Creation Of Chemical Bonds Research Articles

AlN PEALD with TMA and forming gas: study of plasma reaction mechanisms.

The effect of deposition temperature and plasma dose on plasma-enhanced atomic layer deposition (PEALD) of AlN thin films with forming gas plasma and trimethylaluminum (TMA) has been studied. The temperature has a strong effect on TMA absorption considering the d-TMA absorptions at low deposition temperatures. The plasma effect on AlN growth was studied in terms of three aspects: (1) plasma effect on TMA absorption, (2) plasma effect on the insertion of plasma species and creation of chemical bonds with absorbed surface species, (3) plasma effect on the removal of organic ligands and weakly-bonded surface species. Plasma over-dosing and under-dosing not only affect the film growth rate but also the AlN film properties. A three-effect mathematical model of the plasma effect was built based on the three plasma effects, which is consistent with the AlN experimental growth results. The FTIR and dielectric studies of the PEALD AlN films support the model.

Preparation of mesoporous activated carbon from date stones for the adsorption of Bemacid Red.

This work concerns the elimination of the organic pollutant; Bemacid Red (BR), a rather persistent dye present in wastewater from the textile industry in western Algeria, by adsorption on carbon from an agricultural waste in the optimal conditions of the adsorption process. An active carbon was synthesized by treating an agro-alimentary waste, the date stones that are very abundant in Algeria, physically and chemically. Sample after activation (SAA) with phosphoric acid was highly efficient for the removal of BR. The characterization of this porous material has shown a specific surface area that exceeds 900 m2/g with the presence of mesopores. The iodine value also indicates that the activated carbon obtained has a large micro porosity. The reduction of the infrared spectroscopy (FTIR) bands reveals that the waste has been synthesized and activated in good conditions. Parameters influencing the adsorption process have been studied and optimized, such as contact time, adsorbent mass, solution pH, initial dye concentration and temperature. The results show that for a contact time of 60 min, a mass of 0.5 g and at room temperature, the adsorption rate of the BR by the SAA is at its maximum. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were studied to analyse adsorption kinetics. The result shows the adsorption kinetic is best with the pseudo-second-order model. In this study, Langmuir, Freundlich and Temkin isotherms were investigated for adsorption of BR onto SAA. The Freundlich and Temkin isotherms have the highest correlations coefficients. The suggested adsorption process involves multilayer adsorption with the creation of chemical bonds. The mechanism of adsorption of BR by SAA is spontaneous and exothermic, and the Gibbs free energy values confirm that the elimination of the textile dye follows a physisorption.

Atomistic simulation of nanoindentation using the DFTB method

In this work, nanoindentation processes are simulated on the atomistic scale using the density-functional-based tight-binding (DFTB) method. A Si (100) surface was considered as sample and four different indenters, all made of carbon but differing in shape, were considered. As shapes of the tips, we considered a pyramidal, a spherical and two cube-shaped structures. Moreover, the dependence of the results on the start position of the indenters was also studied. The results demonstrate a strong tendency toward the formation of chemical bonds between the atoms of the tips and those of the sample, an effect that most often is neglected in micro- and mesoscale models. The adhesion between the tips and sample was found in all the systems except for the system with spherical tip. From the results of the simulation, we constructed a load–displacement-curve that can be used in identifying elastic-like phases with a monotonously increasing load vs. displacement and plastic-like phases with an irregular load–displacement curve. Ultimately, this is used in determining Young’s modulus of the Si (100) surface. An alternation between elastic and plastic phases was found during the whole simulation. The theoretically determined Young’s modulus were comparable between the different systems and was found to be 2–3 times higher than the experimental value. We argue that this difference may have its root in the neglect of the breaking and creation of chemical bonds between tip and substrate that result in an underestimate of Young’s modulus.

Ferrite Coating on Iron Particles in Aqueous Solution: Effect of Surface Functionalization

Ferrite coating of acid treated iron particles with have been optimized using electroless process. The effect of the functionalization was monitored by XPS and SEM analysis whereas adhesion behavior of ferrite thin films was characterized using a non-conventional ultrasonic test. It is shown that acidic treatments increase the amount of hydroxyl groups on the surface of iron particles, allowing the creation of chemical bonds between the iron core and its ferrite shell. It leads to an increase of the adhesion between both materials. It is shown that the reactivity of iron particles improves the ferrite deposition process. A homogeneous adhesive ferrite coating of around 2 μm with a deposition process of 90 min has been obtained.

2 A prebiotic RNA apparatus functions within the contemporary ribosome

Ribosomes, the universal cellular machines, possess spectacular architecture accompanied by inherent mobility, allowing for their smooth performance as polymerases that translate the genetic code into proteins. The site for peptide bond formation is located within a universal internal semi-symmetrical region, which was identified within all contemporary ribosomes. The high conservation of this region implies its existence irrespective of environmental conditions and indicates that it may represent an ancient RNA molecular apparatus. Hence, we named it the “proto-ribosome”. This prebiotic pocket-like RNA entity is suggested to be capable to accommodate substrates whose stereochemistry enables the creation of chemical bonds. It could have evolved from an earlier catalytic RNA entity that we named the “pre-proto-ribosome”, presumed to be a molecular machine capable of performing various essential tasks in the RNA world, which was snatched by the amino acid invaders for producing proteins.

Self-Assembly of Glass-Ceramic / CdSe / Protein Aggregations in the Optical Trap

ABSTRACTAggregations, created in 2-component suspension inside the optical trap zone were studied. Particles of porous glass-ceramic of CaO-TiO2-P2O5 composition and 1–50 um size were mixed with BSA molecules in water or with CdSe-TOPO 20 nm particles in toluene. Dynamic aggregations up to 300 um size were created inside the optical trap. These aggregations in comparison with one-component aggregations have a 30% higher growth rate. This effect could be explained by the stronger bonding of the protein molecules and CdSe-TOPO particles inside the glass-ceramic particle aggregations. Micro-Raman spectra, taken from dynamic and stable permanent aggregations show several new peaks, possibly associated with creation of chemical bonds.

A Review of Adhesion Mechanisms Using the Peel Test in Air and Liquid Media

Abstract This paper deals with the analysis of peel energy of assemblies measured in different environments, i.e. in air and in the presence of liquids, and constitutes a brief review of the work of Professor Schultz' team in this domain. It is shown how such measurements can lead to a better knowledge of the nature as well as of the magnitude of fundamental interactions established at the interface between two solids. Earlier experiments have shown that peel energy can be expressed as a product of three terms corresponding, respectively, to the reversible energy of interfacial adhesion, the hysteretic losses of the bulk materials and the molecular dissipation near the crack front during peeling. This approach is well-verified when only physical interactions (van der Waals) are involved at the interface. However, more complex cases correspond to systems where specific interactions are also established between both materials, in particular acid-base interactions and creation of chemical bonds. In both case...

A new approach to welding and lamination of polyamides

AbstractAn attempt is made to provide a simple and inexpensive method for the lamination of polyamides. A new application of a known reaction – methoxymethylation of polyamides – is proposed: creation of chemical bonds at the interfacial boundary between two contacting surfaces, i. e. welding and lamination of polymides. Commercial polyamide‐6 films are used in this study. As a result of the creation of methylene bridges between neighboring amide groups welding of the films takes place. After the pressing for 30 h of films coated in a methoxymethylation solution, the welding is so strong that during the mechanical tests, instead of delamination, breaking of the films outside the overlapped area occurs.