Narrow Results

Polymer nanocomposite is commonly used to develop structural components of space, aircraft, biomedical, sensor, automobile, and battery sector applications. It remarkably substitutes the heavyweight metallic and nonmetallic engineering materials. The machining principles of polymer nanocomposites are intensely different and complex from traditional metals and alloys. The nonhomogeneity, abrasive, and anisotropic nature differs its machining aspect from conventional metallic materials. This investigation aims to execute the CNC drilling of modified nanocomposite using Graphene–carbon (G-C) @ epoxy matrix. The process constraints, namely, cutting speed (S), feed (F), and wt.% of graphene oxide (GO) vary up to three levels and are designed according to the response surface methodology (RSM) array. The nonlinear model is created to predict surface roughness (Ra) and delamination (Fd) on regression analysis. It has been found that the average error for Ra is 0.94% and for Fd it is 3.27%, which is acceptable in model predictions. The metaheuristics-based evolutionary Dragonfly algorithm (DA) evaluated the optimal parametric condition. The optimal setting prediction for the DA is observed as cutting speed (S)-37.68m/min, feed (F)-80mm/min, and wt.% of graphene oxide (GO)-1%. This algorithm demonstrates a higher application potential than the previous efforts in controlling Ra and Fd values. Both the drilling response values are found to be minimized when the cutting speed increases and the feed decreases. The best fitness value for the DA is 1.626 for surface roughness and 5.086 for delamination. This study agreed with the prediction model’s outcomes and the process parameters’ optimal condition. The defects generated during the sample drilling, such as fiber pull out, uncut/burr, and fiber breakage, were examined using FE-SEM analysis. The optimal findings of the DA module significantly controlled the damages during machining.

This study investigates the mechanical, fatigue, water absorption, and flammability properties of polyethylene terephthalate (PET) core-pineapple fiber sandwich composites reinforced with silane-treated neem fruit husk (NFH) biosilica additives. The novel approach includes modifying the fiber’s surface and incorporating biosilica to enhance environmental resistance. The composites were prepared using a hand layup method, followed by silane treatment of the biosilica, pineapple fiber, PET core and vinyl ester resin. Subsequently, to evaluate environmental impacts on composite’s performance, sandwich composites were subjected to temperature aging at 40^∘C and 60^∘C in a hot oven for 30 days and warm water aging at the same temperatures in tap water with pH 7.4. According to the results, adding 1%, 3%, and 5 vol.% silane-treated biosilica significantly improved the mechanical properties. The composite with 3% biosilica (L2) showed a tensile strength of 120.8MPa, flexural strength of 194.4MPa, compression strength of 182.4MPa, rail shear strength of 20.21MPa, ILSS of 23.14MPa, hardness of 85 Shore-D, and Izod impact strength of 6.56 J. Even under temperature and water aging conditions, the composites showed only minimal reductions in properties, highlighting the efficacy of the silane treatment. The temperature-aged L2 composite had a tensile strength of 104MPa, flexural strength of 172.8 MPa, compression strength of 164MPa, and ILSS of 22.5MPa, while the water-aged L2 composite exhibited a tensile strength of 96MPa, flexural strength of 152.8MPa, compression strength of 146.4MPa, and ILSS of 21.4MPa. Scanning electron microscope (SEM) analysis confirmed uniform dispersion of biosilica particles, critical for improved performance, though higher concentrations led to agglomeration and stress points. The composites also demonstrated excellent flame retardancy, maintaining a UL-94 V-0 rating with decreased flame propagation speeds, specifically 9.05mm/min for L2. These findings underscore the potential of silane-treated biosilica as a reinforcing additive to enhance the durability and performance of composites in adverse conditions.

The monomeric and polymeric tetra-aminophthalocyane to, cobalt(II) species adsorbed onto graphite electrodes are active in electrocatalytic oxygen reduction. While the monomeric species is unstable, the polymerized species is an effective and stable reduction catalyst over a wide pH range. Both the two-electron reduction of oxygen to hydrogen peroxide and the four-electron reduction of oxygen to water are characterized by cyclic voltammetry, rotating disc and rotating ring-disc studies with appropriate theoretical analysis. Some mechanistic information is obtained. This is the first cobalt phthalocyanine species to provide a four-electron reduction pathway which exists over a wide pH range and is stable. The stability is associated with the polymerization since the monomeric species is not stable.

