原位悬浮乳液聚合制备聚苯胺/纳米金刚石复合微球及结构表征

利用原位乳液聚合的方法合成得到了聚苯胺(PANI)/纳米金刚石复合微球.用X射线衍射(XRD)、热重-差热(Tg-DTA)、透射电子显微镜(TEM)、粒径分析(PSD)、比表面积分析(BET)、红外光谱(FT-IR)及紫外-可见光谱(UV-Vis)等技术分别对获得的PANI/纳米金刚石复合微球进行了结构、形貌、表面表征.结果表明,在PANI/纳米金刚石复合微球中,纳米金刚石为立方相,复合微球介于10～30nm,粒径分布窄,分散性良好,比表面积可达270m2/g,且具有较好的热稳定性.结构分析证实在PANI/纳米金刚石复合物中,PANI与纳米金刚石之间存在氢键键合机制.     

MPCVD制备纳米金刚石真空窗口的研究

微波等离子体化学气相沉积装置用于制备纳米金刚石膜和纳米金刚石真空窗口,气源为H2、CH4、Ar和少量O2。扫描电镜、拉曼光谱、X射线衍射仪、原子力显微镜用于表征和分析纳米金刚石膜,自制的漏气率测量装置测出纳米金刚石真空窗口漏气率。结果表明:金刚石膜厚20μm、表面平均粗糙度Ra=34. 6 nm,平均晶粒尺寸35 nm,金刚石窗口漏气率为2. 78×10-9Pa·m3/s。     

界面聚合法制备十二醇相变微胶囊的工艺及性能

为了解决低温相变材料稳定性差、不易储存运输等问题,以六亚甲基二异氰酸酯(HDI)、1,3-丙二胺为壁材单体,以相变温度较低、相变潜热较高的十二醇为芯材,通过界面聚合法制备了低温相变微胶囊.由于十二醇具有反应活性,本工作研究了不同结构异氰酸酯作为壁材单体的适应性,探索了1,3-丙二胺水溶液的pH值对微胶囊形貌的影响.在1,3-丙二胺水溶液的pH值为9.0的情况下,制备的微胶囊粒径约2.0μm,芯材载量为79.8％,熔融温度为24.47℃,熔融热焓为142.3 J/g.相比于原位聚合法,界面聚合法制备的微胶囊有更好的致密性,在甲醇中的渗透率下降了40％,提高了十二醇相变材料的稳定性,有效改善了其泄漏、储存运输等方面的问题.     

纳米金刚石与聚醚醚酮填充改性聚四氟乙烯复合材料的摩擦学性能

采用模压-烧结方法制备了纳米金刚石(ND)与聚醚醚酮(PEEK)填充改性的聚四氟乙烯(PTFE)复合材料,并研究了复合材料的摩擦磨损性能及其微观结构。结果表明,随着PEEK含量增加到20%(质量分数),复合材料的耐磨性显著提高;而较低填充量的ND可以在降低复合材料摩擦系数的情况下提高其耐磨性能。1.0%ND/20%(质量分数)PEEK/PTFE复合材料的减摩耐磨性能优良,与纯PTFE相比,该复合材料的摩擦系数下降约20%,耐磨性能提高120倍,原子力显微分析表明该复合材料中ND分布均匀。     

纳米金刚石负载Fe2O3的制备及其对高氯酸氨的热分解催化作用

对纳米金刚石（ND）进行羧基化处理以提高其分散性,然后采用沉淀法制备了羧基化ND负载Fe₂O₃的催化剂。利用XRD、TG、BET和TEM对该负载型催化剂进行表征,通过DSC研究其对高氯酸铵(AP)热分解的催化作用。结果表明:ND经过羧基化处理后,在水中的分散性大幅度提高。沉淀法制备了直径5 nm、长50 nm的Fe₂O₃包裹或附着于ND的负载型复合催化剂,该催化剂对AP高温热分解的催化效果优于单一的Fe₂O₃或ND。当Fe₂O₃和ND的质量比为5∶1、在AP中添加质量分数2%的复合催化剂时,AP的高温分解峰温降低约30 ℃,ND负载Fe₂O₃催化剂具有一定的协同催化作用。     

Pechini溶胶-凝胶法制备SiO2/TiO2复合微粒

采用超声St(o)ber法制备了单分散性的纳米载体SiO2,再采用Pechini溶胶-凝胶制备法制备出SiO2/TiO2复合微球.通过X射线衍射仪、场发射扫描电子显微镜(FESEM)对粉体的晶型和显微形貌进行测试分析.结果表明:纳米载体SiO2球形颗粒为无定形态,Ti02粉体为形貌多样的块状颗粒,大颗粒粒径大于10μm...     

