CAHN－2000磁天平的调试与数据处理系统的研制

叙述了ＣＡＨＮ－２０００磁天平（美国）调试过程中如何解决液氮温区的测试，自制了磁天平与计算机的接口，编写了数据采集、处理和控制等方面的软件，节省了几万美元，部分指标超过原配套水平。三年来仪器在对国内外开放过程中，液氮温区的工作一直正常，实测了上千个样品，提供的数据已撰写数十篇文章在国内外刊物上发表。由此说明，要充分发挥进口仪器的使用效率，必须对仪器的工作原理、结构特点有透彻的了解，同时要有相当的自制配套能力。     

一种新型磁天平在配合物磁化率测定中的应用

经典物理化学实验"磁化率测定实验"中,传统方法是使用Gouy磁天平,仪器笨重且操作复杂。本文提供一种新型台式磁天平,用于配合物磁化率的测定。文中通过测量三种亚铁化合物的磁化率,介绍该磁天平的基本原理、使用方法、操作步骤和数据分析。通过比较测量值和标准值,得出该仪器的测量误差小、精确度高,适用于实验教学和科学研究。     

中国化学会一九八六年学术活动(一)

天平是分析化学工作最主要的常用仪器之一。在定量分析基础课实验中,要对学生进行分析天平基本操作的严格训练,要求达到了解构造原理,操作正确熟练,称量准确快速。采用双盘或单盘电光机械天平都可以满足上述要求。近两年,我们从北京光学仪器厂购进一部分DT-100型单盘分析天平,经在定量分析实验课中使用,效果良好。我们体会到单盘天平具有下列优点:     

YBa2Cu3O7-x高Tc超导体的热转变

自朱经武等最先报道液氮温区Y—Ba—Cu—O体系超导体以来，世界上涌现第二次高Tc超导体研究热潮。材料的烧结与退火均在高温下进行，尤以退火条件对超导性能好坏影响为大。因此，高温热转变的研究对于优良材料的获得及超导机制的认识都至为重要。迄今     

La1-xLixMnO3体系的输运特性及EPR研究

利用固相反应法合成了掺杂锂的La_1-xLi_xMnO₃(x=0,0.10,0.15,0.20,0.25,0.30)钙钛矿氧化物.XRD测试表明,所有样品均为菱方结构.除x=0,0.3外,其它样品均随温度的降低在液氮温区可观察到从绝缘态到金属态的转变,其中x=0.15样品的转变温度最高为167K.在H=1T的磁场下,出现了负磁阻现象.EPR谱上的g=2.00信号与Mn³⁺和Mn⁴⁺组成的复合团簇有关.     

煤与废塑料共焦化基础研究Ⅲ. 协同作用的热重研究

采用加压热天平研究煤与废塑料共焦化过程中,不同废塑料对太钢焦煤的热解行为,以及德国废塑料对不同煤种的热解行为的影响。认为不同的废塑料对太钢焦煤热重行为的影响不尽相同;不同的煤种在与德国塑料共热解时的协同作用也不相同,德国废塑料与焦煤的相互作用更大些。共热解中废塑料与煤的协同作用受煤与废塑料二者之间的热解温区、失重峰温、失重速率的重叠程度及煤所形成的胶质体数量的影响。废塑料与煤之间的相互作用使得两者     

神木煤显微组分加氢热解的TG/MS研究

在TG-151热天平上考察了神木煤显微组分加氢热解的热重特性；用质谱对加氢热解气体进行了在线检测分析。结果表明，镜质组比惰质组有较高的挥发分收率和最大失重速率；较低的起始热解温度和热解峰温。镜质组有较高的C1～C4轻质烃类和C6～C8芳香烃类收率，原煤居中，惰质组最少；镜质组比惰质组有较高的水生成， 加氢热解过程中各种烃类和水的逸出都高于相应热解下的。     

稀土铁氧体／聚丙烯酰胺磁性复合微球的响应性研究

在W／O微乳液体系中，制备了稀土铁氧体／聚丙烯酰胺磁性复合微型，并利用磁天平法对其磁响应性进行了研究。结果表明：复合微型的磁响应性与稀土离子磁矩有关，高磁矩稀土离子Dy^3 的加入能够较大地改善复合微型的磁响应性；镝铁氧体／聚丙烯酰胺磁性复合微球的磁响应性与镝含量有关，当n(Dy^3 )：n(∑Fe)=0．20时微球磁响应性最强。     

