Differential Thermal Gravimetric Analysis Research Articles

Effective removal of tetracycline from water by batch method using activated carbon, magnetic carbon nanocomposite, and membrane hybrid technology

Abstract In this study two adsorbents (activated carbon; AC and magnetic activated carbon; MCN) were prepared from Dalbergia sissoo sawdust and used as potential adsorbents for the removal of tetracycline (TC) from water. Both the adsorbents were characterized by instrumental techniques like energy dispersive x-ray (EDX), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), x-ray diffraction (XRD), surface area analyzer and thermal gravimetric/Differential thermal analysis (TG/DTA). The effect of antibiotic initial concentration, contact-time, pH, adsorbent-dose, and temperature were evaluated to determine optimum adsorption conditions. The optimum TC concentration for both AC and MCN was 120 mg/L while optimum time of saturation for both adsorbents was 120 min. The optimum pH determined was five while optimum adsorbent dose was 0.1 g. The adsorption isothermal data of both sets of experiments was best explained by Langmuir model. The kinetic data was well explained by pseudo-second order kinetics model. The ΔH° (enthalpy change) and ΔSo (entropy change) were; −14.989 and 25.174 kJ/mol for AC and −11.628 and 51.302 kJ/mol for MCN respectively. The values of Gibbs free energy (ΔG°) calculated for AC were 7.36, −7.99, −7.36, −7.61, and −8.12 kJ/mol while for MCN these were −15.02, −15.53, −16.05, −16.56, and −17.07 kJ/mol corresponding to temperatures; 298, 303, 313, 323, and 333 K. To control fouling in ultra-filtration, nano-filtration, and reverse osmosis membranes caused by TC, and both adsorbents, a continuous stirred reactor was connected in series with membrane pilot plant. The improvement brought about by both adsorbent in parameters like % retention and permeate flux was also evaluated. Comparatively, better improvement was brought about in % retention and permeates flux by MCN.

Ferric oxide colloid: novel nanocatalyst for heterocyclic nitramines

Highly energetic nitramines such as cyclotetramethylene-tetranitramine (HMX) experience high combustion enthalpy, as well as large volume of gaseous products. Despite the fact that HMX can expose high thermal stability, it exposes low sensitivity to different catalysts. HMX-based propellants will combust at low burning rate. Ferric oxide particles with hydrous surface can offer high catalyzing ability via release of active .OH radicals; active .OH species would attack heterocyclic ring with hydrogen atom abstraction. Highly crystalline, monodispersed Fe2O3 nanoparticles (NPs) of 3.39 nm average particle sizes were developed using hydrothermal processing. Fe2O3NPs were integrated into HMX via co-precipitation technique. The impact of Fe2O3NPs (1 wt%) on HMX thermolysis was investigated using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Fe2O3NPs demonstrated advanced catalytic performance. HMX main exothermic decomposition peak was decreased by 13.0 °C with an increase in decomposition enthalpy by 72.2%. Fe2O3NPs could alter HMX thermolysis from C–N cleavage to hydrogen atom abstraction through the released active surface .OH radical. Additionally released NO2 could be adsorbed on nanocatalyst surface offering high decomposition enthalpy.

Analysis of Thermal Behavior of Crystalline Minerals in Bituminous Coal Samples under Air and Argon Atmospheres.

The thermal behavior of ash components in two bituminous coal samples [Upper Freeport (the “UF”) and Illinois #6 (the “IL”)] was investigated under air and argon atmospheres in the temperature range of 800–1200 °C using thermal gravimetric–differential thermal analysis, X-ray diffraction transmission electron microscopy (TEM), and TEM–energy dispersive X-ray spectrometry measurements. The UF treated under air formed the needle-like crystals which were assumed to be mullite-related substances formed by transformation of andalusite, because the crystals are mainly composed of SiO2 and Al2O3. In contrast to the UF, the IL did not generate such crystals; however, when the IL was treated under air after carbonization under Ar, crystals appeared. The composition of the UF with an Al/Si ratio higher than that of the IL favored the formation of mullite-related substances, while the presence of lime in the IL inhibited the formation of mullite-related substances. Oldhamite was formed by the reaction of lime with sulfur at the carbonization of the IL under Ar and remained even at the successive air treatment. As lime was consumed, the formation of mullite-related substances was ceased to be inhibited under air after Ar treatment.

