Interfacial Characterization of Epoxy-bonded Maraging Steel

Adhesion phenomena involving polymer-metal interfaces have become a central subject for research and technological development, especially in view of adhesive bonding of metallic components in primary load-bearing structures. Since adhesion implies that some sort of chemical and/or physical interactions take place between the metal adherend and the polymeric adhesive, a great deal of attention has been devoted to identification and characterization of such interactions and to the development of techniques to study them. Among the most widely used methods for interfacial studies are: ESCA (Electron Spectroscopy for Chemical Analysis), AES (Auger Electron Spectroscopy), SIMS (Secondary Ion Mass Spectroscopy), IR spectroscopy, optical microscopy, and electron microscopy.     

The application of electron spectroscopy to the study of adhesion

The relevance of electron spectroscopic surface measurements for adhesion studies is discussed, with particular emphasis on surfaces prior to the formation of an adhesive joint and in examination of the surfaces of failed adhesive joints. Auger Electron Spectroscopy (aes) and X-ray Photoelectron Spectroscopy (xps) are reviewed in terms of their basic phenomena and their analytical advantages and disadvantages. Surface chemical contamination is known to be a major cause of adhesive failure. Sources of such contamination are reviewed and particular examples discussed.     

Improving the mechanical behavior of the adhesively bonded joints using RGO additive

In this research, Araldite 2011 has been reinforced using different weight fractions of Reduced Graphene Oxide (RGO). Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses were conducted and it has been shown that introduction of the RGO greatly changes the film morphology of the neat adhesive. Uni-axial tests were carried out to obtain the mechanical characteristics of the adhesive-RGO composites. It has been observed that introducing 0.5 wt% RGO enhances the ultimate tensile strength of the composites by 30%. In addition, single lap joints using neat adhesive and adhesive-RGO composites were fabricated to investigate the effect of the added RGO on the lap shear strength of the joints. Results show that the joints with added 0.5 wt RGO exhibited 27% higher lap shear strength compared to the joints bonded with neat adhesive. Finally, Finite Element (FE) numerical solutions using Cohesive Zone Modeling (CZM) have been carried out to simulate the failure behavior of the joints, and it has been shown that the FE models can predict the joint’s failure load.     

Study of ageing of dry powder inhaler and metered dose inhaler by atomic force microscopy

Investigation by atomic force microscopy (AFM) is necessary for the analysis of the interaction between grains of powder used in dry powder inhalers (DPIs) in controlled atmosphere and metered dose inhalers (MDIs) in liquid phase. Measurements of nanonewton forces leading the powder cohesion resulting between active substances were performed. We have developed a protocol based on standard analysis: Scanning Electron Microscopy (SEM) and nano-analysis. This paper deals with the direct analysis of morphology evolution performed over three months in controlled atmosphere at various relative humidities (RH) and temperatures for DPIs and in a mimetic HFA134a liquid for MDIs in order to understand the behaviour of a binary mixing. Atomic force microscopy was also employed to characterize the interactions between particles.In this study, colloid probe AFM has been used to measure adhesive forces between drug particles in a controlled atmosphere for DPIs and in a liquid medium for MDIs. A link connecting the colloidal powder quality and particle-particle interactions is extracted from this study.     

Influence of Additives in Adhesion of UV Radiation Surface-Treated SBS Rubber

In this study, the effect of additives (oils, lubricants) included in the formulations of different block styrene-butadiene-styrene (SBS) rubbers on the effectiveness of the ultraviolet (UV) radiation treatment to improve adhesion to polyurethane adhesive was analyzed. The modifications on the UV-treated rubber surfaces for different lengths of treatment have been characterized by contact-angle measurements (ethylene glycol, 25°C), Attenuated Total Reflectance-Infrared (ATR-IR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). The adhesion properties have been evaluated from T-peel strengths of treated rubber/polyurethane adhesive/leather joints. The UV-radiation treatment on all rubber surfaces produced an increase in wettability, carbon-oxygen polar moieties, and ablation. The oxidation degree produced on the rubber surface treated with UV radiation was less when oils and lubricants were included in the formulation, likely due to competition of the oxidation process with the migration of low-molecular-weight additives to the rubber surface. On the SBS2 rubber surface (rubber containing carbon black and calcium carbonate fillers), the migration of oils and lubricants was also produced during the UV-radiation treatment, but a decrease in adhesion occured likely due to the lower tensile strength and higher extent of oxidation produced by the UV radiation treatment.     

