Influence of interactions between chromium and cerium on catalytic performances of CrO_x–CeO_2/Ti-PILC catalysts for deep oxidation of n-butylamine

A series of CrOx-CeO2/Ti-PILC （PILC is pillared interlayered clay） catalysts for n-butylamine oxidation were prepared using an impregnation method, and the structures, surface acidity distributions, and redox properties of the catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, H2 temperature-programmed reduction, and NH3 temperature-programmed desorption. The results show that addition of an appropriate amount of CeO2 enhances the interactions between Cr and Ce, and this increases the acid strength and mobility of active oxygen species on the cata- lyst. 8CrCe（6：1）/Ti-PILC（12,20） exhibits the best catalytic performance and control of NOx in n-butylamine oxidation.     

Improvement of oxidation resistance of Nb–Ti–Si based alloys with additions of Al,Cr and B at different temperatures

The effects of Cr,Al and B addition on the microstructure and high-temperature oxidation behaviors(at 1200,1250 and 1300℃) of Nb-Ti-Si based alloys were investigated.The results showed that the addition of Cr stabilized α-Nb₅ Si₃,while Al promoted the formation of β-Nb₅ Si₃ and adding B promoted the formation of γ-Nb₅ Si₃.Among the three elements,Al and Cr were beneficial to oxidation resistance at 1200℃,and B was favorable to the...     

Effects of reconfiguration on the performance of mobile navigation robot

An irmovative mobile robot that has reconfigurable loeomotion chassis and reconfigurable bionic wheels has been developed to meet the needs of different payload and different terrain. Several prototypes have been achieved by the recortfiguration. By modeling relative comparison coefficients, these prototypes are analyzed in terms of geometrical parameter of trafficability, static stability and maneuverability. The effects of reconfiguration on these indices of robot performance can be compared, i.e. the variable height of chassis h has the biggest effect, the variable length of chassis 1 is the second, then is the camber angle β and the caster angle α. Some principles for reconfiguration are proposed.     

Influence of nanometric CeO_2 coating on high temperature oxidation of Cr

Isothermal and cyclic oxidation behavior of chromium and its superficially applied nanometric CeO2 samples were studied at 900℃in air. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and high resolution electronic microscopy (HREM) were used to examine the morphology and micro-structure of oxide films. It was found that ceria addition greatly improved the anti-oxidation ability of Cr both in isothermal and cyclic oxidizing experiments. Acoustic emission (AE) technique was used in situ to monitor the cracking and spalling of oxide films, and AE signals were analyzed in time-domain and number-domain according to the related oxide fracture model. Laser Raman spectrometer was also used to study the stress status of oxide films formed on Cr with and without ceria. The main reason for the improvement in anti-oxidation of chromium was that ceria greatly reduced the growing speed and grain size of Cr2O3. This fine-grained Cr2O3 oxide film might have better high temperature plasticity and could relieve parts of compressive stress by means of creeping, and maintained the ridge character and relatively low internal stress level. Meanwhile, ceria application reduced the size and the number of interfacial defects, while remarkably enhanced the adhesive property of Cr2O3 oxide scale formed on Cr substrate.     

Effects of baria on propane oxidation activity of Pd/Al2O3 catalyst: Pd–BaO interactio n and reaction routes

The BaO-modified Pd/Al2O3exhibits much better catalytic activity than Pd/Al2O3for C3H8 oxidation both before and after the hydrothermal aging treatment. Further studies ascribe its good activity to the influence of BaO species on the physicochemical characteristics of the catalyst and the reaction routes. Firstly, the BaO species inhibits the phase transformation of alumina, resulting in higher surface area of the catalysts and hereby a better dispersion of Pd. Secondly, the basic nature and electron-withdrawing effect of barium oxide maintain palladium at high oxidation state, which leads to a higher PdO content on surface of the BaO-modified catalyst. Finally, the formation/decomposition of carbonate/bicarbonate species can be promoted by the addition of BaO, which provide extra reaction routes and are important for the deep oxidation of C3H8.     

Effect of niobium alloying level on the oxidation behavior of titanium aluminides at 850°C

This work addresses the alloying of titanium aluminides used in aircraft engine applications and automobiles. The oxidation resistance behavior of two titanium aluminides of α₂ + γ(Ti₃Al + TiAl) and orthorhombic Ti₂NbAl, recognized as candidates for high-temperature applications, was investigated by exposure of the alloys for 100 h in air. Thus, oxidation resistance was expressed as the mass gain rate, whereas surface aspects were analyzed using scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy, and the type of oxidation products was analyzed by X-ray diffraction and Raman spectroscopy. The orthorhombic Ti₂NbAl alloy was embrittled, and pores and microcracks were formed as a result of oxygen diffusion through the external oxide layer formed during thermal oxidation for 100 h.     

