炸药爆轰制备纳米石墨粉储放氢性能实验研究

介绍了一种新的制备纳米石墨粉的方法——炸药爆轰法.通过对爆轰合成的黑色粉末进行x射线衍射分析，确认其为六方结构的纳米石墨，平均晶粒度为1.86—2.61nm.用BET气体吸附仪测试纳米石墨粉的比表面积约为500—650m2/g，由比表面积计算得到的纳米石墨粒度为4.41—6.85nm.在室温（≈290K）和12MPa压力条件下对纳米石墨粉进行储放氢气性能测试，结果表明纳米石墨粉样品的储放氢量为0.33wt%—0.37wt％.在相同实验条件下，纳米石墨粉原始样品的储放氢能力较原始纳米炭纤维（0.15wt%—0.35wt％）和多壁碳纳米管（0.15wt%—0.20wt％）的储放氢能力略强,但低于超级活性炭（0.92wt%—0.98wt％）.纳米碳材料的比表面积在其储放氢实验中起关键作用. 关键词： 爆轰 纳米石墨粉 比表面积 储放氢量     

乳化炸药爆轰合成纳米氧化铈及表征

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。     

炸药爆轰法制备的纳米石墨粉的拉曼光谱

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0.25～2 atm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5 cm-1。纳米石墨粉Raman峰的半高宽约为22 cm-1,由此可计算出纳米石墨粉的颗粒大小为2.97～3.97 nm。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2.58 nm(酸处理前)和1.86 nm(酸处理后),与Raman光谱的结果基本吻合。     

气相/凝聚炸药爆轰合成的碳包铜纳米颗粒特征

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。     

掺铕纳米氧化锌的制备及其发光性质

以尿素为沉淀剂，与可溶性硝酸锌、硝酸铕反应制备纳米晶ZnO:Eu3+³⁺，通 过x射线粉末衍射、透射电子显微镜对纳米粒子的组成、结构、形貌及尺寸进行了分析和测定.研究 结果表明，制得的纳米粒子粒度均匀，粒径分布窄，最小粒径为8nm.详细研究了不同制备 方法、不同掺杂浓度及不同粒度等对ZnO:Eu3+³⁺发光性质的影响.为探讨纳米 掺杂材料的制备技术及发光方面的应用提供了可行的方法. 关键词： 光致发光 3+')" href="#">纳米晶ZnO:Eu3+³⁺ 均匀沉淀法     

Cu-MgF2复合纳米金属陶瓷薄膜的电导特性研究

用射频磁控共溅射法制备了Cu体积分数分别为10%，15%，20%和30%的Cu-MgF₂复 合金属陶 瓷薄膜.用x射线衍射、x射线光电子能谱和变温四引线技术对薄膜的微结构、组分及电导特 性进行了测试分析.微结构分析表明：制备的Cu-MgF₂复合薄膜由fcc-Cu晶态纳 米微粒镶嵌 于主要为非晶态的MgF₂陶瓷基体中构成，Cu晶粒的平均晶粒尺寸随组分增加从1 1.9nm增 至17.8nm.50—300K温度范围内的电导测试结果表明：当Cu体积 关键词： 2复合纳米金属陶瓷膜')" href="#">Cu-MgF₂复合纳米金属陶瓷膜 微结构 组分 电导特性 激活能 渗透阈     

爆轰裂解法制备纳米石墨粉的吸附性能研究(英文)

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。     

爆轰裂解法制备纳米石墨粉的吸附性能研究

 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。     

爆轰法合成纳米氧化铈粒径的控制

为获得爆轰合成过程中纳米氧化铈粒径的控制方法,采用乳化炸药爆轰法合成了纳米氧化铈粉末,研究了乳化炸药基质中水相液滴的尺寸对乳化炸药爆速和纳米氧化铈粒径的影响。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和激光粒度仪,对不同乳化条件下得到的乳化炸药基质和相应的纳米氧化铈进行表征。结果表明,乳化炸药基质中水相液滴的尺寸对乳化炸药爆速和纳米氧化铈粒径均有较大的影响,乳化炸药基质中水相液滴的尺寸越小,相应的乳化炸药爆速越高,爆轰合成的纳米氧化铈的粒径越小,且粒径分布越均匀。     

