Silica Core Research Articles

Designer Core-Shell Nanoparticles as Polymer Foam Cell Nucleating Agents: The Impact of Molecularly Engineered Interfaces.

The interface between nucleating agents and polymers plays a pivotal role in heterogeneous cell nucleation in polymer foaming. We describe how interfacial engineering of nucleating particles by polymer shells impacts cell nucleation efficiency in CO2 blown polymer foams. Core–shell nanoparticles (NPs) with a 80 nm silica core and various polymer shells including polystyrene (PS), poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA), and poly(acrylonitrile) (PAN) are prepared and used as heterogeneous nucleation agents to obtain CO2 blown PMMA and PS micro- and nanocellular foams. Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy are employed to confirm the successful synthesis of core–shell NPs. The cell size and cell density are determined by scanning electron microscopy. Silica NPs grafted with a thin PDMS shell layer exhibit the highest nucleation efficiency values, followed by PAN. The nucleation efficiency of PS- and PMMA-grafted NPs are comparable with the untreated particles and are significantly lower when compared to PDMS and PAN shells. Molecular dynamics simulations (MDS) are employed to better understand CO2 absorption and nucleation, in particular to study the impact of interfacial properties and CO2-philicity. The MDS results show that the incompatibility between particle shell layers and the polymer matrix results in immiscibility at the interface area, which leads to a local accumulation of CO2 at the interfaces. Elevated CO2 concentrations at the interfaces combined with the high interfacial tension (caused by the immiscibility) induce an energetically favorable cell nucleation process. These findings emphasize the importance of interfacial effects on cell nucleation and provide guidance for designing new, highly efficient nucleation agents in nanocellular polymer foaming.

Thermal enthalpy regulation of methyl hexadecanoate/silica microcapsules with CTAB as emulsifier maintaining fixed core/shell ratio

The fabrication and thermal enthalpy regulation of phase change materials (PCMs) microcapsules have been researched. Methyl hexadecanoate (MH) melting at about 29 °C was used as PCMs core and encapsulated in silica shell microcapsules by sol–gel method. Based on a fixed core/shell ratio, a series of MH/silica PCMs microcapsules were prepared, and cetyl trimethyl ammonium bromide (CTAB) was used as emulsifier. The morphologies of PCMs microcapsules were studied by scanning electron microscopy. The Fourier transform infrared spectroscopy results exhibited that there was only physical interaction between silica and MH core shell. The heat storage capability and good thermostability of PCMs microcapsules were characterized by differential scanning calorimetry and thermogravimetric analysis. The heating cyclic tests showed that MH in the microcapsules had an outstanding long-term performance. From the results, it was found that the decrease in CTAB content (from 0.60 to 0.03 g) promoted effectively the melting enthalpy of PCMs microcapsules from 18.08 to 71.45 J g−1 with the same core/shell ratio. It provides a promising candidate for the preparation of PCMs microcapsules with adjustable enthalpy and popular price.

Nanostructured active and photosensitive silica glass for fiber lasers with built-in Bragg gratings.

A nanostructured core silica fiber with active and photosensitive areas implemented within the fiber core is demonstrated. The photosensitivity, active and passive properties of the fiber can be independently shaped with this new approach. We show that discrete local doping with active ions in form of nanorods allow to obtain effective laser action as in case of continuous distribution of the ions in the core. Co-existing discrete photosensitive nanostructure of germanium doped silica determine single-mode performance and allow inscription of highly efficient Bragg grating over the entire core area. Each nanostructure do not degrade performance of other one since physical interaction between active and photosensitive areas are removed. As a proof of concept, we have designed and fabricated the nanostructured, ytterbium single-mode silica fiber laser with the Bragg grating inscribed in the entire core area. We demonstrated fiber laser with good quality of generated laser beam (M2=1.1) with lasing efficiency of 44% and inscribed Bragg grating with 98.5% efficiency and -18 dB contrast.

