Comparison of Mechanical Properties of Acid and UV Ozone Treated Nanodiamond Epoxy Nanocomposites

Nanodiamond（ND） powder was successfully activated by wet chemical method and by exposure of UV/O3 in a chamber followed by mixing in triethylenetetramine（TETA） solution.The reinforcement role of activated ND in the mechanical properties of epoxy matrix was studied.Both treatments,i.e.acid and UV/O3 provide ND surface with chemical functionalities for adhesion with epoxy resin.Fourier transform infrared spectroscopy was utilized to confirm the attachment of surface groups to the ND particles.The low content of acid and UV/O3 activated ND was dispersed ultrasonically in the epoxy matrix separately to make nanocomposites.The mechanical properties of the nanocomposites were investigated under three point bending.The strong interactions among activated ND particles and the epoxy resin provide efficient load transfer interfaces,which enhances the mechanical properties of the composites.It was found that the flexural strength,modulus,and toughness of 0.1 wt%ND loaded nanocomposites have been enhanced up to 85%,57%,and 39%,respectively for UV/O3 treated ND powder.It is also found that the optimum ND concentration to achieve maximum reinforcement is 0.1 wt%while higher concentrations lead to decrease in mechanical properties.The significant improvement of the mechanical properties of the ND/epoxy nanocomposites is attributed to the good dispersion of the functionalized ND in epoxy matrix.     

非水介质中纳米金刚石的改性、分散与应用

开展纳米金刚石在非水介质中应用的前提是其在介质中的良好分散与稳定.鉴于此,综述了非水介质中纳米金刚石改性与分散研究进展,以及相关应用现状和前景.     

Study on the Modification of Nanodiamond with DN-10

Fourier transform infrared spectroscopy (FT-IR) and ζ-potential were introduced to study the effect of different modification parameters on the surface properties of nanodiamond (NO). Results showed that under stirring grinding conditions, ND hard aggregates were smashed and some active spots on them reacted with surfactant molecules, which led to the increase in its ζ-potential and stability. Different models of surface modification were also given in this study.     

Study on the Modification of Nanodiamond with DN-IO

Fourier transform infrared spectroscopy （FT-IR） and ζ-potential were introduced to study the effect of different modification parameters on the surface properties of nanodiamond （ND）. Results showed that under stirring grinding grinding conditions, ND hard aggregates were smashed and some active spots on them reacted with surfactant molecules, which led to the increase in its ζ-potential and stability. Different models of surface modification were also given in this study.     

Mechanochemical synthesis of nanocrystalline titanium monoxide

Nanocrystalline cubic titanium monoxide, TiO_x (0.92 < x < 1.19), with mean crystallite size of ≈ 6 nm, was synthesized by mechanochemical treatment of Ti and TiO₂ (rutile) powder mixtures with molar ratios of 1:1, 1.10:1 and 1.25:1. The mechanochemical solid state reaction in a high-energy planetary ball mill was completed for 2 h in either air or argon atmosphere. During heating in vacuum at 900 and 1000 °C for 24 h, nanocrystalline TiO_x transforms to a well-crystallized, cubic or monoclinic TiO_x. The materials prepared were characterized by XRPD, TGA/DSC and SEM/EDS analysis.     

Mechanochemical processing and microstructural characterization of pure Fe2B nanocrystals

The results of current investigation demonstrate that mechanochemical processing can be used to synthesize high purity Fe₂B nanocrystals by selecting well-optimized milling conditions, reaction paths and proper starting materials. Microstructure, phase analyses, specific surface area, and magnetic properties of the synthesized nanocrystals were examined by using X-ray diffraction/spectroscopy, electron microscopy, nitrogen adsorption–desorption methods following Brunauer-Emmett-Teller equation and vibrating sample magnetometer techniques, respectively. Removal of MgO impurity phase by leaching the resulting powder in the acetic acid solution yielded single phase Fe₂B nanocrystals with the crystallite size and specific surface area of 12.5 nm and 29 m²/g, respectively. Magnetization results clearly indicated the ferromagnetic behavior of Fe₂B nanocrystals with saturation magnetization observed around 96.26 emu·g^?1. Electron microscope images revealed coaxial/spherical powder shape and morphology of the single-phase Fe₂B nanocrystals.     

Mechanochemical preparation of magnetite nanoparticles by coprecipitation

A novel simple process for preparing magnetite (Fe₃O₄) nanoparticles by a coprecipitation route without using any additives (e.g., surfactant and oxidizing and reducing agents) has been developed. In this method, a cooled ball mill was used as a synthesis reaction field in order to inhibit progress of both the synthesis reaction and the particle growth by heat energy. The Fe₃O₄ nanoparticles were formed by ball-milling of the starting suspension consisting of ferrous hydroxide and goethite colloids, and the crystallization was simultaneously progressed without heating. The obtained nanoparticles were then characterized through the SEM observation, XRD analysis, EDS analysis and oxidation-reduction titration, and the magnetic properties were measured with a SQUID magnetometer. This preparation process can provide successfully the superparamagnetic Fe₃O₄ nanoparticles of about 10 nm with high crystallinity and saturation magnetization by mechanochemical effect.     

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.     