The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with cadmium(II) was studied spectrophotometrically and its kinetic and equilibrium constants were determined. The influence of temperature on the reaction rate was also studied. At different ratios of [CPI]/[Cd(II)] two types of complex were formed: CdII(CPI) and (CdII)₂(CPI); an investigation of the solution properties and the mechanism of aggregation of (CdII)₂(CPI) at different pH were performed. It is verified that cadmium(II) accelerates the reaction of the incorporation of manganese(II) into CPI by the substitution of cadmium(II) with manganese(II) in the CdII(CPI) complex; the kinetics and mechanism of this substitution reaction at alkaline pH were studied. A sensitive kinetic method for the determination of cadmium(II) at ppb levels has been established; the molar absorptivity and the Sandell's sensitivity (for A = 0.001) of the recommended procedure at 458 nm and 300 s after the start of the reaction are (6.175 ± 0.026) × 10⁵ 1 mol⁻¹ cm⁻¹ and (1.820 ± 0.008) × 10⁻⁴ μg cm⁻² respectively.

Monomeric and polymeric iron phthalocyanine compounds were synthesized and their dielectric properties were measured in the frequency range from 100 Hz to 10 MHz between 25 and 200 °C. The dielectric constant and dielectric loss showed strong frequency and temperature dependences. Interestingly, large dielectric constants were observed around 100 °C for both monomers and polymers. A dielectric constant as high as 5000 at 110 Hz was observed for the iron phthalocyanine polymer. The origin of the large dielectric constant in metallophthalocyanines is discussed.

Polymer-bound cobalt(II) porphyrins were studied for their dioxygen—binding capacity. Tetra—aminoporphyrins were anchored on a divinylbenzene (DVB)-crosslinked chloromethyl polystyrene network. The crosslinked, solid polymers were swelled in chloroform and the swollen polymers were used for the entire studies. Ortho-, meta- and para-substituted porphyrin systems were developed by adjusting the bonding position with the help of suitably substituted aminoporphyrins. The products were characterized by chemical and spectroscopic methods. Cobalt(II) complexes of polymeric porphyrins were synthesized and characterized by electronic and ESR spectral methods. The spectra gave evidence for the systematic variation of electronic properties in ortho, meta and para compounds and for the dioxygen-binding capacity of cobalt complexes. These results are discussed.

We have prepared three C₆₀ polymers under high-temperature and high-pressure conditions, and confirmed them to be orthorhombic (1D), tetragonal and rhombohedral (2D) polymer by XRD method, respectively. The ¹³C MAS NMR spectra of both orthorhombic and rhombohedral polymer have been measured and two resonance peaks observed. One resonance at 73 ppm resulted from the sp³ carbons with an intermolecular bonding, the other at 145 ppm is from the inequivalent sp² carbons on the C₆₀ molecule. For 1D polymer, the fine structure of the main peak at 145 ppm has been analyzed. By simulation of the ¹³C MAS NMR peak shape of the inequivalent carbons, we propose that there exist nine inequivalent carbons on a C₆₀ molecule in the orthorhombic (1D) polymer.

Dynamic Monte Carlo simulations are performed for lattice self-avoiding tail-like polymer chains with one end attached to a non-interacting and impenetrable flat surface. The configurational entropy S_TL of the tail-like chain is determined by the scanning method. The entropy S_TL is smaller than that of the free chain without surface S_F. The entropy drop ΔS=S_F-S_TL increases linearly with lnn for short chains and increases linearly with n for long chains. However, the average entropy drop per bead ΔS/n decreases with n, indicating that the average effect of the surface on one chain bead decreases with the increase in chain length.

The purpose of this study is to obtain some information about the viscoelastic properties of the material and to see the effect of the addition of plasticizer on these properties. In particular, we try to study the loss of plasticizer, caused by ageing under conditions of utilization, on the properties of material at the neighborhood of vitreous transition.

