Influence of Ionic Liquid-Based Metal–Organic Hybrid on Thermal Degradation,Flame Retardancy,and Smoke Suppression Properties of Epoxy Resin Composites

A new multifunctional ionic liquid-based metal–organic hybrid (PMAIL) was synthesized by anion exchange between as-synthesized phosphonate-based ionic liquid and phosphomolybdic acid and applied to epoxy resin (EP) as an efficient flame retardant. As expected, with only 1 wt% addition of PMAIL, the char yield of EP-PMAIL1 composite at 700 °C was significantly improved by 108.3% from 12.0% for neat epoxy resin to 25.0%, demonstrating the outstanding catalytic charring effect of PMAIL. Meanwhile, EP-PMAIL6 composite (6 wt% addition) can reach V-0 rating in the UL-94 vertical burning tests easily, and its peak heat release rate and total smoke production of EP-PMAIL6 were dropped by 31.0 and 15.4%, respectively, compared with neat EP. Moreover, the results from cone calorimetry tests showed that the char yield of EP-PMAIL6 was enhanced by 162% from 9.5 to 24.9% compared with neat EP, resulting in a strong intumescent char layer structure with outstanding fire retardance and mechanical properties. The thermo-oxidative stable protective layer retarded the transfer of heat and flammable volatiles during combustion and protected the epoxy matrix from further degradation. In conclusion, our results might provide a new perspective for producing composites with excellent flame retardancy and smoke suppression properties using ionic liquid-based metal–organic hybrid.     

An Energy Model of a Failure Mechanism and its Application

The energy expression is presented for a failure mechanism, and it is applied in an Acceler-ated Life Test ( ALT) and an Accelerated Reliability Growth Test ( ARGT). The conditions of the common failure mechanism are obtained. The essential relationship between the conditions and the Accelerated Factor ( Af ) is proposed by using the energy model.     

Preparation of γ-alumina thin membrane by sol-gel processing and its characterization by gas permeation

-alumina porous membranes without pinholes or cracks were prepared by the sol-gel process. The boehmite sol obtained from hydrolysation of aluminium isopropoxide was applied to the inner surface of a porous supporting tube by a dipping procedure. The effects of sol concentration and the repetition number of dipping-drying-firing procedure on the membrane performance were investigated by scanning electron microscopy, X-ray diffraction and the Brunauer-Emmett-Teller method in connection with the micro-structure of the membrane. Gas permeation measurements were also conducted. The gas permeation through the thin membranes is well explained by Knudsen's flow, indicating the pores are controlled finely and homogeneously.     

Preparation of graded zirconia–CaP composite and studies of its effects on rat osteoblast cells in vitro

Hydroxyapatite (HAP) has excellent biocompatibility and bone bonding ability, but it is mechanically weak and brittle. To overcome this problem, we prepared a graded composite with calcium phosphide (CaP, decomposed from HAP during sintering) coating on the surface of zirconia (ZrO₂) ceramics. The mechanical properties and microstructure characteristics were studied with various techniques. The biocompatibility of graded ZrO₂–CaP composite was examined with rat osteoblast cells (OB cells) in vitro. Its effects on the production of alkaline phosphatase (ALP), Interleukin-6 (IL-6) and Growth-transforming Factor-β (TGF-β) by the OB cells were measured. The results showed that the mean tensile strength of the graded ZrO₂–CaP composites was 17.8 MPa, the maximum bending strength was 1112.24 MPa, and K_IC was 7.3–11.4 MPa·m^1/2, indicating that the composite was physically strong for use as an implant material. The ALP activity, IL-6 and TGF-β concentrations of the graded composite treated OB cells were much higher than that of the pure ZrO₂ treated group. There was no significant difference in ALP activity, the IL-6 and TGF-β concentrations between the graded ZrO₂–CaP composite group and HAP. The cytotoxicity of the composite material to rat fibroblast cells was insignificant. The graded zirconia–CaP composite greatly facilitated the proliferation and differentiation of rat OB cells in vitro, demonstrating excellent biocompatibility.     

Numerical investigation of onset and evolution of LVI damages in Carbon–Epoxy plates

In order to study the onset and the evolution of low velocity impact damages in Carbon–Epoxy plates, a numerical investigation has been led. A detailed finite element model has been created by using the finite element code Abaqus® which, thanks to the different implemented algorithms, allowed considering both intra-laminar and inter-laminar failure criteria.In particular, the numerical modelling technique of such failure criteria allowed predicting delamination growth, by using special purpose-elements (cohesive elements) and fiber and matrix failure, by using Hashin criteria.Moreover, with the aim to reduce the required CPU time, a global/local finite element modelling approach has been proposed.For validation purpose, numerical results have been compared with data from two sessions of experimental impact tests. The considered impact energy values are 6 J, 10 J and 13 J respectively.     

