电磁波作用下化学反应体系极化特性表征

近年来,微波促进化学反应引起人们的广泛关注,但是热点和热失控等问题限制了微波化学工业的发展。为了解决这些问题,需要研究电磁波与化学反应体系的相互作用规律。其中,电磁波作用下化学反应体系极化特性的表征是研究电磁波与化学反应体系的相互作用的基础。本文通过改进的SmoluchowskiDebye方程,得到了极性分子反应体系的极化特性的表征。由于电磁波作用下化学反应体系的极化过程实际上是一个线性时变系统的响应,只在一定条件下是马尔可夫过程。本文进一步讨论了极化的时域表征与频域表征的关系以及频域表征的局限性。     

2.45GHz下常用有机试剂复介电常数的测量与研究

1986年加拿大的R．Gedye和R．J．Giguere等发现了微波可以显著加快有机合成，他们发现用微波辐射可使反应速率和产率有不同程度的提高。由于微波作用机理的特殊性，微波化学对很多化学领域带来了冲击。但是，微波与化学反应体系之间相互作用的一些重大问题还未得到解决，如微波加热过程中化学反应系统的非线性反射、非均匀加热等。解决这类问题，首先必须了解化学反应过程中混合物的电学性质与磁学性质，而物质的宏观电学和磁学性质都用其介电常数和磁导率来描述。对于大部分是非磁性材料的有机试剂，微波与反应体系相互作用的特性集中体现在体系的等效复介电常数上。了解各种常用试剂的复介电常数，可以进一步了解各种化学试剂对微波的吸收和反射的情况。而很多试剂的复介电常数无法从现有文献中得到。本文利用谐振腔微扰法测定了在2．45GHz室温下各类常用有机试剂的复介电常数，结果显示：醇类试剂复介电常数实部与虚部都较大；酮类试剂复介电常数实部相对较大，而虚部较小；酸类试剂复介电常数实部和虚部都较小；烷烃和苯类试剂实部，虚部更小。同时，随着碳链增加，所有试剂的复介电常数的实部与虚部均有下降趋势。这些测试和分析结果将为微波辅助有机合成提供了有益参考。     

微波干法催化醛酮与胺的缩合反应

利用微波辐射和固体中性Al2 O3 载体催化醛酮与胺的缩合反应的方法合成了十六种亚胺 ,研究了微波功率、作用时间、产物提取方式等因素对反应的影响 ;与无微波作用的一般合成方法相比 ,该法明显地提高反应速度及产率 ;文中用低极性熔点递变物质灌装毛细管的方法观测微波作用下反应温度 ,探讨微波作用化学反应的机理 ,其机理除与微波加热作用有关外还与分子间氢键及分子的缔合性有关。     

微波化学

微波通常是指频率大约 3× 1 0 8～ 3× 1 0 11Ｈｚ(波长 1ｍ到 1ｍｍ)的电磁波。现在 ,微波技术已广泛应用于包括化学在内的许多领域 ,微波化学就是研究微波在化学中应用的一门交叉学科。在我国 ,已出版了有关微波化学的专著[1] ,专门会议也已开了 3届。1　微波与物质的相互作用　　微波作为一种电磁波 ,其与物质的相互作用和一般电磁波有共同之处 ,也可以发生反射、吸收等。在这里我们主要讨论微波能被物质吸收的作用。这种吸收从作用机理上讲可分为 2类 ,一类是吸收微波能引起分子内部能级变化 ,主要是转动能级变化的情况 ,这一类可用量…     

电解质溶液在微波场中升温行为的研究

电解质溶液在微波场中升温行为的研究王真洪品杰戴树珊（云南大学化学系昆明６５００９１）关键词电解质溶液微波温升弛豫近年来，利用微波加热技术加速化学反应已有许多报道，在微波场中体系的升温行为对化学反应有很大的影响［１－５］。水是许多化学反应用得较普通的一...     

微波加热下聚苯乙烯的磺化

微波是频率介于300—300,000兆赫的电磁波。微波能量对材料有很强的穿透力,能对被照射物质产生深层加热作用,因而广泛用于工业加热、干燥和家庭烹调等工艺。在合成化学方面,微波加热已用于有机化合物、有机金属化     

微波技术在有机化合物合成实验中的应用

微波是指电磁波谱中位于远红外与无线电波之间的电磁辐射(波长为10-3m～10-1m),微波能量对材料有很强的穿透力,能对被照射物质产生深层加热作用.     

