Narrow Results

All-cellulose composite (ACC) is a novel single polymer composite (SPC) that consists of cellulose for both reinforcing fiber and matrix phases. ACC has good mechanical, thermal, and optical properties due to compatibility of reinforcing fiber and matrix phases. However, abundant hydroxyl (OH) groups in the cellulose structures resulted in higher hydrophilicity of ACC, thus limiting the potential use in outdoor applications. In this study, ACC was fabricated using solvent infusion processing (SIP) from rayon textile with sodium hydroxide (NaOH)/urea solution to partially dissolve the cellulose fibers, followed by regeneration and drying processes. Subsequently, ACC was treated using two different coating solutions: (i) hexadecyltrimethoxysilane (HDTMS) and (ii) HDTMS/SiO₂ (silica). As a result, an efficient water repellency for HDTMS/SiO₂-treated ACC was observed, showing a water contact angle of 159.3^∘, as compared to HDTMS-treated ACC with a water contact angle of 144.1^∘. However, a slightly higher water absorption of 52% was observed for HDTMS/SiO₂-treated ACC, as compared to only 44% for HDTMS-treated ACC. Both treated ACCs showed smooth and homogeneous structures upon completion of the treatment.

Silica of different surface area and grain size modified by aminopropyl groups reacted with 4-(3,4-dicyanophenoxy)benzoic acid chloride. The reaction of these benzamidophenoxydicarbonitrile modified silica gels with 4-(4-tert-butyl-phenoxy)-1,2-benzenedicarbonitrile in the presence of a zinc(II) salt results in covalently bonded phthalocyanine zinc(II) complexes with a loading between 1.8 × 10⁻⁵ and 1.7 × 10⁻⁶mol g⁻¹ silica. UV/vis reflectance spectra show that the phthalocyanines on the surface exist in a monomeric state. Cleavage at the amide bond between the silica and the phthalocyanine led to the corresponding monocarboxylic acid phthalocyanine derivative.

A detection approach based on the principles of Fourier Transform Infrared Spectroscopy (FTIR) is presented for the trace level detection of toxic compounds in water. The main advantages of this approach are that it operates in heterogeneous aqueous environments, provides fast detection (< 10 min), and exhibits high sensitivity/selectivity to nonvolatile toxic materials with minimal false alarms. The key enablers to using FTIR for aqueous-based detection is the development of a selective and robust sampling protocol coupled to a miniaturized portable FTIR unit. The sampling approaches involve synthesizing and tailoring microporous, mesoporous, and nonporous metal oxide powders/films that are amenable for in situ FTIR measurements. In this paper we provide an overview of the material synthesis and surface modification strategies, and present results obtained using these materials for the low level detection of the organophosphate pesticide phosmet. Phosmet is used as a surrogate for the nerve agent VX.

In order to study the protection behavior of brittle materials against a shaped charge jet, the jet penetration and the fracture behavior have been investigated by the series of photographs taken by the IMACON high speed camera. The examined materials were glass, fused silica, and single crystalline quartz. The trend of crack growth in BK7 glass and fused silica indicated conical shape. In the case of the single crystalline quartz, it was observed that the crack grows fast along the axis of crystal growth. The velocity of shock wave (~ 6km/sec) into glass and fused silica was faster than the sonic velocity. However, the velocity of shock wave in the single crystalline quartz showed to be similar to its sonic velocity. The ballistic protection capability of single crystalline quartz showing fast crack growth has been evaluated to be lower than that of fused silica which has relatively slow crack growth, although the quartz has higher physical and mechanical properties.

Molecular dynamics simulation is carried out for liquid SiO₂ at pressure ranged from zero to 30 GPa and by using BKS, Born–Mayer type and Morse–Stretch potentials. The constructed models reproduce well the experimental data in terms of mean coordination number, bond angle and pair radial distribution function. Furthermore, the density of all samples can be expressed by a linear function of fractions SiO_x. It is found that the topology of units SiO_x and linkages OSi_y is unchanged upon compression although the liquid undergoes substantial change in its network structure. Consequently, the partial bond angle distribution for SiO_x and OSi_y is identical for all samples constructed by the same potential. This result allows to establishing a simple expression between total bond angle distribution (BAD) and fraction of SiO_x and OSi_y. The simulation shows a good agreement between the calculation and simulation results for both total O–Si–O and Si–O–Si BADs. This supports a technique to estimate amount of units SiO_x and linkages OSi_y on base of total Si–O–Si and O–Si–O BADs measured experimentally.

