Use Of Characterization Methods Research Articles

Composition processing property relationship of vitrimers Based on polyethyleneimine

An innovative use of characterization methods to establish correlation between chemical composition and material properties in imine based RCBPs, and a novel understanding of chemical processes that occur during heating\ processing of such polymers.

Nanoindentation testing and simulation of nanocrystalline materials

Nanocrystalline metals have attracted a considerable attention over the past two decades due to their increased tensile strength. The difficulty in producing large quantities of nanocrystalline materials has imposed the use of characterization methods involving small volume samples such as the nanoindentation method. In the present work, the nanoindentation behavior of Tungsten – Copper nanocrystalline alloys was characterized by tests conducted according to ISO 14577 standard and simulated using a finite element model developed in the Abaqus FE code. Tungsten - Copper alloys of coarse-grained and nanocrystalline microstructures were tested and modeled. Using the model, the effects of sharpness of the Berkovich indenter was studied. The experimental results show a superiority of the nanocrystalline material, which is explained by the Hall-Petch effect. Between the model and the tests a good convergence is achieved. The convergence is better for the rounded tip of the indenter.

A new numerical method for axial dispersion characterization in microreactors

Axial dispersion is a key phenomenon in reactor engineering that can affect yield and selectivity when reactions are carried out. Therefore its characterization is necessary for an adequate modelling of the reactor. The development of compact reactors to fit with process intensification expectations requires the use of characterization methods adapted to small-scale devices. An original method not-frequently used up to now for the estimation of axial dispersion coefficients is presented and applied to millimetric wavy channels. It is based on CFD simulations to calculate velocity and concentration fields from which axial dispersion coefficient can be estimated. This method is used to predict the impact of the wavy channel geometry and of the fluid velocity on axial dispersion in laminar flow regime. The investigated geometrical parameters are the hydraulic diameter (2–4mm), the cross-sectional aspect ratio defined as the ratio between the channel width and its depth (0.25–1) and the internal curvature radius of the bends (2–3.4mm). The range of Reynolds number considered is Re=70–1600. Axial dispersion coefficient increases with velocity, values range from 2.8·10−4 to 3.2·10−3m2·s−1. It appears that axial dispersion varies slightly in function of the channel hydraulic diameter. Square wavy channels generate less axial dispersion than rectangular wavy ones. Finally, axial dispersion coefficient increases with the internal curvature radius which shows the positive impact of sharp bends to reduce axial dispersion effect.

Evaluation of the Appropriate Use of Characterization Methods for Differentiation between Cocrystals and Physical Mixtures in the Context of Energetic Materials

Cocrystallization is an attractive method by which to tune the physical properties of energetic materials. However, in the absence of single-crystal X-ray diffraction (SC-XRD), rigorously characterizing the results of cocrystallization attempts can be difficult. Specifically, differentiating between physical mixtures and true cocrystalline materials is challenging due to the propensity for energetic molecules to form solvates and/or polymorphs. The suitability and limitations of morphological analysis, vibrational (infrared and Raman) spectroscopy, and powder XRD are discussed within the context of six previously published materials claimed to be cocrystals but lacking SC-XRD structures. It was found that in all six cases the data originally published are consistent with crystallization of physical mixtures of the two starting components; in three of these cases the crystallization procedures were reproduced and the characterization data support the presence of physical mixtures. Data interpretation is co...

Potential Applications of Nanotechnology in Pavement Engineering

Nanotechnology is the term used to cover the design, construction, and utilization of structures with at least one dimension measured in nanometers. Compared with typical civil engineering structures, the two fields operate on hugely divergent dimensional scales. Nanotechnology initially developed in the fields of physics and chemistry, and most fundamental developments still occur in these fields. However, for the technology to affect society at large, it needs to be applied in areas such as the engineering field. This paper focuses specifically on current and potential developments in pavement engineering where the unique properties of nanomaterials may be used to deliver a better environment to society, based on identified needs and challenges in the pavement engineering field. It is demonstrated that there are essentially two areas where nanotechnology can complement pavement engineering. These are in the development of improved materials and the use of characterization methods to improve the understanding of materials. Examples of current and planned research in these areas are cited and discussed. Finally, current challenges in exploiting the unique properties of nanomaterials in pavement engineering are indicated and discussed. The paper demonstrates that although the majority of the fundamental developments in nanoscale science and technology are occurring in the fundamental physics, chemistry, and typically electronic engineering fields, the potential for this technology to impact on the quality of life of society at large is huge.

Coordinative interactions in a dye-sensitized solar cell

Resonance Raman scattering studies of a complete dye-sensitized solar cell (DSC) including iodine and lithium iodide in the electrolyte indicate that triiodide (I3−) exchange the SCN− ligand of the dye bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II). The choice of cation in the iodide salt influenced the ligand stability of the dye. It was proposed that an ion pair Li+⋯I3− formation occurred which by a reduced electrostatic repulsion between I3− and SCN− facilitated the exchange of these anions at Ru(II) of the dye. The additive 1-methylbenzimidazole (MBI) suppressed the SCN−/I3− ligand exchange by forming a complex with Li+. The concentrations of Li+ and MBI have to be carefully balanced due to the SCN− ligand exchange with MBI in deficiency of Li+. In order to observe and understand the prevailing coordinative interactions between the components in a DSC, the use of characterization methods with which complete devices can be studied is necessary.

Coordinative interactions in a dye-sensitized solar cell

Resonance Raman scattering studies of a complete dye-sensitized solar cell (DSC) including iodine and lithium iodide in the electrolyte indicate that triiodide (I 3 −) exchange the SCN − ligand of the dye bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II). The choice of cation in the iodide salt influenced the ligand stability of the dye. It was proposed that an ion pair Li +⋯I 3 − formation occurred which by a reduced electrostatic repulsion between I 3 − and SCN − facilitated the exchange of these anions at Ru(II) of the dye. The additive 1-methylbenzimidazole (MBI) suppressed the SCN −/I 3 − ligand exchange by forming a complex with Li +. The concentrations of Li + and MBI have to be carefully balanced due to the SCN − ligand exchange with MBI in deficiency of Li +. In order to observe and understand the prevailing coordinative interactions between the components in a DSC, the use of characterization methods with which complete devices can be studied is necessary.

The State of the Practice: Characterizing and Remediating Contaminated Groundwater at Fractured Rock Sites

AbstractCharacterizing and remediating contaminated groundwater in fractured rock are often the most difficult challenges facing environmental professionals. The U.S. Environmental Protection Agency (EPA), other U.S. federal agencies, and the Ontario Ministry of Environment recently supported a workshop, held an international conference, and developed a Web site to promote the understanding of the state of the practice. Field practitioners and researchers were surveyed and questioned concerning their experiences. This article summarizes the results of these efforts and provides an overview of the use of characterization methods and remediation technologies at fractured rock sites. © 2002 Wiley Periodicals, Inc.