炸药爆轰合成纳米金刚石的拉曼光谱和红外光谱研究

用负氧平衡炸药爆轰法合成纳米金刚石,并用粉末X射线衍射(XRD)仪、激光Raman光谱仪和红外光谱仪等分析仪器对其结构进行表征。XRD结果表明,纳米金刚石为立方结构,由于其内部结构的高密度缺陷、杂质原子的夹杂使谱线偏离,晶格常数比静压合成的大颗粒金刚石大0.72%。由于金刚石晶粒细小,Raman光谱特征峰产生宽化,并且向小波数方向偏移了3 cm-1,此外在纳米金刚石中还含有极少量的石墨。红外光谱测试结果中,3 422 cm-1吸收峰为O—H伸缩振动峰;在1 634 cm-1出现了H₂O的弯曲振动峰,表明在纳米金刚石样品粉末中含有水分;2 930和2 857 cm-1是CH₂的反对称和对称伸缩振动吸收峰;2 971 cm-1是CH₃的反对称伸缩振动吸收峰,说明样品中存在极少量的碳氢化合物;1 788 cm-1吸收峰为CO伸缩振动吸收峰。文章从纳米金刚石的生成机理上分析了产生这些峰位的原因,结果表明纳米金刚石属于Ⅰ型金刚石,在它之中含有ⅠaA型和Ⅰb型金刚石,ⅠaA型金刚石的含量比Ⅰb型金刚石多。     

Ignition of fuel/air mixtures by radiatively heated particles

The current work examines the ignition of fuel/air mixtures by particles which have been heated up rapidly by intense electromagnetic radiation from an infrared laser source. Experiments have been conducted at relatively large beam sizes, where ignition times are a function of the irradiance. Particles in the form of fine powders were placed into a chamber filled with ignitable butane/air mixtures. Possible ignition is shown for a range of carbon based materials including different carbon blacks, graphite, the C₆₀ fullerene and diamond powder, as well as for non-reactive powders such as silicon carbide, iron-, copper- and silicon oxides. The irradiance was varied independently and results are shown to become independent of the size of the irradiated area if a sufficiently large area is illuminated. The particle size was found to have a significant impact on the time to ignition. Specifically, finer particles lead to shorter ignition times due to the higher surface area to volume ratio which reduces both particle and gas heating times. Ignition could be achieved across the whole flammability range of butane/air using carbon black and silicon carbide particles, although, near the rich flammability no ignition could be obtained with carbon black.     

高温高压下纳米金刚石粉的特性研究

 研究了炸药爆轰合成的纳米金刚石粉在高温（约1 600 K）、高压（5.2 GPa）条件下的行为。将纳米金刚石粉与粉末合金（Ni₇₀Mn₂₅Co₅、100^#）混合、压制成圆片,与合金片 （Ni₇₀Mn₂₅Co₅）和人造石墨片一起交替放入高温高压合成腔体内,进行高温高压实验。实验结果表明：在高温高压条件下,纳米金刚石粉不能长大,反而石墨化了;在相同的高压和保温时间条件下,随着温度的降低,纳米金刚石粉的石墨化程度减弱,纳米金刚石粉的纳米颗粒长大,可长成0.1 mm尺寸的金刚石颗粒（温度为1 070 K左右）。而在此条件下,人造石墨不能合成金刚石,一般金刚石晶体要变成石墨相。这进一步表明,纳米金刚石颗粒表面的活性使得它可以在较低的温度下长成较大颗粒的金刚石。     

水热法制备ZnS:Cu,Tm超细X射线发光粉

研究了水热法合成的ZnS: Cu,Tm超细X射线发光粉及其光致发光(PL)和X射线激发发光(X-ray excited luminescence,XEL)光谱特性.200 ℃水热处理12 h直接合成样品的纳米晶粒径约15 nm,尺寸分布窄,分散性好,具有纯立方相的类球形结构.氩气保护下900 ℃退火1 h后的样品存在一定的团聚,但团聚后尺寸为200—600 nm,为超细X射线发光粉,此时样品为纯六方相的类球形为主的结构.所有样品的PL和XEL光谱均为宽带谱.水热法直接合成样品的XEL强度最强时,样品的Cu/Zn,Tm/Cu比值分别为3×10^-4和2.在此比值条件下,900 ℃退火1 h样品的XEL发光最强,此时其两个峰值分别位于453,525 nm.发光强度增强的同时粒径很小,对提高成像系统分辨率非常有意义.通过比较PL光谱与XEL光谱特性,讨论了PL和XEL光谱的发光机理和其不同的激发机理. 关键词： ZnS:Cu Tm 水热法 X射线激发发光     

