Bulk synthesis of green carbon nanomaterials from Desmostachya bipinnata for the development of functional polyurethane hybrid coatings

Carbon nanomaterials have been the focal point of intense study in the past few decades owing to its molecularly defined structure, high aspect ratio and extortionate electrical, mechanical and physical properties. In the present study, we report an easy synthesis of carbon nanomaterials from the grass Desmostachya bipinnata. Fresh grass was collected and dried completely under the sun and was subjected to complete incineration in atmospheric oxygen. Scanning electron microscope image reveal the presence of carbon micro- and nanorods in the ash of the burnt grass. Then the ash was treated with piranha solution to obtain carboxyl group on the surface. The surface treatment of the obtained ash was confirmed by infrared spectroscopy and by thermogravimetric analysis. Following the acid treatment, the obtained carboxyl terminated carbon nanomaterials were then reacted with diisocyanate to form amide linkages, which was utilized in the formation of polyurethane films. Minuscle incorporation of ash containing carbon nanomaterial was found to enormously increase the physico-chemical properties of the obtained polyurethane nanocomposite. As compared to the neat polyurethane, the composite material showed a substantial increase in the thermal and mechanical properties.     

SiC nanoparticles incorporation in electroless NiP-Graphene oxide nanocomposite coatings

The presence of SiC nanoparticles within the Graphene oxide (GO) incorporated electroless deposited NiP layers (NiP-GO) on carbon steel substrate was studied in this work. The effect of co-deposition of GO nanoplatelets and/or SiC nanoparticles on the morphology and structure of the heat-treated NiP coatings were investigated by scanning electron microscope and X-ray diffraction, respectively. The results revealed that the heat-treated NiP and NiP–SiC coatings consisted of Ni and Ni₃P phases, whereas the NiP-GO also contains the intermediated Ni₂P and Ni₁₂P₅ metastable phases due to the incomplete precipitation of Ni₃P. Such metastable phases are significantly decreased by the incorporation of SiC nanoparticles in NiP-GO coatings. The mechanical properties of the coatings were characterized by microhardness measurement and “pin on disk” wear test. The corrosion tests were conducted in aqueous 3.5 %wt NaCl using electrochemical measurement for Ni–P, NiP-GO, NiP–SiC, and NiP-GO-xSiC coatings. By co-deposition of SiC nanoparticles, the hardness of NiP-GO is significantly increased and the wear loss is reduced, especially at a high sliding distance during the wear test. The corrosion behavior of the NiP-GO coatings containing different amounts of SiC nanoparticles has been investigated.     

Impact of TiO2 nanoparticles and nanowires on corrosion protection performance of chemically bonded phosphate ceramic coatings

The impact of the addition of TiO₂ nanoparticles and nanowires on the morphology, phase characteristics, contact angle, and electrochemical performance of chemically bonded phosphate ceramic coatings (CBPCs) was investigated. The chemical composition and surface morphology of the TiO₂ nanoparticle and nanowire modified with and without (heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane were characterized. Results indicated that the hydrophobic –CF₂– and –CF₃ groups were successfully introduced into the TiO₂ nanoparticles and nanowires after modification. Corrosion resistance of CBPCs with TiO₂ was evidently improved compared with that without TiO₂. Such improvement was mainly due to the combined effects of low surface energy materials and micro/nano structures. In addition, CBPCs with TiO₂ nanowires exhibited higher hydrophobicity and corrosion resistance than those with TiO₂ nanoparticles because of the special columnar structure of the nanowires.     

一维ZnO纳米材料的制备技术与应用

一维氧化锌纳米材料,由于其优异的性能,已成为当今材料科学的研究热点之一.对一维氧化锌纳米材料的研究进展进行了综述.阐述了一维氧化锌纳米材料的制备方法及生成机理.并总结了其在光电、场发射和纳米发电机等方面的应用.     

Polyols based on isocyanates and melamines and their applications in 1K and 2K coatings

Polyurethane polyols (PUPOs) and melamine polyols (MEPOs), invented by AkzoNobel Coatings, offer valuable alternatives to the commonly used polyester and acrylic polyols and new formulating tools for the development of novel coatings. The resin chemistry is based on the predominantly selective reactivity of α,β- and α,γ-diols with commonly used polyisocyanate and melamine formaldehyde crosslinkers. The resulting low molecular weight, hydroxyl functional resins are suitable for use in low VOC coatings. By choosing the appropriate crosslinker, diol, and modifier, the chemical structures of these resins can be altered to obtain the desired properties of the coatings. Synthesis methods for novel PUPOs and MEPOs and properties of one component and two component coatings containing them are described.     

