Surface Of Zirconia Nanoparticles Research Articles

New Carbamoyl Surface-Modified ZrO2 Nanohybrids for Selective Au Extraction from E-Waste

Efficient and selective extractions of precious and critical metal ions such as Au(III) and Pd(II) were investigated using zirconia nanoparticles surface modified with different organic mono- and di-carbamoyl phosphonic acid ligands. The modification is made on the surface of commercial ZrO2 that is dispersed in aqueous suspension and was achieved by optimizing the Bronsted acid-base reaction in ethanol/H2O solution (1:2), resulting in inorganic-organic systems of ZrO2-Ln (Ln: organic carbamoyl phosphonic acid ligand). The presence, binding, amount, and stability of the organic ligand on the surface of zirconia nanoparticles were confirmed by different characterizations such as TGA, BET, ATR-FTIR, and 31P-NMR. Characterizations showed that all the prepared modified zirconia had a similar specific surface area (50 m2.g-1) and the same amount of ligand on the zirconia surface in a 1:50 molar ratio. ATR-FTIR and 31P-NMR data were used to elucidate the most favorable binding mode. Batch adsorption results showed that (i) ZrO2 surface modified with di-carbamoyl phosphonic acid ligands had the highest adsorption efficiency to extract metals than mono-carbamoyl ligands, and (ii) higher hydrophobicity of the ligand led to better adsorption efficiency. The surface-modified ZrO2 with di-N,N-butyl carbamoyl pentyl phosphonic acid ligand (ZrO2-L6) showed promising stability, efficiency, and reusability in industrial applications for selective gold recovery. In terms of thermodynamic and kinetic adsorption data, ZrO2-L6 fits the Langmuir adsorption model and pseudo-second-order kinetic model for the adsorption of Au(III) with maximum experimental adsorption capacity qmax = 6.4 mg.g-1.

Direct conversion of the water adsorption energy to electricity on the surface of zirconia nanoparticles

Based on the example of a nanopowder system ZrO2–3% mol Y2O3 with atmospheric humidity interaction, the possibility of exothermic heterophase electrochemical energy conversion to electric energy is shown. Electrical properties and structure of the experimental sample were studied under gradient molecular flux density of humidity during sample saturation. The idea of development of the novel chemo-electronic converter device based on nanoscale dielectrics as ZrO2–3% mol Y2O3 is proposed.

Synthesis and mechanical properties of the epoxy resin composites filled with sol−gel derived ZrO2 nanoparticles

Highly dispersive ultrafine zirconia nanoparticles were prepared by a modified sol-gel process and used as fillers added into epoxy resins. Meanwhile, surface modification and ultrasonic mixing process was utilized to achieve homogenous dispersion of the nanoparticles in epoxy resin. The obtained zirconia nanoparticles showed a mainly tetragonal crystalline structure with an average particle size of 11 nm and a specific surface of 53.68 m2 g−1 as detected by XRD analysis, SEM measurements, laser diffraction particle size analyzer, and physisorption apparatus. TEM observations indicated that the nanoparticles modified by KH-550 had better dispersion in the epoxy matrix. FTIR verified that KH-550 successfully grafted onto the surface of zirconia nanoparticles. Several mechanical tests demonstrated the increased mechanical properties for the composites with lower nanoparticle content, which was ascribed to the good dispersion of zirconia nanoparticles in the epoxy resin and improved particle/matrix interface adhesion. The optimal mechanical properties were found when zirconia nanoparticle content is around 3 wt%. Moreover, the maximum tensile strength, tensile modulus, fracture toughness, critical strain energy release rate, and hardness increased by 44%, 29%, 63%, 122 and 17 % compared with the neat epoxy resin, respectively. Results of thermal analysis revealed that the char yield of the composites were significantly improved due to the incorporation of nanoparticles and additional crosslinkage between nanoparticles and matrix.

