排序方式: 共有10条查询结果,搜索用时 15 毫秒
1
1.
Chrissafis K. Efthimiadis K. G. Polychroniadis E. K. Chadjivasiliou S. C. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):761-767
The active sites of hydrogen-exchanged Y zeolite (HY) and dealuminated (HDY) zeolites are investigated by TPD of carbon monoxide. Only the high temperature TPD spectra of CO (TM»620-690°C) were observed, meaning that CO molecules interact with very strong acid sites. The amounts of CO bonded on these sites are small (less than 1 molecule per unit cell). The strong influence of dealumination on the coverage degree is found. The calculated values for kinetic parameters indicate chemisorption of CO in the investigated systems (Edes»240 kJ mol-1, A»1011 s-1). 相似文献
2.
G. Litsardakis I. Manolakis C. Serletis K.G. Efthimiadis 《Journal of magnetism and magnetic materials》2007
The effect of Gd substitution in M-type strontium hexaferrites has been examined in two series of samples, (Sr1-xGdx)O·5.25Fe2O3 and Sr1-xGdxFe12-xCoxO19, both prepared by the ceramic method, where x=0–0.40. The samples have been characterized by XRD, VSM and SEM-EDAX techniques. All substituted samples present primarily the hexaferrite structure. Sample (Sr0.95Gdx0.05)O·5.25Fe2O3 is single phase. Formation of impurity phases is affected by stoichiometry and presence of Co. In Sr–Gd samples, coercivity showed a maximum value of 305 kA/m (3.8 kOe) for x=0.20, while remanence and saturation magnetization did not decrease. Coercivity and magnetization in the Sr–Gd–Co series decreased steadily with substitution degree. 相似文献
3.
Jaka Sunarso Youssof Shekibi Jim Efthimiadis Liyu Jin Jennifer M. Pringle Anthony F. Hollenkamp Douglas R. MacFarlane Maria Forsyth Patrick C. Howlett 《Journal of Solid State Electrochemistry》2012,16(5):1841-1848
Organic ionic plastic crystal (OIPC) electrolytes are among the key enabling materials for solid-state and higher than ambient
temperature lithium batteries. This work overviews some of the parameter studies on the Li|OIPC interface using lithium symmetrical
cells as well as the optimisation and performance of Li|OIPC|LiFePO4 cells. The effects of temperature and electrolyte thickness on the cycle performance of the lithium symmetrical cell, particularly
with respect to the interfacial and bulk resistances, are demonstrated. Whilst temperature change substantially alters both
the interfacial and bulk resistance, changing the electrolyte thickness predominantly changes the bulk resistance only. In
addition, an upper limit of the current density is demonstrated, above which irreversible processes related to electrolyte
decomposition take place. Here, we demonstrate an excellent discharge capacity attained on LiFePO4|10 mol% LiNTf2-doped [C2mpyr][NTf2]|Li cell, reaching 126 mAh g-1 at 50 °C (when the electrolyte is in its solid form) and 153 mAh g-1 at 80 °C (when the electrolyte is in its liquid form). Most remarkably, at high temperature operation, the capacity retention
at long cycles and high current is excellent with only a slight (3%) drop in discharge capacity upon increasing the current
from 0.2 C to 0.5 C. These results highlight the real prospects for developing a lithium battery with high temperature performance
that easily surpasses that achievable with even the best contemporary lithium-ion technology. 相似文献
4.
Shao F Ng TW Efthimiadis J Somers A Schwalb W 《Journal of colloid and interface science》2012,377(1):421-429
As evaporation does not incur energy introduction, the droplet coffee-stain patterning approach is attractive for biochemical tests conducted in the field or in third world environments. A practical strategy uses chemically functionalized microbeads for the coffee stain deposition process. From an application perspective, it will be necessary to minimize the coffee stain deposition time, as evaporation, depending on the volume of the droplet, can be a slow process. The introduction of a porous media will generate a capillary flow (or wicking) that removes any remnant liquid in the droplet, thus permitting it to be done inexpensively and in the field. Using optical profilometry, we were able to establish that polystyrene microspheres developed more copious and defined single ring coffee depositions than silica of the same size and concentration in a suspension. In analyzing the droplet capillary evacuation process with a porous media, we found the liquid bridge formed during the later stages to rupture and leave behind some liquid material for a second stage evaporation process. This was responsible for a two ring structure that was more visible with silica microspheres. A high degree of hysteresis of the contact angle was found to develop at the contact line in which values below 5° could be achieved. Dynamic observations showed the copious and dense packing of polystyrene particles to be more resistant to ring break up from the evacuation flow. Nevertheless, erosion of the back array portions of the ring was evident notwithstanding either type of microsphere used. 相似文献
5.
