Valence band XPS and FT-IR evaluation of thermal degradation of HVAF thermally sprayed PEEK coatings

Coatings of PEEK (poly-ether-ether-ketone) have been produced on stainless steel 304 using the High Velocity Air Fuel (HVAF) thermal spray technique. These coatings were produced using 50 and 100 mm nozzle lengths with 200, 300 and 400 mm gun to substrate distances. The thermal degradation of the PEEK during the production of the coatings was assessed with valence band X-ray Photoelectron Spectroscopy (XPS) and attenuated total reflectance Fourier Transform Infrared Spectroscopy (ATR FT-IR). Valence band XPS shows that in general there is minimal degradation of the PEEK during the HVAF thermal spraying process. The FT-IR results show that at the 200 mm gun to substrate (standoff) distance for both nozzle lengths there is more surface degradation of the PEEK coating than at the longer gun to substrate distances. Specifically absorption bands appeared at 2918 and 2850 cm⁻¹, which correspond to alkane -CH₂- asymmetric stretching modes. The reduction of the 1250 cm⁻¹ band as compared with the 1220 cm⁻¹ band, both representing the stretching modes of the ether bonds in PEEK suggests that the degradation occurs at only one of the ether bonds. The phenyl C-H vibration at 673 cm⁻¹ was split for coatings produced at gun-substrate distance of 200 and 300 mm. This indicates a structural change in the phenyl ring possibly indicating a change in the extent of crystallinity of the PEEK polymer.     

Crosslinking of ethylene-propylene (-diene) terpolymer elastomer initiated by an excimer laser

Excimer laser-induced crosslinking of ethylene-propylene-diene elastomer using a trace amount of photoinitiator, 1-hydroxy cyclohexyl phenyl ketone, was evaluated. Gel content measurements on irradiated samples showed that crosslinking was a natural consequence in all, which had undergone exposure to laser radiation. Degree of crosslinking was found to be linear with the laser exposure energy and was found to reach a saturation value of approximately 80% at about 100 J. However, for thicker samples the dependence of gel content i.e. crosslinking was found to be exponential over the range of laser exposure energy in excess of 200 J. As is expected, the tensile strength increased significantly with the increase of crosslinking. The band at 808 cm⁻¹ in the infrared spectra was attributed to the 5-ethylidene-2-norbornene (ENB) content in the polymer. The ENB has a double bond which is considered to be consumed with a high radiochemical yield and thereby contributes to the increase in rate of the formation of intermolecular bridge density.     

Preliminary study of UV ageing process of proteinaceous paint binder by FT-IR and principal component analysis

This work presents a preliminary study on the ageing process of proteinaceous binder materials used in painting under UV light. With this aim, two sets of model samples were prepared: samples prepared using a single protein material and complex samples prepared in a similar way to the sequence of layers in a real painting from lowest to highest complexity (protein, drying oils, pigment and varnish). The study focuses on acquiring information about the possible degradation process of proteinaceous binders due to ageing and how this process be affected by the presence of characteristic non-proteinaceous painting materials, such as lipids from linseed oil, terpenic compounds from varnish and inorganic pigments. Samples simulated the accelerated ageing process, as did the UV light exposition. The FT-IR spectra were recorded after 100, 500, 1000 and 1500 h of exposition. The study of the accelerated ageing process was performed by means of principal component analysis (PCA) using the FT-IR spectra obtained. Loadings from the significant principal components were analysed to find the FT-IR frequency (cm⁻¹) involved in the degradation process. The study showed the lack of any relevant modification on the proteins in the single model samples. On the contrary, the complex model samples showed the ageing process. The accelerated ageing process can be explained by a principal component from PCA. The most affected IR region was 2900-3600 cm⁻¹, where the amide band was included.     

Quantitative analysis of synthetic calcium carbonate polymorphs using FT-IR spectroscopy

Fourier Transform Infrared Spectroscopy (FT-IR) was used successfully for the simultaneous quantitative analysis of calcium carbonate phases (calcite, aragonite, vaterite) in ternary mixtures. From the FT-IR spectra of pure calcite, aragonite and vaterite powders with KBr, the absorptivities, α, of the absorption bands at 713 cm⁻¹ for calcite, 745 cm⁻¹ for vaterite, 713 and 700 cm⁻¹ for aragonite, were determined. In order to overcome the absorption band overlapping a set of equations based on Beer's law was developed. The detection limits were also established and found to be 1.1×10⁻⁴ mg calcite per mm² of pellet at 713 cm⁻¹, 3.6×10⁻⁴ mg aragonite per mm² of pellet at 700 cm⁻¹, 1.8×10⁻⁴ mg aragonite per mm² of pellet at 713 cm⁻¹ and 3.1×10⁻⁴ mg vaterite per mm² of pellet at 745 cm⁻¹. Analysis of a known ternary mixture of calcium carbonate polymorphs tested the validity of the method.     

