腰果壳油酚醛树脂的应用研究进展

介绍了腰果壳油的结构与性能关系,综述了近几年来腰果壳油代替酚类为原料合成酚醛树脂的一些探索性研究及其在摩擦材料、模塑料、涂料、胶粘剂、泡沫塑料等方面的应用。     

Cure characteristics of alkali catalysed cashew nut shell liquid-formaldehyde resin

Cashew nut shell liquid (CNSL) is a naturally occurring chemical monomer consisting four alkyl substituted phenols. Its phenolic nature makes it suitable for polymerisation into resins by formaldehyde using sodium hydroxide (NaOH) as a catalyst and hexamethylenetetramine (HMTA) employed as a hardener. There is intense interest in understanding the cure characteristics and properties of CNSL-based resins. In this work the DSC technique has been applied to study the change in the glass transition temperature of the oven-cured resin with and without HMTA in order to monitor the extent of cure. The glass transition temperature was found to rise when the alkaline catalysed resin was subjected to higher curing temperatures regardless of the concentration of formaldehyde used. The mode of cure of the NaOH-catalysed CNSL-formaldehyde resin has been found to be more regular with HMTA hardener. FT-IR spectroscopy has been used to study the neat CNSL and polymerised CNSL-formaldehyde resin with and without HMTA. The use of the DSC and FT-IR techniques to elucidate the extent of cure of CNSL resins is a valuable step towards the production of commercially successful CNSL-natural fibre composites.     

The effect of a superplasticizer (from cashew nut shell liquid) on the properties of concrete and mortar

The paper describes a new, cheaper water-reducing compound obtained from cashew nut shell liquid (CNSL). The properties of mortars, namely flow, setting time and compressive strength, were determined in the presence of 0.1 to 1.0% superplasticizer. The compressive strength of mortar containing the superplasticizer from CNSL was higher than that of the control     

Magnetic nanoparticles with core/shell structures

Magnetic nanoparticles with core/shell structures are an important class of functional materials, possessing unique magnetic properties due to their tailored dimensions and compositions. This paper reviews mainly our recent advances in the preparation and characterizations of core/shell structured magnetic materials, focusing in nonmagnetic, antiferromagnetic, or ferro/ferri-magnetic shell coated magnetic core particles. And some of the unique properties of core-shell materials and their self-assembly are presented. Shell layers are shown to serve various functions. A broad demonstration of the successful blend of these types of materials synthesis, microstructural evolution and control, new physics and novel applications that is central to research in this field is presented.     

Process modeling, optimization and analysis of esterification reaction of cashew nut shell liquid (CNSL)-derived epoxy resin using response surface methodology

Concept of five-levels-four-factors central composite rotatable design was utilized for the optimization of reaction conditions of cardanol-based vinyl ester resin production, by employing response surfaces methodology, to establish a relationship between the process variables and the extent of conversion under a wide range of operating conditions which resulted in different extent of conversions. The maximum extent of conversion of cardanol-based epoxidised novolac resin (CNE) and methacrylic acid (MA) catalyzed by triphenylphosphine was found to be 95% at optimum set of conditions of molar ratio (1:0.9) between CNE and MA, catalyst concentration (1.49%), reaction temperature (89.96 °C) and reaction time (17,991s). Geometrical representation of the mathematical models in three-dimensional response surface plots and isoresponse contour plots served as a good aid in understanding the behavior of reaction under different operating conditions by only limited sets of experiments. A statistical model predicted that the highest conversion yield of novolac resin would be greater than 95% at the optimized reaction conditions. The predicted values thus obtained were close to the experimental values indicating suitability of the model.     

Synthesis and characterization of magnetic nanoparticles coated with a uniform silica shell

Magnetic nanoparticles with a proper surface coating are of outstanding interest for several applications, especially in the biomedical field. In this paper we present the synthesis of CoFe₂O₄ magnetic nanoparticles covered by a uniform silica shell. These particles were characterized by means of Transmission Electron Microscopy (TEM) and Small Angle Scattering of Polarized Neutrons (SANSPOL). This newly developed technique, taking advantage from the variation of magnetic contrast, allowed us to verify that the thickness of the silica shell can be accurately tailored through a very simple synthetic approach.     

