石蜡乳液制备及性能研究

以高速分散器为乳化设备,58#工业级全精炼石蜡为原料制备了石蜡乳液.考察了乳化剂的组成及其HLB值,乳化剂用量,乳化温度,转速和乳化时间等因素对石蜡乳液性能的影响.结果表明,适宜的乳化工艺条件为:以Span80,K12和助乳化剂A为复配乳化剂,其HLB值为11,乳化剂用量为7％,乳化温度为85℃,转速为2×2 800 r/min,乳化时间为1min.     

乳化剂分散碳纳米管/复配蜡微胶囊的制备及表征

以熔点29.45℃的复配石蜡为芯材,硬脂酸、司盘-80和OP-10按一定比例混合后为乳化剂,三聚氰胺-尿素-甲醛树脂为壁材,采用原位聚合法,制备了碳纳米管/复配石蜡相变微胶囊。研究不同乳化剂对乳液及碳纳米管分散的影响,并用扫描电镜、差示扫描量热仪对石蜡和微胶囊进行了表征。结果表明,当添加10%的微晶蜡时,复配石蜡的熔点增大0.73℃,吸热过程相变潜热增加30%;当硬脂酸、司盘80和OP-10的比例为1∶2∶2时,乳液稳定性和碳纳米管分散性达到最佳,复合乳化剂添加量为芯材质量的5%时,形成的微胶囊形貌良好;碳纳米管的加入,有利于胶囊的成型,能够提高微胶囊的相变潜热。     

Preparation of highly crystalline carbon nanofibers from pitch/polymer blend

High crystalline carbon nanofibers were prepared by using polymer blend technique. Naphthalene-based mesophase pitch (AR pitch) was dispersed finely in polymethylpentene matrix, spun by using a melt-blown spinning machine, stabilized at 160 °C in an oxygen atmosphere and carbonized at 900 °C in a nitrogen atmosphere. Bundles of the carbon nanofibers with ca. 100 nm in diameter were obtained after removal of polymethylpentene at the carbonization process. No impurity carbon was observed. The carbon nanofibers consisted of fine carbon crystallites with preferred orientation along the fiber axis. After heating to 3000 °C, the carbon crystallites grew drastically to have an interlayer spacing of 0.3367 nm and a crystallite thickness of 56.9 nm, respectively, with remarkable improvement of the preferred orientation of the crystallites. Advantages and disadvantages of the present method were discussed briefly.     

Surface hydrophobicity alteration of fractionated paraffin wax, crude by-product polyolefin wax and their blend

The surface compositions of crude by-product polyolefin wax (wax K) from a naphtha cracking unit, fractionated commercial paraffin wax (wax J) and their blend (wax M) were compared, under various conditions, by using FT-IR. Then a practical criterion was theoretically derived by back-of-the-envelope-calculation to estimate the diffusivity for the surface enrichment of hydrophilic functional groups. The hydrophobicity in terms of chemical structure and functional groups was altered by changing the environment as well as by blending wax K with wax J. The surface properties of wax J and wax M turned out more hydrophobic than that of wax K within the experimental period of water-submerged condition, even though the structure and functional groups on the surfaces of all waxes under ambient atmospheric condition are extremely similar. Thus the blend of wax M behaved unlike wax K but similarly to wax J in terms of alteration of hydrophobicity. Such values of diffusivity as 1.35×10⁻¹¹ cm²/s and 1.96×10⁻¹¹ cm²/s are established for wax J and wax M, respectively, under 1 day water-submerged condition. Furthermore, under 1 week water-submerged condition, the values of their diffusivity for wax J, wax K and wax M are estimated as 3.06×10⁻¹² cm²/s, 7.23×10⁻¹¹ cm²/s and 1.50×10⁻¹¹ cm²/s, respectively. The obtained values of diffusivity are consistent, in terms of the order of magnitude, with the value of diffusion coefficient of 5.75×10⁻¹¹ cm²/s obtained, using a very complicated empirical-formula, by Chen et al. for the investigation of surface-modifier enrichment. Thus, the suggested criterion may be very useful and practically applied to clarify the process of surface enrichment from general polymer-blends.     