Effect of alumina nanoparticles in the fluid on heat transfer in double-pipe heat exchanger system

This study was performed to investigate the convective heat transfer coefficient of nanofluids made of several alumina nanoparticles and transformer oil which flow through a double pipe heat exchanger system in the laminar flow regime. The nanofluids exhibited a considerable increase of heat transfer coefficients. Although the thermal conductivity of alumina is not high, it is much higher than that of the base fluids. The nanofluids tested displayed good thermal properties. One of the possible reasons for the enhancement on heat transfer of nanofluids can be explained by the high concentration of nanoparticles in the thermal boundary layer at the wall side through the migration of nanoparticles. To understand the enhancement of heat transfer of nanofluid, an experimental correlation was proposed for an alumina-transformer oil nanofluid system.     

Impregnated of C6CoFeN6 nanoparticles in poly-1-naphthol for uptake of Cs(I) from aqueous waste

To carry out our research, C₆CoFeN₆@poly-1-naphthol nanoparticles were synthesized and characterized by SEM, X-ray diffraction, Fourier transform infrared, thermogravimetric analysis and Brunauer–Emmett–Teller (BET) analyses. The SEM images indicate that the average particle sizes are about 60 nm in diameter. The BET result provides a clear evidence for the high surface area of the sample 180.6 m²/g. Cs(I) ions removed from the aqueous solution in a batch mode using CoHCF@poly-1-nanphtol as an adsorbent. The adsorption effecting parameters such as the solution pH, initial Cs(I) concentration, contact time and temperature were studied. Maximum sorption capacity for the nanocomposite was found to be 200.5 mg/g at 1000 mg/g, pH = 5 and 298 K. The time-adsorption dependence studies indicated that the maximum Cs(I) uptake was within the initial 40 min contact time and the adsorption mechanism was governed by the double exponential model. The equilibrium sorption data fitted well to the Freudlich model with n ? 1 indicating a stronger interaction and high affinity of C₆CoFeN₆@poly-1-naphthol for Cs(I) ions. The thermodynamic parameters, including changes in Gibbs free energy, entropy and enthalpy, were determined. The results indicated that CoHCF–poly-1-nanphtol could be a potential adsorbent for the uptake of Cs(I) ions from an aqueous solution.     

Photo-induced polymerization in ionic liquid medium: 1. Preparation of polyaniline nanoparticles

Photo-induced polymerization is employed to prepare polyaniline (PAN) nanoparticles in ionic liquid for the first time. Photons and photoactive ionic liquid cations replace conventional oxidants and metal complexes to promote the polymerization of aniline monomer. The diameter of the resulted PAN is confirmed in nano-scale by SEM. With increase of protonic acid in medium, the yield of the PAN increased, the UV absorption of the PAN strengthened, and a blue shift of the π-polaron absorption was observed. And the conductivity of the PAN also increased with the acid content in medium. The potential mechanism of photo-induced polymerization of aniline is proposed. Moreover, after the ionic liquid is separated from the reaction mixture and reused for five times, no obvious decrease in catalytic activity could be found in photo-induced polymerization of aniline. The method may open a new pathway to prepare nano-scale conducting polymers with sunlight.     

High sensitivity and selectivity of ZnO nanoparticle-decorated 1D a-MoO3 nanobelts toward ethanol by microwave heating

One-dimensional layer structure a-MoO₃ nanobelts with abundant oxygen defects were effectively synthesized through a hydrothermal route and decorated by ZnO nanoparticles via a liquid-phase chemical process. ZnO nanoparticles (NPs) with a size of approximately 50 nm were uniformly dispersed on the a-MoO₃ nanobelt surface, forming an n-n heterostructure at the two-phase interface. The crystalline structure, microtopography, element composition, valence state, surface-to-volume ratios, optical properties, and work function of the ZnONP-decorated a-MoO₃ samples were analyzed. ZnONP-decorated a-MoO₃ nanobelts with different proportions of ZnO were synthesized and subjected to ethanol sensing. The 25% loaded ZnONP-decorated a-MoO₃ nanobelts were found to offer the best response (R_a/R_g = 19.2 at 100 ppm), which was 3.6 times higher than that of pristine α-MoO₃ (5.37) with a low detection limit (108 ppb). The response time was significantly lower (14–27 s) than that of pristine a-MoO₃ (5–8 s). Furthermore, the sensor has ultrahigh selectivity and reliable stability for ethanol. Layered MoO₃ nanobelts have a unique sensing mechanism, which is the catalytic oxidation of lattice oxygen on the MoO₃ surface to form oxygen vacancies and free electrons. The excellent sensing performance was ascribed to the unique 1-D nanobelt morphology of the a-MoO₃ carrier, the abundance of oxygen defects, and the formation of heterojunction barriers at the two-phase interface.     