Magnetic properties of magnetite nanoparticles coated with mesoporous silica by sonochemical method

In this paper we present the magnetic properties of mesoporous silica-coated Fe₃O₄ nanoparticles. The coating of magnetite nanoparticles with mesoporous silica shell was performed under ultrasonic irradiation. The obtained mesoporous silica-coated magnetite nanoparticles were characterized by powder X-ray diffraction, focused ion beam-scanning electron microscopy, nitrogen adsorption-desorption isotherms and vibrating sample magnetometer. The hysteretic behavior was studied using first-order reversal curves diagrams. The X-ray diffraction result indicates that the extreme chemical and physical conditions created by acoustic cavitations have an insignificant effect on crystallographic structural characteristic of magnetite nanoparticles. Changes in the coercivity distributions of the magnetite nanoparticles were observed on the first-order reversal curves diagrams for the samples with coated particles compared with the samples containing uncoated particles of magnetite. The coated particles show an increased most probable coercivity of about 20% compared with the uncoated particles which can be associated with an increased anisotropy due to coating even if the interaction field distribution measured on the diagrams are virtually identical for coated/uncoated samples.     

Nano‐zero valent iron impregnated cashew nut shell: a solution to heavy metal contaminated water/wastewater

The present research is focused on the removal of Zn(II) ions from aqueous solution using nano zero‐valent iron impregnated cashew nut shell (NZVI‐CNS). The present system was investigated in batch mode operation. NZVI‐CNS was prepared by the liquid‐phase reduction process. The results showed that the NZVI‐CNS exhibited superior adsorption capacity for the removal of Zn(II) ions. Adsorption isotherm and kinetic models were applied to explain the nature of the adsorption process. Adsorption kinetic data followed the pseudo‐first order kinetic model. Moreover, the equilibrium adsorption data were best fitted with a Freundlich model. Langmuir monolayer adsorption capacity was calculated as 94.46 mg of Zn(II) ions/g of NZVI‐CNS. The thermodynamic parameters explain that the present adsorption system was measured as feasible and spontaneous. This newly prepared adsorbent can be successfully applied for the different industrial wastewater treatment. Finally, the exploration asks about contemplated that NZVI‐CNS has exhibited unrivalled adsorption limit. Additionally, NZVI‐CNS is believed to be extremely green and monetarily neighbourly help for wastewater treatment. The results indicate that the feasible approach could be applied in agricultural waste biomass materials for the productive expulsion of heavy metals from aqueous solution and reusing agricultural wastes to facilitate their disposal problem.Inspec keywords: wastewater treatment, contamination, zinc, reduction (chemical), adsorption, monolayers, renewable materialsOther keywords: nano zero‐valent iron impregnated cashew nut shell, aqueous solution, Zn(II) ion removal, NZVI‐CNS, batch mode operation, liquid‐phase reduction process, adsorption capacity, adsorption isotherm models, adsorption kinetic models, adsorption kinetic data, adsorption process, pseudo‐first order kinetic model, equilibrium adsorption data, Freundlich model, Langmuir monolayer adsorption capacity, thermodynamic parameters, adsorption system, industrial wastewater treatment, agricultural waste biomass materials, productive expulsion, heavy metals, waste disposal, Zn     

Surface-enhanced spectra on D-gluconic acid coated silver nanoparticles

Coated silver (Ag) colloids synthesized with D-glucose permit the observation of surface-enhanced fluorescence (SEF) and surface-enhanced resonance Raman scattering (SERRS) of the rhodamine B (RhB) molecule. The organic coating formed during the synthesis of the Ag nanostructures was identified by its surface-enhanced Raman scattering (SERS) spectrum as D-gluconic acid. The RhB molecule is used to exemplify the distance dependence of SEF and SERRS on the coated Ag nanostructures. The fluorescence enhancement factor for RhB on D-gluconic acid coated silver nanoparticles was determined experimentally and estimated using a simple model. Further support for the plasmon enhancement is obtained from the fact that the measured fluorescence lifetime of RhB on the silver coated with D-gluconic acid is shorter than that found on a glass surface. A very modest enhancement factor is obtained, as expected for very short distance between RhB and the metal surface. Given the very thin metal-fluorophore separation, estimated from the size of the D-gluconic acid, the energy transfer or fluorescence quenching is still efficient and the SEF enhancement is just overcoming the energy transfer. Therefore, both SEF and SERRS are observed. Notably, the aggregation of coated nanoparticles also increases the enhancement factor for SEF.     