Influence of Additives in Adhesion of UV Radiation Surface-Treated SBS Rubber

In this study, the effect of additives (oils, lubricants) included in the formulations of different block styrene–butadiene–styrene (SBS) rubbers on the effectiveness of the ultraviolet (UV) radiation treatment to improve adhesion to polyurethane adhesive was analyzed. The modifications on the UV-treated rubber surfaces for different lengths of treatment have been characterized by contact-angle measurements (ethylene glycol, 25°C), Attenuated Total Reflectance-Infrared (ATR-IR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). The adhesion properties have been evaluated from T-peel strengths of treated rubber/polyurethane adhesive/leather joints. The UV-radiation treatment on all rubber surfaces produced an increase in wettability, carbon–oxygen polar moieties, and ablation. The oxidation degree produced on the rubber surface treated with UV radiation was less when oils and lubricants were included in the formulation, likely due to competition of the oxidation process with the migration of low-molecular-weight additives to the rubber surface. On the SBS2 rubber surface (rubber containing carbon black and calcium carbonate fillers), the migration of oils and lubricants was also produced during the UV-radiation treatment, but a decrease in adhesion occured likely due to the lower tensile strength and higher extent of oxidation produced by the UV radiation treatment.     

Dynamic Mechanical and ESCA Studies of Aluminium-Aluminium Bonding by an Epoxidised Natural Rubber-Polyacrylic Acid Blend

A polyacrylic acid (PAA)-epoxidised natural rubber (ENR) blend becomes crosslinked during high temperature moulding and such a blend was found to be a good adhesive for aluminium (Al)-aluminium (Al) bonding. The joint strength can be improved by the incorporation of silica filler into the adhesive up to a loading of 5 phr. However, higher filler loading causes deterioration of the joint strength. Electron Spectroscopy for Chemical Analysis (ESCA) studies of the peeled and then leached Al surface shows that the ENR phase of the blend is primarily responsible for the adhesion with the Al surface. With the increase in filler loading adhesion with Al increases at the cost of crosslinking between the component polymers. This is substantiated by dynamic mechanical analyses of the blends and joints (that is, Al/blend/Al composites). The changes in dynamic mechanical properties of the blends due to Al adhesion could be correlated with the peel strength of the Al/blend/Al joints.     

Interactions between a collagen-binding adhesive and dental substrate

The adhesion between polymer adhesives and dentin involves the removal of minerals, by acid etching the dentin surface, to allow for monomer infiltration among collagen fibrils. However, instability within this hybrid layer has been observed, which may partially be attributed to a slow degradation of the collagen not protected by the adhesive. The objective of this work was to improve the stability of the hybrid layer by increasing the interactions between adhesives and collagen through the incorporation of a monomer that behaves reactively toward collagen in the adhesive. In this work, a control adhesive was prepared based on a chemical formulation containing Bis-GMA and HEMA, and was modified by incorporating different concentrations (5, 10, and 20%) of NSA (N-acryloxysuccinimide), which contains an ester group capable of interacting with primary amine. These experimental adhesives were applied to bovine dentin for the in vitro production of the interfacial layer, which was analyzed by Raman spectroscopy and scanning electron microscopy. The obtained results showed that it was possible to incorporate the NSA monomer into the adhesive up to a maximum concentration of 10%. The presence of amide bonds in the Raman spectra, as well as the presence of a large amount of experimental adhesive within the interfacial layer, as indicated in the scanning electron microscopy images, may suggest the occurrence of chemical interactions between polymers and dentin collagen fibrils. These interfacial chemical interactions involving dental adhesives and dentin can be an important tool in protecting the hybrid layer from degradation.     