Properties of a field emission lighting plane employing highly crystalline single-walled carbon nanotubes fabricated by simple processes

We developed a new cathode for a visible ray flat plane-emission device formed from a mixture of highly crystalline single-walled carbon nanotubes (SWNTs) dispersed into an organic In₂O₃–SnO₂ precursor solution and a non-ionic surfactant. A thin film field emission cathode having highly homogeneously dispersed SWNTs was able to be fabricated with low driving voltage, high electron emission homogeneity in the plane, and high brightness efficiency by employing a simple scratching process for the film.The turn-on field of a diode using the optimized cathode was 1.2 V/μm, with the brightness homogeneity in that plane being within 5% against the averaged brightness in the lighting plane. Favorable brightness homogeneity from the lighting device to control the content of SWNTs in the coated film was achieved by employing highly crystalline SWNTs. Furthermore, brightness efficiency and emission life-time, which are important factors when comparing luminance devices, totaled more than 70 lm/W and over 5000 h until reaching the half time against the initial field emission current density.This flat plane-emission device has the potential to provide a new approach to lighting in everyday life as it contributes to energy saving through its low power consumption.     

Comparison of thermal properties of crude by-product polyolefin wax, fractionated paraffin wax and their blend

The molecular weight and thermal properties of unfractionated by-product polyolefin wax (wax K) from a naphtha cracking unit, fractionated commercial paraffin wax (wax J) and their blend (wax M) were evaluated and were compared with each other using differential scanning calorimetry (DSC), normal and high-temperature gel permeation chromatography (GPC), and wide-angle X-ray diffraction (WAXD). Such properties as molecular weight distribution, melting temperature and degree of crystallization were altered by blending wax K with wax J. By blending with two parts of wax K and one part of wax J to prepare wax M, M _w of wax K was shifted, by half, to that of wax J in order to approach that of wax M, whereas the M _n of wax K remains almost unaltered to become that of wax M. In particular the effect of blending of wax K and wax J turned out co-crystallization for the sharper lower-melting-temperature endothermic peak of the blend, indicating narrower molecular distribution, than that of wax K at the melting temperature shifted even below that of wax J. The total degree of crystallinity for the blend, wax M, turns out less than that before blending wax K with wax J, which may be attributed to the effect of co-crystallization due to blending.     

Preparation of short carbon nanotubes by mechanical ball milling and their hydrogen adsorption behavior

Short multi-wall carbon nanotubes (MWNTs) with open tips were obtained by mechanical ball milling. The microstructure characteristics of MWNTs before and after ball milling were checked by transmission electron microscopy (TEM). The effect of ball milling on the hydrogen adsorption behavior of the MWNTs was studied. The hydrogen adsorption experiments were carried out at room temperature under a pressure of 8-9 MPa. The hydrogen adsorption capacity of carbon nanotubes milled for 10 h was 0.66 wt%, which was about six times that of MWNTs without milling. For the carbon nanotubes milled with MgO for 1 h, a hydrogen adsorption capacity of 0.69 wt% was obtained. The enhancement of hydrogen adsorption might result from the increase of defects and surface area of the MWNTs caused by ball milling.     

Dramatic change of water-cluster accessibility of highly pure double-walled carbon nanotubes with high temperature annealing

Highly pure double-walled carbon nanotubes (DWCNTs) synthesized by a catalytic chemical vapour deposition method have a well-ordered bundle structure giving explicit diffraction peaks by synchrotron X-ray diffraction measurement. The changes of nanopore structural properties and water adsorptivity of DWCNTs with high-temperature heat treatment were investigated using molecular probe adsorption methods. It was founded that their nanoporosities and apparent hydrophilicities decreased with thermal annealing. However, a specific surface area of 275 m(2) g(-1) and the residual microporosity of more than 60% even after heat treatment at 2673 K suggest their unique applications.     

Preparation and characterization of chitosan-grafted multiwalled carbon nanotubes and their electrochemical properties

A chitosan (CS)-grafted multiwalled carbon nanotubes (MWCNT) composite (CS-MWCNT) was prepared via covalently grafting a biocompatible polymer CS onto the surfaces of MWCNT and was characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), and transmission electron microscopy (TEM). The interaction between MWCNT and CS was investigated and explained according to the FTIR and UV-vis results. More evidence for the presence of the CS-MWCNT was confirmed by TEM images. In the TEM images, a core-shell structure with nanotubes in the center and a CS layer lying around them was observed. The electrochemical properties of the CS-MWCNT were characterized by an electrodeposition method that involves depositing it on a Au electrode. The porous microstructure of the CS-MWCNT modified electrode was observed by scanning electron microscopy. The excellent electrocatalytic ability of the CS-MWCNT modified electrode towards hydrogen peroxide is applicable to the development of oxidase-based amperometric biosensors.     