In the present work, we report the blue phase (BP) in a binary mixture of cholesteryl nonanoate (CN) and N-(4-ethoxybenzylidene)-4-butylaniline (EBBA). The mixture exhibits BP over a temperature range of 2.3 K at optimum composition (50:50) of liquid crystals (LCs). The effect of silica nanoparticles (SNPs) doping on thermal stability of BPs has also been demonstrated and nearly 6 K wide BP temperature range was achieved at 0.5 wt.% of SNPs. A porous type texture was also observed during the BP formation process in the doped samples.

The novel mixed-matrix membrane (MMMs) by incorporating covalently amino groups grafted nano-silica (Amino-NP) into an eco-friendly, organic solvent-free waterborne polyurethane (OSF-WPU) matrix for the separation application of CO₂/N₂. This investigation focused on the gas permeance and separation performance of the MMMs. The optimized CO₂/N₂ separation factor reached $8.21\pm 0.47$, with a CO₂ permeance of $16.72\pm 1.02$ GPU under conditions of 1.0 bar and 25^∘C in a wet mixed-gas state. Incorporating even a tiny amount of Amino-NP efficiently enhanced CO₂ permeability and CO₂/N₂ selectivity. OSF-WPU/Amino-NP MMMs demonstrated superior performance, emphasize their potential for stable long-term operation in practical CO₂ separation applications.

Nucleation, growth, and thermal stability of Pd particles vapor-deposited on an ultra-thin crystalline silica film grown on Mo(112) have been studied by scanning tunneling microscopy, X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and temperature-programmed desorption of CO. No preferential nucleation of Pd on the silica film is found at room temperature deposition: the hemispherical Pd nanoparticles are homogenously dispersed on the support at all coverages studied (0.01 - 1 ML (mono layer)). The Pd particles are resistant toward sintering up to 700 K as judged by STM; however, CO adsorption studies have revealed surface chemical modification at temperatures as low as 550 K. Strong morphological changes are observed above 800 K (ultimately resulting in elongated rectangular islands at ~1000 K), which is accompanied by strong alterations of CO adsorption properties. The results are rationalized in terms of Pd and Mo substrate interdiffusion at elevated temperatures, while the silica film basically preserves its structure.

Enhancing the operation life time or the electrochemical durability is one of the key issues in electrochromic material studies. It is generally accepted that the inorganic–organic hybrid structure is one of the effective ways to enhance the chemical stability of the material. In this study, an electrochromic film made of silica-polyaniline core-shell composite nanoparticles was tested. The composite particles were prepared through a chemical dispersion polymerization of aniline in an aqueous colloidal solution of silica. The synthesized particles were then dispersed into ethanol and the solution was deposited onto an Indium Tin Oxide (ITO)-coated glass substrate. The electrochromic characterization on the prepared films was performed using the cyclovoltammetry and the optical response to a switching potential. The results showed that the inorganic–organic core-shell hybrid nanoparticle could be a promising choice for the enhancement of electrochromic durability.

Superhydrophobic cotton fabrics are prepared using silica and titania hybrid sol and hexadecyltrimethoxysilane. The surface morphology of cotton fabrics is characterized by scanning electron microscopy. The water contact angles on the as-prepared superhydrophobic cotton fabrics is 159° when the volume ratio between sodium silicate solution and titania sol is 1:3, and the corresponding cotton fabrics can keep the contact angle of 152° after 10 cycles of home machine washing. Meanwhile the treated cotton fabrics can also keep superhydrophobicity after 60 min of UV light irradiation. These results indicate that the cotton fabrics treated with silica and titania hybrid sol and modified with hexadecyltrimethoxysilane show excellent superhydrophobic stability under washing and UV light irradiation. This paper provides the new notion and beneficial reference for the application of the superhydrophobic cotton fabrics in the future.

Aluminum and its alloy are versatile metal materials engaged in various applications based on their high strength, corrosion resistance and light weight. However, there are many limitations to its applications when compared with steel. In a bid to improve on the properties, aluminum composites are developed. In this study, Al 6111 composite was developed by the blend of silica and bamboo leaf ash (BLA) as reinforcement employing stir casting process. The input factors for the experiment were silica dosage (A), BLA proportion (B) and stirring temperature (C). The experimental design was carried out via Box Behnken design of the response surface methodology. Composites were fabricated through stir casting process by varying the inputs according to the dictations of the experimental runs. Parameters evaluated are yield strength, ultimate tensile strength, elastic modulus and elongation. Result of the ANOVA analysis showed that the parameters had consequential effect on the response and the developed model for each parameter are fit for predictions. From the surface plot, interaction between 5wt.% and 10wt.% silica and 2wt.% and 4wt.% BLA led to improvement in yield, ultimate tensile strength but decrease in elongation even as proportions 10wt.% and 15wt.% silica and 4wt.% and 6wt.% BLA ensued reduction in the value. Stirring temperature of 700–800^∘C is favorable to the strength parameters while 800–900^∘C led to strength reduction. Optimization via response surface, predicted optimum conditions of 11.6249wt.%, 3.95707wt.% and 789.033^∘C for A, B and C, respectively. Predicted values for yield strength, ultimate tensile strength, elastic modulus and elongation are 278.26MPa, 378.24MPa, 97.7885GPa and 10.132%, respectively. Validation experiment was carried out at the optimum condition and the deviation in parameters between the predicted and validated values is $<5\%$. Hence, the models are statistically fit for property predictions.

