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Raman spectroscopy has become a powerful analytical tool providing detailed and specific information at a molecular level. This benefit together with rapidity and other features of the method yields an advantage of quasi real time monitoring and measuring the structure changes dynamics. There is no doubt that Raman spectroscopy can be ranked among...
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The development of new imaging tools, molecules and modalities is crucial to understanding biological processes and the localised cellular impact of bioactive compounds. A small molecule photosensitiser, DC473, has been designed to be both highly fluorescent and to exhibit a strong Raman signal in the cell-silent region of the Raman spectrum due to...
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The contribution from loss of Li+ inventory to capacity fade is described for slow rates (C/10) and long-term cycling (up to 80 cycles). It was found through electrochemical testing and ex-situ Raman analysis that at these slow rates, the entirety of capacity loss up to 80 cycles can be explained by loss of Li+ inventory in the cell. The Raman spec...
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... The typical Raman spectra of the LE before exposure is presented on Figure 3. It consisted of vibrational peaks from the polymeric matrix close to 1003 cm −1 , between 1100 cm −1 and 1500 cm −1 , close to 1587 cm −1 , around 1610 cm −1 , and between 2800 cm −1 and 3200 cm −1 [23][24][25]. The signal at 1003 cm −1 could also come from toluene or xylene, which are commonly used as solvents in liquid epoxy formulations [26,27]. ...
The use of organic coatings in conjunction with cathodic protection (CP) for buried structures is the usual method for protecting steel against corrosion. When the organic coating loses its protective ability, regardless of the reason, the CP becomes the active protection, leading to a specific local environment. This environment can be characterized by high alkalinity, which can be detrimental for the coated structure, either by weakening the steel-coating interface or by the chemical aging of the coating. Thus, the coating must be compatible with CP and able to sustain aging under an alkaline environment. In this study, the susceptibility to alkaline aging and its consequences in regards to coating performance have been investigated for two commercial coatings used for buried structures-fusion bonded epoxy (FBE) and liquid epoxy (LE)-in free membrane and coated steel configurations. The results showed a clear impact of alkaline aging on the studied LE, leading to a significant reduction in coating resistance and ultimately, failure of the steel-coating interface, whereas the studied FBE remained stable. The presented results relate to a precise formulation of LE and FBE; however, the proposed chemical method appears to be relevant and shows the necessity of considering such specific aging results for coating specifications and improvements.
... Differences among spectra can be observed at Wavenumbers 1, 728,1,525,1,339,1,143,1,000,744,680,585, and 482 cm −1 . Published literature on Raman analysis of epoxy was reviewed to serve as a reference for peak assignments in Table 2 (Daimay 1991;Younes et al. 1994;Rocks et al. 2004;Vaskova and Kresálek 2011;Zapata et al. 2013;Fu et al. 2020). Two peaks related to degradation are of particular interest: the peak corresponding to the carbonyl group and the peak corresponding to tertiary amides. ...
Although carbon fiber-reinforced polymer (CFRP) composites have been extensively used to rehabilitate many deficient bridges, data warranting their long-term performance is lacking. Current durability testing of CFRP composites involves accelerated conditioning as a part of material specification requirements to ensure that they maintain mechanical and physical properties during their service life. However, relating accelerated conditioning test data to material performance under real-time aging is not possible without field data. Work conducted at the University of Delaware in the early 1990s resulted in the first full-scale application of externally bonded CFRP on a publicly owned bridge in the United States. The original intent of CFRP strengthening was to extend the service life of the Foulk Road bridge in Wilmington, Delaware by 5-10 years. As one of the earliest CFRP-rehabilitated bridges in the United States, it offers a unique opportunity to study CFRP durability over a time span of 26 years. Field evaluation and laboratory testing (calorimetry, spectroscopy, scanning electron microscopy, and tensile testing) of CFRP samples collected from several girders were employed to investigate CFRP degradation and bond quality. The results indicate that after 26-year-long service life, the condition of CFRP repairs considerably deteriorated.