Preparation and evaluation of a timolol maleate drug–resin ophthalmic suspension as a sustained-release formulation in vitro and in vivo

Abstract

The aim of this work was to assess the performance of resin as an ocular delivery system. Timolol maleate (TM) was chosen as the model drug and an ion exchange resin (IER) as the carrier. The drug–resin complex was prepared using an oscillation method and then characterized regarding particle size, zeta potential, morphology, and drug content. After in vitro drug release study and corneal permeation study were performed, in vivo studies were performed in New Zealand albino rabbits using a suspension with particles sized 4.8?±?1.2?μm and drug loading at 43.00?±?0.09 %. The results indicate that drug released from the drug–resin ophthalmic suspension permeated the cornea and displayed a sustained-release behavior. Drug levels in the ocular tissues after administration of the drug–resin ophthalmic suspension were significantly higher than after treatment with an eye drop formulation but were lower in body tissues and in the plasma. In conclusion, resins have great potential as effective ocular drug delivery carriers to increase ocular bioavailability of timolol while simultaneously reducing systemic drug absorption.     

Preparation and characterization of maleimide–polystyrene/SiO2–Al2O3 hybrid nanocomposites by an in situ sol–gel process and its antimicrobial activity

Inorganic–organic nanocomposites have unlocked new opportunities in the design of innovative materials and compounds with enhanced and unique properties, based on soft chemistry. In the present study, a hybrid nanocomposite of maleimide–polystyrene (PSMA) with SiO₂ and Al₂O₃ (PSMA-SA) was synthesized by means of the sol–gel approach in the presence of γ-aminotriethoxysilane (γ-APTES), in which tetraethoxysilane (TEOS) and aluminum isopropoxide (AIP) were used as precursors. The Michael reaction led to bonding between the PSMA and SiO₂–Al₂O₃, giving a stable cross-linked network that prevented aggregation and mechanical mixing of the nanoparticles. XRD and FTIR analysis confirmed the effects of the coupling agent in promoting the Michael reaction. Thermal properties of the hybrid nanocomposites were tested through TGA and DSC. SEM, TEM and optical tests confirmed the controlled morphology and optical transparency of the composites. Additionally, the hybrid nanocomposites showed excellent solvent resistance and antimicrobial activity against pathogenic bacteria such as Bacillus cereus and Escherichia coli.     

Synthesis of Micron and Submicron Nickel and Nickel Oxide Particles by a Novel Laser–Liquid Interaction Process

The laser–liquid–solid interaction is a new technique for synthesis of nickel and nickel oxide particles. The process uses a continuous-wave CO₂ laser beam as the source of thermal energy required to induce precipitation reactions in solution. The uniqueness of the process is the synthesis reaction taking place in a localized region, which allows better control of the chemical reaction. Porous nickel and nickel oxide powders have been synthesized by laser-induced reactions between a nickel nitrate hexahydrate [Ni(NO₃)₂·6H₂O] precursor and 2-ethoxyethanol-based mixtures. Nickel powders were produced after irradiating a solution of the precursor salt and a 2-ethoxyethanol and d-sorbitol mixture. Crystalline nickel oxide (NiO) powders were isolated after irradiating a solution containing the precursor salt and a 2-ethoxyethanol and water mixture. Powders containing both nickel and nickel oxide crystalline phases were produced after irradiating a solution of the precursor salt and 2-ethoxyethanol. The mean particle diameter is found to be sensitive to irradiation time, substrate thermal conductivity, irradiation power density, and solution concentration. It is hypothesized that nucleation and growth of crystalline phases occurring in irradiated solutions are thermal driven.     

The Study of Performance in a Novel Gas–Solid Separator

The three slit-type separator is a new separator which can shorten the residence time of oil & gas and improve the separation efficiency. In this study, a critical validation was carried out to examine the separation performances of the three slit-type separator with different inlet velocity and inlet concentration. According to the experimental results, the separation efficiency and pressure drop of the three slit-type separator increase with the increase of inlet velocity and inlet concentration. Numerical simulation of the gas–solid flow field in the three slit-type separator was carried out by the use of Fluent 15.0 platform. The simulated results coincide with the experimental results. The particles move along the inside wall of the separator in the vaulted space, meanwhile, more gas enters into the exhaust pipe through slots, which can improve the separation efficiency. The study shows that the residence time of oil and gas is less than 0.6 and the separation efficiency is up to 99% in the separator, in addition, the pressure drop could be controlled in 4 kPa below.     