甲烷催化裂解制备氢气和碳纳米管

采用浸渍法制备出3种MgO负载型过渡金属催化剂Fe/MgO、Co/MgO和N i/MgO,系统研究了甲烷在3种催化剂上于650,700和750℃下的裂解产物。结果表明,该3种催化剂均对甲烷裂解产氢并协同生长碳纳米管表现出较高活性。     

Superior field emission characteristics of highly crystalline and thermally stable carbon nanotubes grown in N2 and O2 by arc discharge

Multi-walled carbon nanotubes (MWCNTs) grown by chemical vapor deposition (CVD), which are commercially available in large quantities, commonly show poor field emission characteristics due to their low crystallinity. In this study, we fabricated highly crystalline MWCNTs using arc discharge (AD) via a mixture of N₂ and O₂ gases. The AD-MWCNTs showed a high oxidation temperature and lower threshold (V_th) and turn-on (V_to) voltages in repeated field emission measurements compared to CVD-MWCNTs. In a lifetime evaluation performed at an anode current of 3 mA for 20 and 120 h in diode and triode configurations, respectively, AD-MWCNTs showed better long-term stability than the CVD-MWCNTs. Thus, our findings demonstrate that AD-MWCNTs are promising for use in high-performance field emitters.     

石蜡的国内外市场

石蜡在国际市场上相对稳定，预计２０００年的需求量为３５０万ｔ，价格仍将维持在目前的水平。１９９５年我国石蜡的产量为８４．５万ｔ，预计２０００年国内需求量约６０万ｔ，出口量将达５０万ｔ     

Preparation of short and water-dispersible carbon nanotubes by solid-state cutting

A new approach is reported to cut conventionally long (>10 μm) and entangled carbon nanotubes (CNTs) to those with short lengths (∼300 nm) and excellent dispersion in water and ethanol. This was achieved by depositing Fe₂O₃ nanoparticles on CNTs first and then inducing a chemical reaction between them at a temperature of 850 °C. The consumption of carbon during the reduction of Fe₂O₃ with CNTs was responsible for the cutting. Fourier transform infrared, X-ray photoelectron and Raman spectroscopies demonstrated that the cutting had induced little impact on the intrinsic graphitic structure. The present cutting approach based on the localized reaction in solid-state has advantages of producing short CNTs with a narrow length distribution, high dispersion, and a low material loss over previous ones based on gaseous or liquid-state reactions, and would have wide applications.     

改性碳纳米管/壳聚糖复合材料的制备及防污性能

通过控制溶液的pH,在酸性条件下制备了单层多巴胺改性的多壁碳纳米管,然后以戊二醛作为反应中间桥梁,共价接枝制备得到碳纳米管/壳聚糖复合材料。通过透射电子显微镜(TEM)、红外光谱(FTIR)和热重分析法(TGA)对复合材料的结构和性能进行表征,结果表明碳纳米管的管壁外面和管端都被均匀包覆起来,包覆层厚度在6 nm左右;采用多巴胺单层膜包覆碳纳米管,达到了减小对碳纳米管结构造成破坏同时增加表面活性基团数量的目的,使得复合材料中壳聚糖的接枝量增加到71.78%。复合材料兼具了壳聚糖和碳纳米管在抑菌性、缓释、硅藻生长抑制方面优异的性能,在对大肠杆菌、金黄色葡萄球菌、鳗弧菌及小舟形藻、成排舟形藻的防污性能实验中,复合材料在抑菌及抑制硅藻生长方面均表现出广谱、长效的抑制性能。     

钴氮碳/碳纳米管的制备及染料吸附性能

为了解决沸石咪唑酯骨架(ZIF-67)基碳材料比表面积和孔体积较小、氮含量较低、孔径分布不集中的问题,以微米级ZIF-67为模板,引入聚多巴胺(PDA)和三聚氰胺(MA)为共同碳氮前驱体以提升氮掺杂量和调节孔结构,在氢气和氩气的氛围中,利用ZIF-67中钴的自催化作用,经800℃高温一步碳化制备得到钴氮掺杂的中空立方形...     

Solubility of paraffin wax in kerosene

The solubility of fully refined paraffin wax (51–54 °C m.p.) in a commercial kerosene has been determined and compared with theoretical and empirical prediction equations. Over the limited range of these experiments the experimental results and the theoretical and empirical curves show similar trends; at concentrations up to about 10 wt % wax the empirical equation seems to predict the experimental results reasonably well, but between 10 and 50 wt % wax the theoretical equation seems more accurate.     

基于正交设计法的石蜡氧化改性研究

采用H2O2为引发剂,考察了反应温度、反应时间、引发剂加入量、空气流量和搅拌速度等因素对氧化石蜡酸值的影响,结果表明,搅拌速度和空气流量影响不大;当引发剂加入量为5%,反应温度为150℃,反应时间为8 h,空气流量为200 mL/min时,石蜡经氧化后酸值可达到32.1 mg KOH/g。经与硬脂酸作为引发剂进行比较,该改性氧化蜡具有颜色浅、气味轻等优点,可以替代天然蜂蜡制成性质稳定的乳化蜡。