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1.
介绍了一种制备纳米石墨粉的新方法——负氧平衡炸药爆轰法. 对合成的黑粉产物进行x射线衍射分析,确认其为石墨结构,平均晶粒度为2.58 nm. 透射电子显微分析的结果表明,炸药爆轰法制备的黑粉为六方结构的纳米石墨粉,颗粒呈球形或椭球形. 用小角x射线散射法测定纳米石墨粉的粒度分布在1—50 nm,有92.6wt%的粉末粒度小于16 nm. 平均粒径为8.9 nm. 纳米石墨粉的比表面积约为500—650 m2/g. 在六面顶压机中用纳米石墨粉在Fe粉触媒的作用下进行金刚石的高压合成实验 关键词: 纳米石墨粉 爆轰 金刚石 合成  相似文献   

2.
 在酸含量不同的原材料中,通过爆轰的方法制备纳米石墨粉,并利用BET方程以及BJH方法对所得纳米石墨粉进行比表面积和孔径分布分析。分析结果表明,所得爆轰产物中有的比表面积大致为天然鳞片石墨的5.3~9.2倍,而且随酸含量的增大逐渐增大,产物的等温线中存在吸附滞后现象。其中,增大的比表面积主要由分布在3 nm至7 nm之间的孔引起的,而且在爆轰后,孔径4 nm左右的孔,其数量达到最大值。通过对纳米石墨粉的研究,分析了酸在爆轰过程中的积极作用,并为纳米石墨粉的进一步应用提供了结构信息。  相似文献   

3.
在酸含量不同的原材料中,通过爆轰的方法制备纳米石墨粉,并利用BET方程以及BJ H方法对所得纳米石墨粉进行比表面积和孔径分布分析。分析结果表明,所得爆轰产物中有的比表面积大致为天然鳞片石墨的5.3~9.2倍,而且随酸含量的增大逐渐增大,产物的等温线中存在吸附滞后现象。其中,增大的比表面积主要由分布在3 nm至7 nm之间的孔引起的,而且在爆轰后,孔径4 nm左右的孔,其数量达到最大值。通过对纳米石墨粉的研究,分析了酸在爆轰过程中的积极作用,并为纳米石墨粉的进一步应用提供了结构信息。  相似文献   

4.
炸药爆轰法制备的纳米石墨粉的拉曼光谱   总被引:7,自引:2,他引:5  
负氧平衡炸药爆轰法合成的纳米石墨粉,是一种新型的具有良好实用前景的纳米粉体材料。采用负氧平衡炸药梯恩梯(TNT),在分别充有氮气、氩气、二氧化碳等保护性气体、压力为0.25~2atm的密闭容器内爆轰制备了纳米石墨粉。用激光拉曼光谱对制备的样品进行了测试,结果表明样品为石墨结构。纳米石墨粉的Raman峰与块体石墨相比,其峰位向高波数方向偏移了约5cm^-1。纳米石墨粉Raman峰的半高宽约为22cm^-1,由此可计算出纳米石墨粉的颗粒大小为2.97~3.97nm。与高纯石墨Raman峰相比,纳米石墨粉的Raman峰由于尺寸效应出现了蓝移现象,并对此现象进行了讨论。用X射线衍射仪(XRD)和透射电子显微镜(TEM)测定了纳米石墨粉的物相,并对其颗粒粒径进行了估算,其结果为2.58nm(酸处理前)和1.86nm(酸处理后),与Raman光谱的结果基本吻合。  相似文献   

5.
采用气相爆轰法,以乙炔气体、氧气和五羰基铁为原料成功地合成了比表面积为253.857m~2/g的胶囊状碳纳米材料。对反应的前置实验九羰基二铁的热分解反应的研究表明,在60~140℃之间,九羰基二铁热分解为五羰基铁和十二羰基三铁。对爆轰产物进行了XRD、TEM和BET物理吸附实验,结果表明:产物XRD图谱石墨峰明显,产物主要为具有石墨化倾向的薄层胶囊状无定形碳结构;实验产物比表面积为253.857m~2/g,孔体积为0.940cm~3/g,平均孔径为2.731nm;吸附-脱附曲线回滞环类型为H3型,孔结构主要为颗粒堆积而形成的狭缝孔;爆轰产物比表面积较大,具有较强的吸附能力。证实了同样采用铁作为触媒,乙炔在不添加惰性气体作为缓冲剂的情况下,由于爆速过高而无法用于合成碳纳米管。  相似文献   