纳米SiO2制备及改性

为了改善纳米SiO2的分散性,用溶胶-凝胶技术制备了纳米SiO2凝胶,并用不同改性剂对粉末进行了表面改性.采用透射电子显微镜(TEM)、X射线衍射(XRD)、粒度分析仪(PSA)、紫外-可见光分光光度计(UV-VS)等分析了纳米SiO2的粒径及分散性.结果表明,正硅酸乙酯的水解和缩合反应条件直接影响纳米SiO2粉体的粒径大小.KH-550硅烷偶联改性剂用量、改性时间等因素对改性效果有明显的影响.当改性剂用量为4.1%(质量分数),改性时间为2h时,可得到高分散性的纳米SiO2粉体.纳米SiO2粉末易发生团聚,只有对其进行表面改性,才能得到疏水性纳米SiO2粉末.     

金刚石颗粒弥散WC-Co复合物的烧结及其韧化

采用放电等离子烧结(SPS)方法制备了金刚石颗粒(平均粒径为12μm、25μm 及50μm)以20 ％的体积比弥散WC-10 wt％Co硬质合金的致密复合物,为防止金刚石颗粒的氧化和石墨化,用高温化学反应方法在其表面生成了一层牢固结合的纳米尺寸的碳化硅保护膜。所得烧结体的相对密度均可达到98％。弥散金刚石颗粒基本保持了基体的高硬度,但是使复合物的断裂韧性得到了显著提高,金刚石粒度为50μm时,韧性高达17.8MPa·m1/2。沿金刚石颗粒周围可以清晰地观察到裂纹偏转及停止现象。金刚石粒度的变化对力学性能的影响不很明显。      

多层式金刚石薄膜的制备工艺研究

利用热丝化学气相沉积(HFCVD)技术,通过逐次调整气压、碳源浓度等生长参数,沉积了晶粒尺寸逐层减小的多层式金刚石薄膜.场发射扫描电镜(FE-SEM)和原子力显微镜(AFM)测试显示其表层晶粒平均尺寸约为20nm,厚度和表面平均粗糙度分别为35.81μm和18.8nm(2μm×2μm),皆能满足高频声表面波器件用衬底的要求.实验结果表明,多层式生长方法是制备声表面波器件用金刚石衬底的理想方法.     

硅尖上纳米金刚石膜场发射性质的研究

本文采用热灯丝CVD法在硅尖上制备了纳米金刚石膜，并研究了硅尖上纳米金刚石膜的场发射性质，实验结果表明，硅尖上纳米金刚石膜的场发射特性与硅平面上生长的多晶金刚石膜比较，有了极大的提高，硅尖上纳米金刚石膜场发射开启电场最小为2.7V/μm，而多晶金刚石膜为4.5V/μm。利用电子隧穿模型对实验结果进行了理论分析，研究表明实验结果与理论分析相符合。     

Towards dilute magnetic semiconductors: Fe and Co substituted inorganic-organic hybrid materials based on ZnSe

Inorganic-organic hybrid nanostructures doped with magnetic ions have been synthesized via substitution of Zn by Co or Fe in the ZnSe(L)0.5 systems under solvothermal conditions. These dilute magnetic semiconductors (DMS), Zn(1-x)MxSe(L)0.5 (M = Co, Fe; L = ethylenediamine or en, 1,3-propanediamine or pda; 0 < x < 1), are composed of perfectly ordered Zn(1-x)MxSe semiconductor monolayers interconnected by organic diamine molecules. The large blue shifts in their optical absorption edges (approximately 1.1-1.5 eV) compared to the bulk ZnSe are a direct result of a very strong quantum confinement effect (QCE). Magnetic studies show that there exist antiferromagnetic interactions between the Co or Fe centers in the structures and the interaction is enhanced as the doping concentration increases. The introduction of Fe or Co to hybrid inorganic-organic semiconductors provides a promising route to generate materials that combine the advantageous features of inorganic, organic, and magnetic functionalities in a single structure.     

