高取向碳纳米管薄膜和碳纳米管束薄膜的场发射性质研究

采用热解二茂铁/三聚氰氨混合物方法合成了高取向碳纳米管薄膜和碳纳米管束薄膜.二氧化硅基底上生长的碳纳米管具有一致的外部直径约22 nm和一致的长度约40μm;陶瓷基底上生长的碳纳米管具有变化的外部直径为10～90 nm和不同的长度约20～100 μm;合成的纳米管为多壁纯碳管并存在大量的缺陷和石墨断层;高取向碳纳米管薄膜的开启电场为3.9 V/μm,场增强因子为3000;碳纳米管束薄膜的开启电场为2.9 v/μm,场增强因子为5200.     

金刚石膜表面ZnO纳米棒制备及场发射性能研究

以硝酸锌为原料,乌洛托品为催化剂,采用水热法分别在自支撑金刚石膜及硅基底上制备了ZnO纳米棒。采用场发射扫描电子显微镜、X射线衍射、拉曼光谱、PL谱、场发射测试表征了ZnO纳米棒/硅及ZnO纳米棒/自支撑金刚石膜的形貌、尺寸及场发射性能。结果表明,在两种基底上制备的ZnO纳米棒均沿c轴方向生长,其中在自支撑金刚石膜上制备的ZnO纳米棒出现了尖端现象,并且具有更好的结晶度、纯度与更少的结构缺陷,其开启电场为6.8 V/μm,在11.9 V/μm的电场下,发射电流密度为0.20 m A/cm~2,场增强因子比在Si基底上制备的ZnO纳米棒的场发射性能高11.5倍。     

铁基碳纳米管复合材料的制备研究

利用催化裂解法成功地制备了铁基碳纳米管复合材料,并研究了制备温度、丙酮流速对碳纳米管生长的影响规律。试验采用场发射扫描电子显微镜对样品进行了表征与分析。研究结果表明:丙酮流速对碳纳米管的生长有重要影响,碳纳米管的质量随丙酮流速的提高均呈现出先提高后降低的规律。当制备温度为700℃,丙酮流速为2 m L/min时,制得的铁基碳纳米管复合材料碳纳米管分布均匀、与基体结合良好,此试验条件下碳纳米管的生长为顶部生长机理。但铁基碳纳米管复合材料的韧性、可塑性等性能还有待于进一步研究。     

碳纳米管场发射测试方法对其性能的影响

采用丝网印刷技术在金属基片上制备碳纳米管列阵薄膜,应用二极管结构对其场发射性能进行测试,并分析影响碳纳米管阴极场发射性能的因素。结果表明,随着测试次数的增加,碳纳米管阴极场发射性能会有一定程度的提高,同时场发射性能的稳定性增加;阴阳极距离15μm时,碳纳米管具有最好的场发射性能。     

碳纳米管/聚苯胺复合材料的原位合成及其形成机理

用竖式炉流动法，以二茂铁为催化剂，硫为助催化剂，苯为碳源通过催化裂解反应在1100～1200℃制备了直线形多壁碳纳米管，碳纳米管外径为20～50nm，内径10～30nm，长度50～1000μm。在碳纳米管表面原位合成了聚苯胺，制备出碳纳米管／聚苯胺一维纳米复合材料，复合材料的直径为50～60nm。X射线衍射及热重分析表明，原位合成的聚苯胺的结晶程度和热稳定性较高，聚苯胺在碳纳米管表面以枝晶状生长，探讨了聚苯胺在碳纳米管表面的形成机理。     

碳纳米管场发射测试方法对其性能的影响

采用丝网印刷技术在金属基片上制备碳纳米管列阵薄膜,应用二极管结构对其场发射性能进行测试,并分析影响碳纳米管阴极场发射性能的因素。结果表明,随着测试次数的增加,碳纳米管阴极场发射性能会有一定程度的提高,同时场发射性能的稳定性增加;阴阳极距离15μm时,碳纳米管具有最好的场发射性能。     