LCT-1型微量差热天平的性能

差热天平是一种DTA和TG联用的热分析仪,可同时获得DTA曲线和TG曲线。由于两种信息是在同一样品上同时获得,因此不仅升温速率、气氛、试样粒度和重量等各种条件完全相同,而且两者测定是完全同步进行的,便于实验结果的互相补充和验证。故一般研究工作中差热天平采用较多,过去此类仪器都靠进口,1979年北京光学仪器厂首先试制成功LCT—1型微量差热天平,填补了国内空白,仪器各项指标     

电感耦合等离子体原子发射光谱法测定镍钨合金中钨含量

氧化钇钡铜(YBCO)涂层导体在77K的液氮温区具有交流损耗低、不可逆场高、载流能力强等优点,是目前制备液氮温区磁体的唯一选择。目前,低成本、高性能的YBCO涂层导体已成为国际实用化高温超导材料的研究重点。镍钨合金具有磁性小、强度高、良好的高温抗氧化性、易于形成立方织构等优点,是最具应用前景的涂层超导体基带材料[1-2]。其中钨元素的含量、分布均匀性对镍钨合金的强度、     

Methodology for determination of magnetic force of polymeric nanocomposites

Magnetic nanocomposites present several interesting uses. They are very useful in environmental recovery, drug delivery and sensor applications. However, sophisticated magnetic measurements are very complex and present high costs, which may sometimes prevent research on these materials. Therefore, this paper presents a magnetic force test, which can be performed at relatively low cost and produces interesting results, which are very useful to support the development of these magnetic materials. Specifically, polylactic acid (PLA)/maghemite nanocomposites were prepared and characterized using Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS) and size-exclusion chromatography (SEC). Our results demonstrate that nanocomposites, were obtained, which were also subjected to the magnetic force and magnetic susceptibility tests. The results of these latter tests were found to be linearly related, which proves the utility of the magnetic force test as a practical characterization technique.     

Chemical analysis of size-tailored magnetic colloids using slurry nebulization in ICP-OES

In this work, inductively coupled plasma emission spectroscopy was utilized to directly determine the chemical composition of magnetic fluids constituted of size-sorted ferrite nanoparticles in aqueous solution. Nickel and cobalt nanoferrites were chemically synthesized following a bottom-up route and dispersed under various pH conditions. Size and structural characteristics of nanograins were investigated by X-ray diffraction using a synchrotron source. Chemical analysis was then carried out by directly introducing diluted magnetic fluid samples (slurries) into the spectrometer. To achieve reliable measurements, sample conditions and apparatus parameters were carefully investigated. Slurry stability must be optimized in order to obtain reproducible and accurate analysis. The instrument must also be calibrated to minimize the difference between the signal produced by slurries and that of aqueous ordinary solutions. Furthermore, slurry sample introduction offers many advantages over conventional sample digestion, including reduced sample pretreatment time, less possibility of contamination and the use of direct calibration with aqueous solutions.     

Review: A gentle introduction to magnetism: units,fields, theory,and experiment

We present an introduction to the workings, units of measure, and general properties of magnetic materials. This is intended as a “primer to interpretation of magnetic data” for those who are entering the field, or those who are encountering magnetic measurements in the literature. We expect this work will serve as an initial guide to the reader to familiarize them with the basics in the hope that those working in the field of magnetochemistry will wish to explore additional, more detailed literature as their specific investigations demand. Topics covered include: magnetic fields and units (SI and cgs), paramagnetism (magnetization and magnetic susceptibility), Curie and Curie–Weiss behavior, magnetic exchange interactions, magnetic anisotropy, dimeric systems and exchange-coupled networks (including chains, ladders, and layers), and long-range order.     

Different methods for the fractionation of magnetic fluids

 Magnetic fluids are used in many fields of application, such as material separation and biomedicine. Magnetic fluids consist of magnetic nanoparticles, which commonly display a broad distribution of magnetic and nonmagnetic parameters. Therefore, upon application only a small number of particles contribute to the desired magnetic effect. In order to optimize magnetic fluids for applications preference is given to methods that separate magnetic nanoparticles according to their magnetic properties. Hence, a magnetic method was developed for the fractionation of magnetic fluids. Familiar size-exclusion chromatography of two different magnetic fluids was carried out for comparison. The fractions obtained and the original samples were also magnetically characterized by magnetic resonance and magnetorelaxometry, two biomedical applications. The size-exclusion fractions are similar to those of magnetic fractionation, despite the different separation mechanisms. In this respect, magnetic fractionation has several advantages in practical use over size-exclusion chromatography: the magnetic method is faster and has a higher capacity. The fractions obtained by both methods show distinctly different magnetic properties compared to the original samples and are therefore especially suited for applications such as magnetorelaxometry. Received: 12 July 1999/Accepted in revised form: 9 November 1999     