... Furthermore, the relative amount of a component or a chemical bond can be determined. Changes in spectra with advancing curing allow us to monitor the curing process of thermoset resins online (Pallikari et al., 2001;Vašková and Křesálek, 2011). ...
In the research work presented here, an integrating sphere demonstrator which is suitable for the non-destructive determination of the degree of cross-linking or curing and has the potential for use as an at-line device for in-process quality assurance was assembled and explored. The measurement system allows the analysis of absorption and scattering coefficients of materials independently by means of absolute optical spectroscopy. The two optical parameters showed a good correlation with the degree of cross-linking of cross-linked polyethylene (PE-X) and the degree of curing of different thermosets and adhesives, each of which was determined using different reference methods (wet chemical analysis, differential scanning calorimetry (DSC), and dielectric analysis (DEA)). The results show that different PE-X materials can be distinguished well by their absorption and scattering in the visual (VIS) and near-infrared (NIR) wavelength range, respectively, and conclusions on their degree of cross-linking are possible. Also, the curing of resins can be monitored based on the absorption. In addition, Raman spectroscopy was used to achieve a better understanding of the material changes during the cross-linking of the materials. It also showed a good suitability for monitoring the curing processes in thermosets. In summary, the new method can be used to determine the crucial parameters of these industrial important material types and fulfils the great demand for fast, non-destructive testing, which can be carried out during the process or on the finished product.
... The peak around 1400 cm − 1 corresponds to CH3 deformation, Other Raman peaks observed at 840 and 1680 cm − 1 , corresponding to the resin phenyl ring backbone vibrations, do not change in intensity during the curing reaction [68]. A broad Raman peak at 2500 cm − 1 corresponding to the hardener used [69,70] was observed in V-200 specimen. At this pulling speed, resin and hardener come into contact and form a strong network. ...
The economic efficiency of pultrusion can be significantly improved by operating the process at higher pulling speeds. This experimental study analyzed the relationships between the pulling speed, morphology, and mechanical properties of pultruded glass fiber/vinyl ester resin structural composites. Four batches of 150 mm × 3.5 mm flat laminates were produced at pulling speeds of 200, 600, 1000, and 1400 mm/min. Optical and scanning electron microscopy (SEM) were used to study the morphology of the produced flat laminates. The flexural and interlaminar shear properties were determined for both 0° and 90° fiber orientations. The observed difference in the mechanical characteristics of flat laminates can be explained by the presence of bubbles, longitudinal voids, and matrix cracks and by an increase in their density and dimensions with an increase in pulling speed. This study is the first one to demonstrate the possibility of high speed pultrusion of large cross section profiles suitable for structural application. Authors were able to achieve the pulling speed of 1000 mm/min, increasing the output by as much as 1.7 times as compared to the regular speed pultrusion, without compromising significantly the mechanical performance of produced profiles. The results of this study would be of assistance for a better understanding of high-speed pultrusion.
... Figure 15 shows the Raman spectra of worn surfaces of neat Epoxy and different weight percent GNP filled epoxy composites. Epoxide vibration of neat Epoxy is between of 1230 cm −1 and 1280 cm −1 [33]. In figure 15 (a) epoxide band lie at 1260 cm −1 . ...
This paper evaluates the wear properties of epoxy nanocomposites containing GNP (Graphene Nanoplatelets). In this research, variation of GNP (0,0.1, 0.25, and 0.5 wt.%) were used to make nanocomposites. The hand layup technique was used for the fabrication of different composites. The Taguchi method is used to optimize the wear test and its related characteristics. Analysis of variance is used to understand the correlation between input variables and response measurements. Load (0.5,1.0,1.5, and 2.0 kg) and time (4,6,8, and 10 minutes) are the main variable for exploring wear characteristics for this study. It has been discovered that minimum wear in terms of mass loss and friction coefficient are minimum at 0.5wt.% GNP. Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and RAMAN spectroscopy were used to characterize the wear mechanism. The result shows that the optimized value is closer to the experimental value.
