the other thin films, Al doping has remarkably reduced the bandgap and shows a good photosensing activity that may be due to an increase in charge carriers. These outcomes provide a way to assemble good photodetectors and tune their properties in a wide range.

     

An insight into mode II fracture toughness testing using SCB specimen

The effect of friction forces between the test specimen and its bottom supports on the mode II fracture toughness values obtained using the semicircular bend (SCB) specimen is investigated. First, a number of experiments were conducted on SCB specimen in order to determine the mode II fracture toughness of polymethyl methacrylate (PMMA) according to the conventional approaches available in the literature. Three different types of supports that have been frequently employed by researchers in recent years were used to evaluate the effect of support type on the fracture loads. It was found that the friction forces between the supports and the SCB specimen have a significant effect on the value of mode II fracture toughness measured using the SCB samples. Then, the specimen was simulated using finite element method for more detailed investigation on the near crack tip stress field evolution when friction forces increase between the supports and the SCB specimen. The finite element results confirmed that the type of support affects not only the stress intensity factors K_I and K_II but also the T‐stress. The experimental and numerical results showed that the use of the crack tip parameters available in literature for frictionless contact between the supports and the SCB specimen can result in significant errors when the mode II experiments are performed by using the fixed or roller‐in‐grove types of supports.     

Computational investigations of Cu-embedded MoS<Subscript>2</Subscript> sheet for CO oxidation catalysis

Elevated amount of CO levels in the atmosphere poses serious health and environmental hazards. Oxidation of CO using suitable catalysts is one of the methods to control it. By means of DFT calculations, single Cu atom doped in S vacancy of MoS₂ nanosheet is studied for CO oxidation catalysis. Cu atom is strongly confined at the S-defective site of the MoS₂ sheet, possessing high energy barrier for the diffusion to its neighboring sites. Adsorption energy, charge transfer and orbital hybridization of CO and O₂ molecules adsorbed Cu-doped MoS₂ sheet reveal that O₂ is relatively more strongly adsorbed than CO. High adsorption energy of O₂ (??2.115 eV) and large charge transfer between O₂ and Cu–MoS₂ sheet (0.493e), compared to CO, make O₂ adsorption more favorable, which extenuates CO poisoning and hence helps in the efficient CO oxidation process. The complete oxidation of CO takes place in two steps: \( {\text{CO}} + {\text{O}}_{2} \to {\text{OOCO}} \) with activation energy of 0.201 eV, succeeded by \( {\text{OOCO}} + {\text{CO}} \to 2{\text{CO}}_{2} \) without any energy barrier. Our results show that the basal plane of MoS₂ sheet gets activated by embedding it with Cu metal, which can catalyze CO oxidation reaction effectively and without poisoning issues. The high activity, stability and low cost features can possibly encourage fabricating MoS₂-based catalysts for CO oxidation reaction.     

Formation of fine and encapsulated mefenamic acid form I particles for dissolution improvement via electrospray method

The potential of using electrostatic atomizer or electrospray in producing fine and encapsulated particle of mefenamic acid (MA) form I with β-cyclodextrin (βCD) was demonstrated in this study. Encapsulated MA-βCD with a molar ratio of 1:2 was prepared in water-ethanol suspension, followed by the electrospray process to atomize the droplet into fine dried particles. The working distance (WD) between the electrospray needle tip and the substrate were varied from 15 to 25?cm. The sizes of encapsulated MA-βCD particles were found to decrease from 91?±?26 to 42?±?35?nm as the WD increased. The dissolution rate of encapsulated particles of MA-βCD was found to be higher compared to the particles of as-received MA and the unencapsulated MA. The presence of the encapsulated MA-βCD was proven by a thermal analysis with the disappearance of MA peak after the atomization process. The x-ray diffraction and FTIR analysis showed that the encapsulation occurred with the existence of new solid phase that was expected from interaction between MA and βCD and the appearance of C?=?C. Further analysis by transmission electron microscopy showed the size and morphology of MA-βCD particles when immersed in water and acetone. Encapsulated MA-βCD particles were solubilized in water but suspended as spherical shape in acetone.     

Failure behavior of quasi-isotropic carbon fiber-reinforced polyamide composites under tension

In this paper, the microscopic failure behavior of quasi-isotropic carbon fiber-reinforced polyamide-6 (CF/PA6) laminates under tension was investigated experimentally. Laminates of two layups, namely [45°/0°/?45°/ 90°]_s and [45°/0°/?45°/ 90°]_2s, were made from CF/PA6 tapes of two different manufacturers and then subjected to tensile testing. Crack initiation and progression on the polished free edge of specimens were examined using optical microscopy, under several load levels. Crack growth behavior through the specimen width was also traced by observing the crack configurations in different sections in the specimen width direction. The effects of the spatial distribution of fiber on the microscopic damage events were elucidated. The difference in failure behavior between the present CF/PA6 laminates and conventional thermosetting CF/Epoxy laminate is discussed.     

The Effects of Triggering Mechanisms on the Energy Absorption Capability of Circular Jute/Epoxy Composite Tubes under Quasi-Static Axial Loading

The usage of composite materials have been improving over the years due to its superior mechanical properties such as high tensile strength, high energy absorption capability, and corrosion resistance. In this present study, the energy absorption capability of circular jute/epoxy composite tubes were tested and evaluated. To induce the progressive crushing of the composite tubes, four different types of triggering mechanisms were used which were the non-trigger, single chamfered trigger, double chamfered trigger and tulip trigger. Quasi-static axial loading test was carried out to understand the deformation patterns and the load-displacement characteristics for each composite tube. Besides that, the influence of energy absorption, crush force efficiency, peak load, mean load and load-displacement history were examined and discussed. The primary results displayed a significant influence on the energy absorption capability provided that stable progressive crushing occurred mostly in the triggered tubes compared to the non-triggered tubes. Overall, the tulip trigger configuration attributed the highest energy absorption.     

Effects of mean annual temperature and mean annual precipitation on the performance of flexible pavement using ME design

The purposes of this study were to establish the difference between empirical and mechanistic–empirical approaches in the flexible pavement design and to quantify the effects of mean annual precipitation and temperature on the flexible pavement distresses using the Mechanistic-Empirical Pavement Design Guide (MEPDG) software. Seventy-six specific locations from 13 states throughout the USA were selected based on different climate conditions using virtual climate stations based on the interpolation from the nearest weather stations prior to meeting the objectives. Subsequently, analysis was conducted based on the predicted distresses, including longitudinal cracking, transverse cracking, alligator cracking, asphalt concrete rutting and total pavement permanent deformation. Generally, the pavement structure and materials have been set as constant to control the effects of material on the results. On the basis of the MEPDG analysis, the longitudinal cracking of flexible pavement is significantly affected by both factors (temperature and precipitation), particularly in wet climatic regions. The mean annual temperature has a great influence on the alligator cracking, transverse cracking and permanent deformation of flexible pavement. However, neither factors demonstrated a significant impact on the predicted International Roughness Index of flexible pavement surfaces.