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spp1997新蟲(chóng) (初入文壇)
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[求助]
求翻譯，英譯中
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In glass technology crystallization must usually be avoided; however, partially crystallized glasses or ‘glass-ceramics’, containing fine crystallized particles (nanoparticles), have been developed for specific applications. These nanoparticles confer particular characteristics to glasses, such as strength and impact resistance, lower thermal expansion coefficient, partial or complete opacity, etc [1]. A special type of nanoparticles, ferro- or ferrimagnetically ordered crystalline nanoparticles imbedded in different diamagnetic matrices such as fluids or polymers, gives rise to a new kind of magnetism called superparamagnetism and results in a number of properties which are interesting from a technical viewpoint, for example see [2]. Partially crystallized glasses containing ferromagnetic nanoparticles constitute a novel and much more complex class of superparamagnetic materials. Their properties are mainly determined by morphology (size and shape distributions) and magnetic constants of such particles. Electron magnetic resonance, sensitive to both the magnetic constants and the structure of the environment of a magnetic ion, is well adapted to the study of superparamagnetic nanoparticles [3]. In this case it may be called superparamagnetic resonance (SPR) to distinguish it from the resonance of individual electron spins usually referred to as electron paramagnetic resonance (EPR). Up until now, only a few attempts have been made to carry out quantitative, computer-simulation based analysis of SPR spectra of magnetic particles dispersed in polycrystalline or glassy systems [3–5]. In a previous work [3] we have dealt with transformations arising in the electron magnetic resonance spectra of borate glasses containing small amounts of iron oxide after heat treatment above the glass transition temperature. Namely, the resonance characteristic of diluted Fe3+ ions in the glass, observed at the effective g-value gef = 4.3 [6], progressively disappears and a new resonance, consisting of superposed broader and narrower components, grows at gef ≈ 2.0. This compound resonance signal has been ascribed to a superparamagnetic assembly of crystalline ferromagnetic single-domain particles arising in the diamagnetic glassy matrix under heat treatment. Good computer fits to this resonance have been obtained assuming a monodisperse distribution of the particle sizes. This paper presents a more detailed analysis of room temperature X-band SPR spectra obtained after repeated annealing steps of iron-doped borate glass. First, data are reported on the evolution of the number of spins with annealing, as obtained from resonance intensity measurements. Then, geometrical characteristics of the magnetic particles obtained from a series of computer simulations of the spectra are related to the anneal temperature. Finally, the mechanism of growth of crystallized magnetic particles is discussed. |
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jiangguofeng
金蟲(chóng) (著名寫(xiě)手)
- 翻譯EPI: 248
- 應(yīng)助: 41 (小學(xué)生)
- 金幣: 25896.4
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- 蟲(chóng)號(hào): 72410
- 注冊(cè): 2005-06-04
- 專(zhuān)業(yè): 合成藥物化學(xué)
【答案】應(yīng)助回帖
| 在玻璃工藝當(dāng)中通常必須避免結(jié)晶；然而,現(xiàn)已為專(zhuān)門(mén)的應(yīng)用研制出了含有細(xì)小結(jié)晶粒子（納米粒子）的部分結(jié)晶的玻璃或"玻璃陶瓷"。這些納米粒子賦予玻璃一些特殊性能,例如，強(qiáng)度和耐沖擊性,降低熱膨脹系數(shù),部分或全部不透明性,等等[1]。鐵磁或亞鐵磁的有序結(jié)晶納米粒子是一種特殊類(lèi)型的納米粒子,被包埋在流體或高聚體一類(lèi)的不同抗磁基質(zhì)中，產(chǎn)生一種稱(chēng)為超順磁性的新的磁性并帶來(lái)了從技術(shù)視角來(lái)看值得關(guān)注的多種性質(zhì)，具體詳見(jiàn)[2]。含有鐵磁納米粒子的部分結(jié)晶玻璃構(gòu)成了一種新穎的更加復(fù)雜的超順磁性材料類(lèi)型。 它們性質(zhì)主要是通過(guò)此類(lèi)粒子的形態(tài)（大小與形狀分配）和磁常數(shù)來(lái)確定。電子磁共振對(duì)磁常數(shù)和磁離子環(huán)境結(jié)構(gòu)都敏感，非常適于超順磁性納米粒子的研究[3]。在這種情況下，為了與通常稱(chēng)為電子順磁共振(EPR)的單個(gè)電子自旋相區(qū)別，這可以被叫做超順磁共振(SPR)。迄今為止，只有少數(shù)嘗試去進(jìn)行基于分散于多晶或玻璃狀系統(tǒng)中的磁粉的SPR譜圖的定量分析和計(jì)算機(jī)模擬[3-5]。在以前的研究工作中[3]，我們對(duì)經(jīng)高于玻璃態(tài)轉(zhuǎn)化溫度熱處理后的含少量氧化鐵的硼酸鹽玻璃的電子磁共振譜圖中產(chǎn)生的改變進(jìn)行了處理。 也就是,于有效G值gef=4.3觀察到的摻入這種玻璃中的Fe3+離子的共振特性[6]逐漸地消失，于gef≈2.0處逐漸產(chǎn)生一種由重疊的更寬和更窄組分組成的新的共振。 這種化合物共振信號(hào)已分配給熱處理進(jìn)行時(shí)抗磁玻璃基質(zhì)中產(chǎn)生的結(jié)晶鐵磁單疇顆粒的一種超順磁組裝。已經(jīng)得到針對(duì)這種共振的良好計(jì)算機(jī)配置用以擔(dān)任粒子粒徑的單分散分配。本文給出摻鐵硼酸鹽玻璃重復(fù)退火步驟后得到的室溫X波段SPR譜圖更為詳細(xì)的分析。首先,報(bào)告了由共振強(qiáng)度測(cè)定得到的有關(guān)隨著退火自旋數(shù)目演變的情況。然后,由譜圖的一系列計(jì)算機(jī)模擬得到的磁粉的幾何特性與退火溫度有關(guān)。最后,討論了結(jié)晶磁粉的生長(zhǎng)機(jī)理。 |
2樓2015-06-18 11:56:15
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