Preparation and characterization of wollastonite with a β-nucleating surface and its filled isotactic polypropylene composites

To transform α-nucleation into β-nucleation of wollastonite surface for isotactic polypropylene (iPP), the wollastonite with a β-nucleating surface was prepared through the chemical reaction between wollastonite and pimelic acid in both liquid mixing (method A) and powder mixing (method B). The wollastonite with a β-nucleating surface was confirmed using differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy analysis, wide-angle X-ray diffraction under different temperatures, thermogravimetry coupled with Fourier transform infrared spectrometry, and scanning electron microscopy. The crystallization and melting behavior and the crystalline morphology of iPP composites filled by wollastonite with a β-nucleating surface were investigated by DSC and optical microscopy. The results indicated that wollastonite filled iPP composites predominantly crystallize in the α-phase iPP and iPP composites filled by wollastonite with a β-nucleating surface mainly form β-phase iPP. It is proved that heterogeneous nucleating mechanism has been changed from α-nucleation into β-nucleation of wollastonite surface for iPP crystallization. What deserves to be mentioned is that the nucleation density of flat surface in the end of needle-like wollastonite is higher than that of curved surface of wollastonite.     

Preparation of PbGeO<Subscript>3</Subscript> by the oxidation of Pb–Ge melts and its properties

This paper presents experimental data on the oxidation kinetics of a liquid 65 at % Pb + 35 at % Ge alloy in air. Lead metagermanate, PbGeO₃, in a glassy state has been prepared by high-temperature oxidation of the melt at 1273 K. Interaction of molten PbGeO₃ with crucible materials (SnO₂, Au, Pd, and Pt) has been studied by the sessile drop method. Liquid lead germanate has been shown to be highly reactive with substrates from these materials. The heat capacity of the glassy lead metagermanate obtained has been determined by differential scanning calorimetry in the temperature range 300–800 K. In the range 330–630 K, the C_p(T) data for glassy PbGeO₃ can be represented using the Maier–Kelley equation. Above 630 K, there is a characteristic peak due to glass crystallization processes.     

Preparation and characterization of NASICON with a new sol–gel process

NASICON powders with the composition of Na₃Zr₂Si₂PO₁₂ were synthesized by using a sol–gel method. In the course of synthesis, a different material of oxalic acid was used to modify the synthesis process. The resulted precursors were sintered at the temperatures ranging from 700 to 1000 °C to get NASIOCN powders. X-ray diffractometer (XRD), IR and Raman spectra were employed to characterize the sintered products. Also, the ionic conductivity measurement conducted in the temperatures of 150–300 °C was used to evaluate their electronic properties. Furthermore, CO₂ sensor was prepared based on the pressed NASICON bulk. The relationship between its EMF response and the target gas concentration was checked. The experiment results showed that the NASICON material sintered at 900 °C possessed better properties in comparison with those sintered at other temperatures.     

Preparation of non-spherical silica composite abrasives by lanthanum ion-induced effect and its chemical–mechanical polishing properties on sapphire substrates

Chemical–mechanical polishing is the only technology that can provide a global planarization, and has become widely accepted. Abrasives are one of the important factors influencing chemical–mechanical polishing. In order to improve surface planarization and increase material removal rate of sapphire substrates, non-spherical silica composite abrasives were synthesized by lanthanum ion-induced effect-assisted growth method. Scanning electron microscopy showed the morphologies of non-spherical silica composite abrasives were peanut-shaped, chemical–mechanical polishing tests displayed the material removal rate of the non-spherical silica composite abrasives increased by 32.6% compared with spherical silica composite abrasives, Ambios Xi-100 surface profiler indicated the best surface roughness of sapphire substrate was 1.540 nm, and the element compositions of solids after polishing were analyzed by X-ray photoelectron spectroscopy, which investigated the interactions between abrasives and sapphire substrates. Non-spherical silica composite abrasives may lead to more solid-chemical reactions with sapphire substrates, and higher material removal rate may be also attributed to the mechanical grinding effect enhanced owing to the unique shape to achieve the purpose of material removal.     

Preparation and characterization of CuCrO2–CeO2 nanofibers by electrospinning method

Journal of Materials Science: Materials in Electronics - In this study, CuCrO2–CeO2 nanofibers were prepared by the electrospinning method and the influences of different concentrations on...