Reactive compatibilization and properties of low-cost and high-performance PBAT/thermoplastic starch blends

Poly(butylene adipate-co-terephthalate) (PBAT) is widely used for production of biodegradable films due to its high elongation, excellent flexibility and good processability properties. However, PBAT is costly with prices approximately double or even triple the prices of traditional plastics like polyethylene. Fully biodegradable PBAT/TPS blends are prepared through melt extrusion of PBAT and thermoplastic starch (TPS) to significantly reduced PBAT cost. Effects of reactive epoxy compatibilizer (REC) and preparation methods on morphology and properties of PBAT/TPS blends were determined using scanning electron microscopy (SEM), mechanical analysis, rheological measurement, gel permeation chromatography (GPC), differential canning calorimetry (DSC) and thermal gravimetric analysis (TGA). Results indicated that REC effectively improves compatibility of PBAT/TPS blends and extends polymer chains of PBAT. Blends obtained through two-step extrusion showed a bicontinuous phase structure without phase separation or starch particles, which were observed in blends prepared through one-step extrusion. Excellent mechanical properties were obtained even with high contents of TPS through two-step extrusion in the presence of REC.

Thermal analysis of Li2-хNaxGe4O9 glasses crystallization

The glasses of lithium-sodium tetragermanate LiNaGe4O9 and solid solution Li1.8Na0.2Ge4O9 were prepared by quenching the melt and crystallized on heating. The glass crystallization was controlled by differential scanning calorimetry and thermal gravimetric analysis. The DSC measurements performed in the range 300–1200 K show that the crystallization of the glasses occurs through a single stage. There are no anomalies on TGA dependences. It is assumed that LiNaGe4O9 and Li 1.8Na0.2Ge4O9 glasses crystallize in accordance with a polymorphic mechanism.

A Theoretical and Experimental Study on Esterification of Citric Acid with the Primary Alcohols and the Hydroxyl Groups of Cellulose Chain (n = 1-2) in Parched Condition

Esterification of citric acid (CA) with the primary alcohols and the hydroxyl groups of cellulose chain (n = 1-2) in parched condition were investigated by using density functional theory (DFT) method and a two-layer ONIOM approach. Geometry and energy of reactants, products, and transition state (TS) structures were optimized at B3LYP/6-311g (d, p) level and ONIOM (B3LYP/6-311g (d, p):PM3MM) level. The computational results show that the esterification occurs in the two main steps: the first step is the dehydration reaction of CA to form anhydrides of 5-membered ring and 6-membered ring and the second step is the ring opening reaction with the hydroxyl –OH groups to form the ester products. The energy barrier of dehydration reaction step is much higher than that of ring opening reaction step. Effect of substituent R in primary alcohol R-CH2OH (R: CH=CH2, CH2NHCH3, CH2OCH3, CH2Cl) and cellulose chain (1G, 2G) on the reactivity, which has negative inductive effect –I, is significant. The combination of calculation data and experiment data were applied to make findings more rigorous. The activation energy of CA was determined by using differential scanning calorimetry (DSC) and thermal gravimetric (TG) analysis to beEaexp = 47.8 kcal/mol; the experimental data favoured the dehydration reaction step of CA.

Nuclear Magnetic Resonance and Calorimetric Investigations of Extraction Mode on Flaxseed Gum Composition.