... The structural changes on the molecular level of MWCNT based Epoxy composites were investigated using Raman spectroscopy. From Figure 3, the Raman bands located at 878 cm −1 and 1128 cm −1 were assigned to the resin backbone vibrations, whereas Raman bands corresponding to Epoxy ring deformations and Epoxy ring breathing were located at 690 cm −1 and 1251 cm −1 respectively [26,27]. The Raman band at 1671 cm −1 can be assigned to the amide I vibration, predominant of C=O stretching of the amide group [28]. ...
Recently, there has been an inclination towards natural fibre reinforced polymer composites owing to their merits such as environmental friendliness, light weight and excellent strength. In the present study, six laminates were fabricated consisting of natural fibres such as Kenaf fibre (Hibiscus cannabinus L.) and Bamboo fibre, together with multi-walled carbon nanotubes (MWCNTs) as reinforcing fillers in the epoxy matrix. Mechanical testing revealed that hybridization of natural fibres was capable of yielding composites with enhanced tensile properties. Additionally, impact testing showed a maximum improvement of ≈80.6% with the inclusion of MWCNTs as nanofiller in the composites with very high energy absorption characteristics, which were attributed to the high specific energy absorption of carbon nanotubes. The viscoelastic behaviour of hybridised composites reinforced with MWCNTs also showed promising results with a significant improvement in the glass transition temperature (Tg) and 41% improvement in storage modulus. It is worth noting that treatment of the fibres in NaOH solution prior to composite fabrication was effective in improving the interfacial bonding with the epoxy matrix, which, in turn, resulted in improved mechanical properties.
... Raman spectra of the heated reduced GO confirms the RGO-structure and indicates that RGO contains a higher amount of oxygen functional groups and structural defects than the GNP (Fig. 3b). Moreover, the characteristics peaks of epoxy such as CH-wagging (~818 and 1178 cm − 1 ), epoxy ring deformation (~911 cm − 1 ), C-O stretching (~1048 cm − 1 ), epoxy ring breathing (~1248 cm − 1 ), CH 3 bending (~1335 cm − 1 ), CH 2 deformation (~1452 cm − 1 ), aromatic ring stretching (~1590 and 1609 cm − 1 ), CH-aliphatic (~2868 cm − 1 ), C-H aromatic (~3063 cm − 1 ) and some more prominent peaks are also observed (Fig. 3b) [42]. In Fig. 3 (a), Raman mapping of EGAC-2 shows the contrast of the RGO and GNPs to the epoxy matrix. ...
While polymer composites are anticipated as a promising alternative for Joule heating materials, constructing a continuous conductive network of fillers remains an open challenge to obtain high-performance Joule heating properties with the high steady-state surface temperature at low power input, rapid heating/cooling rate, and excellent cycle stability. Herein, we designed a three-dimensional graphene-based aerogel, infiltrated epoxy into it, and demonstrated a key role of 2D materials-based three-dimensional filler on the anisotropic Joule heating performances of the final aerogel composite. The aerogel composite with the highest graphene loading of 4.7 wt% shows outstanding Joule heating performance with a steady-state temperature of 213 °C at a relatively low applied voltage of 5V. Benefiting from the 3D graphene structure, the epoxy/graphene-based aerogel composites show an excellent electrical conductivity of 48.7 S/m and thermal conductivity of 1.1 W/mK along the parallel direction to the lamellar structure growth. The Joule heating performance of epoxy/graphene-based aerogel composite is correlated with the morphology, electrical conductivities, and thermal conductivities. Importantly, the induced steady-state temperature follows a linear relationship with both the electrical and thermal conductivities of materials. Mechanical properties of aerogel composite is also studied. The obtained results indicate that the epoxy/graphene-based aerogel composite can be a promising material for thermal management applications.
... On the other hand, the reaction was not successful in the case of sample E_VAN, which confirmed the results obtained from the in situ FTIR analysis. Even though a lowintensity peak representing C-O stretching in an alkyl aryl ether (1254 cm −1 ) [21] appeared, the previously mentioned epoxy-related peaks, representing a successful epoxidation of vanillin, were absent. When comparing the spectra of E_GUA and pure GUA, an increase in intensity of the peaks around 3000 cm −1 occurred, correlating to the characteristic vibrational peaks of the epoxy group. ...
