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研究了无水乙醇洗涤次数对油酸包覆的Fe3O4磁性纳米颗粒表面包覆结构的影响。采用FT-IR和TGA联合表征了油酸包覆的Fe3O4磁性纳米颗粒经过无水乙醇洗涤前后表面包覆结构的变化,采用TEM观察了油酸包覆后Fe3O4磁性纳米颗粒的形貌。实验结果表明经过无水乙醇5次洗涤后,油酸包覆的Fe3O4磁性颗粒为双层包覆结构;经过无水乙醇20次洗涤后,无水乙醇将双层油酸包覆结构中的物理吸附层洗掉,造成双层油酸包覆的Fe3O4磁性颗粒演变为单层包覆结构。 相似文献
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采用化学镀法制得了表面包覆银层的导电磁性聚甲基丙烯酸甲酯(PMMA)微球。对粗糙度不同的微球进行镀银,研究了银在微球上的沉积机理。表面改性使磁性PMMA微球功能化,具有和银强烈结合的能力,从而得到包覆均匀的导电磁性微球。研究了硝酸银和磁性微球的含量对包覆效果及导电性能的影响,并通过SEM和EDS对镀银磁性微球的表面形貌及组成进行了分析。 相似文献
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快速热解法制备炭包覆纳米金属磁性颗粒(英文) 总被引:1,自引:0,他引:1
以简单金属前躯体为原料通过快速热解法制备炭包覆纳米金属磁性颗粒,通过透射电镜、X-射线衍射、热重-示差扫描同步热分析及振动样品磁强计等对产物形貌、结构、成分与磁性能进行表征。结果表明:采用该方法制备的炭包覆纳米金属磁性颗粒形状为近球形颗粒,粒径均一,其中炭包覆镍纳米磁性颗粒的粒径集中在10nm~30nm范围,炭包覆铁纳米磁性颗粒粒径则在50nm~60nm范围;所制炭包覆纳米金属磁性颗粒在室温下具有顺磁性,其磁性能随金属颗粒含量的变化而改变。该方法有望发展成一种工艺简单,可进行连续工业化生产炭包覆纳米金属磁性颗粒的方法。 相似文献
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目的 针对磁性金属吸波剂由组成元素化学性质活泼导致的高温氧化和电磁性能恶化问题展开现状调研和讨论,解析磁性金属吸波剂高温氧化的机理,并提出相应的解决策略。方法 从氧气在金属吸波剂中的吸附、反应和传质过程出发,讨论高温氧化对吸波剂电磁性能的影响规律,系统总结并评述表面包覆隔绝氧气、生成致密金属氧化膜和抑制氧原子扩散3种策略对吸波剂抗高温氧化的作用机制。结论 表面包覆策略通过引入有机高分子、无机化合物或磁性金属等包覆物质,以隔绝氧气,从而抑制磁性金属吸波剂的高温氧化。其中,无机化合物包覆体系最具潜力,但尚未达到理想的超薄致密状态。生成致密氧化膜策略通过溶质元素的选择性氧化,形成保护膜,能够有效抑制氧化进程,但引入较高含量的非铁磁性溶质元素容易降低磁导率、恶化吸波性能。抑制氧原子扩散策略通过形成晶界氧化物来有效减缓氧化,目前其实现手段有限且不够成熟。在耐温磁性吸波剂的研制中应综合考虑使用温度、基体材料、目标吸波频段和期望吸波性能等,采用合适的抗氧化策略。 相似文献
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The growth of silicon dioxide at low temperature in an oxygen plasma is investigated using a simplified electrodeless microwave discharge arrangement. The growth behaviour of the oxide is discussed in terms of plasma parameters. The compositional and electrical characterization of the grown oxide have been made to examine its performance for device applications. The results are compared with earlier observations by other authors. 相似文献
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二氧化钛作为一种具有光催化活性的氧化物半导体材料,在利用太阳能降解环境污染物的领域具有广阔的应用前景。但是,由于二氧化钛存在光量子产率低,禁带宽度较大,光催化反应活性较低等缺点,严重阻碍了其在实际应用中的发展。目前,为改善二氧化钛的光催化性能,多种化学物质被用于二氧化钛的掺杂研究,包括过渡金属、贵金属、非金属和稀土元素等,不论是对二氧化钛进行单独掺杂或共掺杂都已被广泛地研究,结果表明,适当的掺杂将显著提高二氧化钛的光催化活性。本文对该领域的研究现状进行了综述,在此基础上对二氧化钛掺杂改性研究的发展进行了展望。 相似文献
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Spin-on oxide refers to a thin film of silicon dioxide deposited from an alcohol solution to the surface of a semiconductor wafer by spinning. An investigation was carried out by IR spectroscopy, gravimetric analysis and etch-rate measurements. Electrical conduction in the oxide was also examined. It was found that the oxide is hygroscopic and that the breakdown properties are generally inferior to those of thermally grown oxide, particularly if the samples are annealed at a low temperature only. Attempts were also made to identify the mechanisms responsible for conduction in the oxide. 相似文献
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疏水性光催化剂的制备及其催化动力学 总被引:2,自引:1,他引:1
采用十二烷基硫酸钠(SDS)为改性剂对TiO2进行了疏水改性, FTIR表征表明催化剂表面具有CC和CH烷基疏水基团. 同时采用CuO对催化剂进行了可见光响应改性, UV-Vis表征表明催化剂具有良好的可见光响应性能, 吸收边红移至830nm以上. 三维荧光扫描发现随着CuO和SDS的加入,催化剂的空穴电子分离效果迅速提高. 以硝基苯为处理对象, 考察了体系pH值、污染物初始浓度、催化剂用量和光照强度对光催化反应过程的影响, 建立了动力学模型. 低浓度条件下, 通过模型计算的动力学常数相对误差范围为-16.5%~-4.5%; 高浓度条件下为-11.3%~4.6%. 相似文献