Synthesis and characterization of nanocrystalline titanium nitride powder from rutile and anatase as precursors

In this research nanosized titanium nitride powder was synthesized through reaction of titanium oxide with ammonia gas. The reaction was carried out at a very slow heating rate. Two different TiO₂ starting powders contained rutile and anatase phase and differed in initial particle size and surface area. The crystallite size of TiN powders synthesized at 1000 °C was obtained about 40 nm for anatase sample. Surface area and particle size were found to be 19 m²/g, 70 nm for rutile sample and 31 m²/g, 39 nm for anatase sample, respectively. The rutile sample showed an increasing trend in surface area during conversion to the nitride, whilst the anatase sample followed an adverse trend. TiN powder synthesized from anatase had the highest surface area and smallest particle size due to the specification of initial precursor.     

水热合成ZnTe纳米粉的发光性能

利用Zn粉和Te粉为原材料,通过水热法在160℃下合成了ZnTe纳米粉,并用X射线衍射仪、x射线能谱仪、透射电子显微镜和显微Raman光谱对其进行了表征.X射线衍射谱表明合成的ZnTe具有闪锌矿结构.X射线能谱给出的结果表明合成的ZnTe中主要元素是Zn和Te,并含有杂质O.透射电子显微镜照片显示出合成的ZnTe纳米粉...     

Confocal Raman spectromicroscopy for tin-core/carbon-shell nanowire heterostructure

High density heterostructures of carbon nanotubes encapsulated single crystalline tin nanowires have been characterized by Raman spectromicroscopy. The morphology, composition and structure of the synthesized nanoheterostructures were examined by using scanning electron microscopy, transmission electron microscopy. The Raman spectra obviously manifest the crystalline nano-graphite within amorphous carbon walls in the heterostructures. The Raman image reproduces the pristine heterostructures of the CNTs as seen in SEM image, which illustrate the single nanowires oriented uniformly grown on micro-graphitic fibers. It was found that the resultant heterostructures are luminescent which was attributed to crystalline nano-graphite embedded in the amorphous carbon matrix, which is a consequence of excitons localization within an increasing number of sp² rich clusters. The contrast in the Raman image reflects nonuniform distribution of the graphite cluster size which acts as the radiative centers. The luminescent property was reviewed. The enhanced Raman spectra and luminescent property by the well-defined tin nanowires inside the heterostructures was revealed.     

Synthesis and characterization of nanocrystalline TaN

Tantalum nitride (TaN) nanocrystals have been successfully synthesized at 650 °C through a solid-state reaction in an autoclave. The X-ray powder diffraction pattern indicates that the product is a mixture of hexagonal and metastable cubic TaN. Transmission electron microscopy images and selected area electron diffraction patterns show that the hexagonal TaN crystallites consist of nanorod with a typical size of about 50×1000 nm and the cubic TaN crystallites are composed of uniform particles with an average size of about 30 nm.     

Laser vaporization synthesis of polyhedral graphite

Polyhedral graphite (PG) particles have been synthesized by CO₂ laser vaporization of graphite in high-pressure Ar gas (8×10⁵ Pa). Faceted PG particles, ranging in size from 110 to 500 nm, have a turbostratic structure. The yield of PG is more than 90%. This synthesis is based on the condensation of hot carbon species confined by an Ar-gas atmosphere. Received: 22 January 2003 / Accepted: 24 January 2003 / Published online: 11 April 2003 RID="*" ID="*"Corresponding author. Fax: +81-59/231-9471, E-mail: kokai@chem.mie-u.ac.jp Permanent address: Chemistry Department for Materials, Mie University, 1515 Kamihama, Tsu, Mie 514-8507, Japan