Vibrational assignment of the spectral data and thermodynamic properties of 2-chloro-4-fluorobenzophenone using DFT quantum chemical calculations

The FT-Raman (3500-100 cm⁻¹) and FT-IR (4000-450 cm⁻¹) spectra of 2-chloro-4-fluorobenzophenone were recorded in the solid phase. Density functional theory calculations with B3LYP/6-31G (d, p) basis set was used to determine the ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities and Raman activities of this compound. Potential energy distributions (PEDs) and normal modes, for the spectral data computed at B3LYP/6-31G (d, p) level, have also been obtained from force-field calculations. The wavenumbers found after scaling of the force field showed very good agreement with the experimentally determined values. A comparison of the theoretical spectra and experimental FT-IR and FT-Raman spectra of the title molecule has been made and full vibrational assignments of the observed spectra have been proposed. On the basis of vibrational analyses, the thermodynamic properties of title compound at different temperatures have been calculated.     

Investigation of the dislocation of natural fibres by Fourier-transform infrared spectroscopy

Dislocations were thought the weakest link in natural fibres which had negative effects on the tensile strength of the fibres. This paper presents a systematic approach to examine the dislocations in hemp fibres firstly by optical microscopy (OM) and field emission scanning electron microscopy (FE-SEM) for the morphologies of the dislocations and then by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) for the crystallinity index and hydrogen bonds and main chemical compositions of the dislocation regions in hemp fibres. The results showed that (i) dislocations resulted in fibril distortion and intensified amorphous features of hemp fibres; (ii) crystallinity index reduced from 48.4% examined by FTIR and 56.0% by XRD determination for hemps without dislocations to 41.3% for the dislocation regions; (iii) the FT-IR spectra showed much higher absorbance of hemp fibres without dislocations which was two times that of dislocation regions across the whole range of wavenumbers; (iv) deconvolving spectra in O-H stretching region showed a lower number of hydrogen bonds, weaker inter- and intra-molecular hydrogen bonding in the dislocation regions, indicating a possible decrease in the tensile strength of hemp fibres; (v) the FT-IR spectra indicated the removal of the hemicelluloses in dislocation regions and hence possible loss of lignin because of disappearing the bands at 1368 cm⁻¹, 1363 cm⁻¹ and 1506 cm⁻¹; (vi) the spectra in fingerprint region gave rise to the ratio of syringyl (S)/guaiacyl (G) of 0.9 in dislocation regions which was lower than that (1.1) of hemp without dislocation, this means a significant reduction of lignin content and a higher cellulose content in the dislocation regions.     

Vibrational spectra and reinvestigation of the crystal structure of a polymeric copper(II)-orotate complex, [Cu(μ-HOr)(H2O)2]n: The performance of new DFT methods, M06 and M05-2X, in theoretical studies

The crystal and molecular structure of a polymeric Cu(II)-orotate complex, [Cu(μ-HOr)(H₂O)₂]_n, has been reinvestigated by single crystal X-ray diffraction. It is shown that several synergistic interactions: two axial Cu-O interactions; intramolecular and intermolecular hydrogen bonds; and π-π stacking between the uracil rings contribute to the stability of the crystal structure. The Raman and FT-IR spectra of the title complex are reported for the first time. Comprehensive theoretical studies have been performed by using three unrestricted DFT methods: B3LYP; and the recently developed M06, and M05-2X density functionals. Clear-cut assignments of all the bands in the vibrational spectra have been made on the basis of the calculated potential energy distribution, PED. The very strong Raman band at 1219 cm⁻¹ is diagnostic for the N1-deprotonation of the uracil ring and formation of the copper-nitrogen bond, in this complex. The Cu-O (carboxylate) stretching vibration is observed at 287 cm⁻¹ in the IR spectrum, while the Cu-N (U ring) stretching vibration is assigned to the strong Raman band at 263 cm⁻¹. The molecular structure and vibrational spectra (frequencies and intensities) calculated by the M06 functional method are very similar to the results obtained by the B3LYP method, but M06 performs better than B3LYP in calculations of the geometrical parameters and vibrational frequencies of the interligand O-H?O hydrogen bonding. Unfortunately, the M05-2X method seriously overestimates the strength of interligand hydrogen bond.     