Coating carboxylic and sulfate functional groups on ZrO2 nanoparticles: Antifouling enhancement of nanocomposite membranes during water treatment

This research proposes a novel method for intensifying the presence of nanoparticles on the top layer of blended nanocomposite membranes. To this end, carboxylic acid and sulfate functional groups were coated on the surface of zirconia nanoparticles. The functionalized nanoparticles were embedded in the matrix of PAN and PSf membranes, and six nanocomposite membrane models were synthesized including mZrO2@nPAN, mCZrO2@nPAN, mSZrO2@nPAN, mZrO2@nPSf, mCZrO2@nPSf, and mSZrO2@nPSf. The aim was to exploit proper arrangement of nanoparticles in the membrane matrix to strengthen the antifouling properties of the membrane. Overall, the change made in the superficial and structural properties of the membrane in response to presence of functional groups caused the internal pore blocking in 2.68CZrO2@13PAN and 2.68SZrO2@13PAN to be 50.9 and 41.8% less than that of the raw membrane, respectively. On the other hand, for the membrane lacking the functional group 2.68ZrO2@13PAN, this improvement was calculated to be only 30.9%. In terms of total fouling ratio, 2.68CZrO2@11PAN, 2.68CZrO2@13PAN, and 2.68CZrO2@15PAN membranes had 42.8, 39.3, and 35.6% less total filtration resistance respectively compared to the raw membrane. Considering PWF, 2.68SZrO2@13PAN and 2.68SZrO2@13PSf had 46.2% and 52.1% more PWF than bare 13PAN and bare 13PSf membrane. Regarding the role of functional groups in improving the membrane separation properties, mCZrO2@13PSf membranes improved dye separation percentage by 20%, compared to the raw membrane. On the other hand, 2.68SZrO2@11PSf membranes managed to separate 100% of Red BRLS dye due to the role of sulfate functional group in reducing the size of the membrane pores.

INFLUENCE OF A PULSED MAGNETIC FIELD ON THE ELECTRICAL PROPERTIES OF NANOPOWDER SYSTEM BASED ON ZIRCONIA

A technique for studying of electrical characteristics based on electrochemical impedance spectroscopy of sealed nanopowder compact sets from a powder based on ZrO2 was proposed. The possibility of using this technique for studying of influence of pulsed magnetic field on a charge state of the surface of zirconia nanoparticles is shown. It is established that the action of a weak pulsed magnetic field leads to redistribution of free charge carriers between the volume and the surface of nanoparticles. In particular, different processing times lead to different impedance behaviour: treatment of a pulsed magnetic field with a pulse repetition frequency f = 1 Hz and an exposure time t <15 min leads to an irreversible decrease in the conductivity of the nanoparticle surface by two times (from 3.47 • 10-5 to 1.72 • 10-5 Ohm-1 • m-1), and processing with exposure time 15 <t <90 min leads to its increase by 10 times. Thus, the treatment of PMF causes formation in the near-surface zone of nanoparticles of a region depleted of charge carriers.

Novel flame retardant zirconia-reinforced nanocomposites containing chlorinated poly(amide-imide): synthesis and morphology probe

In the present investigation, a thermally stable poly(amide-imide) (PAI) was synthesised from the polymerisation reaction of 4,4′-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) as a chlorinated diacid with 4,4′-methylenebis(3-chloro-2,6-diethylaniline) using molten tetra-n-butylammonium bromide and triphenyl phosphite as a condensing agent and green media. This methodology offers enhancements for the synthesis of polymers with regard to yield of products, simplicity in operation, and green aspects by avoiding volatile solvents. From the chemical point of view, the chloride and ethylene groups impart to the polymer's chain increased solubility of obtained polymer in organic solvent. Then, the surface of zirconia nanoparticles (ZrO2-NPs) was modified with 3-aminopropyltriethoxylsilane as a coupling agent. The obtained polymer and inorganic metal oxide NPs were used to prepare PAI/ZrO2 nanocomposites through ultrasonic irradiation. The formation of PAI was confirmed by 1H-NMR, FT-IR spectroscopy, and elemental analysis. The obtained polymer was synthesised with good yield (90%) and moderate inherent viscosity (0.48 dL/g). The resulting NP filled composites were also characterised by FT-IR, XRD, FE-SEM, TEM and TGA. The TEM and FE-SEM results indicated a high dispersion level of the nanoscale inorganic particles in the polymer matrix. In this article, ZrO2-NPs are employed to improve flame retardancy of nanocomposites. TGA thermographs confirmed that the heat stability of the prepared NP-reinforced composites was improved in the presence of ZrO2 nanocrystals.