多孔结构碳酸钾的制备方法

公布了一种多孔结构碳酸钾的制备方法,具体步骤为：1）取粒径在100～1000μm的碳酸氢钾晶体,在100～500℃下焙烧;2）同时通入露点在0℃以下CO2干燥气体,气体温度为10—50℃。反应物在外加热式转窑中持续焙烧,以防止生成的碳酸钾和碳酸氢钾粘连。生成的多孔结构碳酸钾孔径在0．1～1．0μm,孔容≥0．08mL／g。     

二甲戊灵的GC和HPLC分析方法研究

采用气相色谱法和高效液相色谱法两种方法分别对二甲戊灵原药进行定量分析,气相色谱法以邻苯二甲酸二戊酯为内标物,采用HP-5石英毛细管色谱柱（30．0m×320μm×0．25μm）和FID检测器,色谱条件为柱箱采用程序升温,200℃保持0．5min,以10℃／min速率升至240℃,保持2．5min;进样口温度260℃,检测器温度250℃,气体流速为载气（N2）1ml／min,燃气（Hz）30ml／min,助燃气（Air）350ml／min,分流比1：40．本方法的变异系数、平均回收率、线性相关系数分别为0．0779％、100．06％、0．9999。高效液相色谱法中使用ZORBOX Eclipse XDB-C18150mm×4．6mm（i．d）不锈钢柱色谱柱,DAD检测器,以甲醇＋水=80＋20（V＋V）为流动相,检测波长为236nm。二甲戊灵的平均回收率为99．08％,方法变异系数为0．112%;,线性相关系数为0．9999。     

有机纤维增强的耐热型酚醛模塑料的研制

介绍了一种有机纤维增强的、可注塑成型的、热性能优越的酚醛模塑料EA—5555J的制备方法。酚醛模塑料采用有机纤维增强，使新产品的耐热温度可达到190℃以上，耐漏电痕迹CTI为3级，阻燃性等级为94V—0／1．6mm。     

生长温度及催化剂结构对碳纳米管形貌的影响

采用热CVD制备了图形化碳纳米管阵列薄膜。着重研究了生长温度、催化剂结构对碳纳米管形貌的影响。结果表明,当温度<800℃时,生长的碳纳米管纯度较低;当温度为850℃时,生长为碳纤维;当生长温度为800℃时,生长纯度较好的碳纳米管,但碳纳米管垂直性较差。采用Al/Fe催化剂结构,生长出图形化的阵列化碳纳米管薄膜。     

Carbon nanotubes grown on cobalt-containing amorphous carbon composite films

Carbon nanotubes (CNTs) have been produced on silicon wafer by filtered cathodic vacuum arc technique using cobalt-containing graphite targets followed by thermal chemical vapor deposition. The Co-containing amorphous carbon (a-C:Co) composite films have various contents of Co as a catalyst for CNTs growth. It is found that dense and random CNTs were grown on the a-C:Co composite film deposited using a 2 at.% Co-containing graphite target and nanoforest CNTs on the composite films using 5, 10 and 15 at.% Co-containing targets. The nanoforest CNTs using a 15 at.% Co-containing target have very good field emission properties with a low threshold field of 1.6 V/μm and a high and stable current density of 2.1 mA/cm² at 3 V/μm, which may result from the smaller diameter of CNTs. It is found that the field emission properties of the CNTs are significantly affected by the diameter of CNTs rather than its orientation.     