FT-IR microscopic imaging of calcified deposit of rotator cuff tendonitis: A pilot study and a randomised identification of the compositional components after extrusion from tendon to muscle

Fourier transform infrared (FT-IR) microspectroscopy with mapping system was applied to identify and evaluate what difference in the distribution and compositional components of the calcified deposit of rotator cuff tendonitis after dislocation from tendon to muscle. A 49 year-old female patient suffered from severe shoulder pain was enrolled in this study. Diagnostic high-resolution ultrasonography (HRUS) was initially carried out to verify the calcific tendonitis. The calcified deposits were then examined by histopathologic assessment and FT-IR microspectroscopy. Diagnostic HRUS reveals that the calcified deposits were observed in the subscapularis tendon and infraspinatus muscle of the shoulder for this patient. FT-IR microspectroscopic imaging results clearly indicate that both IR spectra of the calcified deposits in tendon and muscle were almost the same as that of the IR spectrum of hydroxyapatite except the peak at 873 cm⁻¹. It is also found that the peak intensity at 1030 cm⁻¹ for tendon sample was somewhat more intense than that of the peak at 1031 cm⁻¹ for muscle sample, implying that the calcified sample in the tendon seems to be mature than that in the muscle. The second-derivative IR spectra of two calcified samples exhibit two specific sharp peaks at 880 and 872 cm⁻¹, indicating that the type A and type B carbonated apatites were markedly co-existed in both calcified deposits of tendon and muscle even the calcified deposit was dislocated from tendon to muscle. These carbonated apatites presented in the calcified deposits of either tendon or muscle of the shoulder were also consistent with the nodular or nodular nodular-cystic morphology of calcified plaque of the shoulder after HRUS examination.     

The structure of mimetite,arsenian pyromorphite and hedyphane – A near-infrared spectroscopic study

Electronic and vibrational spectra of mimetite, arsenian pyromorphite and hedyphane minerals have been analysed and the spectra related to the mimetite and arsenian pyromorphite and hedyphane mineral structure. The chief spectral feature in the electronic spectra at ∼10 000 cm⁻¹ (1.00 μm) with variable band position and intensity results from the ferrous ion. The splitting of Fe(II) band is large in mimetites with a separation of 1415 cm⁻¹. An additional band shown by arsenian pyromorphite at 10 735 cm⁻¹ (0.93 μm) is assigned to Cu(II) dd-transition. The substitution of Fe(II) causes a blue shift for Cu(II) band in mimetites and the intensity of this band is enhanced at ∼11 140 cm⁻¹ (0.90 μm). The change in colour from brown to orange-yellow relates to the amount of Cu and/or Fe impurities in the mimetite minerals.     

On the specificity of the amide VI band for the secondary structure of proteins

In this work we analyzed the specificity of the amide VI band for different types of secondary structure elements in protein structures. This band involves the bending motion of the CO group of the peptide chain that is typically observed in the spectral region from 590 to 490 cm⁻¹. The infrared absorbance spectra of a set of polypeptide model compounds of well known secondary structure was obtained at defined pH, including poly (l-lysine), poly (l-tyrosine), poly (l-alanine) and poly (l-histidine). In addition spectra of membrane proteins from the respiratory chain, namely the NADH:ubiquinone oxidoreductase, the cytochrome c oxidase and its Cu_A fragment, the cytochrome bc₁ complex, a Rieske-type protein and in addition myoglobin, have been comparatively investigated. The systematic analysis of the amide VI band of the polypeptides and the proteins allowed correlating the signal appearing at ∼525 cm⁻¹ to α-helical structures and signals at ∼545 cm⁻¹ to β-sheet contributions. Random coils have been found to contribute at ∼535 cm⁻¹ while the β-turns were observed at ∼560 cm⁻¹.     

FTIR study of water clusters in water–triethylamine solutions

The FTIR study presented in this work, on water dissolved in triethylamine (TEA), reveals the formation of water clusters in the TEA liquid phase at tenths of water molar concentrations. In the OH stretching region, the FTIR spectra of water in TEA show, at high frequencies, a narrow band at 3682 cm⁻¹ and, at low frequencies, a wide band that can be resolved into four peaks with maxima at 3249 cm⁻¹, 3348 cm⁻¹, 3440 cm⁻¹ and 3545 cm⁻¹. The results have been rationalised assuming the formation of clusters containing tens of three- and four-coordinated water molecules. TEA molecules surrounding the clusters are hydrogen bonded to one OH of the water molecules at the surface, leaving dangling protons. Further, the analyses of the spectra suggest that, in the used range, the water cluster mean size does not depend strongly on the water concentration.     

