Ring-Opening Competes with Peroxidation in Fenchone Low-Temperature Autoignition

We report an atypical competition between fenchyl radical β-scission and peroxidation at low temperatures and unravel the impacts of strain energy and ring substituent location on their respective contributions. Our RRKM modeling reveals that radicals positioned on secondary carbons are the fastest-scission ones, exhibiting maximum local ring relief. Dimethyl substituents contribute to increased local strain compared to norbornane, hindering bridge scission and leading to cyclopentene and isoprene products. The dimethyl corset generates extra torsional strain during HO2 elimination from QOOH, while ether formation is favored by electron donation from the carbonyl group. The falloff extent is also affected by steric hindrance, insofar as it increases bridge stiffness, leading to a lower vibrational partition function and low-pressure rate constant. Furthermore, methyl-induced restrictions on reactant reorganization are found to modulate an enthalpy-entropy compensation in the Korcek reaction of fenchyl hydroperoxide. Unlike in our previous stirred reactor experiments, the impact of fenchyl peroxidation on reactivity is notable under our new rapid compression machine (RCM) experiments. The present model predicts contrasted fenchyl selectivities with radical position, β-scission and peroxidation prevailing respectively for F1/F2/F3/F4 and F5/F6 radicals. The kinetic mechanism accurately predicts the experimental IDT but indicates a slight first-stage pressure inflection point at the lower experimental temperature, which could not be confirmed experimentally. This new insight into fenchone ring-opening and -closing mechanisms under high-pressure oxidation can be useful for other polycyclic ketones.

Hexagonal boron nitride as a new ultra-thin and efficient anti-coking coating for jet fuel nozzles

The pyrolysis coking of hydrocarbon fuel during active cooling has a significant impact on engine performance. The implementation of a passivation layer with a high aspect ratio within the cooling channel is considered to be an effective approach. The achievement of ultra-thin coatings with high permeability, exceptional mechanical properties, outstanding oxidation resistance, while preserving the physical and chemical characteristics of the substrate and the coating morphology remains a formidable challenge. In this study, a dense hexagonal boron nitride (hBN) film was uniformly deposited onto the surface of Ni using the chemical vapor deposition (CVD) process, serving as an effective passivation layer for anti-coking coatings. We conducted a comprehensive investigation into the thermal oxidation coking process and structural evolution of RP-3 jet fuel on Ni surface utilizing various characterization techniques, including FT-IR, SEM, and other advanced methodologies. The Raman intensity ratio (ID/IG) of the coking carbon material was observed to increase from 0.6286 to 0.8952 with increasing temperature, indicating an enhanced degree of coking order and a more complete cyclization of the precursor. The quality of carbon deposition in coke products was determined using the char firing method, and a quantitative investigation was conducted on the coking resistance of hBN coating. The experimental results demonstrated that the hBN coating exhibited remarkable coking inhibition rates of 83.7%, 87.1%, and 86.9% at temperatures of 450 ℃, 400 ℃, and 350 ℃, respectively. These findings demonstrate the excellent prospects of hBN as a coating for effectively inhibiting coking on metal surfaces.

Candle soot-smoked electrodes as a natural superhydrophobic material for potentiometric sensors

The application of carbon soot as a solid-contact layer in potentiometric sensor is presented. The preparation method of carbon layer from the candle is inexpensive and as short as 10 s and was optimized and described in the scope of this paper. With the use of the proposed procedure, it is possible to cover not only the glassy carbon disc electrodes, but all surfaces of various shapes and types, like foil or paper. Obtained soot layer was casted with potassium-selective membrane, for the comparison of results with other solutions presented in literature, however by changing the composition of ion-selective membrane it is possible to achieve electrodes sensitive to various cations and anions. By introducing the candle soot into the sensor, the electrical and analytical properties of electrode were significantly improved. Designed candle soot-based sensor exhibit repeatable and reversible Nernstian response towards potassium ions, low detection limit (10-6.7 M K+ ions), remarkable potential stability (drift equals to 15 μV/h) enhanced selectivity (in comparison with coated-disc electrode) and short response time. Designed sensors owe its great analytical properties to high electrical capacity (C = 343 μF) and superhydrophobic properties (proven by the high value of contact angle - 165°). Obtained sensors are insensitive to redox conditions and exhibit long lifetime. Performed tests proved that carbon layer obtained directly from the candle is appropriate material for solid-contact layer in potentiometric sensor and allows to obtain robust potentiometric sensor of competitive parameters using simple and fast procedure.

