Mean Pore Diameter Research Articles

Study on the Etching Characteristics and Thermal Conductivity of Porous Silicon Nanowire Arrays Using Highly Doped Silicon

Silicon nanowires (SiNWs) fabricated by metal-assisted chemical etching (MACE) of highly doped silicon are promising thermoelectric materials because of their high conductivity and porosity. However, it is difficult to fabricate long SiNWs using highly doped silicon with doping concentrations higher than 1019 cm−3. In this study, we fabricated SiNWs up to 44 μm in length using highly doped silicon with a doping concentration of 1020 cm−3, analyzed the etching characteristics in SiNWs length and the morphology, and investigated the thermal conductivity. The phenomenon of continuous loss of SiNWs was found, which is a unique phenomenon indicating the presence of loss SiNWs throughout the whole etching process and difficulty of forming long SiNWs with highly doped silicon. On the other hand, the thermal conductivity results showed that the lowest thermal conductivity of the samples reached 2.98 W m−1 K−1, and the mean diameters of pores in these samples were 5−10 nm. Thus, the SiNWs using highly doped silicon is a potential material for thermoelectric device.

A novel self-separating silicon nanowire thin film and application in lithium-ion batteries

Nano silicon structures are important materials for modern electronic devices and have been widely researched with regard to photoelectricity, thermoelectricity, and lithium-ion batteries. However, since the nano silicon structures fabricated by conventional methods cannot be separated from silicon substrates, reuse of the substrate is restricted. Here, we propose a simple fabrication method to separate the nano silicon structures from the silicon substrates, which allows the reuse of the substrates. The fabrication was processed at room temperature, which allows large-area fabrication and is not restricted by the substrate thickness. Honeycomb structures of different length scales observed on both the nano silicon structure and the substrate suggest that the separation occurred due to the amplification of the silicon crystal defects. The nano silicon structures comprised porous silicon with an excellent specific surface area of 480 m2 g−1 and a mean pore diameter of 5.7 nm. Moreover, the nano silicon structures show good potential as anode materials for lithium-ion batteries wherein the measured reversible capacity was 1,966 mAh g−1 after 100 cycles. Based on the proposed method and morphological characteristics, the fabricated nano silicon structures can be considered a low-cost material with suitable applications in the energy field.

CFD analysis on the optimization of POCS performances under randomical transformations: a bridge with open-cell foams

Periodic Open Cell Structures (POCS) have been considered as possible catalytic substrates, thanks to recent developments in the Additive Layer Manifacturing (ALM) technique. In this work, the impact of the POCS cell shape on mass transfer has been investigated through CFD simulations. An algorithm able to increase the wet surface of a simple cubic POCS has been developed, keeping constant the mean pore diameter and with negligible porosity variations. Catalytic performances of the substrates have been evaluated, suggesting the possibility to enhance the mass transfer properties of the POCS up to that of foams by continuous randomical transformation of its shape. A dedicated CFD multi-region solver has been used for this purpose, accounting for heat/mass transfer and catalytic reactions. Moreover, a fluid-dynamic approach has been proposed in order to estimate the value of tortuosity, investigating its dependency on the POCS randomization level and its effect on the flow field.

Composite fabrication and characterization of crosslinked polyaniline/Pterocladia capillacea-activated carbon for adsorption of direct blue-86 dye from water

