Raman and infrared spectroscopic study of kerogen treated at elevated temperatures and pressures

Kerogen was treated for 24 h at temperatures of 250–700 °C and pressures of 500–1500 bar. Raman spectroscopic study of the run products documented systematic changes in both the first- and second-order spectral features with temperature and pressure. The micro-FTIR analysis of the kerogen treated showed that the presence of hydrogenated functional groups and importance of aromatic rings in the structures of the kerogen increased with temperature. An abrupt change in the chemical composition and structural state of the kerogen treated occurred at ∼500 °C.     

Effects of sodium hydroxide treatment on coordination changes of cobalt ions in CoNaY by means of UV/VIS diffuse reflectance spectroscopy

The coordination changes of Co²⁺ in CoNaY/NaOHs, prepared by cobalt ion-exchange and treatment with NaOH, during dehydration at various temperatures have been investigated by UV/VIS diffuse reflectance spectroscopy. After dehydration of CoNaY/NaOHs at 473 K, the DRS bands show the formation of mixed cobalt oxide species interacted with lattice oxygen. This mixed cobalt oxide species interacted with lattice oxygen decompose during further dehydration at 673 K. The strong intensities of the bands at 660, 575 and 530 nm after dehydration of CoNaY/NaOHs at 873 K indicate that a considerable amount of the cobalt ions remains in the sodalite cage with tetrahedral coordination even after dehydration at 873 K.     

In situ FTIR and UV/VIS spectroscopic study of the generation of anionic Pt-carbonyl complexes within a faujasite matrix

The temporal generation of anionic platinum-carbonyl complexes in platinum ionexchanged zeolites X and Y by reductive carbonylation at 10⁵ Pa and 363 K is monitored by in situ UV/VIS and FTIR spectroscopy. A monomer [Pt₃(CO)₆]^2–, exhibiting bands at 318 and 456 nm in the UV/VIS spectra and at 1790 and 2025 cm^–1 in the FTIR spectra, is the only platinum/species formed in NaX. The monomer as well as oligomers are generated in NaY, where the formation of the latter species is due to the stronger acidity in the NaY as compared to NaX. The decomposition of the complexes results in the generation of Pt clusters of the size 1 nm.     

竹活性炭负载催化剂UV/VIS光降解甲醛的研究（摘要）

利用竹活性炭（BAC）的强吸附性和二氧化钛（TiO2）的光催化氧化性二者的协同作用,对水溶液中的甲醛进行处理。在综述国内外研究的基础上,采用溶胶-凝胶法制备TiO2溶胶,采用浸渍法将TiO2负载于竹活性炭的表面,研制了一种以竹活性炭为基质负载TiO2的复合紫外光催化剂（TiO2/BAC）,同时制备了铂、氮共掺杂的可见光...     

Oxidation behavior and mechanism of aluminum oxynitride (AlON) at elevated temperatures

The oxidation behavior and mechanism of aluminum oxynitride (AlON) powder exposed to air at elevated temperatures between 800°C and 1300°C was investigated by X-ray diffractometry (XRD), scanning electron microscope (SEM), electron spin resonance (ESR), nuclear magnetic resonance (NMR), and simultaneous thermogravimetry, differential thermal analysis, and mass spectrometry techniques (TG-DTA-MS). The weight of AlON gradually increases to a maximum value at 1150°C and then decreases with further heating. Meanwhile, AlON powder undergoes chemical changes, as evidenced by lattice expansion, and turns eventually into alumina. ESR spectra reveal the occurrence of lone pair electrons in the oxidized products and the intensity of corresponding resonance signal increases before disappearing with the increase in temperature. Combined with the results of NMR and TG-DTA-MS, the measured data suggest that Al-N in [AlO₃N] tetrahedron and [AlO₅N] octahedron are gradually oxidized into Al-O-N group with lone pair electrons, which causes continuous weight gain and lattice expansion. Further oxidation at higher temperatures results in alumina and N₂.     