We discussed about the influence of extraction mode on the flaxseed gums composition and their thermal stabilities. In order to do so, flaxseed gum was extracted by both classical magnetic stirring method and ultrasonic-assisted extraction (UAE). As a function of time, protein content, gum yield, pH values were evaluated and samples were characterized by 1H and 13C nuclear magnetic resonance (NMR) experiments as well as scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The flaxseed gum extracted in aqueous solution correspond to a mixture of different components, including polysaccharides, proteins and sometimes lignan derivatives. It is found that the protein and gum contents increase with the extraction duration for both the ultrasonic assisted and the traditional extraction while the pH decreases at the same time. As expected, compared to traditional magnetic stirring method, ultrasonic assisted extraction method can significantly enhance the yield of polysaccharides, lignans and proteins. The variation of pH is correlated to the increase of lignan molecules in the extracted samples. For thermic methods, SEM experiments showed that lignan derivatives which ester-bonded to polysaccharides associated to proteins are responsible to the formation of globular aggregates. Supplementary rod-like molecular organization were obtained from UAE and questions on the nature of the amphiphilic mesogen carbohydrate structures.

The novel micro-phase separated CO2-selective mixed matrix membranes (MMMs) modified with ester group by EPEG

In this paper, ethyl phthalyl ethyl glycolate (EPEG) was first introduced into Pebax to prepare Pebax/EPEG MMMs for CO2 separation. The thermal properties and the gas permeation properties of the MMMs were investigated. The micro-nano structure of the MMMs and the interaction between Pebax and EPEG were studied with fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The compatibility of Pebax and EPEG was characterized with FTIR-mapping and DSC. The location and distribution of liquid EPEG was studied with SEM and confirmed visually by cryo-SEM. The strength of hydrogen bonding interaction in the MMMs was characterized by Kwei equation with a parameter q. Pebax and EPEG were almost miscible in the MMMs at the molecular level when the EPEG content was not higher than 20 wt.%, and then micro-phase separation happened at higher EPEG content. The incorporation of EPEG not only enhanced the diffusion coefficients but also the solubility coefficients of the penetrants through the MMMs. The occurrence of micro-phase separation rendered a greater degree of permeability increase. For the MMMs with EPEG content of 60 wt.%, the CO2 permeability was almost 400 Barrer companied with CO2/N2 selectivity of 30. The CO2 permeability was three times that of the pristine Pebax, indicating the good CO2/N2 separation performance of Pebax/EPEG MMMs.

Synthesis and characterization of novel conductive copolymer poly[(phenylazepane-2-one)-co-(pyrrole)] with improved solubility and conductivity properties

An effective technique is proposed in this study to synthesize a novel polymer, based on the copolymerization of pyrrole with a synthesized monomer (phenylazepane-2-one), combining the character of both conductivity and solubility. The reaction was cationically catalyzed, using an acid exchanged clay (Maghnite-H+) as an ecological catalyst. The reaction synthesis of poly[(phenylazepane-2-one)-co-(pyrrole)] abbreviated poly(PAP) has been carried out in dichloromethane. The reaction yield was 85% at a temperature of 25 °C for 4 h using 4% of catalyst. Chemical structures have been characterized by proton and carbon nuclear magnetic resonance (1H-NMR and 13C-NMR), ultraviolet/visible spectroscopy (UV–Vis) and Fourier transform infrared spectroscopy (FT-IR). Thermal properties have been evaluated by differential scanning calorimetry and thermal gravimetric analysis, showing the thermal stability of the poly(PAP) up to 333 °C. Solubility tests confirmed the solubility of poly(PAP) in various common solvents. The indirect band-gap was found 1.22 eV using Tauc’s formula. The semiconductor behavior poly(PAP) has been proven by the evolution of ac electrical conductivity and dielectric properties as a function of frequency and temperature. These new properties allow direct application of poly(PAP) on all desired surfaces rather than conventional materials.