The fabrication of crosslinked polyaniline/Pterocladia capillacea-activated carbon composite (CrossPANI/P-AC) at different ratios (1:0, 1:0.2, 1:0.6, and 1:1) was studied. CrossPANI/P-AC composites were fabricated by the in situ polymerization of aniline using hydrogen chloride as an acidic dopant, and ammonium persulfate as initiator, while Pterocladia capillacea-activated carbon was synthesized by the chemical activation method and incorporated into the polymer matrix. The samples were characterized by the terms such as Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller, X-ray diffraction (XRD), thermogravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (EDX). FTIR spectroscopy showed the main characteristic peak positions of CrossPANI/P-AC; XRD showed low crystallinity of CrossPANI/P-AC. A high specific surface area for CrossPANI/P-AC was achieved at a ratio of 1:0.2 where Brunauer–Emmett–Teller surface area, total pore volume, and mean pore diameter values were 166.10 m2/g, 0.0141 cm3/g, and 3.40 nm, respectively. The capability of CrossPANI/P-AC (1:0.2) composite as adsorbent for Direct blue-86 (DB-86) dye from aqueous solution was investigated. The impact of initial dye concentration, temperature, pH, and contact time on the DB-86 dye adsorption from its water solution was examined. The equilibrium adsorption data were well represented by the Langmuir isotherm achieving maximum monolayer capacity (Qm) of 163.93 mg/g at a dose of 0.5 g/L. In contrast, the kinetic adsorption data were well fit by the pseudo-second-order model. Thermodynamic analysis demonstrated that DB-86 dye adsorption occurs spontaneously, endothermically, and physically in nature. The results demonstrated that these composites effectively removed DB-86 dye from aqueous solutions and could be recycled.Graphical abstract

Design of novel M(MnNi)V2O6 NPs via combution synthesis for photocatalytic performance on dual dye and dopamine biosensing

Herein M(MnNi)V2O6 have been synthesized by a simple and eco-friendly combustion method using dry butterfly pea flowers. The structural, optical, and morphological properties of the Nanoparticles (NPs) were characterized by XRD, FTIR, SEM with EDAX, TEM UV–visible spectroscopy, PL, BET, and. The average crystallite size of M(MnNi)V2O6 from the XRD pattern was found to be 44 nm with single phase. The functional groups present and metal to oxygen bonding of M(MnNi)V2O6 observed in FTIR. SEM shows aggloramated structure for all the ratios of M(MnNi)V2O6 and edax confirm the presence of all the elements, TEM micrograph of M(MnNi)V2O6 shows indicated the hexagonal, pentagonal, and spherical particle. The UV-DRS shows the energy band gap of 2.18 eV, 1.86 eV, 2.04 eV respectively for the for various fuel ratios (1:0.5,1:1,1:1.5) of prepared sample and luminescence spectrum shows blue emission having an emission of 297 and 300 nm. From the BET surface area analysis, total pore volume (VP) and mean pore diameter (rp) was absorbed to be 1.105 m2g-1, 0.004 cm3g-1 and 1.29 nm. The characterized NPs were applied for photocatalytic dye degradation and electrochemical activity. In dye degradation, impact of catalyst load (10–40 mg), pH of the solution (2−12), concentration of dye (5–15 ppm) under visible light at room temperature was investigated on both cationic dye methylene blue (MB) and anionic dye Rose Bengal (RB). These NPs were successfully applied for the detection of dopamine (DA) at micro molar concentration level and it shows an excellent sensing performance.

Comparison of Wound Healing Effect of Skin Micrograft Impregnated into Two Kinds of Artificial Dermis in a Murine Wound Model.

Skin MG was prepared from the skin of C57BL/6JJcl mice using Rigeneracons and administered onto Pelnac Gplus and Integra sheets. The amount of MG suspension impregnated in Pelnac Gplus and Integra was evaluated. Pelnac Gplus and Integra sheets combined with MG were applied to murine defects, and wound area, neoepithelium length, granulation tissue formation, and newly formed capillaries were compared with the control groups on days 7 and 14. The weight percentage of the MG absorbed by Pelnac Gplus and Integra was 88.8% ± 3.5% and 28.2% ± 7.0%, respectively (P < 0.05). In the in vivo experiment, the area of newly formed granulation tissue and both the number and area of newly formed capillaries in the PelnacG + MG group were significantly larger than those in the control group at 14 days after implantation (P < 0.05). Skin MG was successfully impregnated into Pelnac Gplus by simple administration but not into Integra. Administration of skin MG into the Pelnac Gplus promoted granulation formation and angiogenesis. Pelnac Gplus was more suitable than Integra in the combination therapy.