Fabrication of an efficient vanadium redox flow battery electrode using a free-standing carbon-loaded electrospun nanofibrous composite

Vanadium redox flow batteries (VRFBs) are considered as promising electrochemical energy storage systems due to their efficiency, flexibility and scalability to meet our needs in renewable energy applications. Unfortunately, the low electrochemical performance of the available carbon-based electrodes hinders their commercial viability. Herein, novel free-standing electrospun nanofibrous carbon-loaded composites with textile-like characteristics have been constructed and employed as efficient electrodes for VRFBs. In this work, polyacrylonitrile-based electrospun nanofibers loaded with different types of carbon black (CB) were electrospun providing a robust free-standing network. Incorporation of CBs (14% and 50% weight ratio) resulted in fibers with rough surface and increased mean diameter. It provided higher BET surface area of 83.8 m² g^-1 for as-spun and 356.7 m² g^-1 for carbonized fibers compared to the commercial carbon felt (0.6 m² g^-1). These loaded CB-fibers also had better thermal stability and showed higher electrochemical activity for VRFBs than a commercial felt electrode.

Analysis of the Thermal Behavior of Polypropylene-Camphor Mixtures for Understanding the Pathways to Polymeric Membranes via Thermally Induced Phase Separation

An experimental phase diagram of the isotactic polypropylene-camphor system is constructed using an original optical method. It considerably deviates from the dynamic diagram, which can be obtained using conventional differential scanning calorimetry (DSC), and contains an additional boundary line that describes camphor solubility in the polymer. An accurate phase diagram makes it possible to perform a detailed and consistent thermodynamic analysis of the DSC, optical, and scanning electron microscopy data on the cooling of prehomogenized mixtures of different compositions, which leads to the formation of capillary-porous bodies via thermally induced phase separation. The removal of camphor results in the formation of polypropylene membranes, the morphology and functional properties of which, such as the total pore volume, mean pore size, permeability coefficient, and breaking stress, appear to be highly dependent on the composition of the initial binary system. It is shown that thermally induced phase separation induces the formation of microscopic cracks in the studied membranes. The crack density decreases with the polymer content in the initial system, but at 53 wt % of polypropylene, the membrane becomes completely impermeable to isopropanol despite the presence of large ∼4 μm pores, thus questioning the perspectives of its practical use. In general, the study makes it possible to achieve a deeper understanding of the membrane formation process via thermally induced phase separation in the mixtures of semicrystalline polymers with low molar mass substances.

PDMS/camphor soot composite coating: towards a self-healing and a self-cleaning superhydrophobic surface

A novel self-cleaning polymer composite with self-healing ability to self-repair after chemical and mechanical damage using readily available materials like polydimethylsiloxane (PDMS) and camphor soot particles is developed.

Fractal analysis of pre-reduced Pt/TiO2catalysts for formaldehyde oxidation

The amount of reactive sites, usually dispersed noble atoms, on the top of a catalyst rough surface is characterized within the framework of fractal geometry.