连续纤维增强陶瓷基复合材料界面研究进展

在陶瓷基复合材料中引入高强陶瓷纤维的目的是为了增强陶瓷的断裂韧性,纤维与基体的界面是决定CMC韧性的关键因素。国内外许多专家和机构研究重点主要集中于连续纤维增强陶瓷基复合材料的界面,包括纤维与基体的化学相容性和热物理相容性,以及用TEM、HRTEM、SADP、AEM、声学显微法、EDX等微观测试手段研究不同体系的界面形成机理。本文对上述界面研究概况进行了综述,并简述了界面设计原则和近年来计算机技术在界面研究中的应用情况。指出,连续纤维增强陶瓷基复合材料界面研究将一直是复合陶瓷基复合材料界研究的重点和难点。     

Synthesis and Characterization of Novel Hybrids of Tris[3-(trimethoxysilyl)propyl] Isocyanurate (TTPI) Capped Palladium Nanoparticles and Single-Walled Carbon Nanotubes

The conjugation of nanoparticles to carbon nanotubes (CNTs) involves various steps including premodification of the nanotubes, which is known to be a very tedious process and sometimes leads to a mixture of products. In this regard, a direct route to generate such conjugates is a worthwhile endeavor. In this paper, we report a novel, mild, one-pot, approach to a controlled and direct coordination of Pd nanoparticles (Pd NPs) onto the surface of single walled carbon nanotubes (SWNTs), without any pre-modification of the SWNTs surface. We also present detailed characterization of the SWNT-Pd NP hybrid systems using High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive X-ray Spectroscopy (EDS), Mid-Infrared Spectroscopy (Mid-IR) and UV-Visible Spectroscopy (UV–vis) along with the stability studies of the nanoconjugates.     

Influence of the Chemical Structure of Urethane-Based Thickeners on the Properties of Waterborne Polyurethane Adhesives

To analyse the parameters that influence the thickening mechanism of waterborne polyurethane adhesives, different hydrophobically modified ethoxylated polyurethane based thickeners (HEUR) were used. The thickeners were characterized by proton nuclear magnetic resonance (¹H-NMR) and gel permeation chromatography (GPC). The thickened adhesive solutions were characterized by flow rheology, pH, particle size measurements, solids content, and confocal microscopy. The thickened solid adhesive films were characterized by ATR-IR spectroscopy, parallel plate rheology, dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). The adhesion was measured by a T-peel test of leather/polyurethane adhesive/SBR rubber joints. The addition of the different HEUR thickeners increased the viscosity of the polyurethane dispersion to different degrees. Furthermore, whereas the un-thickened polyurethane dispersion showed a Newtonian rheological behaviour, a shear-thinning rheological behaviour was observed in the thickened dispersions due to thickener-thickener and polyurethane-thickener interactions. The viscosity of the thickened polyurethane adhesive solutions increased with the degree of hydrophobicity and the molecular weight of the thickener. The addition of different thickeners increased the pH values due to the ionic adsorption, which is one of the interactions that contribute to the thickening mechanism of the polyurethane thickeners, besides hydrogen bonding and van der Waals hydrophobic interactions (micelles). The entanglement of the thickened polyurethane adhesives was studied by confocal microscopy. Although the addition of the thickeners did not affect the thermal properties of the polyurethanes, the T-peel strength of leather/adhesive/SBR rubber joints was influenced by the rheological properties of the thickened adhesives.     

Silicification and biosilicification Part 1. Formation of Silica Structures Utilizing A Cationically Charged Synthetic Polymer At Neutral pH and Under Ambient Conditions

Summary The formation of uniquely synthesized well-structured nanometer and micrometer sized silica spheres utilizing a cationically charged synthetic polymer at neutral pH and under ambient conditions is reported. The products were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infra Red Spectroscopy (FTIR) and X-Ray Diffraction (XRD). Evidence was found that the final silica structures incorporated the polyallylamine hydrochloride (PAH), the cationically charged synthetic polymer used here. It is proposed that PAH facilitates the formation of silica structures by a similar mechanism to that described previously in the literature for the formation of silica by the silicatein proteins. Received: 8 October 2001/Revised version: 22 April 2002/ Accepted: 23 April 2002     

Addition of different amounts of a urethane-based thickener to waterborne polyurethane adhesive