Effect of membrane mean pore diameter on water and solute flux in forward osmosis processes

Several forward osmosis (FO) experiments were carried out using aqueous solutions of sodium chloride (NaCl) in different concentrations, as draw solution (DS), and freshwater, as feed water (FW). The experiments were conducted at a constant temperature of ~20°C and using a symmetric cellulosic membrane in two grades different in their values of the molecular weight cut-off (MWCO), which is related to the mean pore diameter. This study investigates the effect of the membrane mean pore diameter on water flux and DS solute diffusional flux across the membrane. The value of water flux indicates the performance of the FO process, while solute flux is an important factor that determines its practicality. A proportionality factor is used to specify the relationship between water flux and solute flux for each membrane type and operational conditions. The results of this study show that water flux and solute flux increase as the solute concentration difference across the membrane increases. It is also found that, in the range of the tested membranes, membranes with larger mean pore diameters have lower water flux and higher solute flux.

Opposing Surfactant and Gel Effects of Soil Borne‐Hydrogels on Soil Water Retention

AbstractSoil‐borne hydrogels (e.g., bacterial extracellular polymeric substances, root‐derived mucilage) contain polymeric (i.e., gel‐like) substances as well as surface active substances, which modify the viscosity of soil fluid and wetting properties of soil particles, respectively. In this study, the individual and coupled effects of gel and surfactant on soil water retention were investigated experimentally using xanthan and Triton X‐100 as surrogates for gel and surfactant, respectively. Results show opposing effects that xanthan enhanced soil water retention because of increased solution viscosity and its hygroscopic property while surfactant reduced soil water retention due to reduced surface tension. We applied the modified Kosugi model that considers non‐capillary adsorption to describe the soil water retention curves measured in this study as well as additional curves reported in the literature. The model effectively captured the gel and surfactant effects using two model parameters, ω and μm, representing the weighting factor for capillary retention and the matric potential required to drain the effective mean pore diameter, respectively. Compared with the controls, gel‐dominated samples increased non‐capillary adsorption whereas surfactant‐dominant samples had a smaller (i.e., less negative) matric potential at the onset of drainage. Finally, we provided an explanation for enhanced water retention due to increased solution viscosity considering fluid displacement process. Our study improved the mechanistic understanding of soil water retention as affected by viscosity and surface tension individually as well as their coupled effects.

Microstructure and Mechanical Properties of Porous NiTi Alloy Prepared by Integration of Gel-Casting and Microwave Sintering.

Porous NiTi alloys were manufactured by integration of gel-casting and microwave sintering. The effects of sintering temperature on porosity, compressive strength, pore morphology and phase composition of sintered samples were researched. The results show that the porosity and the mean pore diameter of porous NiTi alloys decrease with increasing sintering temperature, whereas the content of the NiTi phase, the elastic modulus and compressive strength of sintered samples increase. When the gel body with the solid loading of 50 vol.% is microwave sintered at 1000 °C for 30 min, porous NiTi alloys are obtained with the porosity of 38.9%, the compressive strength of 254 MPa, elastic modulus of 4 GPa, and predominant phase of NiTi. The results suggest that the method is suitable for rapid preparation of large-size and complex-shape personalized products similar to human bones at a low cost.

Evaluation of soil macro-aggregate characteristics in response to soil macropore characteristics investigated by X-ray computed tomography under freeze-thaw effects