Using a viscoelastimeter, the study of a polyamide-11 (PA11) at the neighborhood of its temperature of vitreous transition Tv has shown that the increase of the plasticizer rate clearly improves the properties of the material by decreasing its Tv temperature. The comparison of the curves giving the modulus of elasticity E' of the various samples showed that the mechanical properties of the material improve with the increase of the concentration of plasticizer, but ageing reduces this improvement by causing the loss of plasticizer, thus, the temperature range of utilization of material is reduced.

The translocation of polymer chain through an interacting pore under chemical potential difference Δμ is simulated using Monte Carlo technique. Three translocation modes, dependent on the polymer–pore interaction ε and Δμ, are discovered. The translocation process is found to be an nonequilibrium process, which influences the dependence of translocation time τ on ε and Δμ. It is found that τ decreases in a power law relation with the increase of Δμ, and the exponent is dependent on the interaction.

Diffusion of polymer in narrow periodical channels, patterned alternately into part $\alpha$ and part $\beta$ with the same length $l_p/2$, was studied by using Monte Carlo simulation. The interaction between polymer and channel $\alpha$ is purely repulsive, while that between polymer and channel $\beta$ is attractive. Results show that the diffusion of polymer is remarkably affected by the periodicity of channel, and the diffusion constant $D$ changes periodically with the polymer length $N$. At the peaks of $D$, the projected length of polymer along the channel is an even multiple of $l_p/2$, and the diffusion of polymer in periodical channel is nearly the same as that of polymer in homogeneous channel. While at the valleys of $D$, the projected length of polymer is an odd multiple of $l_p/2$, and polymer is in a trapped state for a long time and it rapidly jumps to other trapped regions during the diffusion process. The physical mechanisms are discussed from the view of polymer–channel interaction energy landscape.

Materials having nanoscale structures have shown potentials for applications in microelectronics, biomedicine and energy storage. A continuing challenge is the capability of fabricating multi-function nanodevices with controlled nanostructures and excellent performances. Measurement platforms, which provide accurate and detailed information on internal structures, surface morphologies, mechanical properties and electrochemical properties are a key to this challenge. In this review, we, in particular, highlight the crucial role of measurement techniques in quantifying these nanostructures and their properties.

The measurement of patients’ dosages of radiation caused by medical diagnostics continues to be challenging. A Cantor sequence photonic crystal structure using porous silicon doped with a polymer of polyvinyl alcohol, carbol fuchsin and crystal violet (DPV) is proposed. The influence rules of geometrical and optical parameters such as the radiation doses, number of periods, porosity of porous layers, incident angle and thickness of layers are investigated using MATLAB based on the transfer matrix method. The transmittance of the Cantor sequence of a defective photonic crystal sensor under different conditions is investigated to select the optimum conditions. The proposed system recorded the accepted sensitivity of 0.265nm/Gy, FoM of 6.5Gy${}^{-1}$, Q of 12,701, RS of $6\times 10^{-3}$ and LoD of $8\times 10^{-3}$ for gamma radiation. The suggested detector has simple design, accurate monitoring efficiency and immense potential for gamma radiation sensing.

In this work, the structure, dielectric and optical properties of PVDF/zirconia-based polymer nanocomposites were investigated. The morphology and structure of the nanocomposites were analyzed by XRD, SEM, FT-IR, UV and EDS analyses. It was determined that the forbidden gap for the PVDF/1%ZrO₂-based nanocomposite is 4.7eV, for PVDF/5%ZrO₂-4.5eV, and for PVDF/10%ZrO₂-4.2eV. It is shown that the dielectric permittivity of the nanocomposites increases sharply up to 3% of ZrO₂ nanoparticles in the polymer and then decreases slightly with an increase in the concentration of nanoparticles. An increase in the permittivity indicates an increase in polarization processes in nanocomposites at a 3% conentration of ZrO₂ nanoparticles in the PVDF matrix. It has been established that the dielectric loss tangent at low frequencies starts to decrease, and at high frequencies, it increases. The increase in the dielectric loss tangent at high frequencies is explained by an increase in relaxation processes and energy dissipation in these systems.