Combinatorial delivery of doxorubicin and acridine orange by gold core silica shell nanospheres functionalized with poly(ethylene glycol) and 4-methoxybenzamide for cancer targeted therapy

Combinatorial therapies based on the simultaneous administration of multiple drugs can lead to synergistic effects, increasing the efficacy of the cancer therapy. However, it is crucial to develop new delivery systems that can increase the drugs' therapeutic selectivity and efficacy. Gold core silica shell (AuMSS) nanoparticles present physicochemical properties that allow their simultaneous application as drug delivery and imaging agents. Herein, poly(ethylene glycol) was modified with 4-methoxybenzamide and 3-(triethoxysilyl)propyl isocyanate (TPANIS) to create a novel surface functionalization capable of improving the colloidal stability and specificity of AuMSS nanospheres towards cancer cells. Moreover, a dual drug combination based on Doxorubicin (DOX) and Acridine orange (AO) was characterized and administered using the AuMSS-TPANIS nanospheres. The obtained results show that the DOX:AO drug combination can mediate a synergistic therapeutic effect in both HeLa and MCF-7 cells, particularly at the 2:1, 1:1, and 1:2 ratios. Additionally, the TPANIS functionalization increased the AuMSS nanospheres colloidal stability and selectivity towards MCF-7 cancer cells (overexpressing sigma receptors). Such also resulted in an enhanced cytotoxic effect against MCF-7 cells when administering the DOX:AO drug combination with the AuMSS-TPANIS nanospheres. Overall, the obtained results confirm the therapeutic potential of the DOX:AO drug combination as well as the targeting capacity of AuMSS-TPANIS, supporting its application in the cancer-targeted combinatorial chemotherapy.

Modulation instability induced supercontinuum generation in liquid core suspended photonic crystal fiber with cubic-quintic nonlinearities

In this paper, we propose a liquid core suspended photonic crystal fiber (LCSPCF) as a potential waveguide structure for nonlinear applications. We emphasize the dramatic improvement of the nonlinear properties of the PCF through the infiltration of liquid and highlight the effect of suspension in the further enhancement of nonlinearity. To demonstrate the capability of LCSPCF, we perform a modulation instability (MI) study and illustrate the MI enhancement in the LCSPCF against conventional PCF. We observe that the quintic nonlinearity (QN) increases the MI for cooperating nonlinearities while it suppresses the MI for competing nonlinearities. We have also importantly studied the effect of QN on the MI induced supercontinuum generation (SCG) for silica and CS2 liquid core PCF. Thus, we propose the LCSPCF as a platform for nonlinear applications such as SCG, pulse compression, etc., owing to the presence of high and controllable nonlinear coefficients.

Molecular dynamics study of dispersion and fluidity of porous liquids with different pore sizes

Type I porous liquids (PLs) have been fabricated by cores, coronas and canopies, which combines both the advantages of porous solids and liquids. Therefore, porous liquids have broad application prospects in many areas such as gas sorption and separation, homogeneous catalysis and so on. Using molecular dynamics simulations, we studied the dispersion and fluidity of porous liquids with different pore sizes. It was found that silica cores maintained good dispersion by canopies, which was mainly due to their steric effect. Another factor that affected the stability of porous liquids was the occupancy of pores. Results indicated that pores with large pore size were easy to be blocked by canopies, which make porous liquids “non-porous”. In addition, porous liquids with larger pore size tended to have worse fluidity. It was mainly due to the strong interaction between canopies and pore channels.

Nanoscale zero-valent iron/cobalt@mesoporous hydrated silica core–shell particles as a highly active heterogeneous Fenton catalyst for the degradation of tetrabromobisphenol A