As two complementary aspects of soil structure, the importance of macropore and macro-aggregate characteristics in maintaining soil functions and productivity is paramount. However, the changes in macropores and macro-aggregates and their interactions induced by the effects of freeze–thaw action have rarely been evaluated. This study aimed to evaluate the freeze-thaw effects on soil macropore and macro-aggregate characteristics and their relationships using X-ray computer tomography and dry sieving. Thirty-nine undisturbed soil columns were derived from a depth of 0–15 cm in the Mollisol area of Northeast China. Seven freeze-thaw treatments, including 0 (CK), 1 (FT.1), 3 (FT.3), 5 (FT.5), 7 (FT.7), 10 (FT.10), and 15 (FT.15) freeze-thaw cycles, and two initial soil mass water contents (30% and 40% the initial soil water content (ISWC)) were selected under controlled laboratory conditions. Our results showed that freeze-thaw effects significantly increased the total image porosity, mean pore diameter, porosity with branches, and connectivity density (p < 0.05). However, the total number of pores showed a “first increase – then decrease” trend with an increasing number of freeze-thaw cycles. During the freeze-thaw cycles, the macropore and macro-aggregate size distributions exhibited dynamic processes. Compared to the CK treatment, soils for 30% and 40% ISWC under the FT.15 treatment exhibited a lower > 7 mm macro-aggregates by 27.9% and 43.1%, but a higher < 3 mm macro-aggregates by 78.0% and 88.4%, respectively. The total image porosity, porosity with branches, and connectivity density were significantly positively and negatively correlated (p < 0.05) with the mean weight diameter and fractal dimension of macro-aggregates, respectively. The increase in macroporosity and pore branches easily induced the breakdown of the macro-aggregates. This study can help improve the understanding of the effects of changes in macropore characteristics and the processes of macro-aggregate breakdown and further enable the utilisation of soil structure as an indicator for assessing the sustainability and erodibility of soils.

Adsorption kinetics analysis and optimization of Bisphenol A onto magnetic activated carbon with shrimp shell based precursor

Activated carbons synthesized from biomass (agricultural and food wastes) are considered promising materials for adsorbing organic pollutants. In this study, the mixture of shrimp shell (SS) and cellulose (C) were used as precursors for the synthesis of activated carbon (SS@C) with high surface area, well-developed pore structure and stable structure. On this basis, the magnetic adsorption material was prepared through NaHCO3 activation and Fe3O4 precipitation. Mean pore diameter (nm), surface area (m2·g−1), and micropore size (cm3·g−1) of SS@C.AC-M were characterized by SEM-EDS and N2 sorption analyses. The characterization of SS@C.AC-M revealed that the optimal mass ratio of SS@C and NaHCO3 was 1:1.5. In the absorption of Bisphenol A (BPA), the synergistic effects of BPA concentration, pH, and retention time were analyzed by response surface methodology (RSM). A pseudo-second-order model was proposed, which revealed the maximum adsorption capacity of the BPA onto SS@C.AC-M was 207.77 mg g−1. To test the reusability of SS@C.AC-M adsorbent, 5 cycles of pollutant removal experiments were carried out. This work provides a synthesis and optimization method of biomass-based activated carbons for the absorption of organic pollutants in wastewater.

The influence of electrolytes in the adsorption kinetics of reactive BF-5G blue dye on bone char: a mass transfer model

ABSTRACT The discharge of harmful dyes in water bodies is a serious pollution problem, dangerous for the ecosystem’s equilibrium and human health. In this sense, the aim of this work was to determine the influence of electrolytes (NaCl, KCl, CaCl2 and MgCl2) in the adsorption of Reactive Blue BF-5G dye, the most common dye used in industrial process for fabric colouring, using bovine bone char as the adsorbent. The bovine bone char was characterized by pH of point of zero charge (pHPZC), N2 adsorption–desorption isotherms, Fourier transform-infrared spectroscopy (FT-IR) and X-ray diffractometry (XDR). The characterization revealed a mesoporous structure (pore mean diameter of 94 Å and SBET ∼107 m2 g-1) with negative charge distribution at the surface (pHPZC = 3.8). The adsorption experiments revealed that the presence of KCl enhanced the material adsorption capacity (q max = 195 mg g−1), that the Sips isotherm best fitted the experimental data (R 2 > 0.9 except for KCl solution) and the adsorption process was mono- and multilayered. The kinetic adsorption experiments indicated that the inorganic electrolytes increased the initial adsorption velocity and the data was best modelled by the surface diffusional model (SDM), implying a resistance (aqueous > CaCl2 > NaCl > MgCl2 > KCl) to mass transfer at the surface of the pores which, in turn, prevented the dye diffusion to the interior of the adsorbent (qe = 71 mg g−1). Therefore, small quantities of KCl can be used to lower the mass transfer resistance and provide higher adsorption capacity with reduced time of operation, thus increasing the overall process efficiency.

