D. M. Marulanda

Influence of the percentage of recycled material on the mechanical properties of low-density polyethylene, polyethylene terephthalate, and polyvinyl chloride

The aim of this article was to fabricate virgin polyvinyl chloride, polyethylene terephthalate, and low-density polyethylene blended with their corresponding recycled material in different ratios of virgin/recycled via injection molding and to evaluate their tensile strength, impact fracture, and hardness behavior. Raman spectroscopy was used to qualitatively study the characteristics of the recycled material in comparison with the virgin material. The impact testing method was the Charpy impact test, and for the hardness measurement, the shore D hardness method was used. The tensile tests were performed following the ATSM 683 standard. Scanning electron microscopy was used for chemical analysis and imaging to confirm the presence of contaminants.

Interface formation between pentacene and silver contacts investigated by surface-enhanced Raman spectroscopy

Interface formation between organic semiconductors and substrates or electrodes is of great interest to develop functional devices. In this paper we discuss on the interface formation between the organic semiconductor pentacene and silver as the top electrode. Pentacene is commonly used as active layer in organic field-effect transistors (OFETs). It is known that in OFEts significant percentage of the drain current is realized at organic layer thickness below 5 nm. Therefore, understanding the monolayer regime is vital to identify the physics and chemistry of the organic semiconductor. We report Raman spectroscopy measurements of 1.5 nm pentacene films deposited under high vacuum conditions onto Au or SiO2 and covered by silver contacts. In order to achieve a detailed molecular identity upon metal evaporation, Raman spectra at each evaporation stage was recorded. Analysis proved that a bare 1.5 nm pentacene film on smooth Au substrates reflects significant enhancement of the Raman signal. Silver contact of about 1 nm thickness promotes enhancement of the Raman internal vibrational modes along the activation of normally infrared-active modes, and the enhancement factors are estimated to be close to 100. The Raman spectroscopy measurements indicate absence of metallorganic pentacene-Ag complexes regardless of the substrate.

Deposition And Characterization of (Ti,Zr)N Thin Films Grown Through PAPVD By The Pulsed Arc Technique

The Plasma Assisted Physic Vapor Deposition (PAPVD) by the pulsed arc technique has been used for deposition of Titanium Zirconium Nitride (Ti,Zr)N coatings, using a segmented target of TiZr. The deposition was performed in a vacuum chamber with two faced electrodes (target and substrate) using nitrogen as working gas, and a power‐controlled source used to produce the arc discharges. Films were deposited on stainless steel 304, and they were characterized using the X‐Ray Photoelectron Spectroscopy (XPS), X‐Ray Diffraction (XRD), Energy Dispersion Spectroscopy (EDS) and Scanning Probe Microscopy (SPM) techniques. The XRD patterns show different planes in which the film grows. Through SPM, using Atomic Force Microscopy (AFM) and Lateral Force Microscopy (LFM) modes, a nanotribologic study of the thin film was made, determining hardness and friction coefficient.

Application of Vibration Based Damage Identification Techniques on Metallic Structures

In this work, a vibration based damage identification technique (VBDIT) is used to determine the presence of damages in metallic structures, using the undamaged structure information as reference. A complex structure is used in order to contrast the results obtained with those reported for techniques previously employed specially on single beam simulated structures. A finite element model of the structure is developed and validated as a support tool for the study. Theoretical and experimental modal analysis techniques were used as the main tool for damage identification.

Microstructural characterisation of Cr/CrN nano-multilayers produced by unbalanced magnetron sputtering

The production of Cr/CrN nano-multilayers through the unbalanced magnetron sputtering (UBM) technique was presented, and the influence of the unbalance degree on microstructure was studied. X-ray diffraction (XRD) was used to study phase formation in the coatings, and the presence of a multilayer structure was confirmed through transmission electron microscopy (TEM). Total thickness was measured through profilometry and it was assessed using grazing incidence X-ray reflectometry (XRR), which was also used for density, bilayer period and interface roughness measurements. The sin2 ψ method was used to study residual stresses presence. Results showed that the unbalance degree did not significantly influence the orientation of the multilayer planes, but it had an influence on peak positions, which indicated the presence of residual stresses. The density was also influenced by the unbalance degree, mainly due to ionic bombardment variation with each unbalance degree use.

Effect of period and degree of unbalancing on the structure and resistivity of Cr/CrN magnetron sputtered nano-multilayers

Cr/CrN nano-multilayers have been produced by varying the period and the degree of unbalancing in a magnetron sputtering system in order to study the influence of these parameters in the electrical properties. X-ray Diffraction (XRD) was used to investigate the microstructure characteristics of the multilayers and the Four Point Probe (FPP) technique in the Van der Pawn mode was used to evaluate electrical resistivity. The results show that the resistivity strongly depends on the period and the degree of unbalancing of the magnetron. These nano-multilayers are proposed to be used as contacts in Cu metallization and as diffusion barriers between copper and silicon.

Characterization of Thin Films Using Different Scanning Probe Microscopy (SPM) Modes

Scanning probe microscopy (SPM) is unique among the imaging techniques in which it provides three-dimensional (3-D) real-space images and among surface analysis techniques in which it allows spatially localized measurements of structure and properties. Under optimum conditions, subatomic spatial resolution is achieved. The development given has not been only because of its ability to obtain topographic and structural images of the surface at micro and nano scale, but also for the possibility of performing analysis of superficial properties such as local adhesion properties, chemical heterogeneity, and local mechanical properties [1]. The SPM has different variations depending on the interaction between the tip and the sample surface, such as AFM, which has the ability of showing topographic characteristics at atomic scale, LFM, which measures local friction differences, FMM and PDM that measure differences of local elasticity. The instrument counts with the spectroscopy mode and with this it is possible to obtain Force — distance (F-d) curves that give information about the local elastic properties of the sample surface. In this work, TiN and ZrN thin films grown by the PAPVD by pulsed arc technique were studied, using the AFM, LFM, FMM, PDM and spectroscopy F vs. d techniques.