A Review on Sources,Extractions and Analysis Methods of a Sustainable Biomaterial:Tannins

Condensed and hydrolysable tannins are non-toxic natural polyphenols that are a commercial commodity industrialized for tanning hides to obtain leather and for a growing number of other industrial applications mainly to substitute petroleum-based products.They are a definite class of sustainable materials of the forestry industry.They have been in operation for hundreds of years to manufacture leather and now for a growing number of applications in a variety of other industries,such as wood adhesives,metal coating,pharmaceutical/medical applications and several others.This review presents the main sources,either already or potentially commercial of this forestry by-materials,their industrial and laboratory extraction systems,their systems of analysis with their advantages and drawbacks,be these methods so simple to even appear primitive but nonetheless of proven effectiveness,or very modern and instrumental.It constitutes a basic but essential summary of what is necessary to know of these sustainable materials.In doing so,the review highlights some of the main challenges that remain to be addressed to deliver the quality and economics of tannin supply necessary to fulfill the industrial production requirements for some materials-based uses.

Selected gas response measurements using reduced graphene oxide decorated with nickel nanoparticles

The work reports the synthesis of nickel nanoparticles supported on thermally reduced graphene oxides(rGO)in the ionic liquid[BMIm][NTf_(2)]through microwave decomposition reaction.Ni@rGO with the polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)as binder was positively tested for its response towards the oxidizing gas nitrogen dioxide(10 ppm in air),the reducing gas carbon monoxide(3000 ppm in N_(2))and the volatile organic compound(VOC)acetone(35,000 ppm in air).The results from different gases were compared at different temperatures with the best results for NO_(2) at 200℃.Additionally,it is shown for NO_(2) gas that the Ni@rGO-PEDOT:PSS polymer composite gives better results than the rGO-PEDOT:PSS polymer composite.After the heat treatment the oxidation state of pure nickel nanoparticles were confirmed by powder diffraction.

Impact of Ionic Liquid 1-Ethyl-3-Methylimidazolium Acetate Mediated Extraction on Lignin Features

This study aims at investigating the impact of ionic liquid extraction on lignin structure by studying the mechanism of lignin depolymerization in 1-ethyl-3-methylimidazolium acetate EMIM[OAc]) and comparing it with that of organosolv and milled wood methods. Ionic liquid mediated lignin (ILL) using EMIM[OAc]), ethanol organosolv lignin (EOL) and milled wood lignin (MWL) were isolated from Typha capensis (TC) and subjected to several analytical characterizations. Experimental data shows that ILL exhibited a relatively lower degree of condensation, lower aromatic C-C structures and a higher aliphatic OH with values of 0.42/Ar, 1.94/Ar and 1.33/Ar moieties compared with EOL values of 0.92/Ar, 2.22/Ar and 0.51/Ar moieties respectively. The ILL was depolymerized under mild conditions giving relatively higher β-aryl ether linkages content, higher molecular mass, and exhibited closer structures and reactivity to native lignin than EOL. These insights on TC lignin depolymerization in EMIM[OAc]) acetate may contribute to better value-addition of lignocellulosic biomass.

Modified Nitrogen-Doped Graphene Electrocatalyst for Oxygen Reduction Reaction in Alkaline Fuel Cells

We report modified nitrogen-doped graphene （CN） as electrocatalyst for ORR （oxygen reduction reaction） in alkaline medium. CN was synthesized by a novel procedure based on graphite oxide thermally treated with cyanamide suitable for facile N-doping and large-scale production, whereas cyanamide was used as N-precursor. The structure of the material was characterized by TEM （transmission electron microscopy）, SEM （scanning electron microscopy）, Raman spectroscopy and XPS （X-ray photoelectron spectroscopy）. Structural and electrochemical properties of CN were compared with those of non-modified graphene （TRGO （thermally reduced graphite oxide））. The electrochemical characterization of TRGO and CN in alkaline solution demonstrates enhanced electrocatalytic ORR activity and improved long-term stability for N-doped CN. Voltammetric studies confirmed that, oxygen reduction on CN rather follows four-electron pathway. Compared with commercial 20% PtC catalyst, CN is characterized by exceptional methanol crossover resistance and superb long-term operation stability. Owing to these factors, nitrogen-doped graphene has a great potential to be used as metal-free electrocatalyst in cathodes of alkaline fuel cells.