Silane-modified polyvinylimidazole(1) for corrosion protection on copper at elevated temperatures

Silane-modified N-polyvinylimidazole [PVI(1)] copolymers have been synthesized from various mole ratios of γ-methacryloxypropyltrimethoxysilane (γ-MPS) and N-vinylimidazole, VI(1). Fourier transform infrared reflection-absorption spectroscopy (FTIR-RAS) is used to investigate the modified PVI(1) on copper surfaces. The silane-modified PVI(1) has good corrosion protection and adhesion promotion capabilities for copper substrate under severe environments. The relationship between coating thickness and corrosion protection is studied at elevated temperatures. The relationship between the mole ratio of comonomers and the corrosion processes of a copper surface has also been investigated at elevated temperatures. The corrosion protection improves drastically with increased VI(1) content. An adhesion study of the silane-modified PVI(1) film on a copper surface is also carried out using the ASTM adhesive tape test. From the adhesion strengths between the modified PVI(1) films and copper surface, it has been observed that modified PVI(1) acts as an adhesion promoter and does not depend on the mole ratio of γ-MPS/VI(1) within the range of this experiment. Good adhesion of an anticorrosion coating is important for the corrosion protection of a copper surface. © 1993 John Wiley & Sons, Inc.     

Fracture behavior of polyetherimide (PEI) and interlaminar fracture of CF/PEI laminates at elevated temperatures

To investigate the effects of environmental temperature on fracture behavior of a polyetherimide (PEI) thermoplastic polymer and its carbon fiber (CF/PEI) composite, experimental and numerical studies were performed on compact tension (CT) and double cantilever beam (DCB) specimens under mode‐I loading. The numerical analyses were based on 2‐D large deformation finite element analyses (FEA). Elevated temperatures greatly released the crack tip triaxiality (constraint) and promoted matrix deformation due to low yield strength and enhanced ductility of the PEI matrix, which resulted in the greater plane‐strain fracture toughness of the bulk PEI polymer and the interlaminar fracture toughness of its composite during delamination propagation with increasing temperature. Furthermore, the high triaxiality was developed around the delamination front tip in the DCB specimen, which accounted for the poor translation of matrix toughness to the interlaminar fracture toughness by suppressing the matrix deformation and reducing the plastic energy dissipated in the plastic zone. Especially, at delamination initiation, the weakened fiber/matrix adhesion at elevated temperatures led to premature failure of fiber/matrix interface, suppressing matrix deformation and preventing the full utilization of matrix toughness. Consequently, low interlaminar fracture toughness was obtained at elevated temperatures. POLYM. COMPOS., 26:20–28, 2005. © 2004 Society of Plastics Engineers.     

Imaging gold clusters on TiO2(110) at elevated pressures and temperatures

Variable temperature scanning tunneling microscopy (STM) has been used to image oxide-supported nanoclusters of Au at temperatures from 300 to 450 K and oxygen pressures from 10^–10 to 4 Torr. Oxygen-induced morphological changes of the TiO₂(1×2) reconstruction are apparent at room temperature and prolonged exposure (3×10³ L (langmuir)) at 10^–4 Torr oxygen. Gold clusters with diameters smaller than 4 nm are unstable toward sintering at ca. 450 K and oxygen pressures >10^–1 Torr. Oxygen at pressures >10^–4 Torr weakens the interaction between the gold cluster and the titania support. Increasing the sample temperature to >300 K facilitates disruption of the cluster–support interaction.     

A novel multi-channel reactor system combined with operando UV/vis diffuse reflectance spectroscopy: Proof of principle

A 36 channel reactor system combining high-throughput experimentation (HTE) with operando UV/vis diffuse reflectance (UV/vis-DR) spectroscopy is introduced and applied for the oxidative dehydrogenation of propane (ODP) to propene at 500 °C over polycrystalline V₂O₃, VO₂, and V₂O₅. This set-up enabled to monitor reaction-induced reduction of V₂O₅ to V₂O₃, and VO₂ during the ODP reaction. The operando UV/vis-DR spectroscopic analysis along the catalyst bed demonstrated that the vanadium oxidation state at the reactor inlet is higher than at the reactor outlet. This is due to the depletion of oxygen and the enrichment of propene down stream along the catalyst bed.     