To adjust the rheology of waterborne polyurethane adhesives, different amounts of a hydrophobically modified ethoxylated polyurethane thickener (HEUR) were added. The thickened adhesive solutions were characterized by flow rheology, pH measurements, particle size, solids content and confocal microscopy. The thickened solid adhesive films were characterized by IR spectroscopy, plate-plate rheology, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The adhesion was measured from T-peel test of plasticized PVC/polyurethane adhesive/plasticized PVC and leather/polyurethane adhesive/SBR rubber joints. The addition of the HEUR thickener increased the viscosity of the polyurethane dispersion, and a shear-thinning behaviour was observed due to polyurethane–thickener interactions. The addition of thickener improved the rheological properties of the polyurethane, more noticeable as the content of the thickener increased. The crosslinking of the thickened polyurethane was studied by confocal microscopy. Although the addition of the thickener did not greatly affect the thermal properties of the polyurethane, an improvement in the adhesive strength of leather/adhesive/SBR rubber joints was obtained.     

Scanning Electron Microscopy and Energy Dispersive X-Ray Microanalysis of Perna canaliculus Mussel Larvae Adhesive Secretion

The morphology and nature of the adhesive secretion from Perna canaliculus mussel larvae settled on glass and on Teflon® was observed by scanning electron microscopy techniques. The settled larvae were imaged by field emission scanning electron microscopy and the adhesive footprints left on the substrate after the organisms' removal by cryo-scanning electron microscopy. Environmental scanning electron microscopy images on glass and Teflon substrates showed the adhesive in its natural hydrated condition. Moreover, micrographs under increasing humidity conditions showed swelling behaviour of the larval adhesive which revealed its hygroscopic nature. The mussel larvae adhesive spreading behaviour on glass compared with Teflon showed that it is hydrophilic. Additionally, energy dispersive X-ray microanalysis provided information of the elemental composition of the larval adhesive, revealing the presence of sulfur, phosphorus, and calcium. Calcium may be present due to its favourable interactions with polyanionic moieties leading to formation of a gel-like adhesive secretion.     

Investigation of structural properties of clinoptilolite rich zeolites in simulated digestion conditions and their cytotoxicity against Caco-2 cells in vitro

The use of the clinoptilolite rich natural zeolites in biomedical applications such as in anticancer therapy, drug or drug support systems and as nutritive supplement is highly dependent on their behavior in digestive conditions. Aim of this study is to investigate structural stability of clinoptilolite rich natural zeolites in simulated digestion conditions and their interactions with digestive media and with Caco-2 (human colon adenocarcinoma) cells. X-ray Diffraction (XRD), Fourier Transform InfraRed (FTIR), Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) analyses of the clinoptilolite rich zeolite samples showed that zeolites preserved their structural stabilities during in vitro digestion. Slight interactions were detected in UV measurements of the digestive liquid media and FTIR spectra of the intestinal digested media powders. SEM results implied that zeolites might have a role in the aggregation of the digestive enzymes. Cytotoxicity test using colon cancer cells showed that clinoptilolite rich natural zeolites have cytotoxic effect against Caco-2 cells and cytotoxicity did not significantly change with respect to simulated digestion process.     

The composition and bonding characteristics of the alloying elements in electrodeposited Ni---Cr alloys

Electrodeposited Ni---Cr alloys of different compositions were studied by Auger Electron Spectroscopy (AES) and Electron Spectroscopy for Chemical Analysis (ESCA). It was found that all the chromium in the alloy was present as Cr₂O₃, while nickel was present in the metallic form. The influence of plating parameters on the compositions of the alloy and the efficiency of the deposition process was investigated in detail. The nature of inclusions in the deposit was also studied and quantitatively compared with the impurities found in thermally prepared Ni---Cr alloys.     

Eutectoid scaffold as a potential tissue engineer guide

Biphasic scaffolds were prepared according to the eutectoid composition from subsystem silicocarnotite-tricalcium phosphate by the polymeric replica method. Two polyurethane templates were used to explore the possibility of fabricating the scaffold on demand. The obtained scaffolds were characterized mineralogically by X-Ray Diffraction (XRD), the chemical groups analyzed by Attenuated Total Reflectance-Fourier Transformed Infrared Spectroscopy (ATR-FTIR), microstructurally by Scanning Electron Microscopy (SEM) fitted with Energy Dispersive X-Ray Spectroscopy (EDS), and additionally by field emission SEM (FESEM) for the topography study. Finally, the mercury porosimetry analysis was performed for the microporosity study. The obtained results confirmed the possibility of controlling macro- and microporosity on the scaffold, which allowed their synthesis for specific needs.     