Determination of crystallinity of swollen poly(vinyl alcohol) by laser Raman spectroscopy

Laser Raman spectra of atactic poly(vinyl alcohol) (PVA) after heat treatment and/or swelling in water have been obtained. An amorphous Raman band is observed at 1124 cm^?1, while a crystalline Raman band is found at 1147 cm^?1. A new method for crystallinity determination is proposed, in which the amorphous band is used instead of the crystalline band. The method is superior to others for water-swollen PVA samples. Laser Raman spectra of swollen PVA revealed that swelling causes destruction of a major fraction of the crystalline regions and the remaining intact crystalline part increases with increasing temperature of heat treatment.     

Structural study of the stability of the captopril drug regarding the formation of its captopril disulphide dimer

Captopril disulphide is obtained under hydrothermal conditions. The IR and Raman spectra data are in agreement with the X-ray diffraction results. The disappearance of the band at 2566 cm^–1 (ν(SH)) in both spectra of captopril disulphide is consistent with the formation of the S–S bond. The degradation of the captopril drug is investigated by Raman spectroscopy and the results indicate that after 6 weeks of air exposure, a band at 512 cm^–1, assigned as ν(SS), is observed, suggesting the formation of captopril disulphide. DFT calculations in the solid state are performed for captopril and captopril disulphide. The results indicate that captopril disulphide is approximately 30 kcal?mol^–1 more stable than captopril. The analysis of the total density of states (DOS) reveals that the captopril valence band contains a significant contribution from the S atom, whereas for captopril disulphide, the O atom is the most important for the valence band.     

Regularity modes in Raman spectra of polyolefins: Part II. Polyethylene and ethylene copolymers

In this work, the thermal behavior of the regularity modes in Raman spectra of polyethylene with different densities and random ethylene/1-hexene copolymers with varying content of comonomer are studied. We demonstrate especially that the vibrational modes at 1062 and 2850 cm^↙1 are related to a critical sequence length of trans-conformers of 6⬜8 CH₂ groups, while the modes at 1130, 1170, 1295, and 2883 cm^↙1 indicate a critical sequence length of trans-conformers of 18 CH₂ groups. Upon increasing the 1-hexene content in the ethylene/1-hexene copolymers, the evolution of the intensities of the Raman modes at 1062, 1130, 1170, 1295, and 1417 cm^↙1, normalized to the intensity of the band at 2850 cm^↙1, is similar to the evolution of the intensities of the same modes in the Raman spectra of low density polyethylene at increasing temperature. This observation however contrasts with that in the Raman spectra of polyethylenes with middle and high densities. We suppose that these results can be explained by similarities in the structure of non-crystalline areas of low density polyethylene and the ethylene/1-hexene copolymers, which contain significant amounts of short sequences of trans-conformers.     

FT-Raman spectroscopy: A positive means of evaluating the impact of whale bone preservation treatment

The degreasing methods currently used for osteological collections are not always completely satisfactory. Numerous natural history museums encounter the problem of grease seeping to the surface of bones. FT-Raman spectroscopy was used to characterise cetacean bones, before and after degreasing treatment, in order to evaluate the efficacy of treatment and the impact thereof on bone constituents. The Raman spectra made it possible to monitor the changes in the main bone constituents: the mineral component with the apatite band at 960 cm⁻¹, the organic component with the collagen amide III band at 1270 cm⁻¹ and fat with the lipid CH₂ band at 2850 cm⁻¹. The band associated with lipids decreased and even disappeared with degreasing treatment containing chlorinated solvents. This type of treatment enables fat to be extracted both from the surface and from the bone core; however, it debases the organic component of bone by denaturing collagen. Alternative types of treatment (acetone or enzyme baths) were tested over a limited period, which did not enable their true efficacy to be demonstrated. During the alternative treatments, no bone degradation was observed. Only the acetone solution was able to extract fat, though only from the surface.     

Fourier transform infrared microspectroscopy as a bacterial source tracking tool to discriminate fecal E. coli strains

The aim of this work was to use the FT-IR microspectroscopy technique, a union of a FT-IR spectrometer with a microscope, to discriminate fecal Escherichia coli strains from cows, chickens and humans and to compare the efficiency of this method with the genomic fingerprinting method, BOX-PCR. The obtained BOX-PCR profiles were able to correctly discriminate 93.75% of the chicken strains, 80% of the cow strains and 65% of the human strains. An efficient PLS-DA model was developed, using orthogonal signal correction and the second derivate of the FT-IR spectra. This model allowed the correct discrimination, according to the animal source, of all the E. coli strains analyzed. The bands in the FT-IR spectra that were responsible for the strains discrimination were in the region between 2816 and 3026 cm⁻¹ wavenumber, described as fatty acids. It was demonstrated that FT-IR microspectroscopy can be a suitable tool for fecal E. coli discrimination, because it is fast, easy to carry out and presents a flexible discrimination power.     