Magnetic properties and microstructure of carbon encapsulated Ni nanoparticles and pure Ni nanoparticles coated with NiO layer

Two kinds of nickel nanoparticles—carbon encapsulated Ni nanoparticles Ni(C) and pure Ni nanoparticles coated with NiO layers Ni(O) are successfully prepared. Structural characterizations (HR-TEM, SAED, and XRD) reveal their distinct morphological properties. Magnetization measurements for the assemblies of two kinds of Ni nanoparticles show a larger coercivity and remanence by a deviation between the zero-field-cooled and the field-cooled magnetization below the irreversibility temperature, T_irr, for the assemblies of Ni(O) particles. This deviation may be explained as a typical nanocluster-glass behavior (collective behavior) due to ferromagnetic dipole-dipole interaction effects among the assemblies of Ni(O) particles. However, Ni(C) particles exhibit modified superparamagnetic properties above the average blocking temperature of T_B, which is determined to be around 115 K at 1000 Oe. Moreover, a gradual decrease in saturation magnetization is observed, which is attributed to the nanocrystalline nature of the encapsulated particles, coupled with possible carbon solution in Ni nanocrystals.     

Ultra-fast catalytic reduction of dyes by ionic liquid recoverable and reusable mefenamic acid derived gold nanoparticles

We synthesized mefenamic acid (MA) derived gold nanoparticles (MA-AuNps) in aqueous solution (MA-Au sol). Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) of the sol at 1, 5, 15 and 60 min showed changes in size and shape of formed AuNps. Fourier Transform Infrared (FTIR) Spectroscopy revealed the interaction between AuNps and MA. Each Au sol exhibited exceptional catalytic activity for the reduction of Methylene Blue (MB), Rose Bengal (RB) and Eosin B (EB) dye individually as well as collectively. However, complete reduction of dye(s) was accomplished by Au sol of 5 min in just 15s. The catalytic performance of Ma-Au sol was far superior to that adsorbed on glass. AuNps were recovered with the help of water insoluble room temperature ionic liquid and reused with enhanced catalytic potential. This finding is a novel, rapid and highly economical alternative for environmental safety against pollution by dyes and extendable for control of other reducible contaminants as well.     

Magnetic particles derived from iron nitride

Due to its high saturation magnetization (σ_s(0K)≈208 emu/g) and to the ease of obtaining it as a particulate material, Fe₄N could be a suitable magnetic material for replacing highly reactive metallic iron pigments (σ _s(0K)≈218 emu/g) in high-density recording. Throughout a nitriding process of properly selected precursors Fe₄N can be obtained in either of two morphologies: acicular or isotropic. Further protection of the magnetic particles can be ensured through coating of the precursor particles prior to thermal decomposition in NH₃/H₂ atmosphere or through substitutions with selected elements. The obtained passivated nitrides are characterized by high magnetic properties (H_c≈600 Oe; σ_s≈150 emu/g) and chemical stability well adapted for use as magnetic pigments for high-density recording     

Colloidal stability of amino acid coated magnetite nanoparticles in physiological fluid

We investigated the surface charge effect of surface coating ligands on the colloidal stability of magnetite nanoparticles in a physiological saline solution. We employed the l-lysine and the l-glutamic acid as the surface coating ligands. We investigated the colloidal stability of the l-lysine and the l-glutamic acid coated magnetite nanoparticles by measuring their precipitation times, hydrodynamic diameter distributions, and zeta potentials in a physiological saline solution. From these three measurements, we found that the l-lysine coated magnetite nanoparticles are more stable as colloids than the l-glutamic acid coated magnetite nanoparticles. Based on the bonding structures of the l-lysine and the l-glutamic acid to magnetite nanoparticles, we successfully discussed the colloidal stability in terms of the surface charge effect of the amino acids.     

Silver sulfide nanoparticles with a carbon-containing shell

Silver sulfide nanoparticles have been synthesized through chemical deposition from aqueous solutions of silver nitrate and sodium sulfide in the presence of sodium citrate as a complexing agent and stabilizer. The nanoparticles have a Ag₂S core with a monoclinic crystal structure, covered with a carbon-containing citrate shell. Varying initial reactant concentrations, we can obtain core/shell nanoparticles with a tailored Ag₂S core size and carbon-containing shell thickness.     

