纳米洋葱碳的制备及其纯化研究

以甲烷为碳源,316号不锈钢网为催化剂,800℃下催化裂解甲烷,采用化学气相沉积法制备平均粒径为70~100nm纳米洋葱碳,通过酸洗-低温煅烧-磁选方法对洋葱碳进行纯化处理。X射线衍射、扫描电子显微镜、透射电子显微镜、红外吸收光谱、拉曼光谱和振动样品磁强计对样品的形貌结构、物相组成及磁性能进行表征分析。结果表明,酸洗-低温煅烧能有效去除初产物中裸露的催化剂颗粒及无定型碳,磁选则实现将内包有[Fe-Ni]磁性催化剂的洋葱碳与空心的洋葱碳分离,最终获得纯净的空心纳米洋葱碳。     

Detonation-assisted self-assembly synthesis of carbon onions using organics with long carbon chain

The detonation of mixtures of organics with long carbon chains and explosives has been found to yield carbon onions without use of any catalyst. Octadecanoic acid, hexadecylic acid, behenic acid and CTAB (cetyltrimethylammonium bromide) have been used as raw materials. The recovered products were characterized using various techniques such as scanning electron microscope, transmission electron microscope, Raman spectroscopy, infrared spectroscopy and X-ray diffraction. The prepared carbon onions consist of concentric-shell graphitic layers with a narrow size distribution of 60 to 70 nm, which aggregated to form a chain-like structure. Formation mechanism of the carbon onions was proposed as that the organics with long chains broke their functional groups and self-assembled into carbon onions due to low free energy.     

Solid-state titania-based gas sensor for liquefied petroleum gas detection at room temperature

This paper reports the liquefied petroleum gas (LPG) sensing of titanium dioxide (Qualigens, India). Scanning electron micrographs and X-ray diffraction studies of samples were done. SEM shows that the material is porous and has grapes-like morphology before exposure to the LPG. XRD patterns reveal the crystalline nature of the material. The crystallites sizes of the TiO₂ were found in the range of 30–75 nm. Variations in resistance with exposure of LPG to the sensing element were observed. The average sensitivity for different volume percentages of gas was estimated. The maximum value of average sensitivity was 1·7 for higher vol.% of LPG. Percentage sensor response (%SR) as a function of time was calculated and its maximum value was 45%. Response time of the sensor was 70 s. The sensor was quite sensitive to LPG and results were found reproducible.     

Measurement of the quantity of liquefied petroleum gas in a tank

Measurements of the quantity of liquefied petroleum gas in a tank, based on a radio-frequency method, are considered. The results of experimental investigations are presented. A measuring system for industrial applications is described. __________ Translated from Izmeritel’naya Tekhnika, No. 2, pp. 40–42, February, 2006.     

瓶装液化石油气净含量检验规则探讨

针对目前由于相关技术法规的缺失,导致瓶装液化石油气充装市场混乱,消费者权益受到侵犯,甚至行政执法的权威性受到质疑的状况,通过对现行检验方法的分析,探讨补充了瓶装液化石油气净含量的起点（真空还是标准状态）、空瓶瓶重允许偏差和残液允许量等问题;并提出了一种新的检验方法,即直接抽空钢瓶的检验方法。为瓶装液化石油气净含量检验法规的制定提供了借鉴。     

液化石油气中二甲醚及各烃类组分气相色谱法研究

建立一套气相色谱检测方法,分析条件如下:不锈钢色谱柱(6 m×3 mm);固定液为邻苯二甲酸二壬酯和β-β′-氧二丙腈的混合物,混合比例为1∶1,涂布浓度为20%,载体为6201红色担体,载体颗粒的粒径为1.65~1.98 mm;载气为氢气,流量40m L/min,柱温35℃,气化温度100℃,热导池检测器温度110℃。检测方法的相对标准偏差在0.39%~2.78%之间,加标回收率在94.1%~104.3%之间,操作简洁、分析快速、结果准确。     