FT-Raman spectroscopy: A positive means of evaluating the impact of whale bone preservation treatment

The degreasing methods currently used for osteological collections are not always completely satisfactory. Numerous natural history museums encounter the problem of grease seeping to the surface of bones. FT-Raman spectroscopy was used to characterise cetacean bones, before and after degreasing treatment, in order to evaluate the efficacy of treatment and the impact thereof on bone constituents. The Raman spectra made it possible to monitor the changes in the main bone constituents: the mineral component with the apatite band at 960 cm⁻¹, the organic component with the collagen amide III band at 1270 cm⁻¹ and fat with the lipid CH₂ band at 2850 cm⁻¹. The band associated with lipids decreased and even disappeared with degreasing treatment containing chlorinated solvents. This type of treatment enables fat to be extracted both from the surface and from the bone core; however, it debases the organic component of bone by denaturing collagen. Alternative types of treatment (acetone or enzyme baths) were tested over a limited period, which did not enable their true efficacy to be demonstrated. During the alternative treatments, no bone degradation was observed. Only the acetone solution was able to extract fat, though only from the surface.     

Infrared spectrum and absorption coefficient of the cofactor flavin in water

Flavins play a key role as redox cofactors of enzymes involved in important metabolic processes. Moreover, they undergo photochemical reactions as chromophores in sensors of blue light or magnetic field in many organisms. The reaction mechanisms of flavoproteins have been investigated by infrared spectroscopy and theoretical studies. However, basic information on flavins in the infrared spectral range has been missing, such as absorption spectra in water and absorption coefficients. Here, the cofactors flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) were investigated in aqueous medium by Fourier transform infrared spectroscopy. Transmission and attenuated total reflection (ATR) configuration were employed in direct comparison. Absorption spectra in the range of 920–1800 cm⁻¹ were determined after accurate subtraction of the contributions from the water vibrations. The important carbonyl vibrations were resolved at 1661 and 1712 cm⁻¹. The absorption spectra may serve as a reference for theoretical and experimental studies on the effect of the microenvironment on the flavin cofactor. Furthermore, the molar absorption coefficient of FAD at 1547 cm⁻¹ was determined to 2200 L mol⁻¹ cm⁻¹ with an integral absorption coefficient of ∼50,000 L mol⁻¹ cm⁻². These values are prerequisite for the determination of reaction yields in flavoproteins from reaction-induced difference spectra.     

用差减红外光谱分峰法测定乙丙齐聚物中端羟基的微结构

合成了端羟基乙丙齐聚物。用差减红外光谱对端羟基进行了分析。扣除了溶剂中三氯甲烷的干扰,用RUN.CAPR程序进行分峰,以正戊醇-1、3-甲基丁醇-1和丁醇-2为模型化合物标定伯、仲羟基吸收峰位置,并进行蜂面积积分,用模型化合物回归处理后得到定量公式:A=15.8667×10~3Cp+0.25674,以此求得乙丙齐聚物中伯、仲羟基的官能度。     

Preparation and characterization of nanosized ZSM-5 zeolite using kaolin and investigation of kaolin content, crystallization time and temperature changes on the size and crystallinity of products

Nano sized ZSM-5 zeolite samples were synthesized successively from kaolin clay as alumina source having a large amount of quartz (39%) and silicic acid as silica source by hydrothermal treatment with NaOH in the presence of tetrapropylammonium hydroxide as a template. Then the effect of kaolin content, crystallization temperature and time on the size and crystallinity of the products were investigated. The prepared samples were characterized using XRD, SEM, EDS and FT-IR techniques. The results showed that the synthesized ZSM-5 zeolite samples were almost pure and their crystallization was almost complete. The average particle size, as determined by Debye-Scherrer equation, was in the range of 20-42 nm. Increasing kaolin content on crystal size was more effective than increase in crystallization temperature and time. Additional evidences for the nano sized ZSM-5 zeolite were the asymmetric stretch vibration band at 1225 cm^-1 in the FT-IR spectra and TEM images. The scanning electron micrographs of the synthesized zeolites showed that they are spherical shape crystals.