Near‐infrared laser absorption of poly(vinyl chloride) at elevated temperatures

Modeling laser transmission welding of thermoplastics requires knowledge of the optical properties of the materials being joined. The optical properties are highly dependent on their unique combinations of base polymer, pigments, and fillers. Because of the complex phase transition that occurs when heating thermoplastics, the optical properties are not a constant, but a function of temperature. During laser transmission welding large changes in the material temperature affect the light absorption, thus changing the characteristics of heating owing to the laser radiation. This paper discusses an experiment measuring diode laser transmission through clear poly(vinyl chloride) samples while increasing the material temperature in an oven. It was found that the absorption coefficient follows repeated peaks and valleys between the glass transition temperature and the melting point. Above the melting point the absorption coefficient increases to a plateau before a further increase that is marked by thermal decomposition. In addition, the decomposition temperature was found to be dependent on the rate of heating. J. VINYL ADDIT. TECHNOL., 12:166–173, 2006. © 2006 Society of Plastics Engineers     

Polarized internal reflectance spectroscopic studies of oriented poly(ethylene terephthalate)

Polarized internal reflectance spectroscopy (IRS) has been used to evaluate molecular orientation and crystallinity of poly(ethylene terephthalate) film surfaces. Measurements were taken using samples stretched in both uniaxial and biaxial modes. All bands of interest were normalized with a reference band near 1410 cm^?1, resulting from phenylene ring vibrations. Normalization was performed in order to overcome problems with sample contact and effective thickness. Results obtained using bands representing trans and gauche rotational isomers, present, respectively, at 1340 and 1370 cm^?1, have been related to data acquired using density and birefringence techniques. The polarized IRS technique discussed is well suited for investigations of polymer orientation and crystallinity, since it avoids limitations related to sample thickness and clarity imposed by polarized transmission infrared spectroscopy. Parameters such as orientation functions, attenuation indices, dichroic ratios, and structural factors have been determined from data collected in each of the three spatial directions. Results are correlated with corresponding density, birefringence, and refractive index values and are found to give good agreement with these methods. © 1994 John Wiley & Sons, Inc.     

The electrochemistry of silver in KOH at elevated temperatures—IV. AC impedance study

The ac impedance properties of silver in 1 mol kg^?1 KOH were studied under potentiostatic conditions over the temperature range 295–478 K. Measurements were obtained over the frequency range 0.5 Hz–5 kHz, and were analyzed in terms of equivalent in terms of equivalent circuits. It was shown that provision for surface roughness is required for a satisfactory explanation of the impedance data. Values for the double layer capacity and the concentration AgO^? ions at the electrode surface could generally then be obtained. At potentials corresponding to the formation of Ag₂O, it is demonstrated that both diffusion in solution and diffusion in the oxide film are operative. At elevated temperatures, the rate of growth of Ag₂O centres is controlled partly by diffusion in the oxide and party by a reaction step at the growing interfaces of the centers. The subsequent formation of Ag₂O₂, at all temperatures in the range studied, is interpreted on the basis of an electrocrystallisation impedance.     

Experimental study of micro/macro crack development and stress-strain relations of cement-based composite materials at elevated temperatures

This paper presents the results of observations of scanning electron microscope (SEM) micro/macro crack development and simultaneous measurements of temperature-dependent stress-strain relations of hardened cement pastes (HCP) and mortar under a steady thermal state (up to 500 °C) and a displacement-controlled loading process. The experimental results showed that the thermal damage of HCP was not only due to the recognized decomposition of the hydration products but also to the formation of dehydration-induced microcracks. These damage mechanisms, together with three other types of macrocracks arisen from the mismatch of expansion/shrinkage between the phase materials (HCP and aggregates) contributed to the thermal damage of the mortar. By comparing the evolution of the stress-strain curves for the HCP and the companion mortar specimens, the effects of the damage mechanisms could be separately quantified. In this study, the thermal damage of the mortar specimens was largely caused by the thermal mismatch mechanism.     

Tribological performance of SiC coating for carbon/carbon composites at elevated temperatures

SiC coating was deposited on carbon/carbon (C/C) composites by chemical vapor deposition (CVD). The effects of elevated temperatures on tribological performance of SiC coating were investigated. The related microstructure and wear mechanism were analyzed. The results show that the as-deposited SiC coating consists of uniformity of β-SiC phase. The mild abrasive and slight adhesive wear were the main wear mechanisms at room temperature, and the SiC coating presented the maximum friction coefficient and the minimum wear rate. Slight oxidation of debris was occurred when the temperature rose to 300?°C. As the temperature was above 600?°C, dense oxide film formed on the worn surface. The silica tribo-film replaced the mechanical fracture and dominated the frication process. However, the aggravation of oxidation at elevated temperatures was responsible for the decrease of friction coefficient and the deterioration of wear rate. The SiC coating presented the minimum friction coefficient and the maximum wear rate when the temperature was 800?°C.     

