Thermal reactivities of catechols/pyrogallols and cresols/xylenols as lignin pyrolysis intermediates

Thermal reactivities of lignin pyrolysis intermediates, catechols/pyrogallols (O-CH₃ homolysis products) and cresols/xylenols (OCH₃ rearrangement products), were studied in a closed ampoule reactor (N₂/600 °C/40-600 s) to understand their roles in the secondary reactions step. Reactivity tends to be enhanced by increasing the number of substituent groups on phenol and this effect was greater for -OH than for -CH₃. Thus, catechols/pyrogallols were more reactive than cresols/xylenols and syringol-derived products were more reactive than corresponding guaiacol-derived products. Catechols/pyrogallols were effectively converted into CO (additionally CO₂ in the case of pyrogallols) in the early stage of pyrolysis. In contrast, cresols/xylenols were comparatively stable and produced H₂, CH₄ and demethylation products (cresols and phenol) after prolonged heating. All intermediates except phenol and 2-ethylphenol formed coke during a long heating time of 600 s (second stage coking). Based on the present results, the roles of intermediates in tar, coke and gas formation from guaiacol and syringol are discussed at the molecular level, focusing on their differences. Molecular mechanisms of gas formation from pyrogallols and demethylation of cresols/xylenols are also discussed.     

Preparation and characterization of activated carbon from cotton stalks in a two-stage process

Activated carbons are prepared from cotton stalks by chemical activation with ZnCl₂, H₂SO₄ and physical activation using CO₂ and steam-CO₂ mixture for temperatures of 750, 850 and 900 °C. The effects of activation temperature and duration time, impregnation concentration of agent, impregnation times, and physical activating agent are examined. These materials are characterized by adsorption/desorption of N₂ to determine the BET areas, thermogravimetric analysis (TG, DTA), FTIR and scanning electron microscopy (SEM). ZnCl₂ under CO₂ atmosphere was found more effective than H₂SO₄ as a chemical reagent under identical conditions in terms of porosity development. The maximum BET surface area is found to be 2053 m²/g for active carbons produced with ZnCl₂ activation under CO₂ atmosphere.     

CO2 adsorption studies on hydroxy metal carbonates M(CO3)x(OH)y (M = Zn, Zn-Mg, Mg, Mg-Cu, Cu, Ni, and Pb) at high pressures up to 175 bar

Carbon dioxide (CO(2)) adsorption capacities of several hydroxy metal carbonates have been studied using the state-of-the-art Rubotherm sorption apparatus to obtain adsorption and desorption isotherms of these compounds up to 175 bar. The carbonate compounds were prepared by simply reacting a carbonate (CO(3)(2-)) solution with solutions of Zn(2+), Zn(2+)/Mg(2+), Mg(2+), Cu(2+)/Mg(2+), Cu(2+), Pb(2+), and Ni(2+) metal ions, resulting in hydroxyzincite, hydromagnesite, mcguinnessite, malachite, nullaginite, and hydrocerussite, respectively. Mineral compositions are calculated by using a combination of powder XRD, TGA, FTIR, and ICP-OES analysis. Adsorption capacities of hydroxy nickel carbonate compound observed from Rubotherm magnetic suspension sorption apparatus has shown highest performance among the other components that were investigated in this work (1.72 mmol CO(2)/g adsorbent at 175 bar and 316 K).     

A quintic B-spline finite-element method for solving the nonlinear Schr?dinger equation

The nonlinear Schr?dinger equation is numerically solved using the collocation method based on quintic B-spline interpolation functions. The efficiency and robustness of the proposed method are demonstrated by standard test problems, such as a one-soliton solution, interaction of two solitons, and formation of a soliton. This method is compared with both the analytical and numerical techniques in the computational section.     

A comparison of electromigration failure of metal lines with fracture mechanics

Atoms constructing an interconnecting metal linein a semiconductor device are transported by electron flowin high density.This phenomenon is called electromigration,which may cause the line failure.In order to characterize theelectromigration failure,a comparison study is carried outwith some typical phenomena treated by fracture mechanicsfor thin and large structures.An example of thin structures,which have been treated by fracture mechanics,is silica optical fibers for communication systems.The damage growth ina metal line by electromigration is characterized in comparison with the crack growth in a silica optical fiber subjectedto static fatigue.Also a brief comparison is made betweenthe electromigration failure and some fracture phenomena inlarge structures.     