Synthesis of high surface area mesoporous ZnCl2–activated cocoa (Theobroma cacao L) leaves biochar derived via pyrolysis for crystal violet dye removal

Chemically activated cocoa leaves biochar (CLB) was successfully prepared from fallen cocoa leaves (CLs) via ZnCl2–activation and pyrolysis at 700 °C for sequestration of toxic crystal violet (CV) dye from aqueous solution. CLs and CLB were characterized using elemental analysis (CHN/O), Brunauer-Emmett-Teller method (BET), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), X-ray diffraction (XRD) spectroscopy and scanning electron microscopy (SEM). The optimum conditions for effective removal of CV dye from aqueous solution (75.67% for CLs and 99.87% for CLB) were pH 9, initial CV dye concentration 100 mg/L, adsorbent (CLs/CLB) dose 0.4 g/L, contact time 160 min and temperature 300 K. Modified Ritchie second order best described kinetic and Liu model described equilibrium adsorption. CLs and CLB with maximum adsorption capacities 190.70 and 253.3 mg/g respectively, compete favorably with adsorbents used for removal of CV dye from wastewater in the literature. The high BET surface area (957.02 m2/g) and mean pore diameter (7.21 nm) were indicators of better adsorption efficiency of CLB. CLs showed adsorption to proceed towards endothermic process, while it was exothermic process for CLB. This study established the suitability of cocoa leaves as sustainable and environmental friendly precursor for preparation of adsorbent for the treatment of dye-containing wastewater.

The Role of the Morphological Characterization of Multilayer Hydrophobized Ceramic Membranes on the Prediction of Sweeping Gas Membrane Distillation Performances.

This paper shows which morphological characterization method is most appropriate to simulating membrane performance in sweeping gas membrane distillation in the case of multilayer hydrophobized ceramic membranes. As a case study, capillary four-layer hydrophobic carbon-based titania membranes arranged in bundles in a shell-and-tube configuration were tested with NaCl-water solutions using air as sweeping gas, operating at temperatures from 40 to 110 °C and at pressures up to 5.3 bar. Contrary to what is generally performed for polymeric membranes and also suggested by other authors for ceramic membranes, the mass transfer across the membrane should be simulated using the corresponding values of the mean pore diameter and the porosity-tortuosity ratio of each layer and measured by the layer-by-layer (LBL) method. Comparison of the modeling results with experimental data highlights that the use of parameters averaged over the entire membrane leads to an overestimation by a factor of two to eight of the modeled fluxes, with respect to the experimental values. In contrast, the agreement between the modeled fluxes and the experimental values is very interesting when the LBL parameters are used, with a discrepancy on the order of +/−30%. Finally, the model has been used to investigate the role of operative parameters on process performances. Process efficiency should be the optimal balance between the concomitant effects of temperature and velocity of the liquid phase and pressure and velocity of the gas phase.

Dye removal using novel adsorbents synthesized from plastic waste and eggshell: mechanism, isotherms, kinetics, thermodynamics, regeneration, and water matrices

Abstract High-density polyethylene (HDPE) waste and chicken eggshell were used to synthesize three novel adsorbents, namely mesoporous graphene (MG), nano-eggshell modified graphene (nEMG), and nano-magnetic eggshell modified graphene (nM-EMG) for methyl red (MR) adsorption from simulated wastewater. The effects of adsorption conditions (pH, contact time, initial dye concentration, adsorbent dose, and temperature) were investigated. MG, nEMG, and nM-EMG were characterized using SEM, TEM, BET, EDX, XRD, and FTIR analyses. MG, nEMG, and nM-EMG had specific surface areas of 15, 31, and 179 m2/g and mean pore diameters of 27, 29, and 5 nm respectively. The equilibrium adsorption capacities of MG, nEMG, and nM-EMG were 5.6, 8.1, and 6.5 mg/g respectively at MR concentration of 100 mg/L, pH 4, adsorbent dose of 1.0 g/100 mL, and temperature of 25 °C. All MR sorption processes followed the pseudo-second-order and Langmuir–Freundlich model. The adsorption rates were controlled by intra-particle and film diffusion. MR uptake on the synthesized adsorbents was spontaneous, endothermic, and chemisorption. The adsorption occurred via electrostatic interactions, π electron interactions, and hydrogen bonding. The performance of the prepared adsorbents was examined in different water matrices and compared with other MR adsorbents. After five regeneration cycles, the adsorbent reusability study showed that nM-EMG is the most stable and reusable adsorbent.