Comparison among Different Processing Conditions in Synthesis of Polypropylene/Carbon Nanotubes Composites Using Raman Spectroscopy

This work presents a simple and rapid method for determining which of three combined processing conditions, rotation speed, mixing temperature and duration of mixing that is the most efficient for the preparation of polypropylene/carbon nanotube composites. For this purpose, polypropylene nanocomposites with a constant amount of carbon nanotubes (5.0 wt.%) and different processing conditions are examined through X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Raman Spectroscopy. The latter, Raman Spectroscopy, specializes in and reveals which processing condition among them is the most significant, in order to construct nanocomposites with good dispersion of nanotubes in the polymer matrix.     

Polymerization and adhesion behavior of experimental dental bonding materials with different initiator systems

The use of alternative photoinitiators has been reported as a way to improve physical-mechanical characteristics of dental adhesive systems. In this way, the aim of this study was to evaluate the degree of conversion (DC) and dentin bond strength in dentin cavities of experimental simplified adhesive systems formulated with alternative photoinitiators and diphenyliodonium hexafluorophosphate (DPIHFP). A model simplified adhesive system was formulated by mixing a similar blend of monomers with different photoinitiator systems: camphorquinone (CQ), phenylpropanedione (PPD), bis-alkyl phosphine oxide (BAPO), CQ/PPD, and CQ/BAPO; with or without the addition of DPIHFP. DC was measured using Fourier Transform Infrared Spectroscopy. Bond strength was evaluated in bovine dentin cavities. DPIHFP increased DC for the CQ-based system, but did not affect the dentin bond strength. The PPD system showed the highest DC. All photoinitiator systems provided similar dentin bond strength. DPIHFP seems to increase the DC of CQ-based system, but it had no influence on PPD or BAPO systems. PPD was the most effective for to increase DC without improving bond strength of adhesive systems. Therefore, it is recommended that new adhesive systems to be formulated with phenylpropanedione to increase the DC of tooth restorations caused by traditional camphorquinone-based adhesive systems.     

Polymer-assisted freeze-drying synthesis of Ag-doped ZnO nanoparticles with enhanced photocatalytic activity

Ag-doped ZnO nanoparticles with high and stable photocatalytic activity were prepared by polymer-assisted freeze-drying method with simple process and without organic solvents used. The structural morphology and optical properties of Ag-doped ZnO nanoparticles were characterized by X-ray Diffraction (XRD), Inductive Coupled Plasma Optical Emission Spectrometry (ICP-OES), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and high resolution TEM (HRTEM) with energy dispersive X-ray spectroscopy, Ultraviolet-visible Diffuse Reflectance Spectroscopy (UV–vis DRS), X-ray Photoelectron Spectroscopy (XPS) and Fourier Transmission Infrared Spectroscopy (FTIR). Moreover, the thermoanalytical measurements (TGA–DTG) analysis is carried out for proper calcination temperature. XRD results show that Ag nanoparticles were successfully doped into ZnO lattice, and UV–vis DRS results indicate that the doped Ag nanoparticles result in ZnO exhibiting enhanced light trapping capability in the 400?nm and 600?nm range. The photocatalytic activity of Ag-doped ZnO was examined by analyzing the degradation of methyl orange (MO) and methylene blue (MB) dyes under UV light and solar light irradiation, and the results show that all Ag-doped ZnO nanoparticles exhibit better photocatalytic activity than those of pure ZnO nanoparticles at the same degradation conditions; especially the synthesized Ag-ZnO nanoparticles are easy to be recycled and have high photocatalytic stability. Based on the experimental results, the photocatalytic electron transfer path and the photocatalytic mechanism of Ag-ZnO nanoparticles under UV and solar irradiation conditions are explained and clarified.