Sensing behaviour of nanosized zinc-tin composite oxide towards liquefied petroleum gas and ethanol

A chemical route has been used to synthesize composite oxides of zinc and tin. An ammonia solution was added to equal amounts of zinc and tin chloride solutions of same molarities to obtain precipitates. Three portions of these precipitates were annealed at 400, 600 and 800 °C, respectively. Results of X-ray diffraction and transmission electron microscopy clearly depicted coexistence of phases of nano-sized SnO₂, ZnO, Zn₂SnO₄ and ZnSnO₃. The effect of annealing on structure, morphology and sensing has been observed as well. It has been observed that annealing promoted growth of Zn₂SnO₄ and ZnSnO₃ at the expense of zinc. The sensing response of fabricated sensors from these materials to 250 ppm LPG and ethanol has been investigated. The sensor fabricated from powder annealed at 400 °C responded better to LPG than ethanol.     

Continuous synthesis of carbon nanotubes using a metal-free catalyst by CVD

This study demonstrates the first example of the use of a metal-free catalyst for the continuous synthesis of carbon nanotubes (CNTs) by chemical vapor deposition (CVD). In this paper silica nanoparticles produced from the thermal decomposition of PSS-(2-(trans-3,4-Cyclohexanediol)ethyl)-Heptaisobutyl substituted (POSS) were used as catalyst and ethanol was served as both the solvent and the carbon source for nanotube growth. The POSS/ethanol solution was nebulized by an ultrasonic beam. The tiny mists were continuously introduced into the CVD reactor for the growth of CNTs. The morphology and structure of the CNTs have been investigated by scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. The obtained CNTs have a multi-walled structure with diameters mainly in the size range from 13 to 16 nm. Detailed investigations on the growth conditions indicate that the growth temperature and POSS concentration are important for achieving high-quality nanotubes, and that the existing of small amount of water in ethanol is effective to remove amorphous carbon species during the formation of CNTs. The mass production of CNTs without any metal contaminant will provide a chance for investing and understanding the intrinsic properties of CNTs and applications particularly in nanoelectronics and biomedicines.     

Bottom-up synthesis of oxygen-containing carbon materials using a Lewis acid catalyst

Oxygen-containing carbon materials have been studied extensively because of their excellent dispersibility, absorptivity, separability, and supportability of catalysts. However, structural control by existing top-down methods is almost impossible. Our group has demonstrated that phloroglucinol (PG, 1,3,5-trihydroxybenzene) can be a promising raw material to synthesize structurally controlled oxygen-containing carbon materials. In this study, in addition to PG, hexahydroxybenzene (HHB), which has more oxygen and high symmetry, was used as the raw material, and a Lewis acid catalyst, tris (pentafluorophenyl) borane (TPB), was used to enhance the structural control rate and the removability of catalysts from the carbonized samples. The solubility of heat-treated HHB was lower than that of heat-treated PG, but the oxygen content of heat-treated HHB was higher than that of heat-treated PG even at 673 K. By adding TPB to PG, dibenzofuran-like structures formed, and the structural control rate increased up to 93.6%. Besides, the content of fluorine in the catalyst was reduced to 0%, indicating that TPB can be a promising recyclable catalyst to promote the structural control rate of carbonized PG.

Graphical abstract

     

Physicochemical investigations of Pd2+ substituted ZnO nanoflowers for liquefied petroleum gas sensing

Journal of Materials Science: Materials in Electronics - Present study portrays, physicochemical investigations of pristine and Pd2+ modified ZnO nanoflowers (NFs) compositional series...     

