技术领域technical field
本发明属于驻极体空气净化领域，具体涉及一种基于温度调控的铌酸锂热释电材料在吸附大气颗粒物中的应用。The invention belongs to the field of electret air purification, and in particular relates to the application of a lithium niobate pyroelectric material based on temperature control in adsorbing atmospheric particles.
背景技术Background technique
雾霾天气的出现和持续，严重影响了人们的日常生活，对人们的身体健康带来了极大危害，引起了社会的广泛关注和重视。雾霾包括雾与霾两层含义：雾是由大量悬浮在近地面空气中的微小水滴或冰晶组成的气溶胶系统，多出现于秋冬季节，是近地面层空气中水汽凝结(或凝华)的产物；霾是由空气中的灰尘、硫酸、硝酸、有机碳氢化合物等粒子组成。雾霾主要由二氧化硫、氮氧化物和可吸入颗粒物组成，前两者为气态污染物，最后一项颗粒物才是加重雾霾天气污染的首要原因。特别是涉及雾霾形成的PM10乃至PM2.5，越来越引起人们的关注。而其中PM2.5因其粒径较小、同时比表面积较大，和粗颗粒物相比它更容易富集有毒物质，如细菌和重金属离子等，和人体健康密切相关。The emergence and continuation of smog has seriously affected people's daily life and brought great harm to people's health, which has aroused widespread concern and attention from the society. Haze includes two meanings of fog and haze: fog is an aerosol system composed of a large number of tiny water droplets or ice crystals suspended in the air near the surface, which mostly occurs in autumn and winter, and is the condensation (or sublimation) of water vapor in the air near the surface. Haze is composed of particles such as dust, sulfuric acid, nitric acid, and organic hydrocarbons in the air. Smog is mainly composed of sulfur dioxide, nitrogen oxides, and inhalable particulate matter. The first two are gaseous pollutants, and the last item of particulate matter is the primary cause of aggravating smog weather pollution. In particular, PM10 and even PM2.5 , which are related to the formation of smog, have attracted more and more attention. Among them, PM2.5 is more likely to accumulate toxic substances, such as bacteria and heavy metal ions, than coarse particles due to its smaller particle size and larger specific surface area, and is closely related to human health.
欧美等国都以PM2.5作为评价颗粒物污染的标准，而我国对于PM2.5研究起步相对较晚，主要是基于PM2.5的来源、成分以及与大气压力等气象条件和人为因素之间的关系，并取得了一些进展。目前，国内已有报道，采用多种分析方法对北京等地的污染物颗粒进行了成分、来源等的分析。PMF法被用于对PM2.5进行源解析，确定了北京地区5类细粒子污染源，即土壤尘、煤燃烧、交通运输、海洋气溶胶和钢铁工业。采用离子色谱(IC)对PM10和PM2.5中的水溶性阴离子F-,Cl-,NO3-和SO42-进行测定，结果表明F-主要存在于PM10的粗颗粒部分(10μm>粒径>2.5μm)，而Cl-,NO3-和SO42-离子则更容易在细颗粒中富集。电感耦合等离子体质谱法(ICP-MS)分析了北京市城区冬季雾霾天气PM2.5中的36种元素，并采用富集因子对元素浓度特征进行了分析。所谓富集因子法是指将样品中元素的浓度与基线中元素的浓度进行对比，以此来判断表生环境介质中元素的人为污染状况，为了减小环境介质以及采样制样过程对元素浓度的影响，富集因子的计算常引入参比元素进行标准化，用作标准化的参比元素常选择表生过程中地球化学性质稳定的元素，如Al、Ti、Sc、Zr等。结果表明，雾霾天气发生时，As，Cr，Pb，Ti和Ｖ等重金属是北京PM2.5中的主要无机污染物，36种元素中有27种元素浓度均高于非雾霾天气。元素富集特征表明，雾霾天气发生时，Cr，Cu，Zn和Pb的富集因子高于10，是污染较重的元素，主要是燃煤和工业污染等人类活动引起的各种污染所致。Countries such as Europe and the United States use PM2.5 as the standard for evaluating particulate matter pollution, while China’s research on PM2.5 started relatively late, mainly based on the source, composition, and relationship between atmospheric pressure and other meteorological conditions and human factors of PM2.5 . made some progress. At present, there have been reports in China, using a variety of analysis methods to analyze the composition and source of pollutant particles in Beijing and other places. The PMF method was used for source apportionment of PM2.5 , and five types of fine particle pollution sources in the Beijing area were identified, namely soil dust, coal combustion, transportation, marine aerosol, and steel industry. The water-soluble anions F- , Cl- , NO3- and SO42- in PM10 and PM2.5 were determined by ion chromatography (IC). The results showed that F- mainly existed in the coarse particle part of PM10 (10μm> particle size>2.5μm), while Cl- , NO3- and SO42- ions are more likely to be enriched in fine particles. Inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze 36 elements in PM2.5 in winter haze weather in urban Beijing, and the enrichment factor was used to analyze the element concentration characteristics. The so-called enrichment factor method refers to comparing the concentration of elements in the sample with the concentration of elements in the baseline to judge the man-made pollution of elements in the superficial environmental medium. The calculation of the enrichment factor often introduces reference elements for standardization, and the reference elements used for standardization often choose elements with stable geochemical properties during the supergene process, such as Al, Ti, Sc, Zr, etc. The results show that heavy metals such as As, Cr, Pb, Ti and V are the main inorganic pollutants in Beijing PM2.5 when the haze weather occurs, and the concentration of 27 of the 36 elements is higher than that in the non-haze weather. The element enrichment characteristics show that when the haze weather occurs, the enrichment factors of Cr, Cu, Zn and Pb are higher than 10, which are elements with heavy pollution, mainly caused by various pollution caused by human activities such as coal burning and industrial pollution. Sincerely.