Preparation, characterization and luminescence behavior of some samarium complexes

The synthesis of luminescent complexes of Sm(III) with the general formula [Sm(L)3·(X)] was done in powder form. In the formula, L is 6-methyl-4-oxo-4H-1-benzopyran-3-carboxaldehyde and X represents 2H2O (C1), 1,10-phenanthroline (C2), 2,2′-bipyridine (C3); bathophenanthroline (C4) and neocuproine (C5). The complexes were characterized by using various analytical and spectroscopic tools like elemental analysis, electrospray ionization mass spectrometry (ESI–MS+), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–Vis) spectroscopy, thermo-gravimetric analysis/ differential thermal gravimetric analysis (TGA/DTG), field emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD), and photoluminescence (PL) studies. TGA/DTG showed high thermal stability of synthesized complexes. Powder XRD depicts that the average particle size lies in the nano-range. On monitoring at the excitation wavelength of 370 nm, the complexes display characteristic luminescence peaks of Sm(III) at ~ 564, ~ 600 and ~ 647 nm assigned to 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, and 4G5/2 → 6H9/2 transitions, respectively, with the most intense transition at ~ 600 (orange emission) and ~ 647 nm (bright red emission) in liquid and powder state, respectively. The investigations demonstrate that the synthesized novel complexes might be practically useful in electroluminescent devices, bio-assays, and liquid lasers due to their attractive photoluminescent properties.

Structural and Thermal Study of Mg2TiO4 Nanoparticles Synthesized by Mechanical Alloying Method

Background: Mg2TiO4 – based ceramics have proven their potentiality in the field of wireless communication systems. In the past, Mg2TiO4 ceramics was considered a quite optical response material in thin film form. Moreover, there is very few studies have been done whatever the proposed work in the present study. Objective: To prepare Mg2TiO4 nano-powders with the help of High Energy Ball Mill (HEBM) and intend to investigate its effect on crystal structure, microstructure and on thermodynamic behavior of MgO-TiO2 system. Methods: Mg2TiO4 ceramics were synthesized using Mechanical alloying method from high- purity oxides MgO and TiO2 (99.99%) of Sigma Aldrich (St. Louis, MO). Results: From the experimental studies it is observed that the powder’s particle size decreases with an increase of milling time. XRD analysis is carried out for phase confirmation of the mixed Mg2TiO4 powder. Further, the result also showed that there is structural changes occurred in the sample by high energy ball milling process, milled at different times. The nanocrystalline nature Mg2TiO4 powder was confirmed from microstructure taken by Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). Further, differential thermal gravimetric analysis has been carried out to investigate the thermal behavior of milled Mg2TiO4 -powder (35 hours). Conclusion: In work, the effect of mechanical alloying on structural, microstructural and thermal properties of nanocrystalline Mg2TiO4 powders has been investigated systematically. The effect of milling time on particle size, crystal structure and the microstructure was studied using XRD, FE-SEM, TEM and DSC/TGA analysis. The microstructural analysis (FE-SEM and TEM) reveals the nanocrystallinity nature of MTO ceramics prepared by mechanical alloying method. The thermal decomposition behavior of the milled powders was examined by a Thermo-Gravimetric Analyzer (TGA) in argon atmosphere.

Structural, spectral, dielectric and magnetic properties of indium substituted copper spinel ferrites synthesized via sol gel technique

Indium (In) substituted copper ferrites with nominal composition CuInxFe2-xO4 (where 0.00 ≤ x ≤ 0.32) were prepared via sol gel route. Influence of In3+ on thermal, structural, spectral, magnetic and dielectric properties are elucidated. The complete decomposition and stable phase formation was assessed from thermal gravimetric analysis (TGA) and differential thermal gravimetric analysis (DTA). The structure of copper ferrite is single phase estimated from X-ray diffraction (XRD) analysis. Lattice constant (a) and crystallite size first increased then decreased with the inclusion of In3+ ions. Cell volume, X-ray density and bulk density are improved due to substitution of indium ions. Magnetic studies are carried out by vibrating sample magnetometer (VSM). The various magnetic parameters i.e saturation magnetization (Ms), coercivity (Hc) and retentivity (MR) are elucidated. The value of Ms and Hc are reduced with the substitution of In3+ ions. The squareness ratio, anisotropy constant and Bohr's magneton were also decreased as the inclusion of indium concentration. The value of dielectric constant (ε′), dielectric loss (ε") and tan loss were reduced as frequency increased. The surface morphology was studied by SEM (scanning electron microscopy). The small value of dielectric parameters and coercivity of synthesized ferrites suggested that indium substituted copper ferrites might be useful in switching and high frequency applications.