Nanostructured ZnFe2O4 thick film as room temperature liquefied petroleum gas sensor

In the present work, thick film of nanostructured zinc ferrite was prepared by screen printing method and its liquefied petroleum gas (LPG) sensing properties were investigated. The structural and surface morphological characterisations of the sample were analysed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The minimum crystallite size of ZnFe₂O₄ calculated from Scherrer's formula is found to be 4 nm. SEM images exhibit the porous nature of the sensing material with a number of active sites. Optical characterisation of the film was carried out by ultraviolet–visible spectrophotometer. The estimated value of band gap of the film was found 1.91 eV. The LPG sensing properties of the zinc ferrite film were investigated at room temperature for different vol.% of LPG. The variations in electrical resistance of the film were measured with the exposure of LPG as a function of time. The maximum values of sensitivity and percentage sensor response were found 16 and 1785, respectively, for 5 vol.% of LPG. These experimental results show that nanostructured zinc ferrite is a promising material for LPG sensor.     

计算机技术在液化石油气密度和蒸汽压分析中的应用

本文介绍了液化石油气样品按SH/T0230—1992《液化石油气组成测定在(色谱法)》标准测定组成后(?)据GB/12576—1997《液化石油气蒸汽压和相对密度及辛烷值计算法》标准的算法,利用计算机技术对所测得液石油气的组成进行转换计算,继而快速准确计算出液化石油气的密度和蒸汽压。     

Few layer graphene/silver nanocomposite based flexible and resistive liquefied petroleum gas sensor

The LPG gas sensing characteristics of hybrid few-layered graphene (FLG)/ silver nanoparticles (Ag NPs) nanoarchitecture have been investigated. FLG and silver nanoparticles (Ag NPs) enhance the LPG gas sensing characteristics by collectively involving in the electronic transportation and diffusion mechanisms. FLG, Ag and FLG/ Silver nanocomposites are developed by ultra-sonication assisted method, and the effect of flexibility on gas sensing performance was thoroughly examined. The sensing materials as thin films are developed via drop-casting technique on photo lithography patterned flexible interdigitated electrodes (IDEs). The gas sensing characteristics of the prepared sensor are studied for LPG and other analytes at room temperature. The maximum response is observed for FLG/Ag nanocomposite to 100 ppm LPG at room temperature. FLG/Ag nanocomposite sensor demonstrates rapid response, high selectivity, reproducibility and good stability over a period of 30 days. Further the durability and flexibility tests conducted for the FLG/Ag hybrid sensor at bending angles reveal 78% stability even after 15 days of sensing studies.

     

Preparation and characterization of barium stannate: application as a liquefied petroleum gas sensor†

Barium stannate, BaSnO₃, an n-type semiconducting oxide with cubic perovskite structure, has been prepared by the thermal decomposition of barium carbonate (BaCO₃) and tin tetrahydroxide (Sn(OH)₄). The material was characterized by various physical techniques such as differential thermal analysis (DTA/TG), X-ray diffraction (XRD), BET surface area, Fourier transform infra-red (FT-IR) spectroscopy and scanning electron microscopy (SEM). Of its several applications, this material has proven to be one of the successful candidates for the detection of liquefied petroleum gas (LPG). The sensor has a very good selectivity to detect LPG in comparison to other reducing gases, like carbon monoxide and methane.     

Study on the synthesis of carbon fibers and CNF using potassium iodide catalyst

Most catalysts used in preparing carbon materials by chemical vapor deposition were transitional metals such as Fe, Co, Ni and only a few references were about the synthesis of carbon materials using water-soluble catalysts until now. Compared with metals, water-soluble catalysts can be conveniently removed from products. In our present works, water-soluble salt potassium iodide (KI) was found to be an efficient catalyst to grow carbon fibers and CNF under suitable conditions. Various structures of carbon fibers were synthesized by chemical vapor deposition using KI as the catalyst. And the experimental results showed that the nanostructure evolution of the fibers is strongly dependent on the temperature and history of the catalyst.     