现有的空气净化装置主要由两部分组成，一部分为消除可吸入颗粒物的过滤段，另一部分为消除有害气体的净化段。而在过滤段，空气过滤材料起着决定性作用。The existing air purification device is mainly composed of two parts, one part is a filter section for eliminating inhalable particles, and the other part is a purification section for eliminating harmful gases. In the filter section, the air filter material plays a decisive role.
较早的将过滤材料有目的的用于空气过滤方面是在第一次世界大战期间，石棉纤维作为滤料大量的应用与防毒气面具，在随后的几十年里，玻璃纤维过滤材料、超细玻璃纤维过滤材料、非织造过滤材料等各种性能更为优良的过滤品种相继研发，并且在此基础上还出现了驻极滤料、复合滤料等新型等过滤材料，这些都为空气过滤技术的发展提供了有利的条件。常规滤料即目前所使用的空气过滤器中应用最多的一类，可以分为机织滤料、针织滤料、非织造滤料等三种，其中非织造滤料又可以分为非织造针刺滤料、非织造熔喷滤料等几种。这些材料主要依靠布朗扩散、截留、惯性碰撞、重力沉降等机械阻挡作用，通过纤维网格对空气微粒进行过滤。因此，要想过滤掉PM2.5及以下的颗粒物，需要网格的尺寸足够的小，这样会增加过滤系统的阻力压降，使得过滤系统的能耗随之增加，一方面增加了过滤造价，同时也对空气过滤器的工艺提出很高的要求。而且，这些过滤材料随着吸附颗粒浓度的增大，吸附效率会大大下降，加上对过滤网的清洗往往困难较大，因此几乎都是一次性的，不能重复使用，造成能源浪费和过滤成本的增加。另外一个不可小视的缺点在于其对细小微粒的去除效率低，而且过滤材料上容易孳生有害微生物，存在二次污染的可能。The earlier purposeful use of filter materials for air filtration was during the First World War, when asbestos fibers were used as filter materials in large quantities and gas masks. In the following decades, glass fiber filter materials, ultra- Fine glass fiber filter materials, non-woven filter materials and other types of filters with better performance have been developed successively, and on this basis, new types of filter materials such as electret filter materials and composite filter materials have emerged, all of which are air filter materials. The development of technology provides favorable conditions. Conventional filter material is the most widely used type of air filter currently used. It can be divided into three types: woven filter material, knitted filter material, and non-woven filter material. Among them, non-woven filter material can be divided into non-woven needle filter material. There are several kinds of thorn filter materials, non-woven melt-blown filter materials, etc. These materials mainly rely on mechanical barriers such as Brownian diffusion, entrapment, inertial collision, and gravity settlement to filter air particles through fiber mesh. Therefore, in order to filter out particulate matter of PM2.5 and below, the size of the grid needs to be small enough, which will increase the resistance pressure drop of the filtration system, which will increase the energy consumption of the filtration system. On the one hand, it will increase the cost of filtration. It also puts high demands on the technology of air filters. Moreover, with the increase of the concentration of adsorbed particles, the adsorption efficiency of these filter materials will be greatly reduced. In addition, it is often difficult to clean the filter screen. Therefore, they are almost disposable and cannot be reused, resulting in energy waste and filtration costs. increase. Another disadvantage that cannot be underestimated is that its removal efficiency for fine particles is low, and harmful microorganisms are easy to breed on the filter material, and there is a possibility of secondary pollution.
针对普通滤材中存在的上述问题，一些新型吸附材料(如驻极滤料，复合滤料等)的发现和使用得到了科学家们的关注。尤其是驻极体空气过滤材料，因其具有高效、低阻、节能、抗菌等优点，是一类非常有应用前景的新型空气过滤材料。In view of the above problems in common filter materials, the discovery and use of some new adsorption materials (such as electret filter materials, composite filter materials, etc.) has attracted the attention of scientists. Especially the electret air filter material, because of its advantages of high efficiency, low resistance, energy saving, antibacterial, etc., is a new type of air filter material with very promising application prospects.