Zirconia nanoparticles/ferroelectric liquid crystal composites for ionic impurity-free memory applications

We observed an ionic impurity-free memory effect using a zirconia nanoparticles (ZNPs)/ferroelectric liquid crystal (FLC) composite. The pure and ZNPs doped FLC cells have been analyzed by means of dielectric spectroscopy, polarizing optical microscopy and electrical resistance/conductivity measurements. The memory behavior in ZNPs/FLC composite was confirmed by dielectric dispersion, electrical, and optical studies, whereas dielectric loss spectra confirmed the disappearance of the low-frequency relaxation peak, which appears due to the presence of ionic impurities in FLC materials. The observed memory effect has been attributed to minimization of the depolarization field and ionic charges, whereas the reduction of ionic effects has been attributed to the strong adsorption of ionic impurities on the surface of ZNPs. The ZNPs dispersed in FLCs may play a role in trapping the impurity ions (minimize the depolarization fields) under applied voltage and cause a better memory effect in ZNPs doped FLC material. Moreover, the ion adsorption capability of ZNPs is found to be almost independent of temperature as the value of resistance did not change remarkably on increasing the temperature. The reduction of ionic impurities of FLCs by doping ZNPs did not show degradation over time, as we repeated the experiments on the same sample cells after many days and did not find ionic effects in the ZNPs doped FLC materials. These studies would be helpful to provide an idea for designing ionic impurity-free memory devices.

Variation in the EPR characteristics of nanosized zirconia particles under exposure to X-ray radiation and annealing in hydrogen

The effects of various external factors on the properties of nanosized zirconia particles are studied using electron paramagnetic resonance. It is shown that x-rays initiate radiation-stimulated oxidation of chromium impurity ions according to the scheme Cr3+ → Cr5+. Annealing of samples in hydrogen at temperatures in the range 250–650°C brings about a substantial decrease in the fraction of chromium ions in the Cr5+ charge state, but subsequent annealing of these samples in air leads to an increase in the Cr5+ fraction. Samples annealed in hydrogen generate a singlet EPR signal with the g factor of 2.0033 ± 0.0005 originating from electrically conducting regions which are formed on the surface of zirconia nanoparticles during their annealing in hydrogen.

Polymerization Compounding on the Surface of Zirconia Nanoparticles

AbstractZirconia nanoparticles were encapsulated by polyethylene via a polymerization compounding method using a Ziegler‐Natta catalyst. The chemical reaction was carried out in an organic solvent under moderate pressure of ethylene monomer. Transmission electron microscopy (TEM) indicated the presence of a thin layer of polymer, about 6 nm, uniformly applied around the particles. However, the thickness of coating layer can be controlled as a function of time and operating conditions of the process. The morphology study using scanning electron microscopy (SEM) as well as TEM revealed that although the nanoparticles seem to be coated individually, some agglomerates, encapsulated by a polymer film, could be observed. The grafting of the catalyst to the original surface of particles was further confirmed by X‐ray photoelectron spectroscopy (XPS).

Conformal nanocoating of zirconia nanoparticles by atomic layer deposition in a fluidizedbed reactor

Primary zirconia nanoparticles were conformally coated with alumina ultrathinfilms using atomic layer deposition (ALD) in a fluidized bed reactor. Alternatingdoses of trimethylaluminium and water vapour were performed to depositAl2O3 nanolayers on the surface of 26 nm zirconia nanoparticles. TransmissionFourier transform infrared spectroscopy was performed ex situ. BulkAl2O3 vibrational modes were observed for coated particles after 50 and 70 cycles. Coatednanoparticles were also examined with transmission electron microscopy, high-resolutionfield emission scanning electron microscopy and energy dispersive spectroscopy. Analysisrevealed highly conformal and uniform alumina nanofilms throughout the surface ofzirconia nanoparticles. The particle size distribution and surface area of the nanoparticlesare not affected by the coating process. Primary nanoparticles are coated individuallydespite their high aggregation tendency during fluidization. The dynamic aggregationbehaviour of zirconia nanoparticles in the fluidized bed plays a key role in the individualcoating of nanoparticles.

Polymer coating on the surface of zirconia nanoparticles by inductively coupled plasma polymerization

Polymer coating on the surface of inorganic ceramic nanoparticles is beneficial to decrease agglomeration and improve dispersion in organic solvent in ceramic injection moulding technology. A layer of thin polymer film on zirconia nanoparticles is deposited by inductively coupled ethylene/nitrogen plasma. Transmission electron microscopy photographs indicate the presence of uniform polymer coatings and the thickness of the polymer layer is estimated as several nanometers. The chemical structure of the film is revealed as quasi-polyethylene long hydrocarbon chain by x-ray photoelectron spectroscopy examination.