Synthesis and Enhanced Field-Emission of Thin-Walled,Open-Ended,and Well-Aligned N-Doped Carbon Nanotubes

Thin-walled, open-ended, and well-aligned N-doped carbon nanotubes (CNTs) on the quartz slides were synthesized by using acetonitrile as carbon sources. As-obtained products possess large thin-walled index (TWI, defined as the ratio of inner diameter and wall thickness of a CNT). The effect of temperature on the growth of CNTs using acetonitrile as the carbon source was also investigated. It is found that the diameter, the TWI of CNTs increase and the Fe encapsulation in CNTs decreases as the growth temperature rises in the range of 780–860°C. When the growth temperature is kept at 860°C, CNTs with TWI = 6.2 can be obtained. It was found that the filed-emission properties became better as CNT growth temperatures increased from 780 to 860°C. The lowest turn-on and threshold field was 0.27 and 0.49 V/μm, respectively. And the best field-enhancement factors reached 1.09 × 10⁵, which is significantly improved about an order of magnitude compared with previous reports. In this study, about 30 × 50 mm² free-standing film of thin-walled open-ended well-aligned N-doped carbon nanotubes was also prepared. The free-standing film can be transferred easily to other substrates, which would promote their applications in different fields.     

The effect of atmospheric pressure plasma treatment on the field emission characteristics of screen printed carbon nanotubes

The effects of pin-to-plate type atmospheric pressure plasma treatment on the field emission properties of screen printed carbon nanotubes(CNTs) were investigated using He(10 slm)/N₂(0.1 slm). The plasma treatment for 10 s decreased the turn-on field from 3.13 V/μm to 1.21 V/μm, increased the emission current, and increased the number of emission sites. When, the 10 s plasma treatment was also applied to the CNTs which were previously treated by a tape activation method, the number of emission sites were further increased, therefore, the emission uniformity was improved even though, the plasma treatment on the tape-activated CNTs increased the turn-on field slightly 0.76 V/μm to 1.25 V/μm due to the removal of long CNTs.     

Field emission properties from aligned carbon nanotube films with tetrahedral amorphous carbon coatings

Tetrahedral amorphous carbon (ta-C) film was coated on aligned carbon nanotube (CNT) films via filtered cathodic vacuum arc (FCVA) technique. Field electron emission properties of the CNT films and the ta-C/CNT films were measured in an ultra high vacuum system. The I–V measurements show that, with a thin ta-C film coating, the threshold electric field (E_thr) of CNTs can be significantly decreased from 5.74 V/μm to 2.94 V/μm, while thick ta-C film coating increased the E_thr of CNTs to around 8.20 V/μm. In addition, the field emission current density of CNT films reached 14.9 mA/cm² at 6 V/μm, while for CNTs film coated with thin ta-C film only 3.1 V/μm of applied electric field is required to reach equal amount of current density. It is suggested that different field emission mechanisms should be responsible for the distinction in field emission features of CNT films with different thickness of ta-C coating.     

Novel plasma chemical vapor deposition method of carbon nanotubes at low temperature for field emission display application

We developed a novel growth method of aligned carbon nanotubes. A high density plasma chemical vapor deposition (PECVD) has been employed to grow high-quality carbon nanotubes (CNTs) at low temperatures. High-density, aligned CNTs can be grown on Si and glass substrates. The CNTs were selectively-deposited on the patterned Ni catalyst layer, which was sputtered on Si. The CNTs exhibited a turn-on field of 0.9 V/μm and an emission current of 480 μA/cm² at a field of 3 V/μm.     

Excellent field emission characteristics from few-layer graphene–carbon nanotube hybrids synthesized using radio frequency hydrogen plasma sputtering deposition

The growth of few-layer graphene (FLG) on carbon nanotubes (CNTs) was realized by using radio frequency hydrogen plasma sputtering deposition. A defect nucleation mechanism and a two dimensional growth model of the FLG were proposed, and field emission characteristics of these FLG–CNT hybrids were studied. They show excellent field emission properties, with a low turn-on electric field (0.98 V/μm) and threshold field (1.51 V/μm), large field enhancement factor (～3980) and good stability behavior, which are much better than those of the as-grown CNT arrays. The sharp edges and the low work function of the hybrids are believed to be responsible for the improved field emission properties.     