Accuracy of the Sampling Moiré Method and its Application to Deflection Measurements of Large-Scale Structures

Measuring accurate displacement distributions for large-scale structures is an important issue and a very challenging task. Recently, a simple and accurate phase measurement technique called sampling moiré method [Exp Mech 50–4:501–508, (2010)] has been developed for small-displacement distribution measurements. In this method, the phase distribution of moiré fringes can be analyzed from a single grating image by simultaneously performing down-sampling image processing and intensity-interpolation to generate multiple phase-shifted moiré fringe images. In addition, the phase of the original grating can also be obtained from the phase of the moiré fringe by adding the phase of the sampling grating. In this study, the measurement accuracy of the sampling moiré method was analyzed through computer simulations and a displacement measurement experiment. Four factors of the sampling moiré method were investigated, including the sampling pitch, the order of the intensity-interpolation, random noise, and the form of grating. The results show that determining the optimal sampling pitch is an important factor for obtaining better results but it is not critical. In addition, a practical application of the sampling moiré method is presented that involves a deflection measurement on a 10-meter-long crane. The experimental results demonstrate that submillimeter deflections of the crane can be successfully detected.     

Degradation of substituted phenols with different oxygen sources catalyzed by Co(II) and Cu(II) phthalocyanine complexes

Research on substituted phenol degradations has received substantial attention. In this work, effective Co(II) and Cu(II) phthalocyanine complexes as catalysts were studied to degrade toxic phenols to harmless products. The effect of various process parameters, such as initial concentration of phenol, catalyst, oxygen sources, and temperature on the degradation reaction was investigated to achieve maximum degradation efficiency. The catalytic activities of Co(II) and Cu(II) phthalocyanines were evaluated for oxidation of phenolic compounds such as p-nitrophenol, o-chlorophenol, 2,3-dichlorophenol, and m-methoxyphenol. Co(II) phthalocyanine displayed good catalytic performance in degradation of 2,3-dichlorophenol to 2,3-dichlorobenzaldehyde and 2,3-dichloro-1,4-benzoquinone with the highest TON and TOF values within 3?h at 50?°C. The fate of catalyst during the degradation process was followed by UV–Vis spectroscopy.     

Atomic flux divergence in bamboo line for predicting initial formation of voids and hillocks

A calculation method of the atomic flux divergence due to electromigration, AFD_gen, has been proposed considering two-dimensional distributions of current density and temperature and also simply considering the line structure of not only polycrystalline line but also bamboo line. The validity of AFD_gen for bamboo lines has been verified in comparison of void formation calculated by using AFD_gen with experimental results, and it has been shown that void formation in bamboo line is able to be predicted by using AFD_gen. In this study, angled bamboo lines are treated for prediction of hillock formation, and hillock formation predicted by using AFD_gen is compared with that measured in experiment. In addition to the verification of void prediction, the usefulness of the prediction method for electromigration damage using AFD_gen is discussed in more detail.     

On the measurements of particles by imaging methods: Theoretical and Experimental Aspects

Imaging techniques in particle sizing have always been important. Nevertheless, owing to the progress in CCD cameras, these techniques have found new potential which strongly depends on the capability to describe the image formation. Based on a combination of the generalized Lorenz-Mie theory and the diffraction theory, the image characteristics are described, taking into account the beam size, particle location, direction of observation and collecting optics characteristics. In the case of forward detection, a finite coherence is introduced and the results are compared with those obtained by a convolution approach, with the point spread function assumed to be Gaussian. Then some experimental results are displayed which underline the improvement achieved in particle size measurement.     

Synthesis of monodisperse iron oxide nanocrystals by thermal decomposition of iron carboxylate salts

Iron oxide (Fe(3)O(4), magnetite) nanocrystals of 6 to 30 nm with narrow size distributions (sigma = 5-10%) were prepared by the pyrolysis of iron carboxylate salts.