Degradation of TBBPA by NZVI/NZVC@mHS CSP/H 2 O 2 heterogeneous Fenton system. • Synthesis of NZVI/NZVC@mHS CSP materials by one-pot method. • The core–shell structure of the material reduced aggregation and increased the specific surface area. • The mesoporous network structure effectively prevented the leaching of Co (II). • NZVI/NZVC@mHS CSP efficiently degraded TBBPA as Fenton-like catalyst. While the bimetal heterogeneous Fenton system degraded organic pollutants, the leaching of heavy metals caused secondary pollution. To resolve this problem, nanoscale zero-valent iron/cobalt@mesoporous hydrated silica core–shell particles (NZVI/NZVC@mHS CSP) were synthesized as a novel Fenton-like catalyst for the rapid degradation of Tetrabromobisphenol A (TBBPA). The performance of NZVI/NZVC@mHS CSP in the degradation of TBBPA and the mechanism of their action were investigated through scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. NZVI/NZVC@mHS CSP exhibited a regular spherical shape with a surface area (115.44 m 2 ·g −1 ) that was 5 times more than that of the ordinary NZVI/NZVC (23.59 m 2 ·g −1 ). The core of NZVI/NZVC was covered with a hydrated silica shell that formed a mesoporous network that effectively prevented the leaching of cobalt ions from the core. The best catalytic performance of NZVI/NZVC@mHS CSP was obtained by optimizing the iron-to-cobalt ratio, H 2 O 2 concentration, and the dosage of the catalyst. The optimized NZVI/NZVC@mHS CSP exhibited the greatest mineralization activity (97.13%) for TBBPA removal than those in NZVI/NZVC bimetal (84.49%) and pure NZVI/NZVC@mHS CSP (59.37%). Thus, our results demonstrated that NZVI/NZVC@mHS CSP exhibited excellent reactivity in potential application as a highly active heterogeneous Fenton catalyst for degradation of TBBPA in soil and groundwater.

Asymmetric Colloidal Particles Fabricated by Polymerization-Induced Surface Self-Assembly Approach

In the past decades, the synthesis of asymmetric colloidal particles has been of wide concern in material science because of their anisotropic morphologies and unique properties. However, the synthesis of the asymmetric particles with controllable anisotropy still remains a big challenge because of the lack of effective methods. In this research, polymerization-induced surface self-assembly (PISSA) approach was demonstrated to be an effective method in the synthesis of colloidal particles with tunable asymmetric core–shell structures. Reversible addition–fragmentation chain transfer agents were covalently anchored onto the surfaces of silica particles and coupled onto the ends of methoxy polyethylene glycol (PEG) chains, leading to the synthesis of CTA-modified silica particles (SiO2-CTA) and PEG macro-CTA agents (PEG-CTA), respectively. PISSA process was conducted by using SiO2-CTA and PEG-CTA as co-RAFT agents in RAFT dispersion polymerization of styrene. In the RAFT polymerizations, polymer layers with PS nodules were formed on the surfaces of SiO2 particles. It was demonstrated that the formation of the nodules was related to the production of the PS homopolymer in the PISSA process. In order to control the asymmetric surface structures, RAFT dispersion polymerizations of styrene with added “free” RAFT agents were performed, and it turned out that the eccentrically positioned core–shell structures with silica cores and polymer layers were prepared. The colloidal particles experience morphology changes from surface nodules to snowman-like structures and finally to asymmetric spherical structures, depending on the monomer conversion and the feeding ratio of the co-RAFT agents. Kinetics studies were performed to investigate the mechanism of the formation of the asymmetric particles. After etching the silica cores with HF solution, asymmetric hollow capsules were fabricated.

Investigating the metal-enhanced fluorescence on fluorescein by silica core-shell gold nanoparticles using time-resolved fluorescence spectroscopy

Fluorescein silica core–shell nanoparticles, gold@silica@fluorescein were synthesized to study the effects of metal-enhanced fluorescence (MEF) on fluorescein in neutral and basic ethanol solutions. The interaction between gold nanoparticles and fluorescein with silica shells of different thicknesses as spacers was investigated by time-resolved fluorescence spectroscopy. Only the emission spectra of fluorescein overlapped with the surface plasmon resonance of gold nanoparticles, which is regarded as an example for the study of the emission-enhancement of MEF. The fluorescence spectra of GNP@silica@FiTC were red-shifted from those of silica@FiTC and FiTC in solution. And, the emission curves had biexponential decay, indicating multiple pathways for relaxation of the excited fluorophore. The values of fluorescence enhancement factor (EF) were slightly greater in neutral ethanol solution than in basic solution. The lowest silica shell thickness synthesized, ≈12 nm, had the largest fluorescence EF ≈ 2; this enhancement decreased as the shell thickness increased. At thickness 12 nm, the lifetime of the short component in the emission decay was 60–70 ps and its amplitude close to 90%. Based on the obtained lifetimes, ratios of component amplitudes, and proposed kinetic model, the rate constants for the process of the energy transfer between fluorophores and gold nanoparticles were attained. These rate constants for energy transfer displayed a dependence on the thickness of the silica shell, d-n, where n = 1.3–2.6.