6.
 介绍了爆轰法合成碳包覆钴、镍纳米磁性颗粒研究的初步结果。以黑索今炸药为主体,加入钴、镍金属硝酸盐与有机碳源材料,在爆炸容器中氮气保护下用导爆管雷管引爆,成功地合成了碳包覆钴、镍纳米磁性颗粒。为了探求爆轰固体产物的形貌特征及性能,分别采用了TEM、XRD、VSM等测试手段对其进行表征。实验结果表明,爆轰产物中主要含有碳包覆纳米钴、纳米镍磁性颗粒,成球体或者椭球体,具有完好的核壳结构形貌。合成的碳包覆钴颗粒分布在30~50 nm之间,碳包覆的镍颗粒分布在25~60 nm之间,外层碳壳层主要由无定形碳和石墨构成。磁性测试表明,所得碳包金属钴、镍颗粒在室温下具有良好的软磁特性。  相似文献   

7.
岳兰平  何怡贞 《物理学报》1997,46(6):1212-1216
研究了不同颗粒尺寸的纳米Ge-SiO2镶嵌薄膜的室温荧光光谱以及不同激发光能量对荧光峰的影响.实验结果表明,沉积态Ge-SiO2薄膜样品在可见光区域不发光.退火后的样品(平均锗颗粒尺寸为3.2—6.0nm)在380—520nm波长范围内有明显的蓝光发射现象.当用λ=300nm的光激发,观测到中心波长为420nm(2.95eV)的光致荧光峰;而用633nm波长的光激发,谱图上出现中心波长分别为420和470nm的两个荧光峰.随着纳米锗颗粒尺寸的增加,光致荧光峰的相 关键词:  相似文献   

8.
 介绍了利用氢氧混合气体为原料、以四氯化钛为前驱体、气相爆轰制备纳米二氧化钛粉体的方法。利用XRD衍射结果分析证明,产物为金红石相和锐钛矿相的二氧化钛混晶,其晶粒尺度为纳米量级。通过XRD、SEM、TEM分析可以得出,粒子基本为球形,大部分粒子粒径为10~20 nm,也有少量的100 nm左右的粒子产生。分析后发现,反应发生在爆燃转爆轰的过程中和爆轰管中的湍流现象是导致大粒子产生的主要原因。在对在氢过量和氧过量两种状况下,对爆轰所产生的产物的形貌进行了对比,分析发现两种状况产生纳米二氧化钛粉末粒径分布和形貌并没有太大变化。  相似文献   

9.
为通过爆轰法合成纳米氧化铈,设计并制备了以Ce(NO3)3·6H2O为主要氧化剂的5种乳化炸药。综合考虑Ce(NO3)3含量对乳化炸药爆速的影响和纳米氧化铈的得率,筛选出适用于爆轰法制备纳米氧化铈的乳化炸药配方。通过在爆炸罐中起爆乳化炸药,制备得到了纳米氧化铈。利用X射线衍射仪(XRD)和透射电镜(TEM)对样品进行表征。XRD测试结果表明,乳化炸药爆轰法合成的纳米氧化铈属于立方晶系,理论粒径为74nm。TEM测试结果表明,合成的纳米氧化铈外观呈球形,具有较好的分散性和粒度均一性,平均粒径为70nm。  相似文献   

10.
采用凝聚炸药爆轰和气相爆轰分别制备碳包铜纳米颗粒,并利用XRD,Raman和TEM等方法对合成纳米产物进行对比分析。其中凝聚炸药爆轰法以柠檬酸铜干凝胶、油酸和黑索金为原料按照一定比例配成爆炸源,在氮气的保护氛围中引爆;而气相爆轰法以乙酰丙酮铜为原料,分别以H2和O2,H2和空气为爆炸源,在负氧条件下引爆。通过XRD,Raman和TEM分析结果表明,两类爆轰法均可得到分散性良好的碳包覆铜纳米颗粒,碳壳石墨化程度较高。气相爆轰可以合成10 nm以下的纳米晶粒,而凝聚炸药爆轰合成的晶粒尺寸在20~40 nm,且存在较多空壳结构;气相爆轰产物其碳壳尺寸在2~3 nm,凝聚炸药爆轰产物其碳壳尺寸在2~5 nm。  相似文献   