制备纳米氧化锌的新方法

以草酸和醋酸锌为原料，用室温固相化学反应首先制备前驱物二水合草酸锌，后者在微波场辐射分解得到产物纳米氧化锌。用XRD，TEM和IR等技术对产物的组成，大小及形貌进行了表征。结果表明：产物纳米氧化锌为粒度分布均匀的球形六角晶系结构，平均粒径约为8nm。     

大功率微波促进丙二酸二乙酯烷基化反应

目前，用微波促进的各种有机合成反应基本上采用家用微波炉作为微波功率源，由于功率小，稳定性差，功率波动大，是周期间断工作模式，除满功率档外，其它各档均为脉冲式，其断开时间将产生显著的热损失，对实验数据影响较大，不适合大规模合成及工业化生产的快速合成反应的要求．为此，我们自行设计制造了由5kw／2450MHz高稳定程控微波源、微波传输系统和微波反应腔组成的微波化学反应装置（图1），微波传输系统由三端环行器，水负载，电动三销钉调配器组成，保证微波功率的最佳传输．反应腔带有微波模式搅拌器及测控温装置，腔内可放置开…     

四针状氧化锌晶须的制备及其吸波性能的研究

随着雷达探测、卫星通信、航天航空和电子对抗等高科技的发展，特别是近年来抗电磁波干扰、隐形技术、微波暗室等研究领域的兴起．对电磁波吸波材料的研究日益受到人们的重视。随着现代电子工业和信息产业的高速发展．产生电磁波的电子产品（诸如计算机、电视机、手机、微波炉及电磁炉等）的数量急剧增加，     

Propagation of photosensitive chemical waves on the circular routes

The propagation of chemical waves in the photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated using an excitable field in the shape of a circular ring or figure "8" that was drawn by computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. For a chemical wave in a circular reaction field, the shape of the chemical wave was investigated depending on the ratio of the inner and outer radii. When two chemical waves were generated on a field shaped like a figure "8" (one chemical wave in each circle) as the initial condition, the location of the collision of the waves either was constant or alternated depending on the degree of overlap of the two circular rings. These experimental results were analyzed on the basis of a geometrical discussion and theoretically reproduced on the basis of a reaction-diffusion system using a modified Oregonator model. These results suggest that the photosensitive BZ reaction may be useful for creating spatio-temporal patterns depending on the geometric arrangement of excitable fields.     

具有平方衰减项的平方自催化开放系统中的化学波研究

建立了开放系统中伴随平方衰减反应的双分子自催化反应理论模型,给出了系统的动力学分析,在给定初边值下解的估计及存在化学波的必要条件、化学波波速的最小值及平方衰减项对化学波的影响.随着衰减系数的增加,平方衰减项逐步成为系统反应中化学波波形的决定因素.     

Non-equilibrium thermodynamics of photophoretic motion of colloidal particles

The behavior of electromagnetic radiation in colloidal systems is studied by non-equilibrium thermodynamics methods. Phenomenological equations of non-equilibrium thermodynamics are derived preliminarily for discontinuous systems where photon exchange occurs. Phenomenological equations describing the radiative transfer in absorbing medium are also considered. The equations responsible for the motion of particles in a nonuniform absorbing medium with the directed flux of electromagnetic radiation are derived. These equations describe thermo-and photophoretic motion of colloidal particles. The effect related to the radiation of electromagnetic waves by a colloidal particle moving in a uniform medium under the action of an external force is a cross effect with respect to photophoresis. The Onsager’s relations for kinetic coefficients are shown to be valid for all considered systems.     

Ground‐State Chemical Reactivity under Vibrational Coupling to the Vacuum Electromagnetic Field

The ground‐state deprotection of a simple alkynylsilane is studied under vibrational strong coupling to the zero‐point fluctuations, or vacuum electromagnetic field, of a resonant IR microfluidic cavity. The reaction rate decreased by a factor of up to 5.5 when the Si?C vibrational stretching modes of the reactant were strongly coupled. The relative change in the reaction rate under strong coupling depends on the Rabi splitting energy. Product analysis by GC‐MS confirmed the kinetic results. Temperature dependence shows that the activation enthalpy and entropy change significantly, suggesting that the transition state is modified from an associative to a dissociative type. These findings show that vibrational strong coupling provides a powerful approach for modifying and controlling chemical landscapes and for understanding reaction mechanisms.     