... Moreover, after the reaction, two peaks appeared at 1139 cm −1 and 866 cm −1 , which represent the asymmetric and symmetric stretching C-O-C vibrations of epoxy molecules [20]. At 1259 cm −1 , an increase in the peak intensity could be seen in the case of E_GUA, representing the epoxy ring vibration, while an increase in the peak at 917 cm −1 represents the epoxy ring deformation [21]. The Raman spectrum of E_GUA, therefore, indicates the successful epoxidation of GUA. ...
... On the other hand, the reaction was not successful in the case of sample E_VAN, which confirmed the results obtained from the in situ FTIR analysis. Even though a lowintensity peak representing C-O stretching in an alkyl aryl ether (1254 cm −1 ) [21] appeared, the previously mentioned epoxy-related peaks, representing a successful epoxidation of vanillin, were absent. ...
A bio-epoxy surface adhesive for adherence of the metal component species to glass substrate with desirable adhesion strength, converted controlled removal upon request, and bio-based resource inclusion was developed. For the development of resin, three different lignin-based aromatic monophenols, guaiacol, cresol, and vanillin, were used in the chemical epoxidation reaction with epichlorohydrin. The forming transformation process was studied by viscoelasticity, in situ FTIR monitoring, and Raman. Unlike other hydroxyl phenyls, guaiacol showed successful epoxide production, and stability at room temperature. Optimization of epoxide synthesis was conducted by varying NaOH concentration or reaction time. The obtained product was characterized by nuclear magnetic resonance and viscosity measurements. For the production of adhesive, environmentally problematic bisphenol A (BPA) epoxy was partially substituted with the environmentally acceptable, optimized guaiacol-based epoxy at 20, 50, and 80 wt.%. Mechanics, rheological properties, and the possibility of adhered phase de-application were assessed on the bio-substitutes and compared to commercially available polyepoxides or polyurethanes. Considering our aim, the sample composed of 80 wt.% bio-based epoxy/20 wt.% BPA thermoset was demonstrated to be the most suitable among those analyzed, as it was characterized by low BPA, desired boundary area and recoverability using a 10 wt.% acetic acid solution under ultrasound.
... In Fig. 5a, all the marked peaks correspond well to epoxy related peaks, in good accordance with the literature. Namely, 640 cm −1 is related to epoxy ring deformation, 822 cm −1 to -CH wagging, 1113 cm −1 to epoxy ring deformation, 1460 cm −1 to -CH 2 deformation and 1610 cm −1 to aromatic ring stretching [25,26]. In Fig. 5b, the two spectra after DNA immobilization and hybridization differ significantly from the epoxy reference. ...
The applicability of a novel gold–epoxysurface nanocomposite for surface-enhanced Raman scattering (SERS) is investigated. The nanocomposite consists of ellipsoidal nanoparticles in a hexagonal arrangement, where the average particle diameter (D0) and interparticle gap (D) can be controlled in the 0.15–1.00 (D/D0) range on a large surface area (several cm ²). Numerical simulations were used to estimate the SERS enhancement factors of substrates with five different particle arrangements. The fabricated substrates’ surface was functionalized with 20 base-pair long double-stranded DNA molecules and the intensities of the characteristic Raman peaks related to DNA were used to quantify the substrate performance. It was proved that by optimizing the fabrication parameters and maximizing the interparticle coupling, the characteristic Raman intensities could be increased by more than 2.5 orders of magnitude.
... The measurements were performed after binding target-DNA to the nanocomposites. Substrate A shows almost no peaks corresponding to DNA, and the majority of the peaks can be clearly assigned to the epoxy substrate, as shown in Table 2. [9,10]. On the other hand, peaks corresponding to DNA were observed on the type B sample with a significant intensity increase. ...
