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81.
82.
Infrared radiant emissivities of ceramics with spinel structure 总被引:1,自引:0,他引:1
Jiemo Tian W. R. Zhu H. D. Li 《International Journal of Infrared and Millimeter Waves》1993,14(9):1855-1863
The infrared radiant ceramic materials were prepared by calcination at high temperature. Based on the study of infrared radiant emissivity and X — ray diffraction spectra, the results indicate that spinel structure possesses the higher infrared radiant emissivity. The reason of the higher infrared emissivity of the spinel structure has been explained according to the Group Theory. 相似文献
83.
氧化铝基表层镁铝尖晶石的研究──Ⅰ.表层镁铝尖晶石的相结构、孔结构、表面酸性及负载钯的化学状态 总被引:1,自引:0,他引:1
对<1000℃焙烧的γ-Al2O3载镁体系进行了相表征,发现在基质氧化铝上形成了表层镁铝尖晶石,具有“原尖晶石结构”的γ-Al2O3则在<1000℃保持物相不变.进一步研究了这种氧化铝基表层镁铝尖晶石的孔结构、表面酸性以及负载耙的分散与化学状态,结果表明:氧化铝基表层尖晶石的孔结构和表面酸性由构成的氧化铝基决定,并随温度变化,表层尖晶石仅可稳定氧化铝基的物相,与其孔性质和酸性无关;负载在氧化铝基表层尖晶石上的钯,主要分布在表层镁铝尖晶石上,有强的载体一金属相互作用,以Pd0和Pd2+两种状态存在. 相似文献
84.
采用一种特殊微波合成法,流变相辅助微波合成法,制备了结晶度好、纯度高的尖晶石相的锂离子电池正极材料LiAl0.03Mn1.97O4。对其进行了XRD分析和SEM研究,并就结构、形貌与传统固相法制备的LiMn2O4、LiAl0.03Mn1.97O4进行了比较。采用这种流变相辅助微波合成法制备的LiAl0.03Mn1.97O4具有优良的电化学性能,电化学性能测试表明,这种材料具有比较高的首次放电容量(115mAh/g)以及良好的可逆性、优异的循环性能,25次循环结束比容量几乎不变,保持在115mAh/g左右,衰减性得到很好的改善。 相似文献
85.
86.
C.A. d’Azevedo F.M.S. Garrido M.E. Medeiros 《Journal of Thermal Analysis and Calorimetry》2006,83(3):649-655
Samples
of the MgO–Al2O3–SiO2
ternary system, constituted by 28.5 mol% ofMgO, 28.5 mol% of Al2O3
and 43mol%of SiO2, were activated in a roll mill and
calcined at different temperatures. The influence of the grinding time, the
used SiO2 precursor and activation medium, furthermore
the mass ratio between the powdered sample and zirconia cylinders was investigated
on the reactivity of the MgO–Al2O3–SiO2
ternary system. FTIR spectra and the X-ray powder diffraction patterns indicates
the formation of Mg(OH)2 at 393 K, of forsterite (MgSi2O5)
and enstatite (MgSiO3) at 1223 K and of spinel (MgAl2O4)
between 1223 and 1523 K in some samples. The presence of cordierite (Mg2Al2Si5O18) was observed at 1523 K, a reaction pathway concerning
its formation was proposed. 相似文献
87.
Geok B. TehDavid A. Jefferson 《Journal of solid state chemistry》2002,167(1):254-257
Nanocrystal specimen of cobalt (II)-doped magnetoplumbite (M-type) BaFe12O19 were synthesized via a sol-gel method using ethylene glycol as precursor. Hexagonal-like platelets and other morphologies of ferrites were obtained at the final stage of annealing process. The specimens were characterized using X-ray diffraction, SQUID magnetometry measurement and high-resolution transmission electron microscopy. The saturation magnetization of the specimen at 300 K was found to be greatly reduced from 48 (3) emu/g in parent ferrite to 28 (3) emu/g in the doped ferrite. A total reduction of 74% in the value of intrinsic coercivity was recorded, 276 (15) G from the doped ferrite compared to 1080 (54) G in the parent ferrite. 相似文献
88.
多元掺杂尖晶石型Li1.02MxMn2-xQyO4-y正极材料的电化学特性 总被引:2,自引:0,他引:2
The effect of doping on the electrochemical performance was studied for spinel type Li1.02MxMn2-xQyO4-y used as cathode material in lithium-ion battery. TG/DTA curves of the precursor(the raw materials) doped with different elements were studied. The spinel materials Li1.02Mn2O4, Li1.02Co0.02Cr0.01La0.01Mn1.96F0.02O3.98, Li1.02Co0.02Cr0.01 La0.01Mn1.96Cl0.02O3.98, Li1.02Co0.02La1.02Mn1.97Cl0.02O3.98, Li1.02Co0.02Cr0.01Mn1.97O4, were prepared by solid-state reaction method after the pretreatment of conversion under low temperature and uniform mixing. X-ray diffraction patterns showed that all the samples had perfect spinel structure. SEM indicated that the particles of the samples had uniform size and were distributed evenly. The results of the charge/discharge curves showed that Li1.02Co0.02Cr0.01La0.01Mn1.96F0.02O3.98 had better performance than other materials according to the inhibition of decline of reversible capacity of spinel Li1.02MxMn2-xQyO4-y. Therefore, cycle performance had been improved so obviously that 93.9% of the initial capacity were preserved after 100 cycles. Furthermore, electrochemical impedance tests were carried out with the spinel Li1.02Co0.02Cr0.01La0.01Mn1.96F0.02O3.98 as working electrode, Lithium as counter electrode and reference electrode. Results showed that this material possessed good charge/discharge reversible capability and had the lowest impedance in 3.95~4.25 V range (on the stage of charge / discharge). 相似文献
89.
采用脉冲微反色谱研究了噻吩在不同方法制备的四种纳米HZSM-5沸石催化剂上的催化转化,并利用色质联用技术对反应产物定性.结果表明,在370℃下,噻吩在各种催化剂上除了脱硫生成硫化氢以外,还生成少量2-甲基噻吩、3-甲基噻吩和苯并噻吩等新的硫化物.噻吩转化率和脱硫率受反应气氛和催化剂酸度影响很大.氢气气氛比氮气气氛有利于提高噻吩转化率和脱硫率.临氢作用的实质是气相中的分子氢被催化剂上的L酸活化向噻吩裂化脱硫反应供氢.通过改性适当降低催化剂上的B酸中心数量和强度,增加L酸的比例,有利于发挥临氢作用. 相似文献
90.
铜、锰氧化物的表面过剩氧及其甲苯催化燃烧活性 总被引:9,自引:0,他引:9
研究了负载型Cu-Mn-O催化剂对烃类深度氧化的活性,并将XRD分析、电子探针考察和表面过剩氧浓度的分布测定等结果与催化剂活性进行了关联.以甲苯催化燃烧为模型反应,除用常规的微反考察其动力学性质外,还用脉冲反应技术研究了表面过剩氧的氧化功能和甲苯的吸附等.Mn/Cu原子比为0.88~0.9时,催化剂活性最好.这是由CuO和CuMn2O4的功能匹配决定的,后者提供与催化作用有关的表面过剩氧,前者促进甲苯的吸附.对催化剂的作用机理也进行了初步的探讨. 相似文献