Curcumin-loaded hybrid particles for drug delivery applications

• A novel freeze-drying approach has been discussed for the preparation of collagen-lipid particles • Thermally stable, surfactant free hybrid biomaterial has been developed for drug delivery applications • Interaction of hydrogenated lecithin with collagen has been studied through turbidity assay The development of biopolymeric drug carriers is gaining interest due to their biocompatibility. Porous particles are the preferred drug-loading choice due to the high surface area. Lipids and collagen are widely explored biopolymers for various tissue engineering applications as drug carriers. In the present study, an attempt has been made to develop porous particles using collagen and lipid through a freeze-drying technique in cyclohexane and t-butyl alcohol. Porous particle formation has been confirmed using a Scanning Electron microscope (SEM) in three different solvent ratios (1:2, 2:1, 1:1). The particle size of the lipid-collagen particles was found to be 1032nm (1:1), 1612 nm (1:2), and 589 nm (2:1). The mean pore diameter of prepared particles in 1:2 and 2:1 solvent mixture found to be 3.64 and 3.97 nm respectively. Similarly, the lipid -collagen interaction has been ascertained through the TEM image. The influence of lipid on collagen has been studied using a fibrillogenesis assay and found that a higher incubation period influences the self-assembling process of the collagen. However, it aids in particle formation. Furthermore, a model drug curcumin has been loaded in the prepared particles and assessed for loading efficiency and release. From the drug release studies, it can be sustained drug release pattern acts as a prominent drug carrier for therapeutic applications prepared through the simple freeze-drying technique.

Mn-Fe catalyzed microwave combustion-plasma hybrid synthesis of 2D chips-like Mn-Fe boosted TiO2 architecture self-assembled of nano-walled honeycomb-like super-macroporous: Green fuel generation

The productive 2D chips-like Mn-Fe boosted TiO2 as self-assembled nano-walled honeycomb-like super-macroporous was synthesized via the Mn-Fe catalyzed microwave combustion-plasma hybrid to generate biodiesel. The physicochemical property of Mn-Fe doped TiO2 (Mn = 2at% & Fe = 2at.%) were executed by X-ray diffraction, FESEM, BET-BJH, TEM, and TPD-NH3 analyses. Fe and Mn increased the rutile phase and widened pores. 2D surface analysis of plasma-treated catalyst displayed the chips-like framework constructed of nanosheets comprising super-macropores. Plasma destroyed crumbly walls between pores. Hence more acidic sites were exposed, and the diffusion of large feed molecules within pores was eased. The total pore volume was 0.058 and 0.111 cm3/g, and the mean pore diameter was 2.94 and 4.57 nm, based on BET-BJH results. Besides, conversion was 91.9 and 96.1 % and after six runs conversion loss was 2.17 and 0.21 % for MnFe(2:2)TiO2 (MWC) and MnFe(2:2)TiO2 (PMWC), respectively. Conversion loss in MnFe(2:2)TiO2 (MWC) was because of the formation of a composite between undoped Mn and Fe and Ti oxides. The plasma made the bond between the composite components stronger and inhibited the leaching of components, so plasma made leaching slight.