目前，用作驻极体空气过滤材料主要是以高聚物为主的有机驻极体材料，如非极性材料：聚丙烯、聚四氟乙烯、六氟丙烯－聚四氟乙烯共聚物等；极性或弱性材料：聚三氟氯乙烯、聚丙烯即(共混)及聚醋等。这类材料除了惯性碰撞、拦截效应、扩散效应等传统滤料作用机理外，还通过库仑力实现对空气微粒的捕获。当空气微粒经过过滤器时，静电力不仅能有效地吸引带电微粒，而且以静电感应效应捕获极化的中性粒子，因此具有高效性。与此同时，这类材料在吸附过程中产生的流阻较小，大大减小了能耗，在空气过滤系统中得到了广泛的应用。然而，驻极体滤料纤维的生产工艺要求较高，驻电过程复杂，且由于大气微粒中带电电荷的中和作用或微粒沉积产生静电力的屏蔽作用使得滤料表面电荷衰减较快，吸附效率降低，耐湿耐热性能差，容易老化等，以及消防要求必须选用不燃材料和火灾时不发生有毒气体的材料等原因，很大程度上限制了有机驻极体滤料的应用。At present, the electret air filter materials are mainly organic electret materials based on high polymers, such as non-polar materials: polypropylene, polytetrafluoroethylene, hexafluoropropylene-polytetrafluoroethylene copolymer, etc. ; Polar or weak materials: polychlorotrifluoroethylene, polypropylene (blend) and polyester, etc. In addition to the traditional filter mechanism such as inertial collision, interception effect, and diffusion effect, this kind of material also captures air particles through Coulomb force. When air particles pass through the filter, electrostatic force can not only effectively attract charged particles, but also capture polarized neutral particles with electrostatic induction effect, so it has high efficiency. At the same time, this type of material has a small flow resistance during the adsorption process, which greatly reduces energy consumption, and has been widely used in air filtration systems. However, the production process of electret filter fiber has high requirements, and the electrification process is complicated, and due to the neutralization of charged charges in atmospheric particles or the shielding effect of electrostatic force generated by particle deposition, the surface charge of the filter material decays quickly, and the adsorption Reduced efficiency, poor moisture and heat resistance, easy aging, etc., and fire protection requirements must use non-combustible materials and materials that do not produce toxic gases during fires, etc., which largely limit the application of organic electret filter materials.
铌酸锂是一类典型的热释电无机驻极体材料，所谓热释电性是指，当晶体温度发生变化(受热或冷却)，正负电荷的中心会发生位移，从而极化强度随着温度的改变而发生变化，导致晶体表面的束缚电荷随之发生变化。铌酸锂是无色或者带有黄绿色的透明晶体，铌酸锂的表面居里温度Tc是1210℃，铌酸锂晶体属于三方晶系，3m点群，在Tc以下为铁电相，在Tc以上为顺电相。对处于单畴铁电相的铌酸锂晶体施加外电场，当外电场逐渐增加到铌酸锂的矫顽场时，由于有1/3氧八面体的体心空着，Nb5+和Li+开始逐渐向负光轴方向开始移动，最终稳定在氧八面体体心的另一侧，结果铌酸锂的极化方向会发生翻转即畴反转，如图1所示。Lithium niobate is a typical pyroelectric inorganic electret material. The so-called pyroelectricity means that when the crystal temperature changes (heated or cooled), the center of the positive and negative charges will shift, so that the polarization intensity varies with As the temperature changes, the bound charge on the surface of the crystal changes accordingly. Lithium niobate is a colorless or yellow-green transparent crystal. The surface Curie temperature Tc of lithium niobate is 1210°C. Lithium niobate crystals belong to the trigonal crystal system with a 3m point group. It is a ferroelectric phase below Tc , aboveTc is the paraelectric phase. An external electric field is applied to the lithium niobate crystal in the single-domain ferroelectric phase. When the external electric field gradually increases to the coercive field of lithium niobate, since the body center of 1/3 oxygen octahedron is empty, Nb5+ and Li+ began to gradually move towards the negative optical axis, and finally stabilized on the other side of the oxygen octahedral body center. As a result, the polarization direction of lithium niobate would be reversed, that is, domain inversion, as shown in Figure 1.
发明内容Contents of the invention
本发明的目的之一是提供基于温度调控的铌酸锂热释电材料的一种新用途。One of the objectives of the present invention is to provide a new application of lithium niobate pyroelectric material based on temperature control.
本发明所提供的铌酸锂热释电材料的新用途是其作为空气过滤材料在吸附大气颗粒物中的应用。The new application of the lithium niobate pyroelectric material provided by the invention is its application as an air filter material in adsorbing atmospheric particles.
所述应用中，铌酸锂通过加热产生温差，使得铌酸锂表面产生大量自由电荷，再利用所述自由电荷捕获空气中的极性颗粒，或使中性颗粒极化后将其捕获。In the application, lithium niobate is heated to generate a temperature difference, so that a large amount of free charges are generated on the surface of lithium niobate, and then the free charges are used to capture polar particles in the air, or polarize neutral particles to capture them.
所述大气颗粒物包括：粉尘、PM10、PM2.5以及亚微米颗粒。The atmospheric particulate matter includes: dust, PM10 , PM2.5 and submicron particles.
所述铌酸锂为单畴生长的Z轴方向的晶片，并进行了双面抛光。The lithium niobate is a single-domain grown wafer in the direction of the Z axis, and has been polished on both sides.
本发明的再一个目的是提供一种吸附大气颗粒物的方法。Another object of the present invention is to provide a method for adsorbing atmospheric particulate matter.
本发明所提供的吸附大气颗粒物的方法是采用铌酸锂作为空气过滤材料，使其在温差刺激作用下释放电荷，从而实现对大气颗粒物的吸附。The method for adsorbing atmospheric particles provided by the present invention is to use lithium niobate as an air filter material to make it release electric charge under the stimulation of temperature difference, thereby realizing the adsorption of atmospheric particles.
所述铌酸锂为单畴生长的Z轴方向的晶片，并进行了双面抛光。The lithium niobate is a single-domain grown wafer in the direction of the Z axis, and has been polished on both sides.
所述的温差刺激为加热。The temperature difference stimulus is heating.
在上述方法中，通过加热产生温差，使得铌酸锂表面产生大量自由电荷，再利用所述自由电荷捕获空气中的极性颗粒，或使中性颗粒极化后将其捕获，从而实现对大气颗粒物的吸附。In the above method, the temperature difference is generated by heating, so that a large amount of free charges are generated on the surface of lithium niobate, and then the free charges are used to capture polar particles in the air, or capture them after polarizing neutral particles, so as to achieve air pollution. Adsorption of particulate matter.
加热时，铌酸锂表面呈现正电荷，可吸附空气中的负电性微粒(大气中污染物颗粒绝大多数呈现负电性)。When heated, the surface of lithium niobate presents a positive charge, which can absorb negatively charged particles in the air (most of the pollutant particles in the atmosphere are negatively charged).
所述大气颗粒物包括：粉尘、PM10、PM2.5以及亚微米颗粒。The atmospheric particulate matter includes: dust, PM10 , PM2.5 and submicron particles.
所述方法具体包括下述步骤：先将铌酸锂热释电材料进行加热处理，然后将加热后的铌酸锂置于大气环境中对大气颗粒物进行吸附。The method specifically includes the following steps: first heat-treating the lithium niobate pyroelectric material, and then placing the heated lithium niobate in an atmospheric environment to adsorb atmospheric particles.
所述加热后的铌酸锂的温度为30-150℃，优选80-150℃，最优选100℃。The temperature of the heated lithium niobate is 30-150°C, preferably 80-150°C, most preferably 100°C.
为了保持较高的吸附效果，所述吸附过程中优选对铌酸锂进行持续加热。In order to maintain a high adsorption effect, it is preferable to continuously heat the lithium niobate during the adsorption process.
所述持续加热的温度可为100℃。The temperature of the continuous heating may be 100°C.
所述方法还可进一步包括下述步骤：在铌酸锂吸附饱和后(即铌酸锂表面不能再有明显的吸附)，用水清洗所述铌酸锂热释电材料去除吸附的颗粒物并中和铌酸锂表面剩余电荷，重新加热所述铌酸锂热释电材料，以实现铌酸锂对颗粒物的可重复释电吸附。The method may further include the following steps: after the lithium niobate adsorption is saturated (that is, the lithium niobate surface can no longer have obvious adsorption), washing the lithium niobate pyroelectric material with water to remove the adsorbed particles and neutralizing The residual charge on the surface of lithium niobate is reheated to reheat the lithium niobate pyroelectric material, so as to realize the repeatable discharge and adsorption of lithium niobate to particles.
利用温差调控的热释电材料能够方便地进行反复充电，简化了注电过程。基于静电吸附的方法可以直接捕获大气中的极性细微颗粒物，同时还能够使中性颗粒物极化，然后将其捕获。该方法对于颗粒物的尺寸没有选择性，尤其对于微纳米尺度的细小颗粒物具有较高的吸附效率。同时，铌酸锂晶体的耐损耗性能则大大提高了其使用寿命。The pyroelectric material regulated by temperature difference can be conveniently charged repeatedly, which simplifies the charging process. Electrostatic adsorption-based methods can directly capture polar fine particles in the atmosphere, while also being able to polarize neutral particles and then capture them. This method has no selectivity for the size of the particles, and has a high adsorption efficiency especially for fine particles of micro-nano scale. At the same time, the wear resistance of lithium niobate crystal greatly improves its service life.
本发明利用无机驻极体热释电材料铌酸锂在温度调控下产生的表面电荷的静电作用吸附大气中的污染颗粒物。由于该热释电材料仅需温度调控即可快速产生大量电荷，通过对吸附颗粒的大小和所含元素的分析证实，铌酸锂在加热时能够产生足够的静电吸附力，有效的吸附空气中的粉尘，PM10，PM2.5以及亚微米颗粒，展现了铌酸锂作为过滤材料的应用潜力和前景。The invention utilizes the electrostatic action of the surface charge generated by the inorganic electret pyroelectric material lithium niobate under temperature control to absorb the pollutant particles in the atmosphere. Since the pyroelectric material can quickly generate a large amount of charge only by temperature regulation, the analysis of the size of the adsorbed particles and the elements contained proves that lithium niobate can generate sufficient electrostatic adsorption force when heated, and can effectively adsorb in the air. Dust, PM10 , PM2.5 and submicron particles, show the application potential and prospect of lithium niobate as a filter material.
与通常用于静电吸附的聚合物驻极体材料不同，该热释电材料在温度作用下的介电损耗小，因此能够对其进行反复充电，且能稳定储存电荷，从而延长了使用寿命。对热释电材料铌酸锂表面电势衰减的研究表明，该热释电材料铌酸锂表面的电荷衰减缓慢，一次释电可以维持很长时间，吸附效率高。该热释电材料价格低廉，制备方法简单易行，实验表明，铌酸锂在反复加热200次后，其吸附能力没有发生明显的变化。而且由于其仅需温差即可调控表面电势，因此具有注电简单、操作方便、可反复充放电等优点，在空气净化领域有很好的应用前景。Unlike polymer electret materials commonly used for electrostatic adsorption, the pyroelectric material has low dielectric loss under temperature, so it can be recharged repeatedly and can store charges stably, thereby prolonging the service life. The study on the surface potential decay of the pyroelectric material lithium niobate shows that the charge decay on the surface of the pyroelectric material lithium niobate is slow, a discharge can last for a long time, and the adsorption efficiency is high. The price of the pyroelectric material is low, and the preparation method is simple and feasible. Experiments show that the adsorption capacity of lithium niobate does not change significantly after repeated heating for 200 times. And because it can adjust the surface potential only by temperature difference, it has the advantages of simple power injection, convenient operation, repeated charge and discharge, etc., and has a good application prospect in the field of air purification.
附图说明Description of drawings
图1为铌酸锂在强电场下进行畴反转的晶体结构示意图。Figure 1 is a schematic diagram of the crystal structure of lithium niobate undergoing domain inversion under a strong electric field.
图2为实施例1中加热至不同温度的铌酸锂对300μm聚苯乙烯(PS)小球的吸附图。其中，图(a)－图(m)分别对应温度30℃－150℃，温度梯度为10℃。FIG. 2 is an adsorption graph of lithium niobate heated to different temperatures on 300 μm polystyrene (PS) pellets in Example 1. FIG. Among them, Figure (a)-Figure (m) correspond to the temperature of 30°C-150°C respectively, and the temperature gradient is 10°C.
图3为实施例2中具有同一初始加热条件(100℃)的铌酸锂晶片在加热后1h(烘箱内冷却至室温的时间)、25h、73h和121h对PS小球的吸附图。其中，图(a)－图(d)分别对应加热后1h、25h、73h和121h，铌酸锂晶片对PS小球的吸附图。Figure 3 is the adsorption graph of PS pellets on lithium niobate wafers with the same initial heating condition (100°C) in Example 2 after heating for 1h (the time for cooling to room temperature in the oven), 25h, 73h and 121h. Among them, Figures (a) to (d) correspond to the adsorption diagrams of lithium niobate wafers on PS pellets at 1h, 25h, 73h and 121h after heating, respectively.
图4为实施例3中加热至不同温度的铌酸锂对PS小球的吸附图。其中，a，b，c对应的加热后的铌酸锂的温度分别为100℃、150℃和200℃。FIG. 4 is an adsorption diagram of lithium niobate heated to different temperatures on PS pellets in Example 3. FIG. Wherein, a, b, and c correspond to the temperatures of the heated lithium niobate being 100° C., 150° C. and 200° C., respectively.
图5为实施例4中雾霾天气下，铌酸锂吸附空气颗粒的扫描电子显微镜(SEM)图。5 is a scanning electron microscope (SEM) image of lithium niobate adsorbing air particles under haze weather in Example 4.
图6为实施例4中雾霾天气下，铌酸锂吸附空气颗粒的原子力显微镜(AFM)图。Fig. 6 is an atomic force microscope (AFM) image of lithium niobate adsorbing air particles under haze weather in Example 4.
图7为实施例5中铌酸锂吸附空气颗粒的X射线能谱(EDS)分析图。FIG. 7 is an X-ray energy spectrum (EDS) analysis diagram of lithium niobate adsorbing air particles in Example 5. FIG.
图8为实施例5中铌酸锂吸附颗粒的X射线光电子能谱(XPS)分析图。FIG. 8 is an X-ray photoelectron spectroscopy (XPS) analysis diagram of lithium niobate adsorption particles in Example 5. FIG.
图9为实施例6中铌酸锂反复加热至100℃时，对PS小球吸附情况的对比图。其中，a，b，c，d所对应的加热次数分别为50，100，150和200次。FIG. 9 is a comparison chart of adsorption of PS pellets when lithium niobate is repeatedly heated to 100° C. in Example 6. FIG. Among them, the heating times corresponding to a, b, c, and d are 50, 100, 150, and 200 times, respectively.
具体实施方式Detailed ways
下面通过具体实施例对本发明进行说明，但本发明并不局限于此。The present invention will be described below through specific examples, but the present invention is not limited thereto.
下述实施例中所使用的实验方法如无特殊说明，均为常规方法；下述实施例中所用的试剂、材料等，如无特殊说明，均可从商业途径得到。The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents and materials used in the following examples can be obtained from commercial sources unless otherwise specified.
实施例1、铌酸锂最佳吸附温度的确定Embodiment 1, determination of optimum adsorption temperature of lithium niobate
热释电效应的强弱可以用热释电系数表示。极化的改变和热释电温度的改变公式如下：ΔP＝pΔT(p是热释电系数，ΔT是晶体温度的改变，ΔP为极化的改变量)。从原理上来讲，只要存在温度差就可以使铌酸锂材料表面产生电荷。由于铌酸锂晶片厚度较大，无法使用静电力显微镜直接表征其表面电势，因此，通过在不同温度下对负电性PS小球的吸附量可以间接表征其表面电势大小，并据此筛选出最佳的热释电温度。The strength of the pyroelectric effect can be expressed by the pyroelectric coefficient. The formula for the change of polarization and the change of pyroelectric temperature is as follows: ΔP=pΔT (p is the pyroelectric coefficient, ΔT is the change of crystal temperature, and ΔP is the change of polarization). In principle, as long as there is a temperature difference, the surface of the lithium niobate material can be charged. Due to the large thickness of the lithium niobate wafer, the surface potential cannot be directly characterized by electrostatic force microscopy. Therefore, the surface potential can be indirectly characterized by the amount of adsorption of negatively charged PS beads at different temperatures, and the best Optimum pyroelectric temperature.
将铌酸锂热释电材料裁切成13片2cm×2cm的小片，分别加热到不同温度(30℃、40℃、50℃、60℃、70℃、80℃、90℃、100℃、110℃、120℃、130℃、140℃、150℃)，对呈负电性的聚苯乙烯(PS，300μm)小球进行吸附。Cut the lithium niobate pyroelectric material into 13 small pieces of 2cm×2cm, and heat them to different temperatures (30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C °C, 120 °C, 130 °C, 140 °C, 150 °C), to adsorb negatively charged polystyrene (PS, 300 μm) pellets.
图2为加热至不同温度的铌酸锂对300μm PS小球的吸附图。其中，图(a)－图(m)分别对应温度30℃－150℃，温度梯度为10℃。Figure 2 is the adsorption diagram of lithium niobate heated to different temperatures on 300 μm PS beads. Among them, Figure (a)-Figure (m) correspond to the temperature of 30°C-150°C respectively, and the temperature gradient is 10°C.
从图中可以明显的看出，随着温度的升高，铌酸锂对PS小球的吸附量逐渐增大，当温度到达100℃时，PS小球已将铌酸锂表面完全覆盖，说明铌酸锂在较低的温度下就已经表现出热释电性，且随着温度升高，表面的电荷量逐渐增大，库仑力作用越来越强，对PS小球的吸附也越明显。通过对比不同温度下的吸附情况发现，当温度超过100℃时，对PS小球的吸附量没有太大的变化。因此，在后续的实验里，我们将吸附温度设为100℃。与这也说明铌酸锂对热释电温度要求不高，一个较低的温度就能产生很强的吸附力，用做空气过滤材料时具有耗能低的优点。It can be clearly seen from the figure that as the temperature increases, the adsorption amount of lithium niobate to PS pellets gradually increases. When the temperature reaches 100°C, PS pellets have completely covered the surface of lithium niobate, indicating that Lithium niobate already exhibits pyroelectricity at lower temperatures, and as the temperature rises, the charge on the surface gradually increases, the Coulomb force becomes stronger, and the adsorption on PS beads becomes more obvious. . By comparing the adsorption conditions at different temperatures, it was found that when the temperature exceeded 100 °C, the adsorption amount of PS pellets did not change much. Therefore, in subsequent experiments, we set the adsorption temperature to 100 °C. This also shows that lithium niobate does not require high pyroelectric temperature, and a relatively low temperature can produce strong adsorption force, which has the advantage of low energy consumption when used as an air filter material.
实施例2、铌酸锂储电能力Embodiment 2, lithium niobate storage capacity
裁取若干片面积相同(1cm×2cm)的铌酸锂晶片清洗干净，放于洁净的培养皿中，同时置于烘箱中，加热至100℃后，待烘箱温度降至室温后取出。随后每隔24h取出一片做吸附实验，并记录和观察吸附量的变化，此方法保证了每一片铌酸锂都是在同一初始条件下的自然衰减。Cut several pieces of lithium niobate wafers with the same area (1cm×2cm), clean them, put them in a clean Petri dish, and put them in an oven at the same time. After heating to 100°C, take them out after the oven temperature drops to room temperature. Then take out one piece every 24 hours for adsorption experiment, and record and observe the change of adsorption amount. This method ensures that each piece of lithium niobate is naturally attenuated under the same initial conditions.
图3为具有同一初始加热条件(100℃)的铌酸锂晶片在加热后1h(烘箱内冷却至室温的时间)、25h、73h和121h对PS小球的吸附图。其中，图(a)－图(d)分别对应加热后1h、25h、73h和121h，铌酸锂晶片对PS小球的吸附图。Figure 3 is the adsorption graph of PS pellets on lithium niobate wafers with the same initial heating conditions (100°C) at 1h (the time for cooling to room temperature in the oven), 25h, 73h and 121h after heating. Among them, Figures (a) to (d) correspond to the adsorption diagrams of lithium niobate wafers on PS pellets at 1h, 25h, 73h and 121h after heating, respectively.
由图可知：随着时间的推移，在开始的两天内，铌酸锂晶片表面电荷衰减较慢，吸附PS小球量没有发生明显改变；而在随后的几天里，铌酸锂的表面电荷存在明显衰减，到第6天已经失去了对PS小球的吸附能力。与聚合物驻极体的电荷的快速衰减相比，铌酸锂具有优良的储电能力。因此，通过一次热释电就可以在很长的一段时间内保持对大气颗粒物的吸附能力。It can be seen from the figure that as time goes by, in the first two days, the surface charge of lithium niobate wafer decays slowly, and the amount of adsorbed PS pellets does not change significantly; while in the following days, the surface charge of lithium niobate wafer There was obvious attenuation, and the adsorption ability to PS pellets had been lost by the 6th day. Lithium niobate has excellent electricity storage capacity compared with the rapid decay of the charge of polymer electret. Therefore, the ability to adsorb atmospheric particulate matter can be maintained for a long period of time through one pyroelectric discharge.
实施例3、铌酸锂晶片热释电性质Embodiment 3, pyroelectric properties of lithium niobate wafer
由于铌酸锂晶体厚度较大，热释电产生的表面电荷无法通过原子力测量表面电势的方法表征，因此，本发明通过热释电后铌酸锂对于呈负电性的聚苯乙烯小球的吸附间接表征其表面电势。不同加热条件下，铌酸锂均能吸附粒径300μm的PS小球。Due to the large thickness of lithium niobate crystals, the surface charge generated by pyroelectricity cannot be characterized by the method of measuring the surface potential by atomic force. Therefore, the present invention uses lithium niobate for the adsorption of negatively charged polystyrene pellets Indirectly characterize its surface potential. Under different heating conditions, lithium niobate can adsorb PS pellets with a particle size of 300 μm.
图4为加热至不同温度的铌酸锂对PS小球的吸附图。其中，a，b，c对应的加热后的铌酸锂的温度分别为100℃、150℃和200℃。Fig. 4 is the adsorption diagram of lithium niobate heated to different temperatures on PS pellets. Wherein, a, b, and c correspond to the temperatures of the heated lithium niobate being 100° C., 150° C. and 200° C., respectively.
由图可知：加热后的铌酸锂，表面呈现大量的正电荷，有较强库仑作用，表现出对PS小球极强的吸附作用。It can be seen from the figure that the heated lithium niobate has a large amount of positive charge on the surface, has a strong Coulomb effect, and shows a strong adsorption effect on PS pellets.
实施例4、铌酸锂吸附大气中细微颗粒物的粒径分析Example 4, Particle size analysis of fine particles in the atmosphere adsorbed by lithium niobate
将铌酸锂切成1cm×1cm大小，在重度雾霾天气时，将切好的铌酸锂晶片放于热台上加热，至加热后的铌酸锂晶片的温度为100℃，然后将整个装置放于室外100℃下持续加热，吸附大气中的雾霾成分以做分析，吸附时间为10h。Cut the lithium niobate into 1cm×1cm size, put the cut lithium niobate wafer on the hot stage and heat it until the temperature of the heated lithium niobate wafer is 100°C in heavy haze weather, then cut the whole The device is placed outdoors at 100°C for continuous heating to absorb the smog components in the atmosphere for analysis. The adsorption time is 10 hours.
图5为雾霾天气下，铌酸锂吸附空气颗粒的SEM图。Figure 5 is an SEM image of lithium niobate adsorbing air particles in haze weather.
图6为雾霾天气下，铌酸锂吸附空气颗粒的AFM图。Figure 6 is an AFM image of lithium niobate adsorbing air particles in haze weather.
从图中可以看到，铌酸锂能够对雾霾天气，空气中的各种尺寸微粒，包括粉尘，PM10，PM2.5和亚微米颗粒都能够有效的吸附。吸附的颗粒物粒径分布范围大，粒径尺寸范围包括几百纳米至几十微米。这说明静电吸附对于颗粒物的粒径没有选择性，因此能够在很大程度上吸附PM2.5及以下尺寸的颗粒物。It can be seen from the figure that lithium niobate can effectively adsorb various sizes of particles in the air, including dust, PM10 , PM2.5 and submicron particles in haze weather. The particle size distribution range of the adsorbed particles is large, and the size range of particle size ranges from hundreds of nanometers to tens of microns. This shows that electrostatic adsorption has no selectivity for particle size, so it can adsorb PM2.5 and below particles to a large extent.
实施例5、铌酸锂吸附大气中细微颗粒物的成分分析Example 5, Composition Analysis of Lithium Niobate Adsorption of Fine Particles in the Air
将铌酸锂热释电后和未释电的铌酸锂同时放置于有雾霾存在的大气中，并利用EDX能谱，X射线光电子能谱(XPS)以及电感耦合等离子体与质谱联用(ICP-MS)对所吸附的颗粒物进行元素成分分析。Lithium niobate pyroelectrically discharged and undischarged lithium niobate were placed in the atmosphere with smog at the same time, and used EDX energy spectroscopy, X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma coupled with mass spectrometry (ICP-MS) for elemental composition analysis of the adsorbed particles.
图7为铌酸锂吸附空气颗粒的EDS分析图。Fig. 7 is an EDS analysis diagram of lithium niobate adsorbing air particles.
由图7可知：O，Na，Al等元素有明显的峰值，可确定为吸附颗粒物所含元素。该结果与报道的雾霾颗粒中的元素成分大致相符，说明所吸附的颗粒确为空气中的雾霾颗粒。It can be seen from Figure 7 that: O, Na, Al and other elements have obvious peaks, which can be determined as the elements contained in the adsorbed particulate matter. This result is roughly consistent with the elemental composition in the reported haze particles, indicating that the adsorbed particles are indeed haze particles in the air.
所检测出的元素及含量见表1。The detected elements and their contents are listed in Table 1.
表1EDS分析的空气颗粒所含元素种类和含量Table 1 Types and contents of elements contained in air particles analyzed by EDS
图8为铌酸锂吸附颗粒的XPS分析图。Fig. 8 is an XPS analysis diagram of lithium niobate adsorption particles.
结果显示，所吸附的颗粒中含有Si，Zn，O，S，Ca，C，Fe，N等元素，该结果与EDS结果相符合。The results show that the adsorbed particles contain Si, Zn, O, S, Ca, C, Fe, N and other elements, which is consistent with the EDS results.
考虑到EDS和XPS灵敏度较低的问题，进一步利用ICP-MS对热释电后和未释电的铌酸锂在相同条件下吸附的样品进行分析，结果如表2所示。Considering the problem of low sensitivity of EDS and XPS, ICP-MS was further used to analyze the pyrocharged and undischarged lithium niobate samples adsorbed under the same conditions, and the results are shown in Table 2.
表2ICP-MS对铌酸锂吸附的空气颗粒所含元素的分析结果Table 2 ICP-MS analysis results of elements contained in air particles adsorbed by lithium niobate
结果显示，Co，Zr，Ag，Sn，Sb，Au，Hg，Pb，In，Mo等元素的样品信号强度明显高于空白对照样品的信号强度，为吸附颗粒所含元素。这与大量报道的关于空气颗粒，尤其是PM2.5成分的ICP-MS测试结果一致。The results show that the signal intensity of Co, Zr, Ag, Sn, Sb, Au, Hg, Pb, In, Mo and other elements is significantly higher than that of the blank control sample, which are elements contained in the adsorption particles. This is consistent with the widely reported ICP-MS test results on air particles, especially PM2.5 components.
这些检测结果充分说明，利用铌酸锂吸附的物质确为空气污染颗粒物，证实了铌酸锂用作空气过滤材料的可行性。These test results fully demonstrate that the substances adsorbed by lithium niobate are indeed air pollution particles, which confirms the feasibility of using lithium niobate as an air filter material.
实施例6、铌酸锂热释电寿命测试Embodiment 6, lithium niobate pyroelectric life test
本发明中利用同一片铌酸锂晶片，加热至100℃后，随即对PS小球做吸附实验。待吸附量达到饱和后，用水清洗铌酸锂晶片上的PS小球，与此同时，水也可以将铌酸锂表面的电荷中和。如此反复多次，并记录下实验结果以作对比。In the present invention, the same lithium niobate wafer is used, and after being heated to 100° C., adsorption experiments are performed on PS pellets. After the adsorption amount reaches saturation, wash the PS pellets on the lithium niobate wafer with water, and at the same time, water can also neutralize the charge on the lithium niobate surface. Repeat this many times, and record the experimental results for comparison.
图9为铌酸锂反复加热至100℃时，对PS小球吸附情况的对比图。其中，a、b、c、d所对应的加热次数分别为50、100、150和200次。Figure 9 is a comparison chart of the adsorption of PS pellets when lithium niobate is repeatedly heated to 100°C. Wherein, the heating times corresponding to a, b, c, and d are 50, 100, 150, and 200 times, respectively.
从图中可以观察到，反复加热吸附50、100、150和200次后的铌酸锂对PS小球的吸附没有明显的变化，充分证明了铌酸锂的介电损耗小，可以用于反复的加热和清洗，且清洗比较容易，使用寿命长。It can be observed from the figure that the adsorption of lithium niobate to PS pellets after repeated heating and adsorption for 50, 100, 150 and 200 times has no obvious change, which fully proves that the dielectric loss of lithium niobate is small and can be used for repeated Heating and cleaning, and cleaning is relatively easy, long service life.
铌酸锂这种可重复释电吸附的特性弥补了传统过滤材料不能重复使用和清洗困难的缺陷，体现了铌酸锂用作空气过滤材料的可行性和优点。The characteristics of lithium niobate, which can be repeatedly discharged and adsorbed, make up for the shortcomings of traditional filter materials that cannot be reused and are difficult to clean, reflecting the feasibility and advantages of lithium niobate as an air filter material.
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| CN201410242576.9ACN105195325B (en) | 2014-06-03 | 2014-06-03 | Application of the lithium niobate pyroelectricity material based on temperature regulation and control in Atmospheric particulates are adsorbed |
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