Spreading—boiling model for instantaneous spills of liquefied petroleum gas (LPG) on water

An experimental and theoretical investigation was carried out to study the boiling and spreading of liquefied petroleum gas (LPG) on water, in a one-dimensional configuration.Experimental work involved the design and construction of a spill/spread/boil apparatus which permitted the measurement of spreading and local boil-off rates. With the equations of continuity and momentum transfer, a mathematical model was developed to describe the boiling—spreading phenomena of cryogens spilled on water. The model accounts for a decrease in the density of the cryogenic liquid due to bubble formation.The boiling and spreading rates of LPG were found to be the same as those of pure propane. An LPG spill was characterized by the very rapid and violent initial boiling and highly irregular ice formation on the water surface. The measured local boil-off rates of LPG agreed well with theoretical predictions from a moving-boundary heat-transfer model. The spreading velocity of an LPG spill was found to be slightly less than predicted by the spreading model as the rough ice formed on the surface impeded the flow of the LPG.     

基于Modelica的生物质燃气内燃机性能模拟研究

针对由沼气成分及其理化特性导致的内燃机燃用沼气时会发生燃烧速度慢、后燃严重、排气温度高等问题,将生物质燃气内燃机作为研究对象,基于可重用性及面向对象的Modelica语言建立内燃机模型库,将生物质燃气为燃料对四缸四冲程火花点火内燃机性能进行分析.通过仿真研究不同比例天然气(体积分数分别为33%,67%及100%)和LP...     

Flame synthesis of carbon nano-onions enhanced by acoustic modulation

Ethylene jet diffusion flames modulated by acoustic excitation in an atmospheric environment were used to synthesize carbon nano-onions (CNOs) on a catalytic nickel substrate. The formation of CNOs was significantly enhanced by acoustic excitation at frequencies near either the natural flickering frequency or the acoustically resonant frequency. The rate of yield of CNOs was high at 10 and 20 Hz (near the natural flickering frequency) for a sampling position z = 5 mm above the burner exit where the gas temperature was about 450-520?°C, or at 10, 20 and 30 Hz for z = 10 mm with the gas temperature ranging from 420 to 500?°C. Additionally, for both z = 5 and 10 mm, a quantity of CNOs can be obtained at 60-70 Hz, near the acoustically resonant frequency, where the gas temperature was between 620 and 720?°C. Almost no CNOs were produced for the other frequencies due to low temperature or lack of carbon sources. CNOs synthesized at low frequencies had a greater diameter and a higher degree of graphitization than those at high frequencies.     

Hydrothermal synthesis and characterization of micro to nano sized carbon particles

Experiments under hydrothermal conditions were carried out to study the formation of elemental carbon through the decomposition of β-Silicon carbide (β-SiC) in the presence of organic compounds. The organic compounds were known to dissociate at low P-T conditions and produce the C–O–H supercritical fluids, which will have great influence on the decomposition of β-SiC. These hydrothermal runs under the influence of supercritical fluids will not only help in dissociating the silicon carbide into SiO₂ and free elemental carbon but also control the type of carbon phase formation. The Scanning Electron Microscopic (SEM) studies of the run products indicate the formation of the micron sized carbon particles having characteristic shapes like spherical/ovoid, scaly with metallic lustre and in some runs we find the formation of nano sized octahedral crystallites. Micro Raman study of these carbon particles reveals that bulk of the carbon formed in these runs were disordered / sp²–hybridized carbon but we also noticed the formation of black scales over the spherical particles and the octahedral crystallites which exhibits the sp³-hybridization having the characteristic sharp band at 1332 cm^-1, comparable to that of diamond powder. The octahedral crystallites are formed at the inner walls of the hollow spherical carbon particles. In any of the experimental runs we haven't used either the metal catalysts or the diamond seed with the charge material. Thus, the nucleation and formation of nano sized octahedral crystallites of diamond (sp³-hybridized carbon) in the present study at lower P-T conditions compared to that of its formation in nature is a significant breakthrough in the study of diamond synthesis.