Soluble functionalized carbon nanohorns

Carbon nanahorns (CNH) were functionalized following the methodology of 1,3-dipolar cycloaddition of azomethine ylides and found to form stable solutions in either organic solvents or water. The number of added functional units, in the form of pyrrolidine moieties, was calculated when a pyrene chromophore was utilized in the modification scheme. Moreover, complementary theoretical calculations revealed that reactivity enhancement is expected at locations near the conical-shaped tip of CNH, where the highest curvature and strain exist. Finally, additional organic transformation of already modified CNH was exploited by covalently linked ferrocene units.     

Covalent functionalization of metal oxide and carbon nanostructures with polyoctasilsesquioxane (POSS) and their incorporation in polymer composites

Polyoctasilsesquioxane (POSS) has been employed to covalently functionalize nanostructures of TiO₂, ZnO and Fe₂O₃ as well as carbon nanotubes, nanodiamond and graphene to enable their dispersion in polar solvents. Covalent functionalization of these nanostructures with POSS has been established by electron microscopy, EDAX analysis and infrared spectroscopy. On heating the POSS-functionalized nanostructures, silica-coated nanostructures are obtained. POSS-functionalized nanoparticles of TiO₂, Fe₂O₃ and graphite were utilized to prepare polymer-nanostructure composites based on PVA and nylon-6,6.     

Analysis of the nanodiamond particle fabricated by detonation

In order to comprehensively analyse the structures and the surface states of the nanodiamond particles fabricated by detonation, various apparatus were used to investigate the nanodiamond powder including a high-resolution transmission electron microscope, an energy diffraction spectrometer, an X-ray diffractometer, a Raman spectrometer, a Fourier transform infrared spectrometer and differential scanning calorimeter. The grain size of the nanodiamond particles was in the range of 2–12 nm. However, the average grain size of the nanodiamond was approximately 5 nm. Moreover, the shapes of the nanodiamond particles were spherical or elliptical. The nanodiamond as fabricated was very pure, containing almost only the element of carbon. The contents of the impure element including O, Al and S were very small, which came from the synthesis and purification processes when fabricating the nanodiamond. The surfaces of the nanodiamond particles absorbed many functional groups, such as hydroxy, carbonyl, carboxyl and ether-based resin. The initial oxidation temperature of the nanodiamond powder in the air was about 520°C, which was lower than that of the bulk diamond. However, the oxidation temperature of the nanographite existing in the nanodiamond powder was about 228°C. The graphitisation temperature of the nanodiamond powder in the Ar gas was approximately 1305°C.     

Covalent and noncovalent functionalisation and solubilisation of nanodiamond

Covalent functionalisation of nanodiamond has been carried out by employing several methods. One of them involves the reaction of acid-treated nanodiamond with thionyl chloride followed by reaction with a long-chain aliphatic amine to produce the amide derivative. The second method involves reaction of acid-treated nanodiamond with an organosilicon or organotin reagent such as hexadecyltrimethoxysilane, dibutyldimethoxytin, and perfluoro-octyltriethoxysilane. The products of covalent functionalisation produce excellent dispersions in CCl₄ and toluene. SiO₂–and SnO₂–covered nanodiamond are obtained by heating the nanodiamond coated with the organosilane and the organotin reagents, respectively. By interaction of nanodiamond with surfactants such as sodium bis(2-ethylhexyl) sulphosuccinate (AOT), Triton X-100 (TX-100), polyvinyl alcohol (PVA), cetyltrimethylammonium bromide (CTAB), and tert-octylphenoxy poly(oxyethylene)ethanol (IGEPAL) gives good dispersions in water, the best dispersion with the lowest surfactant concentration being obtained with IGEPAL.     