Microstructure and oxidation resistance of SiC–MoSi2 multi-phase coating for SiC coated C/C composites

In order to improve the anti-oxidation of C/C composites, a SiC–MoSi2multi-phase coating for SiC coated carbon/carbon composites(C/C)was prepared by low pressure chemical vapor deposition(LPCVD) using methyltrichlorosilane(MTS) as precursor, combined with slurry painting from MoSi2 powder. The phase composition and morphology were analyzed by scanning electron microscope(SEM) and X-ray diffraction(XRD) methods, and the deposition mechanism was discussed. The isothermal oxidation and thermal shock resistance were investigated in a furnace containing air environment at 1500 1C. The results show that the as-prepared SiC–MoSi2coating consists of MoSi2 particles as a dispersing phase and CVD–SiC as a continuous phase. The weight loss of the coated samples is 1.51% after oxidation at 1500 1C for 90 h, and 4.79% after 30 thermal cycles between 1500 1C and room temperature. The penetrable cracks and cavities in the coating served as the diffusion channel of oxygen, resulted in the oxidation of C/C composites, and led to the weight loss in oxidation.     

SEM analysis of the changes of carbon layer structure of mesocarbon microbeads heat-treated at different temperatures

Mesocarbon microbeads (MCMB) with narrow size distribution, excellent sphericity and no obvious conglutination have been prepared with a coal tar pitch containing quinoline insolubles (QI) as the raw material. Optical microscopy and scanning electron microscopy (SEM) are used to examine the structure of the MCMB. It has been found that SEM technique shows the structural information of MCMB clearly in the form of micrographs even when the structure of MCMB is complex, while the optical technique is useful for analysis of the regular structure of the mesophase spheres but cannot be effectively used to analyze either the complex structure of the green MCMB or the structures of the further heat-treated ones at different temperatures. According to the characteristics of the carbon layers, the structures of the as-prepared MCMB in the present experiment could be classified as (I) Parallel Layer type structure and (2) Bent Layer type structure with the carbon layers gathering at one or two points in the MCMB. In the experiments, SEM is also utilized to investigate the structures of MCMB that are heat-treated at different temperatures. It has been found that the MCMB without any further heat-treatment show no layered-carbons, while the ones heat-treated at temperaturehigher than 1000℃ exhibit obvious layered carbons across their sections. When increasing the heat-treatment temperature, the carbon layers become thinner and flatter.     

Effects of biological pre-treatment of pine chips on the beating performance of Kraft pulp

The Calabrien pine (Pinus brutia) wood chips prior to kraft pulping were biologically pre-treated with selected white-rot fungi (Ceriporiopsis subvermispora), which was recorded to be preferentially attacking the lignin component of the wood. The effects of this treatment on beating performance and physical strength of resultant papers were studied in detail. Bio-treated samples showed comparable and, in most cases, higher physico-mechanical properties than those obtained from untreated controls. Under the same beating conditions the bio-treated kraft pulp was noted to have the lower SR° indicating a lower degree of external fibrillation. The paper made from bio-treated kraft pulp has a higher density, tensile property, air permeability and swellability. Furthermore, remarkable energy savings up to 33 % were observed when beating bio-treated kraft pulp. This study contributes to a better understanding of the mechanisms taking place during bio-treatment and the modification processes of cell wall components.     

Effects of biological pre-treatment of pine chips on the beating performance of Kraft pulp

The Calabrien pine (Pinus brutia) wood chips prior to kraft pulping were biologically pre-treated with selected white-rot fungi (Ceriporiopsis subvermispora), which was recorded to be preferentially attacking the lignin component of the wood. The effects of this treatment on beating performance and physical strength of resultant papers were studied in detail. Bio-treated samples showed comparable and, in most cases, higher physico-mechanical properties than those obtained from untreated controls. Under the same beating conditions the bio-treated kraft pulp was noted to have the lower SR' indicating a lower degree of external fibrillation. The paper made from bio-treated kraft pulp has a higher density, tensile property, air permeability and swellability. Furthermore, remarkable energy savings up to 33 % were observed when beating bio-treated kraft pulp. This study contributes to a better understanding of the mechanisms taking place during bio-treatment and the modification processes of cell wall components.     