In this article, we describe synthesis of a novel drug delivery vector (DDV) for photodynamic therapy (PDT). The DDV consists of a magnetite core surrounded by a thin layer of functionalized silica. These core–shell structures are loaded with a photosensitizer (PS) drug "Methylene Blue" (MB). Magnetite nanostructures are produce by the well-established chemical co-precipitation technique and encapsulated in silica shell by modified process of hydrolysis and condensation of tetraethyl orthosilicate (TEOS). MB is grafted into the pores of silica shell by demethylation reaction. Reaction kinetics has been established for tunable loading of PS in DDV. Physical and chemical properties of composite nanostructures are determined by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometry (VSM). Amount of PS loading in DDV is measured by UV-Visible spectroscopy. Smaller size, biocompatibility, tunable loading of PS and capabilities of magnetic guidance, makes this DDV, a potential candidate for the treatment of malignant tumors by PDT.

Hierarchically structured micrometric mesoporous silica spheres have been synthesized by evaporation driven self assembly of silica colloids under slow drying condition. The inter particle correlation inside grains has been investigated by small-angle neutron scattering. In a slow drying regime, droplets shrink isotropically leading to spherical dried grains. However, the packing of nanoparticles depends on the initial colloidal concentration. The packing of the nanoparticles for low colloidal concentration is uniform throughout the grain but at higher concentration of the colloids, dried grains possess nonuniform radial packing of the nano-particles. The average packing fraction of the nanoparticles decreases with increasing colloidal concentration due to modification in viscosity of the colloidal dispersion prior to drying.

In this paper, magnetic mesoporous silica nanoparticles (Fe₃O₄–nSiO₂–mSiO₂) were synthesized using trimethylbenzene (TMB) as a swelling agent. These composite nanoparticles have a typical sandwich structure with a magnetic core, a nonporous silica middle layer and an ordered mesoporous silica outer shell. The experimental results indicate that the magnetic mesoporous silica nanoparticles have high specific surface area (510 m²/g), large pore size (3.8 nm) and pore volume (1.04 cm³/g). The thickness and pore structure of the out shell can also be easily tailored by adjusting the reaction conditions. The obtained nanomaterials were characterized by X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption measurements.

The present work deals with the synthesis of bi-continuous macro and mesoporous crack-free titania–silica monoliths, with well-defined structural dimensions and high surface area. The work also highlights their potential photocatalytic environmental applications. The highly ordered titania–silica monoliths are synthesized through direct surface template method using organic precursors of silica and titania in the presence of surface directing agents such as pluronic P123 and PEG, under acetic acid medium. The monoliths are synthesized with different Ti/Si ratios to obtain monolithic designs that exhibit better photocatalytic activity for dye degradation. The titania–silica monoliths are characterized using XRD, SEM, EDAX, FT-IR, TG–DTA and BET analysis. The photocatalytic activity of the synthesized monoliths is tested on the photodegradation of a textile dye (acid blue 113). It is observed that the monolith with 7:3 ratio of Ti/Si showed significant photocatalysis behavior in the presence of UV light. The influence of various physico-chemical properties such as, solution pH, photocatalyst dosage, light intensity, dye concentration, effect of oxidants, etc. are analyzed and optimized using a customized photoreactor set-up. Under optimized conditions, the monoliths exhibited superior degradation kinetics, with the dye dissipation complete within 10min of photolysis. The mesoporous catalysts are recoverable and reusable up to four cycles of repeated usage.

Mesoporous silica monoliths are an attractive area of research owing to their high specific surface area, uniform channels and mesoporous size (2–30nm). This paper deals with the direct templating synthesis of a mesoporous worm-like silica monolithic material using F127 — a triblock copolymer, by micro-emulsion technique using trimethyl benzene (TMB), as the solvent. The synthesized silica monolith is characterized using SEM-EDAX, XRD, BET, NMR and FT-IR. The monolith shows an ordered worm-like mesoporous structure with tuneable through pores, an excellent host for the anchoring of chromo-ionophores for the naked-eye metal ion-sensing. The mesoporous monoliths were loaded with 4-dodecyl-6-(2-pyridylazo)-phenol (DPAP) ligand through direct immobilization, thereby acting as solid-state naked-eye colorimetric ion-sensors for the sensing toxic Pb${}^{\mathrm{\text{(II)}}}$ ions at parts-per-billion (ppb) level in various industrial and environmental systems. The influence of various experimental parameters such as solution pH, limiting ligand loading concentration, amount of monolith material, matrix tolerance level, limit of detection and quantification has been studied and optimized.