A Study on the Action of Ozone and on the Thermal Stability of Nanodiamond

Ultradisperse detonation diamond (UDD), a nanodiamond having particle size around 4 nm has been treated with ozone in an aqueous slurry. The reaction kinetics appeared to be relatively slow and long ozonation times were needed in order to functionalize the surface of a special nanodiamond sample with a very low degree of oxidation and foreign groups. The resulting ozonated nanodiamond has been studied by FT-IR and electronic spectroscopy. It has been shown that the ozonation of cyclohexane and adamantane can be taken as a model reaction for the ozonation of diamond. Together with ketonic groups of various nature formed on the surface of nanodiamond, the ozonation leads also to the formation of simple molecules like for instance HCOOH and HCHO which remain in the water solution and which have been detected by HPLC analysis using a diode-array detector. The thermal stability of the nanodiamond sample has been studied by thermogravimetric analysis (TGA-DTG) combined with differential thermal analysis (DTA) both under inert atmosphere and in air flow. The studies on thermal stability have been conducted in comparison to a sample of bulk diamond. It appears that the behavior of nanodiamond is completely different than the bulk diamond sample. For instance, under inert atmosphere and at 900°C the weight loss undergone by the nanodiamond is 11.5% while it is negligible in the case of bulk diamond under the same conditions. Similarly, in air flow the nanodiamond burns abruptly above 450°C while bulk diamond starts to burn only above 850°C. These differences have been explained in terms of different particle size and surface functionalization.     

In situ formation of β-silicon carbide nanorods from the hybrid of an organic moiety and methyltriethoxysilane

Silicon carbide (SiC) nanorods were prepared by the pyrolysis of a hybrid of organic moiety (1,3-propanediamine) and methyltriethoxysilane (MTEOS). The organic-inorganic hybrid was developed using a sol-gel process and blending it with the organic moiety. The nanostructures were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which revealed the continuous formation of β-SiC nanorods having a 30-100 nm diameter and a length of a few micrometers. The unreacted silica agglomerated to form lumps with the release of excess carbon during oxidation. Electron diffraction patterns from the nanowires revealed them to have the cubic β-SiC structure. This was in agreement with XRD data. There were found to be many periodically twinned or stacking faulted regions observed along the length of the nanowires. While this yielded a zig-zag pattern to the outside of the core and changes to the local internal diameter of the nanowires, there was no correspondence to the changes to the diameter of the outer sheaf. The Raman shifts for β-SiC appeared as small peaks at 795.6 and 983.1 cm⁻¹ respectively. The characteristic vibration of SiC at 795 cm⁻¹ in Fourier Transform Infrared Spectroscopy (FTIR) was also observed.     

A Study on the Action of Ozone and on the Thermal Stability of Nanodiamond

Abstract

Ultradisperse detonation diamond (UDD), a nanodiamond having particle size around 4 nm has been treated with ozone in an aqueous slurry. The reaction kinetics appeared to be relatively slow and long ozonation times were needed in order to functionalize the surface of a special nanodiamond sample with a very low degree of oxidation and foreign groups. The resulting ozonated nanodiamond has been studied by FT‐IR and electronic spectroscopy. It has been shown that the ozonation of cyclohexane and adamantane can be taken as a model reaction for the ozonation of diamond. Together with ketonic groups of various nature formed on the surface of nanodiamond, the ozonation leads also to the formation of simple molecules like for instance HCOOH and HCHO which remain in the water solution and which have been detected by HPLC analysis using a diode‐array detector. The thermal stability of the nanodiamond sample has been studied by thermogravimetric analysis (TGA‐DTG) combined with differential thermal analysis (DTA) both under inert atmosphere and in air flow. The studies on thermal stability have been conducted in comparison to a sample of bulk diamond. It appears that the behavior of nanodiamond is completely different than the bulk diamond sample. For instance, under inert atmosphere and at 900°C the weight loss undergone by the nanodiamond is 11.5% while it is negligible in the case of bulk diamond under the same conditions. Similarly, in air flow the nanodiamond burns abruptly above 450°C while bulk diamond starts to burn only above 850°C. These differences have been explained in terms of different particle size and surface functionalization.     

Characterization of structures and surface states of the nanodiamond synthesized by detonation

Nanodiamond is a relatively new nanomaterial with broad prospects for application. In this paper, a variety of methods were used to analyze comprehensively the structures and the surface states of the nanodiamond synthesized by detonation, for example, X-ray diffraction (XRD) spectroscopy, energy diffraction spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman) and differential scanning calorimeter (DSC). The results show that, the nanodiamond particles are spherical or elliptical in shape. The average grain size is approximately 5 nm. The surfaces of the nanodiamond contain hydroxy, carbonyl, carboxyl, ether-based resin, and other functional groups. The initial oxidation temperature of the nanodiamond in the air is about 550 °C, which is lower than that of the bulk diamond.