Improvement of electron field emission from carbon nanotubes by Ar neutral beam treatment

To improve the field emission properties of screen printed carbon nanotube (CNT) films, an Ar neutral beam was used as one of the surface treatment techniques and the CNT field emission characteristics after the treatment were compared with those after Ar ion beam treatment. The Ar neutral beam treatment enhanced the field emission properties of the CNTs and by decreasing the turn-on field and by increasing emission sites. When the field emission properties were measured after the treatment for 10 s with an energy of 100 eV, the turn-on field decreased from 1.7 to 0.9 V/μm while that after the ion beam treatment increased from 1.7 to 2.8 V/μm showing damage of exposed CNTs due to the intensive bombardment by the positive ions in the beam. The neutral beam treatment appeared to expose more CNT field emitters from the CNT paste without cutting or severely damaging the already exposed long CNT emitters because there were no charged particles in the beam.     

The use of camphor-grown carbon nanotube array as an efficient field emitter

Three-dimensional growth of well-aligned high-purity multiwall carbon nanotubes (CNTs) is achieved on silicon, nickel-coated silicon and cobalt-coated silicon substrates by thermal decomposition of a botanical carbon source, camphor, with different catalyst concentrations. Field emission study of as-grown nanotubes in a parallel-plate diode configuration suggests them to be an efficient emitter with a turn-on field of ∼1 V/μm (for 10 μA/cm²) and a threshold field of ∼4 V/μm (for 10 mA/cm²). Maximum current density lies in a range of 20-30 mA/cm² at 5.6 V/μm with significant reversibility. Prolonged stability test of camphor-grown CNT emitters suggests a life time of ∼5 months under continuous operation. A new feature, metal-assisted electron emission from CNTs, has been addressed. Isolated nanotubes used as a cold cathode in a field emission microscope reveal the pentagonal emission sites and hence the atomic structure of the nanotube tips.     

Improved field emission properties of carbon nanotubes decorated with Ta layer

The field emission (FE) properties of vertically aligned carbon nanotube (CNT) arrays having a surface decorated with Ta layer were investigated. The CNTs with 6 nm thickness of Ta decoration showed improved FE properties with a low turn-on field of 0.64 V/μm at 10 μA/cm², a threshold field of 1.06 V/μm at 1 mA/cm² and a maximum current density of 7.61 mA/cm² at 1.6 V/μm. After Ta decoration, the increased emission centres and/or defect sites on the surface of CNTs improved the field enhancement factor. The work function of CNTs with Ta decoration measured with ultraviolet photoelectron spectroscopy decreased from 4.74 to 4.15 eV with increasing Ta thickness of 0–6 nm. The decreased work function and increased field enhancement factor were responsible for the improved FE properties of the vertically aligned CNTs. Moreover, a significant hysteresis in the cycle-testing of the current density with rising and falling electric field process was observed and attributed to the adsorption/desorption effect, as confirmed by the photoelectron spectrum.     

Catalyst-free,self-assembly,and controllable synthesis of graphene flake–carbon nanotube composites for high-performance field emission

Catalyst-free and self-assembled growth of graphene flakes (GFs) on carbon nanotube (CNT) arrays have been realized by using microwave plasma enhanced chemical vapor deposition. The shape of GFs was highly manipulated by adjusting the growth time, C concentration, and microwave power. We qualitatively discussed the nucleation and growth mechanism of GFs based on the growth parameter–GF shape studies. The field emission (FE) properties of graphene flake–carbon nanotube (GF–CNT) composites for different GF shapes were measured and found to be strongly influenced by the GF distribution. The optimal shape of GFs for FE had small scales, sharp edges, and sparse distribution on CNTs. The best FE properties with the optimal shape were observed with a low turn-on electric field of 0.73 V/μm and excellent stability, which are superior to those of the as-grown CNT arrays and GF–CNT composites covered by densely distributed GFs. We consider that the large aspect ratio of CNTs and the unique FE stability of GFs play a synergetic effect on the improved FE properties.