The two-temperature description of the RNA-like molecule is invented. Instead of equilibrium treatment of the polymer state, the steady state viewpoint is proposed. The molecule is considered as being in an adiabatic steady state, which is a non-equilibrium one. The general approach to the molecule in such a steady state is discussed and the simple model with saturating bonds is considered. The relation between mean square end-to-end distance and the number of monomers is derived for the simple system under condition T>Θ. The obtained relation depends on additional so-called disorder temperature.

In this paper, a Mach–Zehnder interferometer (MZI) variable optical attenuator (VOA) based on Norland Optical Adhesive73 (NOA73) material has been designed and fabricated. At 1550 nm wavelength, the insertion loss of the VOA was measured to be about 8.1 dB. The developed VOA exhibited ultra-low power consumption of 1.96 mW and high optical attenuation of -29.3 dB. When the attenuation at 1550 nm wavelength was -24.6 dB, the spectral variation was ±2.5 dB within wavelength range of 1510 nm to 1590 nm. The rise and fall times of the device were 1.7 ms and 1.3 ms, respectively.

Formation of laterally continuous ultrathin gold films on polymer substrates is a technological challenge. In this work, the vacuum thermal evaporation method is adopted to form continuous Au films in the thickness range of 7–17 nm on polymers of Poly(methyl-methacrylate-glycidly-methacrylate) and SU-8 film surface without using the adhesion or metallic seeding layers. Absorption spectrum, scanning electron microscope and atomic force microscope images are used to characterize the Au film thickness, roughness and optical loss. The result shows that molecular-scale structure, surface energy and electronegativity have impacts on the Au film morphology on polymers. Wet chemical etching is used to fabricate 7-nm thick Au stripes embedded in polymer claddings. These long-range surface plasmon polariton waveguides demonstrate the favorable morphological configurations and cross-sectional states. Through the end-fire excitation method, propagation losses of 6-$\mu \mathrm{\text{m}}$ wide Au stripes are compared to theoretical values and analyzed from practical film status. The smooth, patternable gold films on polymer provide potential applications to plasmonic waveguides, biosensing, metamaterials and optical antennas.

Dynamical systems and defects in liquid crystals (LCs) are described using topological methods. Meanwhile, the director field distribution in LC droplets is affected by many bulk and surface factors that are difficult to take into account in the topological analysis. Therefore, the structural instability of a LC droplet formed in a magnetic field has been investigated by us in the framework of the catastrophe theory. The effect of temperature on the control parameters of the cusp catastrophe, which leads to the transition from a bipolar structure with extended poles to the homogeneous or radial configuration, has been estimated. It has been established from the potential curves that the transition is induced by the variation in the LC director orientation between the potential minima related to the LC polymer anchoring energy and magnetic field. The interplay of the cusp catastrophe control parameters and anchoring parameters has been elucidated.

In this study, we describe the synthesis, characterization and evaluation of colloidal dispersion gels (CDGs) to be used as in-situ fluid diversion. The chemical stability of CDGs was improved by modifying the polymer mixture. The CDGs were synthesized by free radical crosslinking polymerization using 2-acrylamido-2-methylpropane sulfonic acid (AMPS), Acrylic acid (AAc), partially hydrolyzed polyacrylamide (HPAM) and chromium triacetate crosslinker. The effect of crosslinker/polymer concentration, salinity, gelation time, rheological behavior, particle size distribution of CDGs, also their thermo-chemical stabilities and resistance/residual resistance factor (RRF) were investigated.

Thermal hysteresis and stability of agarose–water gelling systems were studied by the spectrophotometer for different concentrations at different temperatures. Gelation temperature depends on the concentration of agarose. With the increase in the concentration of agarose gelation temperature, strength of agarose increases too. With the increase in the concentration of polymer solvent–gel phase transition, gel melting happens at higher temperatures. The price of enthalpy was determined (150.0127 KC/mol). In gelation process, the phase separation is completed and in this process, the value of this $\mathrm{\Delta }t=t_{\mathrm{\text{melting}}}-t_{\mathrm{\text{gelation}}}$ equally increases.