Multifunctional paraffin wax/carbon nanotube sponge composites with simultaneous high-efficient thermal management and electromagnetic interference shielding efficiencies for electronic devices

As the operating speed and efficiency of electronic devices increase continuously, developing their thermal management and electromagnetic shielding capabilities has become extremely important. In this study, we prepared a paraffin wax/carbon nanotube sponge (PW@CNS) composite with simultaneous high-efficient thermal management and electromagnetic interference shielding functions via the simple vacuum impregnation method. The PW component functions as the phase change working substance for thermal management applications, and whereas the three-dimensional electrically conductive CNS component forms the matrix supporting the PW and a shielding structure against electromagnetic waves. The properties of PW@CNS are characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Its latent heat and relative enthalpy efficiency during melting and freezing process are as high as 248.8 J/g and 247.7 J/g, and 96.2% and 96.3%, respectively. After 100 thermal cycles, the latent heat remained nearly constant, and the prepared PW@CNS exhibited the excellent thermal management behavior and electromagnetic interference (EMI) shielding effectiveness (SE). All the results indicate that this PW@CNS has great potential as a thermal management and electromagnetic interference shielding material for electronic devices.

Influence of chain interaction and ordered structures in polymer dispersed liquid crystalline membranes on thermal conductivity

Abstract Polymer dispersed liquid crystalline (PDLC) membrane with intrinsic thermal conductivity was prepared by dispersing liquid crystalline polysiloxane containing crosslinked structure (liquid crystalline polysiloxane elastomer (LCPE)) into polyvinyl alcohol (PVA). Chemical structures were characterized by Fourier transform infrared (FT-IR) and 1H-NMR, and microscopic structures were analyzed by polarizing optical microscope (POM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The thermal conductivity of PDLC membrane was characterized by hot disk thermal constants analyzer, and the tensile properties were measured by tensile testing machine. Thermal properties were characterized by differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA). The results show that LCPE was dispersed in PVA uniformly, and the mesogenic monomer of LCPE formed microscopic ordered structures in PDLC membrane. Meanwhile, hydrogen-bond interaction was formed between LCPE and PVA chain. Both microscopic-ordered structure and the hydrogen-bond interaction improved the phonon transmission path, and the thermal conductivity of PDLC membrane was up to 0.74 W/m⋅K, which was 6 times higher than that of pure PVA film. PDLC membrane possessed proper tensile strength and elongation at break, respectively 5.18 MPa and 338%. As a result, PDLC membrane can be used as thermal conductive membrane in electronic packaging and other related fields.

Preparation and thermal properties of lauric acid/raw fly ash/carbon nanotubes composite as phase change material for thermal energy storage