An investigation on wear behavior of UHMWPE/carbide composites at elevated temperatures

Ultra-high molecular weight polyethylene (UHMWPE) is extensively used in frictional applications due to its advanced wear resistance. This advanced polymer is reinforced with hard particulate fillers for further developments against wear conditions. Since elevated temperatures prevail in the service conditions, wear behavior of UHMWPE composites is an important issue for the engineering applications. In the present work, UHMWPE-based composites including silicon carbide (SiC) fillers were fabricated in a compression molding chamber. In the specimen preparation stage, molding pressure, filler amount, and filler particle size were varied to investigate the influence of these variables. Upon deciding the optimum parameters from the wear tests conducted at room temperature, the wear experiments were repeated for the optimum specimen at elevated temperatures, such as 40 and 60°C. According to the results, the wear behavior of the SiC/UHMWPE composites is heavily changed by the effect of elevated temperature. Adhesive effect is pronounced at elevated temperatures while the wear characteristics possess the abrasive effect in the sliding path. In addition, the composites exhibit an accelerated material loss as temperature increases during the frictional system.     

IR spectroscopic study of Pt/Kl zeolites using adsorption of CO as a molecular probe

FTIR spectra of CO adsorbed on Pt/KL catalysts show that the relative band intensities and the total dispersion markedly depend on the catalyst preparation method (ion exchange, incipient wetness impregnation or co-impregnation with KCl). The CO stretching frequency of the dominant band for linear CO is shifted to higher wavenumbers, parallel with the proton concentration in the reduced catalyst, which is derived independently from the intensity of the IR bands of the OH groups. The results are in accordance with the model that electron-deficient platinum particles are platinum-proton adducts.On leave from: N.D. Zelinsky Institute of Organic Chemistry, Academy of Sciences, Moscow, USSR.     

The electrochemistry of silver in koh at elevated temperatures—III. Potentiostatic study

The electrochemistry of polycrystalline silver in 1 mol kg^?1 KOH at temperatures between 295 K and 478 K has been studied using potentiostatic polarization. At potentials corresponding to silver dissolution and to the early stages of Ag₂O formation, the transient current data at all the temperatures studied exhibit regions that are linearly dependent on the inverse square root of time. This dependence indicates mass transport to be a rate limiting step in these processes. Log (steady-state current) vs potential data show that at all temperatures silver undergoes an active-to-passive transition. However, the potential of the transition shifts to less positive values and the passive current increases with increasing temperature. In the region of formation of surface oxide phases, the transients exhibit maxima due to nucleation and growth phenomena. The effect of temperature on the transients is similar to the effect of overpotential; in both cases, the time taken to reach the maximum current decreases.     

Electron beam irradiation of polytetrafluoroethylene in vacuum at elevated temperature: An infrared spectroscopic study

Electron beam irradiation of polytetrafluoroethylene (PTFE) has been performed in vacuum both at elevated temperature above the melting point of PTFE and at room temperature for comparison. The changes in the chemical structure were studied by Fourier‐transform infrared (FTIR) spectroscopy. The formation of double bonds in PTFE was confirmed as a result of irradiation in vacuum. Moreover, trifluoromethyl (CF₃) branches were detected. The concentration of CF₃ branches was found to be much higher in irradiation at elevated temperature than in room temperature irradiation. The CF₃ branches are assumed to cause the reduced crystallinity indicated by the transparency of PTFE specimens irradiated in the molten state. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1571–1576, 1999     

Effects of Na2O on calcium silicate hydrates at elevated temperatures

Pectolite is a stable phase in large areas of the system NCSH at 180 to 325°C; it may coexist, depending on Na₂O concentration and temperature, with tobermorite, xonotlite or foshagite. Sodium carbonate and $\text{N}\text{S}$ reacted with Ca²⁺ in Al₂O₃ substituted tobermorite to form slightly soluble C$\text{C}$ and C$\text{S}$ NSH and NaOH. The possible destructive effects of these reactions are considered. Sodium chloride had no detectable corrosive effect on the tobermorite.