This study aims to analyze the spectral properties of plasma produced from rice husk(Rh) using the laser breakdown spectroscopy (LIBS) method. The plasma generation process used the fundamental harmonic (1064 nm) of a Q-switched Nd:YAG laser. Yttrium aluminum garnet (YAG) is a man-made crystalline material. The laser fired pulses with a duration of 10 ns and a repetition rate of 6 Hz. Thus, the energy outputs achieved were 50–200 mJ at the wavelength of 1064 (nm). The silica content in the rice hulls was verified using an XRF measurement, which revealed the presence of silica in the rice hulls in a high percentage. Precise beam focusing was achieved by focusing the laser on the target material. This target material is placed within an atmospheric environment at standard pressure settings. The electron temperature was derived using the Boltzmann diagram method by harnessing experimental data for the linear properties associated with the neutral lines (Si II), (O II), and ion lines (Si I). The use of analytical methodology led to the determination of electron temperature values from 0.79 eV to 1.16 eV for the fundamental harmonic of the laser. At the same time, the electron (ne) density was determined by analyzing the Stark broadening profile associated with the neutral silica line. Furthermore, the study included an additional dimension by determining the plasma properties (electron temperature and electron density) by adjusting the laser energy on the target surface longitudinally along the path of the plasma plume.

Ab initio molecular dynamics simulations of SiO₂ in supercritical water at temperatures of 900 K and 1200 K and a pressure of 1.5 GPa at concentrations of 5 wt% and 16 wt% have been carried out. The different polymeric forms SiO₄H₄, Si₂O₇H₆, and Si₃O₁₀H₈ are found to be energetically similar within the statistical error, suggesting that all three polymeric forms play an important role in solutions at the above conditions. However, neither spontaneous polymerization nor depolymerization has been observed during the 10-ps time span of the simulations. The dynamic and structural properties of the supercritical solutions have been analyzed in terms of diffusion coefficients, vibrational spectra, and radial pair distribution functions.

Experimental study and quantum chemical calculations have been used to study the adsorption of Cu²⁺ and Mg²⁺ on silica gel derived from rice hulls ash. XRD measurements showed that the silica obtained has amorphous structure with BET of 250.1m²/g and pzc at pH 2. Adsorption of Cu²⁺ and Mg²⁺ on silica at 28^∘C showed maximum capacities of 0.26 and 0.20mmol/g, respectively. In both cases of metal ions, the interaction was explained to proceed via hydrogen bonding through the outer hydration shell. Using density functional theory (DFT), interactions of hydrated metal ions with naked, mono- and di-hydrated silanol have been investigated. Calculations at the used level predict an increase of the entropy upon adsorption interaction with dehydrated silanol. Adsorption of hydrated Cu²⁺ and hydrated/un-hydrated Mg²⁺ on silanol is an exothermic process as predicted by B3LYP/6-31+G(d)//HF/6-31+G(d). This, in turn, leads to more negative free energy of reaction compared to experiment, $-$59.8 versus $-$25.8kJ/mol for Cu²⁺ and $-$53.8 versus $-$22.6kJ/mol for Mg²⁺. However, the strength of interaction between silica and both ions was reproduced correctly by theory.

Nowadays, hybridization of different algorithms for the optimization of non-conventional machining processes tries to accomplish better results. The paper consists of experimental evolutionary-particle Swarm Optimization (PSO), Quantum-PSO and Gaussian Quantum Particle Swarm Optimization (G-QPSO)-based ANN modeling and comparative investigation on performances such as material removal rate (MRR), machining depth (MD), roughness of surface and overcut (OC) for machining of silica by ECDM process using mixed electrolyte. The paper also shows the co-efficient of NN models for different machining criteria and G-QPSO and also the comparative study of MD, roughness (SR), overcut (OC) as well as MRR using different algorithms and convergence test for fitness of experimental results also propounded to achieve cross-validation of models and multi-response optimal results for micro-machining of Silica by ECDM using PSO, QPSO and GQPSO. It is found that Gaussian Quantum Particle Swarm Optimization (G-QPSO)-ANN is more efficient for ECDM and achieves optimal results at 55-volt, pulse on time 52.3 s, inter-electrode gap (IEG) 30 mm, duty ratio 0.475 and electrolytic concentration 30 (wt.%).