Unique cyclic deformation behavior of a heavily alloyed Al–Si piston alloy at different temperatures

The cyclic deformation behavior of a near-eutectic Al–Si piston alloy with a variety of alloying elements is investigated. Due to the distinctive microstructure, the alloy exhibited various cyclic deformation characteristics at different temperatures. Unique double-stage cyclic hardening occurred at room temperature, while the first hardening was mainly caused by the interaction between the dislocations and the finely dispersive precipitates, and the dislocation/dislocation interaction resulted in the second hardening. At elevated temperatures (200 1C and 350 1C), the alloy mainly presented cyclic softening because of the fact that the thermally activated dislocations could bypass or shear the obstructive precipitates.     

Effects of binders on the performance of electric double-layer capacitors of carbon nanotube electrodes

Polarizable electrodes of electric double layer capacitor (EDLCs) were made from carbon nanotubes. Effects of different binders, which are phenolic resin (PF) and polytetrafluoroethylene (PTFE), on the properties of polarizable electrodes are studied. Results indicate that the microstructure, pore size distribution and specific capacitance of the electrodes with PTFE binder are superior to those electrodes with PF binder after carbonization. The suitable binder (PTFE) for carbon nanotubes electrodes is proposed.     

Effect of Zr addition on the stability of precipitated Laves phase and mechanical properties of Fe–Cr–Al-based alloys at high temperatures

The effect of a small amount of Zr addition on the temperature-dependent stability of Laves phase particles and mechanical properties of Fe-13.5Cr-4.73Al-2.07Mo-(0.34–0.5)Nb-(0.65–0.98)Ta-(0–0.33)Zr (wt. %) ferritic alloys was investigated in the present study. The designed alloy ingots were hot-rolled, aged at 1073 ?K for 24 ?h, and then re-treated at 1273 ?K, 1323 ?K, 1373 ?K, and 1473 ?K for 1 ?h, respectively. It was found that the Zr addition could not only stabilize the Fe₂M Laves phase (M ?= ?Mo,Nb,Ta,Zr) to a much higher temperature, but also induce the formation of stable Fe₂₃Zr₆ phase. The high-temperature (HT) microstructural stability of the alloys significantly was improved, as evidenced by the fact that a certain amount (0.66–1.19%) of precipitates (Fe₂M, Fe₂₃Zr₆, and core(Fe₂₃Zr₆)-shell(Fe₂M)-structured particles) with an appropriate size (～1.0 ?μm) uniformly distributed in the ferritic matrix even after being re-treated at 1473 ?K. Particularly, the formation of core-shell-structured particles at HTs was studied from the viewpoint of both solid solubility and diffusion coefficient of M in the matrix. All these aged alloys exhibited prominent mechanical properties at both room and elevated temperatures, showing high yield strength with σ_YS ?= ?490–560 ?MPa at room-temperature and σ_YS ?= ?80–85 ?MPa at 1073 ?K. The strengthening effect was further discussed in light of various strengthening mechanisms, and the calculated strength are in good agreement with the experimental results.     

Effects of deposition parameters on the properties of VO2 thin films

The vanadium oxide thin films are deposited for microbolometers by radio frequency reactive sputtering method at room temperature. The effects of the oxygen partial pressure on the deposition rate, electrical properties and compositions of the films are discussed. The as-deposited VO_x thin films with x value of nearly 2 are deposited by adjusting the oxygen partial pressure. After oxidation annealing of these films in air, the VO₂ films with high temperature coefficients of resistivity (about -4%/℃) and low resistivity can be obtained. The square resistances of the films are in the range of 100 kΩ/squ?300 kΩ/squ. All films are deposited at room temperature and annealed at 400℃, in which the compatibility between VO_x deposition process and MEMS (micro electromechanical systems) is greatly improved.     

Effects of deposition parameters on the properties of VO2 thin films

The vanadium oxide thin films are deposited for microbolometers by radio frequency reactive sputtering method at room temperature. The effects of the oxygen partial pressure on the deposition rate, electrical properties and compositions of the films are discussed. The as-deposited VO_x thin films with x value of nearly 2 are deposited by adjusting the oxygen partial pressure. After oxidation annealing of these films in air, the VO₂ films with high temperature coefficients of resistivity (about -4%/℃) and low resistivity can be obtained. The square resistances of the films are in the range of 100 kΩ/squ?300 kΩ/squ. All films are deposited at room temperature and annealed at 400℃, in which the compatibility between VO_x deposition process and MEMS (micro electromechanical systems) is greatly improved.     