This work reveals the performance of a trihexyl(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)amide ([P6,6,6,14][NTf2]) ionic liquid (IL) conversion coating upon AZ91D. Such conversion coatings represent a novel avenue for chromate replacement. An optimization of coating performance was pursued by careful alloy pretreatment to generate a surface on which the coating performs best, as the AZ91 substrate is distinctly different from pure or dilute Mg alloys. The results reveal that a functional conversion coating can be achieved, retarding anodic dissolution kinetics, causing a significant decrease in corrosion rate. The coating efficacy is closely tied to the pretreatment performed, which dictates both the microstructural and electrochemical heterogeneity of the surface. The resulting coatings were found to contain MgxFx and phosphonium cation related components, the proportions of which were dependent on the pretreatment. 相似文献
6.
This work is an investigation of the experimental method used for measuring the magnetic viscosity in a hard ferromagnetic material, i.e. the recording of the magnetization under constant applied field and temperature, after the material has been magnetically saturated. It investigates how the experimental results are affected by the initial conditions of the method (saturation field, field change rate and field oscillation prior to its stabilization), and by minor variations of field and temperature during the recording. Based on the arising conclusions and the use of a more complex fitting function of measurements, the accuracy and repeatability of experimental results is improved. 相似文献
7.
S.S. Makridis I. Panagiotopoulos I. Tsiaoussis N. Frangis E. Pavlidou K. Chrisafis G.F. Papathanasiou K. Efthimiadis G.C. Hadjipanayis D. Niarchos 《Journal of magnetism and magnetic materials》2008
In boron-substituted melt-spun Sm(Co,Fe,Cu,Zr)7.5-type alloys a nanocomposite microstructure and high coercivities in both as-spun and short-time annealed ribbons can be obtained. In the present study three different compositions, namely Sm(Co0.73Fe0.1Cu0.09Zr0.04B0.04)7.5, Sm(Co0.70Fe0.1Cu0.12Zr0.04B0.04)7.5 and Sm(Co0.70Fe0.1Ni0.12Zr0.04B0.04)7.5 have been examined in order to investigate the influence of composition on the magnetic properties and the microstructure. Melt-spun ribbons have been obtained and annealing has been followed under argon atmosphere for 30–75 min at 600–870 °C. For the as-spun ribbons the TbCu7-type of structure and fcc-Co as a secondary phase have been identified in the X-ray diffraction patterns. For the annealed ribbons above 700 °C the 1:7 phase transforms into 2:17 and 1:5 phases. The TEM studies have shown a homogeneous nanocrystalline microstructure with average grain size of 30–80 nm. Coercivity values of 15–27 kOe have been obtained from hysteresis loops traced in non-saturating fields. The coercivity decreases with temperature, but it is sufficiently large to maintain values higher than 5 kOe at 380 °C. 相似文献
8.
Filomena Gon?alves George E. Marnellos Evangelos A. Efthimiadis José L. Figueiredo 《Reaction Kinetics and Catalysis Letters》2003,80(1):153-159
The simultaneous reduction of N2O+NO with carbon supported Ni/K catalysts was studied. High conversions of both compounds were obtained at 400°C, and a synergystic
effect between Ni and K was observed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Electrowetting of ionic liquids 总被引:1,自引:0,他引:1
Millefiorini S Tkaczyk AH Sedev R Efthimiadis J Ralston J 《Journal of the American Chemical Society》2006,128(9):3098-3101
We have successfully demonstrated that imidazolium- and pyrrolidinium-based commercial room-temperature ionic liquids can electrowet (with a dc voltage) a smooth fluoropolymer (Teflon AF1600) surface. Qualitatively, the process is analogous to the electrowetting of aqueous electrolyte solutions: the contact angle versus voltage curve has a parabolic shape which saturates at larger voltages (positive or negative). On the other hand we observed several peculiarities: (i) the efficiency is significantly lower (by about an order of magnitude); (ii) the influence of the bulky cation is larger and the importance of the smaller anion is lesser, especially with respect to electrowetting saturation; (iii) there is an asymmetry in the saturation contact angles found for positive and negative voltages. The asymmetry may be correlated with the cation-anion asymmetry of the ionic liquids. The low efficiency may be caused by the presence of water and other impurities in these commercial materials. 相似文献
10.
K. G. Efthimiadis G. Stergioudis S. C. Chadjivasiliou I. A. Tsoukalas 《Crystal Research and Technology》2002,37(8):827-833
Experimental results are presented regarding the variation of the atomic magnetic moment, the Curie temperature and the crystallization temperature of Fe78‐cMcSi9B13 (M = V, Nb, Mo) and Fe75‐cMcSi9B16 (M = Ni, Cu, Pd, Ag) amorphous alloys. Efforts were made to explain qualitatively the phenomena, based on the behavior of the amorphous alloys when various admixtures substitute Fe atoms. 相似文献
1