11.
The sorption of hydrogen on carbon structures and nanostructures offers a way to reduce the storage pressure of hydrogen with respect to compression storage while achieving interesting gravimetric storage densities. The most readily available carbon structures, activated carbons, can achieve reproducible, high gravimetric storage densities under cryogenic operating conditions: 5–6% at 35 bar and 77 K, in excess of the normal density that would be present in the pore volume under compression at the same temperature and pressure. We discuss and compare the adsorption of hydrogen on high specific surface activated carbons, nanofibres and nanotubes from experimental and theoretical considerations. In particular, we present gravimetric and volumetric hydrogen sorption measurements on single-walled carbon nanotubes (SWNTs) at (1 bar, 77 K) and (1 bar, 295 K) within the context of our ongoing work on the storage of hydrogen on activated carbon and carbon nanostructures. BET surface area and XRD characterization results on SWNTs are also presented. The experiments were performed on as received, chemically treated and metal-incorporated SWNT samples. Hydrogen sorption capacities measured on treated samples ranged from 0 to about 1 wt.% at 1 bar and 295 K and reached about 4 wt.% at 1 bar and 77 K. Our results show that under certain conditions, SWNTs have better hydrogen uptake performance than large surface area activated carbons. PACS 81.07.de; 81.05.Uw; 68.43.h  相似文献   

12.
Activated carbon fibers were prepared from rayon-based carbon fibers by two step activations with steam and KOH treatments. Hydrogen storage properties of the activated rayon-based carbon fibers with high specific surface area and micropore volume have been investigated. SEM, XRD and Brunauer-Emmett-Teller (BET) were used to characterize the samples. The adsorption performance and porous structure were investigated by nitrogen adsorption isotherm at 77 K on the base of BET and density functional theory (DFT). The BET specific surface area and micropore volume of the activated rayon-based carbon fibers were 3144 m2/g and 0.744 m3/g, respectively. Hydrogen storage properties of the samples were measured at 77 and 298 K with pressure-composition isotherm (PCT) measuring system based on the volumetric method. The capacities of hydrogen storage of the activated rayon-based carbon fibers were 7.01 and 1.46 wt% at 77 and 298 K at 4 MPa, respectively. Possible mechanisms for hydrogen storage in the activated rayon-based carbon fibers are discussed.  相似文献   

13.
戴伟  肖明  李志浩  唐永建 《物理学报》2012,61(1):16801-016801
运用巨正则Monte Carlo方法, 模拟了H2在自由扩散状态下及碳纳米管吸附状态下的分布, 对H2的自由扩散和吸附状态进行了对比研究. 研究表明: 77 K和2 MPa下, (30, 30)扶手椅型碳纳米管质量储氢密度为3.74%, 77 K和10 MPa下, 质量储氢密度为7.4%. 吸附状态的H2分子主要汇聚在碳纳米管内外两个壁面. 关键词: 储氢 碳纳米管 巨正则Monte Carlo  相似文献   

14.
Artificial graphite anode material was modified by coating an amorphous carbon layer on the particle surface via a sol-gel and pyrolysis route. The electrochemical measurements demonstrate that appropriate carbon coating can increase the specific capacity and the initial coulombic efficiency of the graphite material, while excessive carbon coating leads to the decrease in specific capacity. Thick coating layer is obviously unfavorable for the lithium ion diffusion due to the increased diffusion distance, but the decreased specific surface area caused by carbon coating is beneficial to the decrease of initial irreversible capacity loss. The sample coated with 5 wt.% glucose exhibits a stable specific capacity of 340 mAhg?1. Carbon coating can remarkably enhance the rate capability of the graphite anode material, which is mainly attributed to the increased diffusion coefficient of lithium ion.  相似文献   