Porous ternary complex metal oxide nanoparticles converted from core/shell nanoparticles

We demonstrate an easy and scalable low-temperature process to convert porous ternary complex metal oxide nanoparticles from solution-synthesized core/shell metal oxide nanoparticles by thermal annealing. The final products demonstrate superior electrochemical properties with a large capacity and high stability during fast charging/discharging cycles for potential applications as advanced lithium-ion battery (LIB) electrode materials. In addition, a new breakdown mechanism was observed on these novel electrode materials.

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Plasma spraying of stainless-steel particles coated with an alumina shell

The effect of an alumina coating, obtained by mechanofusion, on stainless-steel particles used in plasma spraying has been studied by examining sprayed particles in mid-flight and their resulting splats and coatings. The mean size of the injected powders is about 65 μm and the thickness of the alumina shell 4 μm. The results show that without preheating the substrate the splats of both types of powder are extensively fingered and become circular when the substrate surface is preheated over 200°C. For the case of the stainless steel/alumina composite splats, Energy dispersive spectroscopy (EDS) analysis of the distribution of the various elements shows that the alumina is either spread exactly on the stainless-steel splat or is dispersed in pieces and frozen over the surface of the stainless-steel splat. The first case corresponds to well molten particles where, after their flight in the plasma jet, all the alumina shell has flowed to the tail of the particle; the second case is related to particles which have still an alumina shell uniformly distributed around the stainless-steel core. Finally, a composite stainless steel/alumina coating sprayed on a rough (R_a 6.7±0.3 μm) stainless-steel substrate preheated to 400°C is compared with a pure stainless-steel coating. Both hardness and cohesion are found to improve for the alumina-coated particles.     

Magnetic colloidosomes derived from nanoparticle interfacial self-assembly

Based on the interfacial self-assembly of magnetite nanoparticles, we demonstrate the formation of colloidosomes with shells predominantly composed of monolayers of liquid-like, close-packed nanoparticles. The gelation of aqueous phase with agarose leads to robust and water-dispersible nanoparticle colloidosomes, allowing encapsulation of various water soluble materials. The cutoff of the nanoparticle colloidosomes obtained is primarily defined by the nanoparticle size. This controllable permeability should be of great importance for the encapsulation application.     

Pentagonal nanorods and nanoparticles with mismatched shell layers

Nano-scale rods and particles having the axes of fivefold symmetry, i.e., pentagonal nanorods and nanoparticles, are theoretically and experimentally investigated. Such objects possess elastic strains and mechanical stresses. In the present research a new mechanism of stress relaxation in nanorods and nanoparticles is considered. The mechanism is implemented by a formation of a surface layer with crystal lattice mismatch. The elastic fields and energies for nanorods and nanoparticles with the mismatched layers are calculated in the framework of the disclination model. The optimal mismatch parameter giving the maximal energy release is determined. The threshold radius as the minimal radius of nanorods or nanoparticles for which the formation of the layer is energetically favorable, is found. The threshold radius is approximately 10 nm for nanoparticle and 100 nm for nanorod of typical FCC metal.     

Preparation and characterization of Ni-nitrilotriacetic acid bearing poly(methacrylic acid) coated superparamagnetic magnetite nanoparticles

Stable superparamagnetic magnetite (Fe3O4) nanoparticles were synthesized via co-precipitation in the presence of poly(methacrylic acid) (PMAA) in aqueous solution. The polymer coated Fe3O4 nanoparticles were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thermal analysis, and vibrating sample magnetometry (VSM) techniques. These measurements reveal the presence of magnetite nanoparticles with a size of approximately 8 nm inside the PMAA matrix. The magnetization value of these superparamagnetic nanoparticles at room temperarure and 7 T was measured as about 40 emu/g. PMAA-coated Fe3O4 nanoparticles were further assembled with Ni-chelate through a reaction between a primary amine-bearing NTA (nitrilotriacetic acid) ligand and carboxy-functional groups of PMAA. NTA-PMAA-coated magnetite nanoparticles were then loaded with nickel ions and characterized using FTIR. The average amount of binded Ni on the surface of the NTA-modified PMAA coated Fe3O4 was calculated as 1.65 +/- 0.3 x 10(-6) mol nickel(II) ions per g of the magnetic particles from the inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements.