CN104785777A - Method for preparing compounds of iron nano-particles coated with carbon nano tube/graphite - Google Patents
Method for preparing compounds of iron nano-particles coated with carbon nano tube/graphite Download PDFInfo
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Abstract
采用等离子体增强化学气相沉积技术，通过控制CH4和H2的含量，以沉积在硅片上的Co（Fe, Ni）颗粒作为催化剂来合成碳纳米管，以此为基体，合成了碳纳米管/石墨包覆的铁纳米颗粒的复合物；沉积过程中发现，随着沉积时间的延长，碳纳米管上涂覆了越来越多的球形的纳米颗粒，颗粒直径在1-30nm之间，经证实是石墨包覆着纳米铁颗粒；碳纳米管/石墨包覆的铁纳米颗粒的复合物在室温下表现出典型的软铁磁特性，饱和磁化强度为80emu/g，与块体的Fe的矫顽力（1Oe）相比，所制备复合物的矫顽力增大到60Oe。
Using plasma-enhanced chemical vapor deposition technology, by controlling the content of CH 4 and H 2 , using Co(Fe, Ni) particles deposited on silicon wafers as a catalyst to synthesize carbon nanotubes, and using this as a substrate, carbon nanotubes were synthesized A composite of tube/graphite-coated iron nanoparticles; during the deposition process, it was found that as the deposition time prolongs, more and more spherical nanoparticles are coated on the carbon nanotubes, and the particle diameter is between 1-30nm , it has been confirmed that graphite is coated with nano-iron particles; the composite of carbon nanotubes/graphite-coated iron nanoparticles exhibits typical soft ferromagnetic properties at room temperature, with a saturation magnetization of 80emu/g, which is comparable to that of the bulk Compared with the coercive force of Fe (1Oe), the coercive force of the as-prepared composite increases to 60Oe.
Description
技术领域 technical field
本发明涉及一种制备碳纳米管/石墨包覆的铁纳米颗粒的复合物的方法，更具体的说，本发明以单晶硅片作为基底，Co（Fe, Ni）颗粒作为催化剂来合成碳纳米管，通过控制CH4和H2的含量和沉积时间，制备出碳纳米管/石墨包覆的铁纳米颗粒的复合物。 The invention relates to a method for preparing a composite of carbon nanotubes/graphite-coated iron nanoparticles. More specifically, the invention uses a single crystal silicon wafer as a substrate and Co(Fe, Ni) particles as a catalyst to synthesize carbon nanotubes, composites of carbon nanotubes/graphite-coated iron nanoparticles were prepared by controlling the contents of CH4 and H2 and the deposition time.
背景技术 Background technique
二十多年来，碳纳米管因独特的物理、化学性能、高的比表面积、高的热稳定性、高电导率而受到了人们的极大关注，将金属纳米颗粒涂覆在碳纳米管上从而获得新颖的复合物，此复合材料具有有气敏、催化、传导和磁性功能；由于金属铁、钴、镍等磁性纳米颗粒在空气中或酸性环境中是不稳定的，近年来人们一直在广泛探索如何在纳米金属颗粒表面包覆一层硅、有机聚合物或者碳等作为保护壳，然而，目前所面临的挑战是如何用一种简单的方法来合成尺寸可控的碳包覆的金属纳米颗粒。 For more than two decades, carbon nanotubes have attracted great attention due to their unique physical and chemical properties, high specific surface area, high thermal stability, and high electrical conductivity. Coating metal nanoparticles on carbon nanotubes In order to obtain a novel composite, this composite material has gas-sensing, catalytic, conductive and magnetic functions; because magnetic nanoparticles such as metal iron, cobalt, and nickel are unstable in the air or in an acidic environment, people have been researching them in recent years. In the extensive exploration of how to coat a layer of silicon, organic polymers or carbon on the surface of metal nanoparticles as a protective shell, however, the current challenge is how to use a simple method to synthesize carbon-coated materials with controllable size. metal nanoparticles.
发明内容 Contents of the invention
本发明的目的在于，从以上背景出发，提出一种简单有效的制备碳纳米管/石墨包覆的铁纳米颗粒的复合物的方法，首先通过等离子体增强化学气相沉积 （plasma enhanced chemical vapor deposition, PECVD）作为手段，以甲烷和氢气作为反应气体，制备出碳纳米管/石墨包覆的铁纳米颗粒的复合物。 The object of the present invention is to, starting from the above background, propose a simple and effective method for preparing a composite of carbon nanotubes/graphite-coated iron nanoparticles, first through plasma enhanced chemical vapor deposition (plasma enhanced chemical vapor deposition, PECVD) was used as a means to prepare carbon nanotube/graphite-coated iron nanoparticles composites by using methane and hydrogen as reaction gases.
可实现上述目的的本发明的制备方法的特征是：在等离子体增强化学气相沉积的方法下，以硅片基片为基底，通过CH4和H2的流量比固定在5-8/60-80sccm区间，沉积时间分别为5-25min，在750-850℃，制备出碳纳米管/石墨包覆的铁纳米颗粒的复合物。 The feature of the preparation method of the present invention that can realize the above-mentioned purpose is: under the method for plasma-enhanced chemical vapor deposition, with the silicon chip substrate as the base, by CH And H The flow ratio is fixed at 5-8/60- In the interval of 80sccm, the deposition time is 5-25min respectively, and the composite of carbon nanotube/graphite-coated iron nanoparticle is prepared at 750-850°C.
本发明的基本技术方案的概括如下：The summary of basic technical solution of the present invention is as follows:
选用单晶硅片作为基片，使用烃类气体甲烷作为碳源气体，同时通入氢气作为反应气体，控制反应温度和时间，从而制备出碳纳米管/石墨包覆的铁纳米颗粒的复合物。 A single crystal silicon wafer is selected as the substrate, the hydrocarbon gas methane is used as the carbon source gas, and hydrogen gas is introduced as the reaction gas at the same time, and the reaction temperature and time are controlled to prepare a composite of carbon nanotubes/graphite-coated iron nanoparticles .
本发明的具体技术参数及最优选取方案介绍如下：Concrete technical parameter of the present invention and optimum selection scheme are introduced as follows:
本发明中碳纳米管/石墨包覆的铁纳米颗粒的复合物的制备，选取硅片作为基片，优选等离子体增强化学气相沉积技术。该过程主要可以分为三个步骤： In the preparation of the composite of carbon nanotubes/graphite-coated iron nanoparticles in the present invention, a silicon wafer is selected as a substrate, and plasma enhanced chemical vapor deposition technology is preferred. The process can be divided into three main steps:
1）使用磁控溅射技术沉积在硅片上的Co（Fe, Ni）颗粒作为合成碳纳米管的催化剂，在碳纳米管的基体上，合成了石墨包覆的铁纳米颗粒。 1) Co(Fe, Ni) particles deposited on silicon wafers by magnetron sputtering technology were used as catalysts for the synthesis of carbon nanotubes, and graphite-coated iron nanoparticles were synthesized on the substrate of carbon nanotubes.
2）制备碳纳米管/石墨包覆的铁纳米颗粒的复合物的过程中，取两端被厚钢板密封的陶瓷管，在两片钢板的中心位置分别钻一个小孔，将高纯度的二茂铁分别放入在陶瓷管，然后，将陶瓷管的两端用两片薄的钢板封住，用短而细小的铝线将薄的钢板牢牢地固定在陶瓷管上，以防止二茂铁在升温过程中快速挥发。将事先沉积在硅片上的碳纳米管放在气流下端，距离陶瓷管4mm左右。随着温度的升高，我们通过反应室的窗口可以看到铝线逐渐熔化，在800℃附近，我们发现两块薄钢板开始慢慢偏离陶瓷管两端，此时，二茂铁分解出来的铁原子将会在碳纳米管的管壁上快速聚集成铁的纳米小颗粒，我们开启射频电源，调节功率为200-240W，调节好基底温度和沉积时间以及甲烷和氢气的流量比。 2) In the process of preparing the composite of carbon nanotubes/graphite-coated iron nanoparticles, take a ceramic tube sealed by thick steel plates at both ends, drill a small hole in the center of the two steel plates, and put high-purity di Put the ferrocene into the ceramic tube respectively, and then seal the two ends of the ceramic tube with two thin steel plates, and use short and thin aluminum wires to firmly fix the thin steel plate on the ceramic tube to prevent ferrocene Iron evaporates rapidly during heating. Place the carbon nanotubes deposited on the silicon wafer in advance at the lower end of the airflow, about 4mm away from the ceramic tube. As the temperature rises, we can see that the aluminum wire is gradually melting through the window of the reaction chamber. At around 800°C, we find that the two thin steel plates begin to slowly deviate from the two ends of the ceramic tube. At this time, the ferrocene decomposed Iron atoms will quickly gather on the tube wall of carbon nanotubes to form small iron nanoparticles. We turn on the radio frequency power supply, adjust the power to 200-240W, and adjust the substrate temperature and deposition time as well as the flow ratio of methane and hydrogen.
3）甲烷气体与氢气合理配比，即CH4/H2在5-8/60-80sccm区间。调整反应气压，反应时间，使反应原料充分离化、分解、转变成活性基团, 合成了碳纳米管/石墨包覆的铁纳米颗粒的复合物。通过控制反应时间，达到控制石墨包覆Fe颗粒的直径。 3) The ratio of methane gas to hydrogen is reasonable, that is, CH 4 /H 2 is in the range of 5-8/60-80sccm. Adjust the reaction pressure and reaction time to fully ionize, decompose and convert the reaction raw materials into active groups, and synthesize the composite of carbon nanotubes/graphite-coated iron nanoparticles. By controlling the reaction time, the diameter of graphite-coated Fe particles can be controlled.
本发明中，在碳纳米管/石墨包覆的铁纳米颗粒的复合物的制备过程中，碳源气体优选甲烷，背底压强应小于10Pa，以保证碳纳米管/石墨包覆的铁纳米颗粒的复合物的纯度。 In the present invention, in the preparation process of the composite of iron nanoparticles coated with carbon nanotubes/graphite, the carbon source gas is preferably methane, and the back-bottom pressure should be less than 10Pa to ensure that the carbon nanotubes/graphite-coated iron nanoparticles the purity of the complex.
本发明中，在碳纳米管/石墨包覆的铁纳米颗粒的复合物的制备过程中，步骤1）的升温过程，气体优选氢气。氢气升温处理的目的是为了更彻底的排除氧氮等杂质气体，从而为后续的等离子体化学气相沉积过程提供条件，以得到高纯度的碳纳米管/石墨包覆的铁纳米颗粒的复合物。 In the present invention, in the process of preparing the composite of carbon nanotubes/graphite-coated iron nanoparticles, in the heating process of step 1), the gas is preferably hydrogen. The purpose of hydrogen heating treatment is to more thoroughly remove impurity gases such as oxygen and nitrogen, thereby providing conditions for the subsequent plasma chemical vapor deposition process to obtain high-purity carbon nanotube/graphite-coated iron nanoparticles composites.
综上所述，本发明中优选技术参数的基本构成是：硅片基底材料在甲烷、氢气共存的条件下，通过等离子体放电作用，可以实现简单有效的碳纳米管/石墨包覆的铁纳米颗粒的复合物，其操作流程的简单化，有望投入到产业化当中，为工业生产、产品优化升级提供了条件。 In summary, the basic composition of the preferred technical parameters in the present invention is: under the condition of the coexistence of methane and hydrogen, the silicon chip base material can realize simple and effective carbon nanotube/graphite-coated iron nanometer through plasma discharge. The simplification of the operation process of the particle compound is expected to be put into industrialization, which provides conditions for industrial production and product optimization and upgrading.
本发明具有以下明显的优点：The present invention has the following obvious advantages:
1）首先，本发明中，硅片作为衬底材料，采用等离子体增强化学气相沉积的方法，直接在碳纳米管上沉积石墨包覆的铁纳米颗粒，且沉积时间短。大量球型的纳米颗粒涂覆在碳纳米管的管壁上，颗粒直径在1-30nm之间。 1) First, in the present invention, silicon wafer is used as the substrate material, and the method of plasma-enhanced chemical vapor deposition is used to directly deposit graphite-coated iron nanoparticles on carbon nanotubes, and the deposition time is short. A large number of spherical nanoparticles are coated on the walls of the carbon nanotubes, and the diameter of the particles is between 1-30nm.
2）其次，本发明中催化剂的选取，甲烷气体、氢气配比是经过反复实验测试得到的，并且可以重复实验参数，保证了实验操作可重复性。 2) Secondly, the selection of the catalyst in the present invention, the ratio of methane gas and hydrogen gas are obtained through repeated experiments and tests, and the experimental parameters can be repeated to ensure the repeatability of the experimental operation.
3）最后，本发明所制备的碳纳米管/石墨包覆的铁纳米颗粒的复合物的生长机理进行了解释。 3) Finally, the growth mechanism of the composite of carbon nanotubes/graphite-coated iron nanoparticles prepared in the present invention is explained.
具体实施方式：Detailed ways:
实施实例1： Implementation example 1:
1) 采用硅片为基底，利用PECVD，以Co（Fe、Ni）为催化剂，在氢气氛围中升温至800℃，升温速率为20℃/min,当到达该温度后，通入甲烷气体，使甲烷与氢气配比为6/80sccm，总压强控制在1200Pa； 1) Using silicon wafers as the substrate, using PECVD, using Co (Fe, Ni) as the catalyst, heating up to 800°C in a hydrogen atmosphere, and the heating rate is 20°C/min. When this temperature is reached, methane gas is introduced to make The ratio of methane to hydrogen is 6/80sccm, and the total pressure is controlled at 1200Pa;
2）在PECVD设备中，完成步骤1）后，开启射频电源，射频功率控制在230W，沉积时间为20min； 2) In the PECVD equipment, after completing step 1), turn on the RF power supply, control the RF power at 230W, and the deposition time is 20min;
3）反应结束后，继续通氢气至室温； 3) After the reaction is over, continue to pass hydrogen to room temperature;
根据上述发明的举例方法，可以制备出碳纳米管/石墨包覆的铁纳米颗粒的复合物，该材料具有如下特征： According to the example method of the above invention, a composite of carbon nanotubes/graphite-coated iron nanoparticles can be prepared, and the material has the following characteristics:
1）对通过上述发明所用方法得到的样品进行扫描（SEM）和透射电镜（TEM）表征，大量球型的纳米颗粒涂覆在碳纳米管的管壁上，颗粒直径在1-30nm之间。 1) Scanning (SEM) and transmission electron microscope (TEM) characterization of the sample obtained by the method used in the above invention shows that a large number of spherical nanoparticles are coated on the tube wall of carbon nanotubes, and the diameter of the particles is between 1-30nm.
2）对通过上述发明所用方法得到的样品进行透射电镜分析，是沉积20min的碳纳米管/碳包覆的Fe纳米颗粒复合物的透射电镜图，从图中我们可以看出，大量球型的纳米颗粒涂覆在碳纳米管的管壁上，颗粒直径在1-30nm之间。从高分辨透射电镜图中可以看出，复合物中的碳纳米管属于多壁碳纳米管，碳管的碳原子层间距大约为0.34nm，与纯石墨的原子层之间的间距基本相等，包覆的Fe纳米颗粒近似球形结构。 2) TEM analysis of the sample obtained by the method used in the above invention is a TEM image of the carbon nanotube/carbon-coated Fe nanoparticle composite deposited for 20 minutes. From the figure, we can see that a large number of spherical Nanoparticles are coated on the tube wall of carbon nanotubes, and the particle diameter is between 1-30nm. It can be seen from the high-resolution transmission electron microscope that the carbon nanotubes in the composite belong to multi-walled carbon nanotubes, and the carbon atomic layer spacing of the carbon tubes is about 0.34nm, which is basically the same as that of pure graphite. The coated Fe nanoparticles have an approximate spherical structure.
3）我们对碳纳米管/石墨包覆的Fe纳米颗粒复合物进行了SAED表征，衍射环中（110）、（200）、（211）、（220）晶面的存在证明了Fe的结构是体心立方结构，在碳纳米管的管壁上存在石墨包覆的Fe纳米颗粒。 3) We performed SAED characterization of the carbon nanotube/graphite-coated Fe nanoparticle composite, and the existence of (110), (200), (211), (220) crystal planes in the diffraction ring proved that the structure of Fe is Body-centered cubic structure, graphite-coated Fe nanoparticles exist on the walls of carbon nanotubes.
根据上述发明的举例方法，可以实现碳纳米管/石墨包覆的铁纳米颗粒的复合物的制备，该材料具有如下特征： According to the exemplifying method of the above invention, the preparation of a composite of carbon nanotubes/graphite-coated iron nanoparticles can be realized, and the material has the following characteristics:
1）对通过上述发明所用方法得到的碳纳米管/石墨包覆的铁纳米颗粒的复合物进行扫描电镜（SEM）观察，发现石墨包覆的铁纳米颗粒的复合物，且均匀地分布在碳纳米管上； 1) Scanning electron microscope (SEM) observation of the composite of carbon nanotubes/graphite-coated iron nanoparticles obtained by the method used in the above invention, it was found that the composite of graphite-coated iron nanoparticles was evenly distributed on the carbon on nanotubes;
2）对通过上述发明所用方法进行透射电镜（TEM）和SAED表征，证实了碳纳米管/石墨包覆的铁纳米颗粒的复合物。 2) The transmission electron microscopy (TEM) and SAED characterization of the method used in the above invention confirmed the composite of carbon nanotubes/graphite-coated iron nanoparticles.
3）对通过上述发明所用方法得到碳纳米管/石墨包覆的铁纳米颗粒的复合物生长机理进行了分析。基于气固液模型，随着真空室温度的升高，二茂铁将快速分解成Fe原子，由于Fe和C有很好的亲和力，Fe原子将沉积在预先制备的碳纳米管上，形成了非常细小的Fe颗粒，并且，C易融于Fe颗粒中。由于Fe纳米颗粒的熔点低于块体的Fe，我们推测，Fe团簇在二茂铁分解的过程中是以液态形势存在的。这些液态的Fe团簇在表面张力的作用下将形成液态的Fe纳米小颗粒，随着分解反应的进行，Fe纳米颗粒将长大，由于在离化的CH4和H2的环境中，这些Fe颗粒将成为吸附碳基团的位置。 3) The composite growth mechanism of carbon nanotubes/graphite-coated iron nanoparticles obtained by the method used in the above invention was analyzed. Based on the gas-solid-liquid model, as the temperature of the vacuum chamber increases, ferrocene will rapidly decompose into Fe atoms, and due to the good affinity between Fe and C, the Fe atoms will be deposited on the pre-prepared carbon nanotubes to form a Very fine Fe particles, and C is easily fused in Fe particles. Since the melting point of Fe nanoparticles is lower than that of bulk Fe, we speculate that Fe clusters exist in a liquid state during the decomposition of ferrocene. These liquid Fe clusters will form small liquid Fe nanoparticles under the action of surface tension, and as the decomposition reaction proceeds, Fe nanoparticles will grow up, because in the environment of ionized CH 4 and H 2 , these Fe particles will be the sites for adsorbed carbon groups.
附图说明： Description of drawings:
图1-3是实施实例1中的样品进行的SEM测试，图1是原始碳纳米管SEM图片，从图中可以看出，碳纳米管的直径和长度分别约为30nm和2mm。碳纳米管的生长是在短时间内完成的，沉积时间约为10min，进一步延长沉积时间，发现碳纳米管的长度和直径基本不发生变化。图2和图3为800oC下，在H2和CH4的离化状态下，分别用时8和20min在已制备出的碳纳米管上生长石墨包覆的铁纳米颗粒的SEM图片。从图中可以看出，随着沉积时间的延长，碳纳米管上涂覆了越来越多的球形的纳米颗粒。其形成过程，在800oC高温下，二茂铁将分解出大量的Fe原子，由于陶瓷管的端口位于进气口的下方，所以，流动的反应气体对Fe原子具有一定的输运作用，大量的Fe原子瞬间吸附在碳纳米管的管壁上将发生碰撞、聚集、最后成为Fe的纳米小颗粒。在高氢含量的等离子体环境中，氢的刻蚀作用将导致纳米尺寸的Fe颗粒均匀地分散在碳纳米管的管壁上。在离化的CH4和H2的气氛下，沉积的碳将包覆Fe颗粒，这一点可从TEM图中得到证实。 Figures 1-3 are the SEM tests carried out on the samples in Example 1. Figure 1 is the SEM picture of the original carbon nanotubes. It can be seen from the figure that the diameter and length of the carbon nanotubes are about 30nm and 2mm respectively. The growth of carbon nanotubes is completed in a short time, and the deposition time is about 10 minutes. Further prolonging the deposition time, it is found that the length and diameter of carbon nanotubes basically do not change. Figure 2 and Figure 3 are the SEM pictures of graphite-coated iron nanoparticles grown on the prepared carbon nanotubes in the ionized state of H 2 and CH 4 at 800 o C for 8 and 20 min, respectively. It can be seen from the figure that as the deposition time prolongs, more and more spherical nanoparticles are coated on the carbon nanotubes. During its formation, at a high temperature of 800 o C, ferrocene will decompose a large number of Fe atoms. Since the port of the ceramic tube is located below the air inlet, the flowing reaction gas has a certain transport effect on Fe atoms. A large number of Fe atoms are instantly adsorbed on the wall of the carbon nanotubes to collide, aggregate, and finally become Fe nanoparticles. In a plasma environment with high hydrogen content, the etching effect of hydrogen will lead to the uniform dispersion of nanometer-sized Fe particles on the walls of CNTs. Under an atmosphere of ionized CH4 and H2 , the deposited carbon will coat the Fe particles, which can be confirmed from the TEM images.
图4-6是实施实例1中的样品进行的TEM测试。图4是沉积20min的碳纳米管/碳包覆的Fe纳米颗粒复合物的透射电镜图，从图中我们可以看出，大量球型的纳米颗粒涂覆在碳纳米管的管壁上，颗粒直径在1-30nm之间。从高分辨透射电镜图5-6中可以看出，复合物中的碳纳米管属于多壁碳纳米管，碳管的碳原子层间距大约为0.34nm，与纯石墨的原子层之间的间距基本相等，包覆的Fe纳米颗粒近似球形结构。 4-6 are TEM tests carried out on the samples in Example 1. Figure 4 is a transmission electron microscope image of a carbon nanotube/carbon-coated Fe nanoparticle composite deposited for 20 min. From the figure, we can see that a large number of spherical nanoparticles are coated on the tube wall of the carbon nanotube, and the particles The diameter is between 1-30nm. It can be seen from the high-resolution transmission electron microscope Figure 5-6 that the carbon nanotubes in the composite belong to multi-walled carbon nanotubes, and the carbon atomic layer spacing of the carbon tubes is about 0.34nm, which is the distance between the atomic layers of pure graphite. Basically equal, the coated Fe nanoparticles have an approximate spherical structure.
图7是以Co作为催化剂合成碳纳米管的磁滞回线，从图中我们可以看出，碳纳米管表现出很强的抗磁特性。 Figure 7 is the hysteresis loop of carbon nanotubes synthesized with Co as a catalyst. From the figure, we can see that carbon nanotubes exhibit strong diamagnetic properties.
图8是碳纳米管/石墨包覆的铁纳米颗粒复合物的磁滞回线，从图可以看出，此复合物表现出典型的软铁磁特性，并且，其磁滞回线呈S型闭合对称的特点，图中显示的饱和磁化强度为80emu/g。由于碳纳米管上金属颗粒的小尺寸效应，其饱和磁化强度较块体的Fe（222emu/g）有所减少，减少的原因是无磁性的碳与具有无序磁化方向的纳米颗粒共存所导致。与块状Fe的矫顽力（1Oe）相比，我们所制备的复合物矫顽力增大到60Oe。 Figure 8 is the hysteresis loop of the carbon nanotube/graphite-coated iron nanoparticle composite. It can be seen from the figure that this composite exhibits typical soft ferromagnetic properties, and its hysteresis loop is S-shaped The characteristics of closed symmetry, the saturation magnetization shown in the figure is 80emu/g. Due to the small size effect of metal particles on carbon nanotubes, its saturation magnetization is reduced compared with that of bulk Fe (222emu/g). The reason for the reduction is the coexistence of non-magnetic carbon and nanoparticles with disordered magnetization directions. . Compared with the coercive force of bulk Fe (1Oe), the coercive force of our as-prepared composite increases to 60Oe.
基于气固液模型，我们可以理解碳纳米管/石墨包覆的铁纳米颗粒复合物形成过程。虽然人们通过湿化学方法在碳纳米管的管壁上成功涂覆了各种各样纳米颗粒，这些纳米颗粒的尺寸在几纳米到十几纳米之间，但是，很难将特别小的纳米颗粒均匀稳定地涂覆在碳纳米管上。而在PECVD实验过程中，我们克服了这一难点。在沉积过程中，由于等离子体的刻蚀作用将导致Fe纳米颗粒的生长受到抑制，同时，等离子体中碳氢基团分解出来的碳原子将溶入Fe的颗粒中，当CH4/H2流量比很小时，碳将在铁纳米颗粒中难以达到过饱和状态，不利于碳纳米管的形成，因此，在Fe纳米颗粒的表面易于形成石墨层，这些石墨层将包覆Fe纳米小颗粒，体系自由能降低。在实验中，我们发现CH4/H2的流量比起决定作用。 Based on the gas-solid-liquid model, we can understand the carbon nanotube/graphite-coated iron nanoparticle composite formation process. Although people have successfully coated various nanoparticles on the tube wall of carbon nanotubes by wet chemical methods, and the size of these nanoparticles is between a few nanometers and more than ten nanometers, it is difficult to coat particularly small nanoparticles Uniformly and stably coated on carbon nanotubes. In the PECVD experiment process, we have overcome this difficulty. During the deposition process, the growth of Fe nanoparticles will be inhibited due to the etching effect of the plasma. At the same time, the carbon atoms decomposed from the hydrocarbon groups in the plasma will dissolve into the Fe particles. When CH 4 /H 2 When the flow ratio is very small, carbon will be difficult to reach supersaturated state in iron nanoparticles, which is not conducive to the formation of carbon nanotubes. Therefore, graphite layers are easy to form on the surface of Fe nanoparticles, and these graphite layers will cover Fe nanoparticles. The free energy of the system decreases. In experiments, we found that the flow ratio of CH 4 /H 2 plays a decisive role.
本发明可用其他的不违背本发明的精神或主要特征的具体形式来概述。因此，无论从哪一点来看，本发明的上述实施方案都只能认为是对本发明的说明而不能限制本发明，权利要求书指出了本发明的范围，而上述的说明并未指出本发明的范围，因此，在与本发明的权利要求书相当的含义和范围内的任何改变，都应认为是包括在权利要求书的范围内。 The present invention may be embodied in other specific forms without departing from the spirit or main characteristics of the invention. Therefore, no matter from which point of view, the above-mentioned embodiments of the present invention can only be regarded as descriptions of the present invention and cannot limit the present invention, and the claims have pointed out the scope of the present invention, and the above description does not point out the scope of the present invention. Therefore, any change within the meaning and scope equivalent to the claims of the present invention should be considered to be included in the scope of the claims.
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| 徐强等: "碳纳米管基复合物的制备及性能研究", 《物理实验》 * |
| 杨光敏: "碳纳米管、纳米金刚石、空心碳球及其复合物的PECVD制备和特性研究", 《吉林大学博士学位论文》 * |
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