15.
This work describes the production and characterization of carbon-iron nanocomposites obtained from the decomposition of iron pentacarbonyl (Fe(CO)5) mixed with different carbon materials: a high surface area activated carbon (AC), powdered graphite (G), milled graphite (MG), and carbon black (CB). The nanocomposites were prepared either under argon or in ambient atmosphere, with a fixed ratio of Fe(CO)5 (4.0 mL) to carbon precursor (2.0 g). The images of scanning electron microscopy and the analysis of textural properties indicated the presence of nanostructured Fe compounds homogeneously dispersed into the different classes of pores of the carbon matrices. The elemental Fe content was always larger for samples prepared in ambient atmosphere, reaching values in the range of 20–32 wt%. On the other hand, samples prepared under argon showed reduced Fe content, with values in the range 5–10 wt% for samples prepared from precursors with low surface area (G, MG, and CB) and a much higher value (~19 wt%) for samples prepared from the precursor of high surface area (AC). Mössbauer spectroscopy and X-ray diffractometry showed that the nanoparticles were mostly composed of iron oxides in the case of the samples prepared in oxygen-rich ambient atmosphere and also for the AC-derived nanocomposite prepared under argon, which is consistent with the large oxygen content of this precursor. For the other precursors, with reduced or no oxygen content, metallic iron and iron carbides were found to be the dominant phases in samples prepared under oxygen-free atmosphere. The samples prepared in ambient atmosphere and the AC-derived sample prepared under argon exhibited superparamagnetic behavior at room temperature, as revealed by temperature-dependent magnetization curves and Mössbauer spectroscopy.  相似文献   

16.
Hydrogen storage using carbon adsorbents: past, present and future   总被引:8,自引:0,他引:8  
Interest in hydrogen as a fuel has grown dramatically since 1990, and many advances in hydrogen production and utilization technologies have been made. However, hydrogen storage technologies must be significantly advanced if a hydrogen based energy system, particularly in the transportation sector, is to be established. Hydrogen can be made available on-board vehicles in containers of compressed or liquefied H2, in metal hydrides, via chemical storage or by gas-on-solid adsorption. Although each method possesses desirable characteristics, no approach satisfies all of the efficiency, size, weight, cost and safety requirements for transportation or utility use. Gas-on-solid adsorption is an inherently safe and potentially high energy density hydrogen storage method that could be extremely energy efficient. Consequently, the hydrogen storage properties of high surface area “activated” carbons have been extensively studied. However, activated carbons are ineffective in storing hydrogen because only a small fraction of the pores in the typically wide pore-size distribution are small enough to interact strongly with hydrogen molecules at room temperatures and moderate pressures. Recently, many new carbon nanostructured absorbents have been produced including graphite nanofibers and carbon multi-wall and single-wall nanotubes. The following review provides a brief history of the hydrogen adsorption studies on activated carbons and comments on the recent experimental and theoretical investigations of the hydrogen adsorption properties of the new nanostructured carbon materials. Received: 16 October 2000 / Accepted: 15 November 2000 / Published online: 9 February 2001  相似文献   

17.
A green and facile strategy of preparing graphene by reducing exfoliated graphite oxide (GO) with glucose was developed in this study. The as-prepared samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Atomic force microscopy (AFM). The characterization results indicated that the graphene sheets (GS) were of high quality with smooth surface, rich pore structure and few layer graphene. The samples have a BET specific surface area of 1205.8 m2 g−1 measured by N2 adsorption at 77 K. The hydrogen storage capacity of 2.7 wt.% at 298 K and 25 bar demonstrated that the as-prepared graphene employing glucose as reductant is supposed to be a promising material with outstanding property for hydrogen storage.  相似文献   

18.
任娟  张宁超  刘萍萍 《计算物理》2019,36(6):749-756
采用基于Metropolis蒙特卡罗和Reverse蒙特卡罗的杂化逆向蒙特卡罗方法,构建碳气凝胶的微孔结构模型,根据碳气凝胶的介孔尺寸构建介孔模型.设计不同形状、不同孔径的介孔模型,使用巨正则蒙特卡罗方法详细模拟在298 K和77 K下的储氢量.结果显示,在77 K时,所设计的碳气凝胶的储氢量几乎是室温下的4倍.在77 K,100 bar时,储氢量最高可达到11.12 wt%和45.68 g·L-1.  相似文献   

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