In this study, a novel ternary system form-stable phase change material (FSPCM) composed of lauric acid (LA)/raw fly ash (RFA)/carbon nanotubes (CNT) was prepared via low cost, easy and industrially applicable fabrication process for low-temperature heat storage. Particularly, the unmodified RFA was directly acted as supporting material to prevent the leakage of the melted LA almost at no cost. A series of leakage experiments were performed to evaluate the package efficiency. The maximum mass fraction of LA absorbed in RFA and CNT was found to be 25 wt% without the LA leakage. Hence, the LA/RFA/CNT (25/75/5 wt%) composite was characterized as FSPCM. The chemical structures, microstructure thermal properties and thermal stability of the FSPCM was investigated by Fourier transformation infrared spectroscope (FTIR), scanning electronic microscope (SEM), differential scanning calorimetry (DSC) and thermal gravimetric analyzer (TGA). The SEM and FTIR results indicated that LA was adsorbed on the RFA’s surface porous or into the porous structure of CNT. And there was good chemical compatibility among LA, RFA and CNT. The DSC results demonstrated that the phase change temperatures and latent heats of LA/RFA/CNT FSPCM were 45.36 °C and 37.83 J/g for melting and 40.51 °C and 36.48 J/g for freezing, respectively. TGA analysis test revealed that the composite PCM had excellent thermal stability. Moreover, the heat transfer efficiency of LA/RFA/CNT FSPCM has been improved by the addition of RFA and CNT. In short, the LA/RFA/CNT FSPCM has a promising application prospect in low-temperature application due to feasible and in large scale industrial preparation, low-cost, simple and facile process.

Yellowish-orange and red emitting quinoline-based iridium(III) complexes: Synthesis, thermal, optical and electrochemical properties and OLED application

Two novel heteroleptic iridium(III) acetylacetonate (acac) complexes K3a and K3b were synthesised from cyclometallating ligands of 2-(4′-formylphenyl)quinoline 11a and 2-(5′-formylphenyl)quinoline 11b. Complexes K3a and K3b were fully characterised by NMR spectroscopy, mass spectrometry and FT-IR. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) indicate that both complexes were amorphous solids, stable up to 303 °C and 313 °C, respectively. Complexes K3a and K3b showed strong, high-energy absorption bands (<400 nm) due to ligand-centred (1LC) transitions and weaker, low-energy absorption bands (400−600 nm) arising from a mixture of metal-to-ligand charge transfer (1MLCT/3MLCT) and ligand-centred (3LC) transitions. In degassed dichloromethane solutions, complexes K3a and K3b gave yellowish-orange and red phosphorescent emissions at 579 nm and 630 nm, with quantum efficiencies of 99.3 % and 79.3 %, respectively. At positive potential, complexes K3a and K3b exhibited a one-electron reversible oxidation (Eox1/2) peak at 0.69 V and a quasi-reversible oxidation (Eox1/2) peak at 0.60 V, respectively, which were assigned to the Ir(III)/Ir(IV) couple. At negative potentials, complexes K3a and K3b exhibited a one-electron irreversible reduction peak at -1.79 V and -1.94 V, respectively. Phosphorescent organic light-emitting diodes (PhOLEDs) were fabricated with a device configuration of ITO/PEDOT:PSS/EML/TPBi/LiF/Al, in which K3a and K3b gave yellowish-orange and red electroluminescence (EL) at 572 nm and 628 nm, respectively. Complex K3a gave the highest luminance of 2773 cd/m2, current efficiency of 3.3 cd/A, external quantum efficiency of 1.2 % and maximum power efficiency of 1.05 lm/W with a turn-on voltage of 5.0 V (Device A).

The special effect of the Aspergillus flavus and its enzymes on biological degradation of the intact polylactic acid (PLA) and PLA-Jute composite

The biodegradation of PLA and PLA-Jute (64/36) in an aqueous media with Aspergillus flavus CCUG 28296, as well as its cell-free enzyme extract, was investigated through their physical, molecular, and thermal characterization. Results indicated that the thicknesses of the fungal treated PLA and PLA-jute samples during seven months have reduced by 52% and 63%, respectively while for the enzyme-treated samples, 45% and 49% reduction in the thickness has occurred. Moreover, the gel permeation chromatography (GPC) revealed a substantial decrease (about 75%) in the weight average molecular weight (Mw) of PLA and PLA-Jute treated with fungus, which confirmed the effective performance of A. flavus on the biological degradation of PLA. The obtained results were further supported by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) of the treated and control samples as well. Interestingly, the observed reduction in the Mw of PLA in PLA-Jute was 64% after the enzymatic treatment, while for the unblended PLA, it was just about 32%. These results pointed to the synergistic effect of jute on PLA degradation because of the promiscuous activity of the effective enzymes on jute degradation, which could accelerate the PLA decomposition.