Kinetic, Isotherm and Thermodynamic Studies of the Adsorption of Thymol Blue onto Powdered Activated Carbons from <i>Garcinia cola Nut</i>Shells Impregnated with H₃PO₄and KOH: Non-Linear Regression Analysis

In this work, activated carbons (ACs) prepared by chemical activation of garcinia cola nut shell impregnated with H3PO4 (CBH2/1) and KOH (CBK1/1) were used to study the kinetics, equilibrium and thermodynamics of the adsorption of thymol blue from aqueous solution. The characterization of ACs showed the BET measurements gave surface area and total pore volume respectively of 328.407 m2·g-1 and 0.1032 cm3·g-1 for CBH2/1 and 25.962 m2·g-1 and 0.03 cm3·g-1for CBK1/1;elemental analysis showed a high percentage of carbon in both ACs. Influence of parameters such as initial pH, contact time, adsorbent mass, initial concentration, ionic strength and the effect of temperature on the removal of thymol blue from aqueous solution were studied in batch mode. The studies showed that equilibrium adsorption was attained after 60 minutes for the two ACs, adsorption capacity increased with increasing concentration of thymol blue, and maximum adsorption capacity was obtained at an acidic environment with pH 2. Avrami’s non-linear kinetic expression was the best suited for describing the adsorption kinetics of thymol blue onto ACs, while equilibrium data showed that the three-parameter isotherms better described the adsorption process since R2 > 0.96, and the error functions were lowest for all of them. Maximum adsorption capacity values obtained using the three-parameter Fritz-Schlunder equation were 32.147 mg·g-1 for CBH2/1 and 67.494 mg·g-1 for CBK1/1. The values of the model parameters g and mFS respectively, obtained using the Redlich-Peterson and Fritz-Schlunder III isotherms below 1, showed that the adsorption of thymol blue by the ACs occurred on heterogeneous surfaces. Thermodynamic analyses of the data of the adsorption of thymol blue onto ACs revealed that the adsorption process was temperature dependent, endothermic and spontaneous.

Surface passivation and boundary lubrication of self-mated tetrahedral amorphous carbon asperities under extreme tribological conditions

Tetrahedral amorphous carbon coatings have the potential to significantly reduce friction and wear between sliding components.Here,we provide atomistic insights into the evolution of the sliding interface between naked and hydrogen-passivated ta-C sliding partners under dry and lubricated conditions.Using reactive classical atomistic simulations we show that sliding induces a sp3 to sp2 rehybridization and that the shear resistance is reduced by hydrogen-passivation and hexadecane-lubrication-despite our finding that nanoscale hexadecane layers are not always able to separate and protect ta-C counter surfaces during sliding.As asperities deform,carbon atoms within the hexadecane lubricant bind to the ta-C sliding partners resulting in degradation of the hexadecane molecules and in increased material intermixing at the sliding interface.Hydrogen atoms from the passivation layer and from the hexadecane chains continue to be mixed within a sp2 rich sliding interface eventually generating a tribo-layer that resembles an a-C:H type of material.Upon separation of the sliding partners,the tribo-couple splits within the newly formed sp2 rich a-C:H mixed layer with significant material transfer across the sliding partners.This leaves behind a-C:H coated ta-C surfaces with dangling C bonds,linear C chains and hydrocarbon fragments.

Damping of Pressure Pulsations in Mobile Hydraulic Applications by the Use of Closed Cell Cellular Rubbers Integrated into a Vane Pump

The present study evaluates the potential of a bio-inspired pulsation damper in a vane pump used in mobile hydraulic ap- plications. Pressure pulsations caused by such positive displacement pumps can lead to malfunctions and noise in a hydraulic system. A common measure to reduce pressure pulsations is the integration of pressure pulsation dampers downstream of the pump. This type of damping measure can also be found in biology as e.g. in the human blood circulatory system. Such working principles found in living organisms offer a high potential for a biomimetic transfer into technical applications. The newly developed bio-inspired damper consists of cellular rubbers with non-linear viscoelastic material properties. In order to evaluate the new damping method, pressure pulsations were measured at two different back pressures and at a wide engine speed range of the vane pump. For further assessment, different setups, varying the stiffness of the cellular rubber materials and the damper volume, were tested. Within the tested back pressures, the pressure pulsations could be reduced by up to 40%. The developed integrated pulsation damper offers a high potential to dampen pressure pulsations of positive displacement pumps used in mobile hydraulic applications ooeratin~ below 10 bar.

Simulation of secondary nucleation of polymer crystallization via a model of microscopic kinetics

We present simulations of the mechanism of secondary nucleation of polymer crystallization,based on a new model accounting for the microscopic kinetics of attaching and detaching.As the key feature of the model,we introduced multibody-interaction parameters that establish correlations between the attaching and detaching rate constants and the resulting thickness and width of the crystalline lamella.Using MATLAB and Monte Carlo method,we followed the evolution of the secondary nuclei as a function of various multibody-interaction parameters.We identified three different growth progressions of the crystal：（i） Widening,（ii） thickening and（iii） simultaneously thickening and widening of lamellar crystals,controlled by the corresponding kinetic parameters.