Structure and Energy Spectra of a Class of Polybenzenoid Clar's Hydrocarbons and 1-D Polymers

The energy spectra of a class of 2-D polybenzenoid Clar 's hydrocarbons with a large number N(N ～ 10⁴) of carbon atoms is studied theoretically. It is shown that at the asymptotic case N ∞) the energy gap (EG) δE (N ∞) is different from zero, i.e., the π-systems should possess semiconductor properties. The results for the EG ΔE (N ∞) ≠ 0 of the hydrocarbons are in qualitative agreement with the results for the EG calculated for a class of 1-D ladder polymers having the same edge structure as the hydrocarbons. With increasing the number (M) of the π-centers of the elementary unit of the polymers, the band gap ΔE(M ∞) approaches also to a value different from zero. The quantitative results on the equilbria geometries of the hydrocarbons and the polymers correspond to Clar 's qualitative characterization of benzenoids composed of disjoint “π-sextets”. The energetics of the hydrocarbons with different types of defects and the corresponding Tamm and Frenkel states were also investigated.     

Demonstration of a minimum in the recovery of nanoparticles by flotation: Theory and experiment

The flotation of nano- and submicron particles does not follow the conventional collection theory based on the interception and collision mechanisms, which predicts extremely low collection efficiency for particles smaller than 10-μm. Brownian diffusion and colloidal forces strongly influence the collection of such particles by air bubbles in flotation. In this paper, a theoretical model is presented for predicting the collection efficiency of nanoparticles. The theory incorporates mass transfer by Brownian diffusion, microhydrodynamics of particles in the vicinity of a slip surface of rising air bubbles, and colloidal interactions that come into effect at small separation distances. The governing equation was solved numerically using the Crank-Nicolson method with variable step size. A finite difference scheme with mesh refinement in the vicinity of the air bubble surface was used to discretise the stiff partial differential equation for the particle concentration. The mesh refinement produced correct numerical solutions without oscillation in the particle concentration distribution, which otherwise occurred due to the stiffness of the differential equation and coarseness of the numerical mesh. Predictions from the model were compared with experimental results obtained with a small laboratory column cell, in which colloidal silica particles with diameters in the range were floated using fine bubbles of typical average diameter . The particle concentration in the pulp was about 1% by weight. Cetyltrimethyl ammonium bromide and Dowfroth 250 were used as the flotation collector and frother, respectively. Both the theory and experiment show significant effect of the electrical double-layer and non-DLVO hydrophobic attractive forces on the collection of nanoparticles by air bubbles. The theoretical and experimental results show the collection efficiency to have a minimum at a particle size in the order of . With larger particles, the interception and collision mechanisms predominate, while the diffusion and colloidal forces control the collection of particles with a size smaller than the transition size.     

Development of poly(vinylcarbazole)/alumina nanocomposite coatings for corrosion protection of 316L stainless steel in 3.5% NaCl medium

Poly(vinylcarbazole) (PVK) and PVK‐alumina (Al₂O₃) nanocomposite coatings were electrochemically coated on 316 L stainless steel (SS) substrates for corrosion protection of 316 L SS in 3.5 weight (wt) % NaCl medium. The formation of PVK and incorporation of nanoalumina particles in PVK‐Al₂O₃ nanocomposite coatings were confirmed from attenuated total reflectance‐infrared spectroscopy (ATR‐IR). Thermal analysis (TG) results showed enhanced thermal stability for the composites relative to PVK. Incorporation of Al₂O₃ nanoparticles enhanced the micro hardness of PVK coated 316 L SS. The dispersion of alumina nanoparticles was examined via scanning electron microscope (SEM) and tunneling electron microscopy (TEM) and revealed distinct features. The influence of nanoparticles on the barrier properties of PVK and PVK‐Al₂O₃ nanocomposites was evaluated in aqueous 3.5 wt % NaCl by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies. The results proved that PVK nanocomposite coatings provided better protection for 316 L SS than PVK coatings. The drastic increase in impedance values is due to the high corrosion resistance offered by the PVK nanocomposite coatings that arises due to the interaction between Al₂O₃ nanoparticles and PVK. The highest corrosion protection shown by the 2 wt % nano Al₂O₃ incorporated PVK composite coatings proved enhanced corrosion resistance compared to PVK. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44937.     