Assessment of effectiveness factor in porous catalysts under non-symmetric external conditions of concentration

Abstract the present paper, the effectiveness factor of porous catalytic particles is evaluated in the absence of boundary conditions symmetry over the external surface by computational fluid dynamic (CFD) techniques. The first-order kinetics of decane oxidation, already evaluated experimentally, is taken as a representative reaction. Our study arises from the fact that, in the open literature, the effectiveness factor is usually calculated considering conditions of symmetry of concentration field around particles. However, depending on the fluid dynamics of the system, such conditions are not always established and, thus, our work aims at studying for the first time the behaviour of particle catalysts with non-uniform concentration fields over the surface. In particular, the effectiveness factor of the particles in a catalytic layer is calculated in the absence of symmetry by changing several parameters (temperature, tortuosity and mean pore diameter of particle) using two different methods, named Sphere-by-Sphere (SbS) and Equisized-Volume (EV), respectively. The results of these two methods are then compared to the theoretical one obtained in the presence of spherical symmetry. As a main result, we found that, for moderately low values of Thiele modulus (&lt;1.3 ca.), the analytical expression of the effectiveness factor obtained under spherical symmetry can be also applied in non-symmetric conditions. On the contrary, this cannot be done for higher values of Thiele modulus, for which we propose an empirical correlation of the effectiveness factor based on a corrected Thiele modulus. The efficacy of our approach is stated by the fact that pseudo-homogeneous-mode simulations of the heterogeneous system show results that match very well those obtained in heterogeneous mode, with an important reduction of calculation time and memory. The presented methodology can be also applied to n-order kinetics.

Synthesized NaA Nanozeolite as a Catalyst for the Preparation of 3-amino imidazo[1,2-a]pyridines under Solvent-Free Conditions

Abstract:The present study explores a new method for the fabrication of NaA nanozeolite as a simple and efficient catalyst for producing 3-aminoimidazo [1,2-a] pyridines via the 3-component reaction of aldehydes, 2-aminoperidines and isocyanides under solvent-free conditions. The production of the organic template-free (OTF) NaA nanozeolite was performed at room temperature. The prepared nanozeolite was identified by X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), Field Emission Scanning Electronic Microscopy (FESEM), N2 sorption isotherm and Particle Size Analysis (PSA). The particle sizes of synthesized spherical NaA nanozeolite were under 100 nm via the FESEM method. BET surface area, total pore volume, and mean pore diameter of the created sample were attained to be 362 m2g-1, 0.44 cm3 g-1 and 5.9 nm, respectively. The developed method has some advantages, such as OTF production of NaA nanozeolite, a simple synthesis method with short reaction time and easy separation using filtration, and the ability to recycle and reuse the catalyst several times without reducing its efficiency.

Corrosion protection and mechanical properties of the electroless Ni-P-MOF nanocomposite coating on AM60B magnesium alloy

Al-based MIL-53 MOF nanostructure was synthesized hydrothermally and then co-deposited in the electroless nickel coating on AM60B magnesium alloy using Zr pretreatment as an eco-friendly underlayer. The MIL-53(Al) nanostructure was synthesized in the form of layered semi-cube crystals with the surface area and mean pore diameter of 985.72 m 2 g −1 and 2.00 nm, respectively. The SEM images captured with two various zooming scales from the surface of the plain and MOF containing electroless layers showed cauliflower-like morphology with even distribution of nodule size. Also, the sub-grains of the plain coating disappeared after incorporation of the MOF. Although, both the normal and nanostructure-containing electroless layers have crystalline-amorphous structure, but the nanocomposite coating showed less crystallinity. The average surface roughness of the plain electroless coating was about 309 nm, which decreased to about 222 nm after incorporation of the MOF. The XRD patterns showed that the characteristic peak of Ni broadened after incorporation of the MOF, probably due to the decreasing of the crystallinity. For the heat-treated normal and MOF containing coatings at 200 °C no phase transition takes place, but new peaks appeared for heat-treated coatings at 400 °C due to the crystallization and second-phase precipitation. The results of the EIS tests showed an increase in the amount of the charge transfer resistance (from 19 to 29 kΩ cm 2 ) after addition of the MOF, which means an improvement in the corrosion resistance. Also, low J corr of the composite coating represents its higher corrosion resistance with respect to the plain coating. The micro-hardness values of the composite coating before and after the heat treatment were higher than the plain coating. Also, the Ni-P-MOF coating has a lower wear rate both before and after the heat treatment due to an improvement in its micro-hardness.