Fabrication of Fe–TiC–Al2O3 composites on the surface of steel using a TiO2–Al–C–Fe combustion reaction induced by gas tungsten arc cladding

The aim of the present study was to fabricate Fe–TiC–Al₂O₃ composites on the surface of medium carbon steel. For this purpose, TiO₂–3C and 3TiO₂–4Al–3C–xFe (0 ≤ x ≤ 4.6 by mole) mixtures were pre-placed on the surface of a medium carbon steel plate. The mixtures and substrate were then melted using a gas tungsten arc cladding process. The results show that the martensite forms in the layer produced by the TiO₂–3C mixture. However, ferrite–Fe₃C–TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO₂–4Al–3C mixture. The addition of Fe to the TiO₂–4Al–3C reactants with the content from 0 to 20wt% increases the volume fraction of particles, and a composite containing approximately 9vol% TiC and Al₂O₃ particles forms. This composite substantially improves the substrate hardness. The mechanism by which Fe particles enhance the TiC + Al₂O₃ volume fraction in the composite is determined.     

Effects of deposition parameters on the properties of VO_2 thin films

Up to now, much attention has been paid tovanadiumoxide (VOx) thinfil ms due to their exten-sive applications in the infrared microbolometers .Incontrast tothe conventional photon detectors ,the mi-crobolometer using VOxthinfil ms as sensitive materi-als can offer decreased systemcost ,i mproved reliabil-ity,low power-consumption and high sensitivity inthe spectral range of 8—14μm.Vanadiumoxides have various crystal structuresand valency states ,such as VO, V2O3, VO2, V2O5,whichleads tol…     

In situ reaction mechanism of MgAlON in Al–Al_2O_3–MgO composites at 1700°C under flowing N_2

The Al–Al_2O_3–MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M_1, M_2, and M_3, respectively, were prepared at 1700°C for 5 h under a flowing N_2 atmosphere using the reaction sintering method. After sintering, the Al–Al_2O_3–MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen M_1 was composed of MgO and MgAl_2O_4. Compared with specimen M_1, specimens M_2 and M_3 possessed MgAlON, and its production increased with increasing aluminum addition. Under an N_2 atmosphere, MgO, Al_2O_3, and Al in the matrix of specimens M_2 and M_3 reacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al–Al_2O_3–MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an N_2 atmosphere, the partial pressure of oxygen is quite low; thus, when the Al–Al_2O_3–MgO composites were soaked at 580°C for an extended period, aluminum metal was transformed into AlN. With increasing temperature, Al_2O_3 diffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with Al_2O_3 to form MgAl_2O_4. When the temperature was greater than(1640 ± 10)°C, AlN diffused into Al_2O_3 and formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and Mg Al_2O_4 at high temperatures because of their similar spinel structures.     

Effects of different aggregation forms of LHC Ⅱ from Bryopsis corticulans on the excited state properties of Chl a

Steady-state and time-resolved fluorescence spectroscopies have been used to study the excited state properties of Chl a in different aggregation forms of light-harvesting complex Ⅱ （LHC Ⅱ） from an intertidal green alga, Bryopsis corticulans, i.e. LHC Ⅱ monomer, trimer and oligomer. When either Chl a or Chl b was selectively excited, the observed decrease in Chl a fluorescence in the oligomer is proved to be caused mainly by the fast fluorescence quenching among Chl a molecules, rather than by the decrease in Chl b-to-Chl a singlet excitation transfer efficiency. Analyses of the picosecond time-resolved fluorescence kinetics identified two exponential decay components in all of the three forms of LHC Ⅱ： a longer-lived component （4.1 -4.7 ns） originating from fluorescence emission of Chl a, and a shorter-lived one （135-540 ps） from the rapid equilibration of singlet excitation among Chl a molecules. The time constant of excitation equilibration is 135 ps in oligomer, 520 ps in trimer and 540 ps in monomer. These results imply that LHC Ⅱ in oligomer form is inherently able to quench Chl a excitation, a mechanism which may be related to the photoprotection of PS Ⅱ via changing the degree of LHC Ⅱ aggregation in Bryopsis corticulans.