Direct synthesis of L10 type Fe-Pt nanoparticles using microwave-polyol method

We report the synthesis of Fe-Pt nanoparticles with microwave irradiation during polyol-reduction reaction. Chemically ordered Fe-Pt nanoparticles with L1₀ structure are fabricated at 250 °C using a microwave-polyol method without any post-synthesis treatments. Mössbauer analyses reveal the nanoparticles have partially ordered L1₀ structure. The partially ordered Fe-Pt nanoparticles exhibit coercivity of 3.4 kOe, saturation magnetization of 49 emu/g, and anisotropy field of 83 kOe at room temperature.     

Iron (III) oxide nanoparticles within the pore system of mesoporous carbon CMK-1: intra-pore synthesis and characterization

Iron (III) oxide nanoparticles were synthesized inside the pore system of mesoporous carbon CMK-1. This intra-pore synthesis was carried out using several cycles of wet impregnation, drying and calcination procedures. The existence of iron (III) oxide nanoparticles within the pore system was proved by powder X-ray diffraction, nitrogen physisorption, preservation of the host structure by Raman spectroscopy and transmission electron microscopy. Finally, the local structure of the iron oxide was determined by X-ray absorption spectroscopy.     

Preparation and optimization of matrix metalloproteinase-1-loaded poly(lactide-co-glycolide-co-caprolactone) nanoparticles with rotatable central composite design and response surface methodology

Matrix metalloproteases are key regulatory molecules in the breakdown of extracellular matrix and in inflammatory processes. Matrix metalloproteinase-1 (MMP-1) can significantly enhance muscle regeneration by promoting the formation of myofibers and degenerating the fibrous tissue. Herein, we prepared novel MMP-1-loaded poly(lactide-co-glycolide-co-caprolactone) (PLGA-PCL) nanoparticles (NPs) capable of sustained release of MMP-1. We established quadratic equations as mathematical models and employed rotatable central composite design and response surface methodology to optimize the preparation procedure of the NPs. Then, characterization of the optimized NPs with respect to particle size distribution, particle morphology, drug encapsulation efficiency, MMP-1 activity assay and in vitro release of MMP-1 from NPs was carried out. The results of mathematical modeling show that the optimal conditions for the preparation of MMP-1-loaded NPs were as follows: 7 min for the duration time of homogenization, 4.5 krpm for the agitation speed of homogenization and 0.4 for the volume ratio of organic solvent phase to external aqueous phase. The entrapment efficiency and the average particle size of the NPs were 38.75 ± 4.74% and 322.7 ± 18.1 nm, respectively. Further scanning electron microscopy image shows that the NPs have a smooth and spherical surface, with mean particle size around 300 nm. The MMP-1 activity assay and in vitro drug release profile of NPs indicated that the bioactivity of the enzyme can be reserved where the encapsulation allows prolonged release of MMP-1 over 60 days. Taken together, we reported here novel PLGA-PCL NPs for sustained release of MMP-1, which may provide an ideal MMP-1 delivery approach for tissue reconstruction therapy.     

掺杂1-萘硼酸的荧光纳米颗粒的制备及其在奥硝唑测定中的应用

采用水包油微乳液聚合法制备了一种掺杂1-萘硼酸的荧光纳米颗粒,并用于奥硝唑的测定。当荧光纳米颗粒的浓度固定为0.2 mg/mL时,对奥硝唑的线性响应范围为8.0×10-7~8.0×10-5mol/L,检测下限为5.0×10-7mol/L。掺杂1-萘硼酸的荧光纳米颗粒的耐光漂白性与游离萘硼酸的耐光漂白性相比有一定程度的提高。     

Assessment of UV-permeability in nano-ZnO filled coatings via high throughput experimentation

The degree of UV protection afforded by nano-ZnO in a polyurethane/acrylic clear topcoat was investigated. The influence of nano-ZnO concentration and dry film thickness on the optical properties (e.g., UV permeability and visible transmittance) of the coating was probed using a library of 28 samples that were prepared by high throughput techniques. A model for predicting the UV permeability of nano-ZnO filled coatings was developed and the nano-ZnO loading condition required to block >99% UV radiation was determined to be 2.0 g/m². This model can be used to assist in the development of coatings and other polymeric systems embedded with nano-ZnO to protect the coating and underlying materials (i.e., substrate) from UV degradation.