Preparation and characterization of hollow carbon sphere supported catalysts (M@HCS [M=Pt, Ir, Ni]) for HI decomposition in the iodine–sulfur cycle for hydrogen production

Catalysts for HI decomposition are important in hydrogen production via the iodine–sulfur cycle. The catalysts should have a good activity, excellent thermal stability at 400 °C-500 °C, and corrosion resistance to HI and iodine. In this study, a series of hollow carbon sphere (HCS) supported mono-metallic catalysts M@HCS (M = Pt, Ir, Ni) were fabricated by coating the silica core with dopamine, carbonization, and sacrificial core technique. Active carbon-supported monometallic catalysts (M/C) were also prepared via the impregnation method. Catalytic activities of M@HCS and M/C during HI decomposition at 500 °C were compared. The composition, structure, specific surface area, morphology, and surface chemical states of M@HCS and M/C were characterized via inductively coupled plasma (ICP), X-ray diffraction (XRD), Brunauere-Emmette-Teller (BET) surface area, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Results showed that the catalytic performance of M@HCS was better than that of M/C probably because of the synergistic effects between the active metals and HCSs.

Scale sensor: Rapid monitoring of scale deposition and inhibition using fiber optics in a geothermal system and comparison with other monitoring devices

A scale sensor was a newly developed using fiber optics to evaluate scale deposition that occurs at hot spring waters and geothermal brines. This proposed sensor is also capable of assessing the effect of various scale suppression methods. The sensor is fabricated by removing the cladding of a multimode fiber to expose the silica core which then detects the scale deposition from the changes in the refractive index. The effectiveness of the proposed sensor was validated using the carbonated water samples at Matsushiro Hot Spring in Nagano Prefecture and brines from three geothermal power stations in Japan. A comparative performance evaluation between the proposed scale sensor and other monitoring devices were investigated at the same locations. The result of the analysis clearly indicates that the silica deposition and depression effects for geothermal brines under standard atmospheric conditions is rapid, ranging from several hours to half a day by the scale sensor. From the results obtained at the Sumikawa geothermal power station, it was found that the silica scale deposition can be sufficiently evaluated by a scale sensor even at high temperatures and pressure.

Highly sensitive temperature sensor based on multimode‐interference fiber structure with gel cladding

AbstractWe present a temperature‐sensitive, single‐mode–multimode–single‐mode (SMS) fiber structure with an index‐matching gel as a cladding material in a multimode segment. A silica core with the surrounding gel is supported straight by a thin glass tube to produce a bandpass transmission response. The passband wavelength shifts by 96 nm from 1624.5 to 1528.5 nm as the temperature increased from 40 to 200°C. The maximum sensitivity obtained is 2 nm/°C in the temperature range 40–70°C, whereas the minimum sensitivity is 0.13 nm/°C in the temperature range 125–200°C. The SMS fiber structure, including the gel cladding, allows high operating temperatures and high thermal sensitivities.

Molecular Imaging of Infarcted Heart by Biofunctionalized Gold Nanoshells.