Magnetic Field and Magnetic Isotope Effects upon Reactions of Heavy Atom-Centered Radicals

We present our recent studies on magnetic field effects (MFEs) observed in reactions of heavy atom-centered radicals such as Si-,P-, Ge-, and Sn-radicals with a ns-laser photolysis technique under magnetic fields of 0–10 T. Although the MFES of heavy atom-centered radicals are much smaller than those of C-radicals due to the spin-orbit interaction of heavy atoms, we have found appreciable MFEs in many reactions of such heavy atom-centered radicals. Comparing the MFES of C-radicals with those of heavy atom-centered ones, we have explained the MFEs of heavy atom-centered radicals in terms of the Δg and relaxation mechanisms. We have found that the separation between the MFES due to the Δg mechanism and those due to the relaxation one is possible with the enhancement of spin relaxation by the addition of a paramagnetic ion. We have also tried to enrich magnetic isotopes of heavy atoms with the magnetic isotope effect (MIE), using the reactions which show fairly large MFES. Recently, we have succeeded in enriching ⁷³Ge. This is the heaviest isotope which has so far been enriched with the MIE from samples of natural abundance.     

磁性珠状纤维素制备工艺研究

本文较系统地研究了在采用反相悬浮包埋技术制备磁性珠状纤维素的过程中，纤维素的分子量、分散介质的性质、搅拌速度和O／W值等诸因素对磁性纤维素珠体的粒径、粒径分布和磁性材料包封率的影响。得到平均粒径在300微米以下，粒径分布指数小于1．4的磁性珠状纤维素，收率可达90％以上，且磁性材料（γ－Fe2O3）包封率较高。     

Mn0.6 Zn0.4 Fe2 O4 磁性亚微球的可控合成及磁性能

采用溶剂热法制备了单分散Mn0.6Zn0.4Fe2O4磁性亚微米球, 研究了反应工艺参数对磁性亚微米球结构形貌、 直径和静磁性能的影响规律. 研究发现, 随着反应时间的延长, 体系中的金属离子首先水解沉淀, 形成羟基氧化铁及Mn, Zn氢氧化物, 然后脱水转化为Mn0.6Zn0.4Fe2O4球形纳米粒子, 这些纳米粒子发生团聚, 形成结构疏松、 大小不均匀的亚微米粒子, 最后通过Ostwald熟化过程, 形成致密的单分散亚微米球. 降低反应溶液的pH值、 增加乙二醇或聚乙二醇的用量, 均会使亚微球的直径增大, 并可在150~500 nm范围内调控微球的粒径; 但组成磁性亚微球的纳米粒子的粒径逐渐减小, 产物的饱和磁化强度增大, 矫顽力和剩磁减小.     

磁性珠状纤维素的性能表征

本文采用反相悬浮包埋技术制各了磁性珠状纤维素（magneticcellulosebead缩写MCB），并对MCB各方面的性能进行了全面的评价：湿态孔度高达80％以上，磁化率在10-3emu／g数量级，磁性铁分布均匀，且磁稳定性较高。     

Advances in Molecular Diamagnetism

At the present state of instrumentation and quantum-mechanical approximations, diamagnetic measurements can supply information on chemical structure which complements the result of other approaches, such as infrared and NMR spectroscopy. General applicability and relatively low cost of equipment are among the advantages of this technique. There is growing interest in the relation to chemical shifts in NMR spectra and in the possibility offered by this technique for testing quantum-chemical approximations.     

Review: Preparation and Application of Magnetic Chitosan Derivatives in Separation Processes

Chitosan is one of the most abundant natural polysaccharide in nature. Due to its unique properties, chitosan has fascinated the scientific community since its discovery. When modified with other materials and combined with magnetic particles, the resulting composite material, a magnetic chitosan derivative, is provided with three significant characteristics. First, chitosan has excellent properties for preconcentration/extraction, such as adsorption and chelating effects, low cost, and nontoxicity. Second, new functional groups have enhanced the properties of chitosan that include water solubility, stability, recyclability, and enhanced adsorption capacity. Finally, due to the efficient and fast adsorption processes, as well as simple and convenient magnetic separation, the magnetic adsorbents greatly reduce the time of sample handling. In this article, recent synthesis and modification methods of magnetic chitosan derivatives are reviewed along with some applications in analytical separations.