Interactive propagation of photosensitive chemical waves on two circular routes

The propagation of chemical waves in the photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated using an excitable field composed of two rings in slight contact, which were drawn using computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. When the initial phase difference between the two chemical waves in the individual rings was smaller than a critical value, this initial value was maintained after collision of the chemical waves. However, when the initial phase difference was larger than this critical value, the phase difference converged to the same value after the second collision. The critical value increased with an increase in the thickness of the rings. These experimental results on the geometry of the excitable field are discussed in relation to the nature of chemical wave propagation. These results suggest that the photosensitive BZ reaction may be useful for creating spatiotemporal patterns that depend on the geometric arrangement of excitable fields.     

响应性凝胶与非线性化学反应相互作用研究进展

本文综述了响应性凝胶与非线性反应动力学相互作用的研究进展,从实验及理论方面评述了pH振荡器中响应胶的振荡行为、P(NIPAAm-co-Ru(bpy)3)共聚凝胶中Belousov-Zhabotinsky(BZ)化学反应引起的膨胀-收缩振荡、行波和纳米制动器的制备及生理条件下凝胶自振荡行为,成为化学能向机械能转化的智能材料领域中活跃的研究方向; 同时凝胶的响应性作用于非线性化学反应可控制反应动力学的分岔行为.最后对该研究领域的发展方向和应用前景进行了展望.     

Sintered Silicon Carbide: A New Ceramic Vessel Material for Microwave Chemistry in Single‐Mode Reactors

Silicon carbide (SiC) is a strongly microwave absorbing chemically inert ceramic material that can be utilized at extremely high temperatures due to its high melting point and very low thermal expansion coefficient. Microwave irradiation induces a flow of electrons in the semiconducting ceramic that heats the material very efficiently through resistance heating mechanisms. The use of SiC carbide reaction vessels in combination with a single‐mode microwave reactor provides an almost complete shielding of the contents inside from the electromagnetic field. Therefore, such experiments do not involve electromagnetic field effects on the chemistry, since the semiconducting ceramic vial effectively prevents microwave irradiation from penetrating the reaction mixture. The involvement of electromagnetic field effects (specific/nonthermal microwave effects) on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave‐transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature. For most of the 21 reactions, the outcome in terms of conversion/purity/product yields using the two different vial types was virtually identical, indicating that the electromagnetic field had no direct influence on the reaction pathway. Due to the high chemical resistance of SiC, reactions involving corrosive reagents can be performed without degradation of the vessel material. Examples include high‐temperature fluorine–chlorine exchange reactions using triethylamine trihydrofluoride, and the hydrolysis of nitriles with aqueous potassium hydroxide. The unique combination of high microwave absorptivity, thermal conductivity, and effusivity on the one hand, and excellent temperature, pressure and corrosion resistance on the other hand, makes this material ideal for the fabrication of reaction vessels for use in microwave reactors.     

光敏性BZ反应的时空动力学

作为研究非线性时空动力学最理想的化学反应体系之一,三联(2,2'-联吡啶)钌(Ⅱ)(Ru(bpy)₃²⁺)为催化剂的Belousov-Zhabotinsky (BZ)振荡反应具有独特的光敏特性并能呈现丰富的时空动力学行为。研究光控BZ反应有助于我们对一系列物理、化学和生命体系中复杂动力学现象的理解。本文综述了不同实验条件下光效应对钌催化BZ反应均相复杂振荡和空间反应扩散化学波的影响, 以及光响应BZ反应与软物质耦合体系的复杂动力学行为,在此基础上介绍光抑制和光诱导反应机理和模型。对光控BZ反应体系存在的问题和发展方向进行了探讨。     

Chemical waves

In our paper we try to describe the basic concepts of chemical waves and spatial pattern formation in a simple way. We pay particular attention to self-organisation phenomena in extended excitable systems. These result in the appearance of travelling waves, spiral waves, target patterns, Turing structures or more complicated structures called scroll waves, which are three-dimensional systems. We describe the most famous oscillating reaction, the Belousov-Zhabotinsky (BZ) reaction, in greater detail. This is because it is of great interest in both physical chemistry and in studies on the evolution and sustenance of self-organising biological systems.     

Dissipative structures in systems of diffusion-bonded chemical nano- and micro oscillators

In spatially extended classical Belousov-Zhabotinsky (BZ) reaction, trigger spiral or concentric waves usually occur. If the BZ reaction is dispersed into nanodroplets of water-in-oil emulsion, new patterns are observed such as standing waves, anti-spirals, oscillons, dash-waves, jumping waves, Turing patterns, and other. If the size of water droplets is increased up to tens of micrometers, coupled micro-oscillators produce new stationary and oscillatory discrete dissipative patterns. In the review, comparative analysis of these patterns is done and a possibility of creating a chemical computer on the basis of dissipative patterns is discussed.