The unique combination of physical and optical properties of silica (core)/gold (shell) nanoparticles (gold nanoshells) makes them especially suitable for biomedicine. Gold nanoshells are used from high-resolution in vivo imaging to in vivo photothermal tumor treatment. Furthermore, their large scattering cross-section in the second biological window (1000-1700 nm) makes them also especially adequate for molecular optical coherence tomography (OCT). In this work, it is demonstrated that, after suitable functionalization, gold nanoshells in combination with clinical OCT systems are capable of imaging damage in the myocardium following an infarct. Since both inflammation and apoptosis are two of the main mechanisms underlying myocardial damage after ischemia, such damage imaging is achieved by endowing gold nanoshells with selective affinity for the inflammatory marker intercellular adhesion molecule 1 (ICAM-1), and the apoptotic marker phosphatidylserine. The results here presented constitute a first step toward a fast, safe, and accurate diagnosis of damaged tissue within infarcted hearts at the molecular level by means of the highly sensitive OCT interferometric technique.

Zinc-doped silica/polyaniline core/shell nanoparticles towards corrosion protection epoxy nanocomposite coatings

Commercial paints and coatings can serve as a protective barrier for metallic substrates in a corrosive environment. A considerable variety of nanostructures can be embedded in a polymeric coating to achieve both barrier and active protection. This research aims to elucidate the role of polyaniline (PANI) as an active polyelectrolyte modifier for the surface modification of mesoporous silica nanoparticles (MSNs) doped with zinc cations (Zn2+). To characterize the samples, we employed different techniques, including field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), inductively coupled plasma optical emission spectroscopy (ICP-OES), rheometric mechanical spectroscopy (RMS), differential scanning calorimetry (DSC), tensile, and electrochemical impedance spectroscopy (EIS). Characterization of PANI-MSNs proved the formation of PANI shells onto the surface of silica cores, and pH triggered the release of Zn2+ at the alkaline condition. Enhancement in rheological, thermal, and mechanical characteristics revealed good dispersion and chemical interaction between PANI coated nanoparticles and the epoxy matrix. Moreover, epoxy nanocomposite coatings illustrated a dual barrier/active protection after 50 days of salt immersion.

Independent and mixed transmission of 166.5 Gb/s PM‐8QAM and 222 Gb/s PM‐16QAM Nyquist‐wavelength division multiplexed superchannel for long‐haul metro network

SummaryThis paper investigates the Nyquist‐wavelength division multiplexed (Nyquist‐WDM) terabit superchannel by employing independent and mixed line rate (MLR) transmission of different polarization‐multiplexed quadrature amplitude modulation (PM‐QAM) subcarriers. Here, terabit superchannel transmission including forward error correction overhead is successfully achieved by employing either 7 × 166.5 Gb/s PM‐8QAM or 5 × 222 Gb/s PM‐16QAM or both 2 × 166.5 Gb/s PM‐8QAM and 3 × 222 Gb/s PM‐16QAM simultaneous transmission. Considering linear filtering penalties and nonlinear propagation effects, the proposed superchannel is transmitted over standard single‐mode fiber (SSMF) and pure silica core fiber (PSCF) along with erbium‐doped fiber amplifier (EDFA) at 19.8‐ and 15.12‐dB span loss for SSMF and PSCF, respectively. The performance of both terabit superchannels is analyzed in terms of maximum reach, good spectral efficiency, highest transmission capacity, and optimum launch power with variation in channel spacing from 50‐GHz fixed ITU‐T grid to 29 GHz, at an acceptable bit error rate (BER). To achieve BER 4 × 10−3, MLR‐based 166.5 Gb/s PM‐8QAM and 222 Gb/s PM‐16QAM suffer a penalty of 5.5‐ and 9.2‐dB OSNR over Nyquist‐only 7 × 166.5 Gb/s PM‐8QAM and 5 × 222 Gb/s PM‐16QAM transmission at the advent of a flexible multi‐flow transponder. It is observed that at 33.33‐GHz Nyquist spacing over PSCF, 5 × 222 Gb/s PM‐16QAM and 7 × 166.5 Gb/s PM‐8QAM superchannels deliver a reach up to 1800 and 2970 km, while MLR approach results in extreme reach of 2250 and 3600 km over PSCF as per MLR PM‐16QAM and PM‐8QAM subcarriers, respectively. Hence, an appreciable spectral efficiency–distance product (SEDP) is achieved due to PSCF at Nyquist spacing of 33.33 GHz with 5.25 bit/s/Hz spectral efficiency. A good link power budget is also calculated for the proposed MLR‐based Nyquist‐WDM superchannel. MLR‐based PM‐16QAM and PM‐8QAM subcarriers deliver excellent SEDP of 11,812 and 18,900 bit/s/Hz·km, respectively, which is, to the best of author's knowledge, better on comparing with the other existing literature for single‐core channel explorations.