The effect of Cu nanoparticle adding on to epoxy-based adhesive and adhesion properties

Epoxy-based adhesives are widely used for repairing or jointing the metal sheets in the industry. Because of their superior mechanical properties, the metallic nanoparticles can be selected as the additive of the epoxy adhesive. The strength of the Cu nanoparticles (CuNPs) can be expected to improve the mechanical properties of neat epoxy. In this study, CuNPs were added at various weight ratios, such as 1, 2, 5, 10, 15, and 20% into the epoxy resin adhesive. Tensile tests of the dog-bone specimens and the lap-shear tensile tests of the single lap joints were performed for obtaining the mechanical properties. In order to investigate the failure mechanisms, the fractured surfaces of the tensile test samples and adhesively joined sheets were imaged by using a Scanning Electron Microscope. The thermal properties of the adhesives were obtained by using Thermo Gravimetric Analysis and Differential Thermal Analysis. The mechanical and thermal properties of epoxy resin adhesive were improved by adding the CuNPs. The best adding ratios of CuNPs into epoxy were obtained by both mechanical and thermally point of views. As a result of this study, 15 wt% the ratio of Cu nanoparticle adding into the epoxy-based adhesive is suitable for improving the mechanical properties. On the other hand, 20% is the proper Cu nanoparticle adding ratio for the thermal properties improving.

One‐pot synthesis of 1,4‐dihydropyridines and N‐arylquinolines in the presence of copper complex stabilized on MnFe2O4 (MFO) as a novel organic–inorganic hybrid material and magnetically retrievable catalyst

In this work, the design and synthesis of a heterogeneous catalyst based on functionalization of manganese ferrite nanoparticles encapsulated in a silica layer with Schiff base and subsequent incorporation of copper is presented. The fabricated hybrid material was characterized by employing Fourier‐transform infrared spectroscopy, X‐ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, differential thermal gravimetric analysis, vibrating sample magnetometry and inductively coupled plasma‐optical emission spectrometry techniques. The prepared organic–inorganic hybrid material was successfully used as an efficient and recoverable catalyst for the synthesis of 1,4‐dihydropyridines and N‐arylquinolines under mild and green reaction conditions. The results showed that the catalyst exhibited excellent catalytic activity under optimum reaction conditions and the desired products were obtained in good to excellent yields. The new 1,4‐dihydropyridines and N‐arylquinolines were characterized by Fourier‐transform infrared spectroscopy, 1H NMR and Elemental analysis of Carbon, Hydrogen and Nitrogen (CHN) analyses. Study of the catalyst reusability confirmed that the catalyst could be recycled for five reaction runs with slight loss of the catalytic activity and negligible copper leaching.

Preparation and Characterization of Poly(lactic acid) Micro- and Nanofibers Fabricated by Centrifugal Spinning

In this paper, poly(lactic acid) (PLA) micro- and nanofibers were successfully prepared by centrifugal spinning which is a more simple and effective approach to produce micro/nanofibers. The morphology of fibers was investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), while their thermal properties by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). The results showed that the diameter of PLA fibers increased significantly with increasing solution concentration and decreased slightly with increasing collection distance. It can be controlled below 500 nm at the optimal process parameters which were found to be spinning solution concentration of 6 %, spinneret diameter of 0.11 mm, rotational speed of 5500 rpm and collecting distance of 15 cm. Although the crystallinity of the PLA fibers was weaker than that of the PLA pellets due to the insufficient adjustment of the molecular chain in rapid solvent evaporation and short stretching time, it can be improved by increasing the rotational speed from 4500 to 7000 rpm. The glass transition temperature (Tg) and melting temperature (Tm) of the fibers were nearly keeping constant compared to the PLA pellets. Its good degradability was demonstrated by the loss of fibers structure completely within 5 hours of immersion in NaOH at pH 13.