Temperature Assisted in-Situ Small Angle X-ray Scattering Analysis of Ph-POSS/PC Polymer Nanocomposite

Inorganic/organic nanofillers have been extensively exploited to impart thermal stability to polymer nanocomposite via various strategies that can endure structural changes when exposed a wide range of thermal environment during their application. In this abstraction, we have utilized temperature assisted in-situ small angle X-ray scattering (SAXS) to examine the structural orientation distribution of inorganic/organic nanofiller octa phenyl substituted polyhedral oligomeric silsesquioxane (Ph-POSS) in Polycarbonate (PC) matrix from ambient temperature to 180 °C. A constant interval of 30 °C with the heating rate of 3 °C/min was utilized to guise the temperature below and above the glass transition temperature of PC followed by thermal gravimetric, HRTEM, FESEM and hydrophobic analysis at ambient temperature. The HRTEM images of Ph-POSS nano unit demonstrated hyperrectangular structure, while FESEM image of the developed nano composite rendered separated phase containing flocculated and overlapped stacking of POSS units in the PC matrix. The phase separation in polymer nanocomposite was further substantiated by thermodynamic interaction parameter (χ) and mixing energy (E_mix) gleaned via Accelrys Materials studio. The SAXS spectra has demonstrated duplex peak at higher scattering vector region, postulated as a primary and secondary segregated POSS domain and followed by abundance of secondary peak with temperature augmentation.

Superhydrophobic meshes that can repel hot water and strong corrosive liquids used for efficient gravity-driven oil/water separation

Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health.

B. Bionic creation of nano-engineered Janus fabric for selective oil/organic solvent absorption

We present a self-driven and tunable hydrophobic/oleophilic, wettability-modified Janus fabric composed of a cellulosic substrate engineered with nanofibers via facile a electrospinning technique that exhibits one-step selective oil absorption capacity from water.

B. Multifunctional nano-engineered and bio-mimicking smart superhydrophobic reticulated ABS/fumed silica composite thin films with heat-sinking applications

There are increasing requirements for engineered surfaces with distinct properties such as superhydrophobicity, self-cleaning, high thermal stability, and anti-corrosion.

Inhibitory effect of MnCr2O4 spinel coating on coke formation during light naphtha thermal cracking

MnCr₂O₄ spinel coating can significantly affect coke morphology and coke microstructure.

Single-step flame synthesis of carbon nanoparticles with tunable structure and chemical reactivity

Single-step flame synthesis technique providing the opportunity for in situ manipulation of the structure and chemical reactivity of carbon nanoparticles.

Nanotexturing of PC/n-HA nanocomposites by innovative and advanced spray system

Nanoscale texturing of n-HA filler on PC matrix is ameliorated by advanced engineered spray techniques viz. spary gun and centrifuged spray dryer, modifying properties of biomedical grade screw/plate coating application.

Metallization of electrospun PAN nanofibers via electroless gold plating

An electroless gold plating process was investigated for the metallization of an electropun PAN fibre by utilizing a non-cyanide based gold complex i.e. gold thiosulfate.

Molecularly imprinted and nanoengineered camphor soot functionalized PAN-nanofibers for effluent treatment

A novel platform for the synthesis of ion-imprinted electrospun PAN–camphor soot nanofibers for the speciation and treatment of radioactive metal ions is proposed.

Cost-effective, low density, carbon soot doped resorcinol formaldehyde composite for ablative applications

Successful in situ polymerization of highly ablation-resistant composites of resorcinol formaldehyde (RF) modified with carbon soot (CS) was carried out for the first time.

A nanocellular PVDF–graphite water-repellent composite coating

We have developed a cost-effective method for the preparation of a porous superhydrophobic polyvinylidene fluoride (PVDF)/graphite composite with an induced nanocellular patterned surface.

An effective technique for removal and recovery of uranium(vi) from aqueous solution using cellulose–camphor soot nanofibers

Speciation and recovery of U(vi) ions from nuclear wastewater is a heavy challenge for various nuclear centers and research organizations.

Nanostructured microporous polymer composite imprinted with superhydrophobic camphor soot, for emphatic oil–water separation

The pollution of water devastatingly affects the marine environment by physical smothering and intoxication.