Corrosion protection of 1Cr18Ni9Ti stainless steel by polypyrrole coatings in HCl aqueous solution

Electrically conducting polypyrrole (Ppy) coatings doped with sodium dodecylsulfate (SDS) have been deposited on 1Cr18Ni9Ti stainless steel by anodic polymerization from aqueous solutions of pyrrole and sodium dodecylsulfate. The corrosion behavior of Ppy coated steel was investigated in 0.3 M HCl aqueous solution at room temperature by a combination of electrochemical measurement techniques and scanning electron microscopy. The steel is in active state at the open circuit potential and suffers from pitting corrosion when the polarization potential is higher than 210 mV versus SCE. The Ppy coating can increase the corrosion potential of the steel by more than 600 mV versus SCE, and the pitting corrosion potential by more than 500 mV versus SCE. Fifty-day exposure experiments indicated that the Ppy coating shows high stability, and can inhibit effectively the corrosion of the steel.     

Shape controlled spherical (0D) and rod-like (1D) silica nanoparticles in silica/styrene butadiene rubber nanocomposites: Role of the particle morphology on the filler reinforcing effect

Silica/styrene butadiene rubber (SBR) nanocomposites were prepared by blending method using shape-controlled spherical and rod-like nanoparticles with different aspect ratios as filler for the rubber reinforcement. The differently shaped silica particles were synthesized by sol–gel method using tetraethoxysilane (TEOS) and (3-mercaptopropyl) trimethoxysilane (MPTSM) as silica precursors, and cetyltrimethylammonium bromide (CTAB) as structure directing agent. This strategy allowed to study the influence of the particle morphology on the reinforcing effect independently of the silica surface chemistry and considering the aspect ratio as the only geometrical variance. Spherical and anisotropic rod-like particles, dispersed in the nanocomposites, formed a network of particles bridged by thin rubber layers throughout the SBR matrix. Moreover, differently oriented domains of aligned rods are observed when the aspect ratio of particles increases and is ≥2. Dynamic-mechanical properties demonstrated that the rod-like particles with the higher aspect ratio provided stronger reinforcement of the rubber. This was related to the self-alignment of the anisotropic particles and to the consequent larger filler/polymer interface, compared to that of spherical ones.     

Fabrication of composite coatings of 4-(pyrrole-1-yl) benzoate-modified poly-3,4-ethylenedioxythiophene with phosphomolybdate and their application in corrosion protection

We propose a novel composite (hybrid) organic/inorganic system that can be prepared as a coating (on 1 μm level) on glassy carbon and metal electrode substrates. Poly(3,4-ethylenedioxythiophene) or PEDOT based composite coatings were electrodeposited using cyclic voltammetry on glassy carbon and stainless steel substrates in the presence of 4-(pyrrole-1-yl) benzoic acid (PyBA) and phosphododecamolybdic acid (PMo₁₂). The coating growth was facilitated by the addition of polyoxyethylene-10-laurylether (BRIJ10) neutral surfactant at the level of 0.04 mol dm⁻¹ to improve solubility of the 3,4-ethylenedioxythiophene monomer and to form an aqueous micellear solution in the reaction medium. The fact that carboxylate-containing PyBA units link positively charged PEDOT structures tends to improve overall stability and adherence of composite coatings to stainless steel. The PEDOT/PyBA composite serves as a stable host matrix for large negatively charged polymolybdate inorganic species. Consequently, due to the formation of denser polymeric structures and to the existence of electrostatic repulsion effects, the polyanion-containing composite coatings are capable of largely blocking the access of pitting-causing anions (chlorides) to the surface of stainless steel. Interaction of phosphomolybdate with metal ions, namely with chromium(III) or even iron(III) or iron(II) that exist at the stainless steel–composite coating interface, may lead to the formation of insoluble deposits and exhibit overall passivating effect.