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Magnetic recording coatings are still made predominantly of iron oxide particles but the newer particles are significantly better in magnetic properties, dispersibility and orientability than the particles used, say, ten years ago. Chromium dioxide particles show excellent recording performance (particularly at densities above 1000 flux changes per millimeter) but they are presently being challenged by the new cobalt-modified iron oxides. These are formed by diffusing cobalt into the surface of acicular iron oxide particles and it is claimed that the particles prepared in this way are much more stable with respect to temperature and stress than the older cobalt-substituted iron oxides. Metal particles, by virtue of their high moment density and high coercivity, would be ideal for high density recording if they could be passivated permanently. The paper reviews improvements which have been made within the last nine years in the properties of particles for magnetic recording applications and discusses how the improvements were effected. 相似文献
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The visible photoluminescence of porous Si is quenched by nitric oxide and nitrogen dioxide to detection limits of 1.4 × 10(-)(3) and 5.3 × 10(-)(5) Torr, respectively (corresponding to 2 ppm and 70 ppb). At analyte partial pressures in the low milliTorr range, the photoluminescence quenching is partially reversible; recovery from nitrogen oxide exposure occurs on a time scale of minutes. For both NO and NO(2), the reversible photoluminescence quenching response fits a Stern-Volmer kinetic model. At higher partial pressures, quenching deviates from Stern-Volmer kinetics and some permanent loss of photoluminescence intensity occurs due to oxidation of the porous Si surface. Photoluminescence from porous Si is not quenched by nitrous oxide or carbon dioxide and only slightly quenched by carbon monoxide and oxygen. 相似文献
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文中利用双金属催化剂(DMC)催化二氧化碳和环氧乙烷共聚,催化效率最高达到1139g/g催化剂,远远高于以前报道,其中碳酸酯键含量最高可达50%。实验发现,催化剂浓度是影响催化效率的重要因素,而温度的高低基本决定了碳酸酯键含量的多少。文中还研究了聚碳酸亚乙酯的体外降解性能,在降解液中经历大约70 d后,共聚物几乎全部降解为二氧化碳和低分子量聚乙二醇。 相似文献
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Souvik Bhattacharyya Anirban Garai Jahar Sarkar 《International Journal of Refrigeration》2009,32(5):1077-1084
In this study, a natural refrigerant based cascaded system, with nitrous oxide as the low temperature fluid and carbon dioxide as the high temperature fluid, is analyzed for simultaneous cooling and heating applications. Effects of significant design and operating parameters on system performance are studied. Optimization of intermediate pressure for maximum COP for various design and operating parameters are presented as well. Results show that use of internal heat exchanger has marginal influence on system performance. Due to similar thermodynamic properties of nitrous oxide and carbon dioxide, the optimized intermediate temperature turns out to be independent of the performance of gas cooler and evaporator for a given operating condition. Due to the same reason, N2O as low temperature fluid and CO2 as high temperature fluid in a cascade arrangement exhibit similar behavioural trends in a system where the fluids are swapped. 相似文献
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Demazeau G. Maestro P. Plante T. Pouchard M. Hagenmuller P. 《IEEE transactions on magnetics》1980,16(1):9-10
A new oxidative method of preparation of the chromium dioxide from Cr2 O3 is described. For the improvement of magnetic properties, in particular coercive field, of such a ferromagnetic oxide a substitution by rhodium +IV leads to the new interesting material Cr1-x Rhx O2 with needlike particles (H_{c} simeq 500 Oe). 相似文献