Fabrication of Core‐Shell Nanocolloids with Various Core Sizes to Promote Light Capture for Green Fuels

Core-shell nanocolloids with tailored physical and chemical merits hold attractive potential for energy-related applications. Herein, core-shell nanocolloids composed of zinc/copper sulfide (ZnS/CuSx ) shells and silica (SiO2 ) cores were fabricated by a template-engaged synthetic method. Interestingly, the sizes of SiO2 cores can be tuned by different sulfurization time. In virtue of the light scattering and reflection on the SiO2 surface, the efficiencies of light capture by ZnS/Cu2 S shells were highly dependent on the SiO2 sizes. The as-fabricated SiO2 @ZnS/Cu2 S with a core size of 205 nm exhibited the highest and broadest absorption within a light wavelength of 380-700 nm. In virtue of the structural and componential features of these nanocolloids, maximum photocatalytic hydrogen (H2 ) production rates of 2968 and 1824 μmol h-1 g-1 under UV-vis and visible light have been delivered, respectively. This work may provide some evidence for the design and fabrication of core-shell nanomaterials to convert solar energy to green fuels.

Comparison of thermal insulation performance of vacuum insulation panels with EPS protection layers measured with different methods

For reducing the energy use of buildings, the application of insulation materials can be a possible solution to improve energy efficiency. However, with the continuously tightening regulations, thicker and thicker insulations should be used (e.g., up to 20–25 cm in Hungary and about 40–50 cm in the Nordic countries) to fulfil the directives. In the past decades, developmental research started to focus on both decreasing the thickness and decreasing the thermal conductivity of materials parallels. With this research direction, the investigations of the new type of insulation materials took place. The use of materials having thermal conductivity with less than 0.020 W/mK spread over. These materials are the so-called super insulation materials. Besides Vacuum Insulation Panels (VIPs), aerogel-based materials belong to this group, too. This paper will present laboratory tests executed on two altered types of protected Vacuum Insulation Panels: a one side and a 2 side protected VIP, also called Vacuum Insulation Sandwich (VIS). The first one, type “A” contains 20 mm thick laminated fumed silica, covered with 10 mm thick expanded polystyrene on one side, while type “B” was the one where the 10 mm thick laminated fumed silica core was packed between two 10 mm thick EPS slabs. Firstly, thermal insulation performance was investigated by the so-called guarded hot-box method for U-value, where the samples were placed on a solid brick wall. Furthermore, the thermal insulation performance of protected VIPs was also tested with Hukseflux heat flux plates. To reveal the applicability limits caused by the thermal bridges infrared thermography images (IR) were taken, too. From the images and the measurement results, a theory was formed regarding the heat flow directions inside the encapsulated panels. The current article emphasizes the equivalent thermal conductivity for the assessment of the thermal protection performance of vacuum insulation panels. The paper states that by using VIPs at least, 70% reduction can be reached in the U-value compared to the value of the solid brick wall. Moreover, the paper points out that the use of EPS protection layer on both sides of the VIP has a promising effect by reducing the thermal bridges. Furthermore, the VIP protected with EPS slabs on both sides results in less equivalent thermal conductivity.

An environmentally friendly titania–silica core–shell nanoparticles coating for protection of tiled facade of cultural-historical buildings

The purpose of the current research was to synthesize and characterize a hydrophobic ultraviolet (UV) absorbent coating for protection of tiled facade of cultural-historical buildings. Considering the environmental and conservational issues for such applications, using toxic materials is limited. A silicone-based nanocomposite coating was prepared in which organically modified silicates (ormosil) and titania–silica core–shell nanoparticles were used as matrix and reinforcing phase, respectively. Nanocomposite coatings were prepared by sol–gel method. Hydroxy-terminated polydimethylsiloxane (PDMS-OH) and tetraethoxysilane (TEOS) were used to form the ormosil matrix. Titania nanoparticles in anatase crystalline phase were used. To control their photocatalytic activity, silica–titania core–shell nanoparticles were prepared. Nanocomposite coatings were applied on microscope slides and historic tiles by dip-coating and simple brushing. The coatings were characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), water contact angle measurements and photocatalytic activity measurements. The results revealed that a transparent hydrophobic coating of prepared ormosils could obtain by adding a maximum amount of 20 wt% of PDMS-OH to the initial sols without addition of highly toxic solvents and catalysts. The FT-IR spectra of ormosil gels exhibited Si–O–Si bond corresponding to silica gels. It also showed that PDMS formed covalent bonds to silica networks. The XRD patterns showed that titania maintained its anatase crystalline structure after core–shell treatment. TEM images of core–shell treated nanoparticles illustrated the formation of continuous silica shell with less than 4 nm thickness around titania cores. Water contact angle measurements on tiles showed an increase in contact angle from 30° to 97° after coating. The results of UV–Vis spectrophotometry confirmed that the continuous silica layer acted as a barrier between photocatalytic titania and Methylene blue. Overall, the best composition for obtaining an environmentally friendly, transparent, hydrophobic, and UV absorbing nanocomposite coating could contain 20 wt% of PDMS-OH and about 0.025 wt% of silica–titania core–shell nanoparticles.

Retrospective analysis of a multi-stage experiment on developing high-performance insulation panels to sustain jet impingement at high temperatures

Over the years, numerous insulation panels have been developed to reduce heat transfer and meet the growing requirements imposed by industries. For a panel, the topology of the core can be delicately designed while novel and advanced materials are put into use. However, in the shipbuilding industry, the development of high-performance insulation panels using low-cost or cost-effective materials is still in great demand. A four-stage experimental study was conducted to develop high-temperature-proof panels without major thermal bridges caused by fastening methods for ships. A specimen chamber matching setup was used to test 36 panels based on nine designs with three commonly found core materials, i.e., polycrystalline filaments (PF), silica aerogel (SA), and aluminum silicate, under an impinging jet at temperatures ranging from 500 to 585 °C for 30 min. Besides analyzing overall heat transfer coefficient (U), heat flux (q), and Fourier number (Fo) for all panels, a method was proposed to estimate thermal diffusivity at testing temperatures (α) based on the Levenberg–Marquardt algorithm and an analytical model of heat conduction. Major conclusions include the following: First, thermal properties varied among the eligible panels: U: 0.4–1.43 W·m−2·°C−1; q: 100–318 W/m2; α: 6.0 × 10–8–1.3 × 10–6 m2/s; and Fo: 0.07–0.35. Second, because the improvement of thermal performance by adding an air interlayer was not significant, traditional panel designs with internal insulation were preferable. Third, by balancing thermal performance and economic and practical considerations, panels with SA or PF core and fastened by in-core battens were recommended for large-scale industrial applications, and it would be more cost-effective to use PF core.

Swelling-Based Distributed Chemical Sensing with Standard Acrylate Coated Optical Fibers

Distributed chemical sensing is demonstrated using standard acrylate coated optical fibers. Swelling of the polymer coating induces strain in the fiber’s silica core provoking a local refractive index change which is detectable all along an optical fiber by advanced distributed sensing techniques. Thermal effects can be discriminated from strain using uncoated fiber segments, leading to more accurate strain readings. The concept has been validated by measuring strain responses of various aqueous and organic solvents and different chain length alkanes and blends thereof. Although demonstrated on a short range of two meters using optical frequency-domain reflectometry, the technique can be applied to many kilometer-long fiber installations. Low-cost and insensitive to corrosion and electromagnetic radiation, along with the possibility to interrogate thousands of independent measurement points along a single optical fiber, this novel technique is likely to find applications in environmental monitoring, food analysis, agriculture, water quality monitoring, or medical diagnostics.