Mechanochemical synthesis and spark plasma sintering of hafnium carbonitride ceramics

Submicron powder of non-stoichiometric hafnium carbonitrides (HC_0.5N_0.2) was fabricated by the mechanochemical synthesis method. It was shown that during the first milling stages, primarily reaction between hafnium and carbon took place. The nitridation occurred later when fresh metal surfaces started to form through defragmentation of the brittle layer of a carbon-solid solution. The synthesized powder was consolidated by spark plasma sintering approach to producing dense bulk hafnium carbonitride ceramics. Hardness and fracture toughness measured on consolidated samples were 20.8 ± 1 GPa и 3.5 ± 0.2 MPa?m^1/2, respectively. The obtained results were compared with previously reported data.     

Mechanochemical effect on the microstructure and mechanical properties in ultraprecision machining of AA6061 alloy

The mechanochemical effect on the microcutting of AA6061 alloy is studied through characterization on the microgroove surface. There is a reduction in cutting and thrust forces with the application of ink during microcutting. Moreover, the microhardness of the ink-affected microgroove is lower than that of the ink-free microgroove. Numerous substructured grains exist in the ink-affected microgroove zone whilst deformed grains dominate in the ink-free microgroove zone produced by microcutting. Furthermore, the mechanochemical effect can facilitate the nucleation of precipitates in the microgroove zone and induce the formation of subgrains with multiple orientations. According to the analysis and calculation, the main texture components of the ink-affected sample are Goss {110}001 and R {124}211, and that of the ink-free sample are Brass {110}112, Copper {112}111 and S {123}634. Besides, a clear difference of slip systems is found between the ink-free and ink-affected microgrooves, and the results show that R texture is easier to form on the ink-affected microgroove.     

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.     

Nanocrystalline Growth Activation Energy of Zirconia Polymorphs Synthesized by Mechanochemical Technique

The synthesis of ZrO_2 by mechanochemical reaction using ZrCI_4 and CaO as raw materials and subsequent annealing of the products were investigated.The effect of thermal treatment on the structural evolution and morphological characteristics of the nanopowders was studied by X-ray diffractometry,Raman spectroscopy,transmission electron microscopy,scanning electron microscopy,differential thermal analysis and Rietveld refinement.The results showed that the average crystallite size of ZrO_2 was less than 100 nm up to around1100 ℃.The activation energy for ZrO_2 nanocrystallite growth during calcination was calculated to be about13,715 and 27,333 J/mol for tetragonal(t-ZrO_2) and monoclinic(m-ZrO_2) polymorphs,respectively.Mechanism of the nanocrystallite growth of the ZrO_2 polymorphs during annealing is primarily investigated.     

方解石晶体色散方程的研究

根据Sellmeir方程的系数在Lorentz模型中的意义所表明的数量关系,将该方程简化.对实验数据作适当的组合和变量替换,将修正的Sellmeir方程展开成多项式对实验数据进行拟合.根据对误差曲线的分析以及有关系数在Lorentz模型中作用,对该系数作进一步优化,最后确定修正的Sellmeir方程系数.得到在近紫外和近红外光谱区,方解石的修正的Sellmeir方程的系数分别为别为 Ao=2.6926,Bo=0.0192,Co=0.0195,Do=0.0143;和Ae=2.1846,Be=0.0085,Ce=.0143,De=0.0023,拟合结果的误差平方和分别为1.13×10-7和1.72×10-8.本结果可在计算方解石色散特性时使用,本方法可在拟合其它材料的色散方程时使用.     

Mechanochemical synthesis,structural, magnetic,optical and electrooptical properties of CuFeS2 nanoparticles

The rapid mechanochemical synthesis of nanocrystalline CuFeS₂ particles prepared by high-energy milling for 60?min in a planetary mill from copper, iron and sulphur elements is reported. The CuFeS₂ nanoparticles crystallize in tetragonal structure with mean crystallite size of about 38?±?1?nm determined by XRD analysis. HRTEM study also revealed the presence of nanocrystals with the size of 5–30?nm with the tendency to form agglomerates. The Raman spectrum confirms the chalcopyrite structure. Low temperature magnetic data for CuFeS₂ support the coexistence of antiferromagnetic and paramagnetic spin structure. Moreover, the hysteresis loops taken at temperatures from 5?K to 300?K revealed a presence of very small amount of ferromagnetic phase, which seems to be associated with the non-consumed elemental Fe in as-prepared nanoparticles. The optical band gap of CuFeS₂ nanoparticles has been detected to be 1.05?eV, larger than band gap of the bulk material. The wider gap possibly resulted from the nano-size effect. Photoresponses of CuFeS₂ nanoparticles were confirmed by I-V measurements under dark and light illumination. It was demonstrated that mechanochemical synthesis can be successfully employed in the one step preparation of nanocrystalline CuFeS₂ with good structural, magnetic, optical and electrooptical properties.     

Mechanochemical degradation treatment of TBBPA: A kinetic approach for predicting the degradation rate constant

Persistent organic pollutants (POPs) have been banned from production and use. The brominated flame retardant TBBPA is a type of POP and has been widely used in plastics to enhance their fire resistance. However, because the natural degradation of TBBPA is a difficult process, it is particularly important to propose an appropriate treatment method. Hence, the mechanochemical degradation of TBBPA is a feasible method because it does not require high temperature heating and does not produce secondary pollutants after the reaction is completed. In this study, we performed a series of TBBPA degradation experiments with a planetary ball mill and confirmed the degradation efficiency and the rate under various conditions. Then, we conducted a discrete element method (DEM) simulation to compute the collision energies in the ball mill. By comparing the degradation rate and collision energies, we revealed that the mechanochemical degradation rate of TBBPA can be predicted by a normal collision energy computed by DEM simulation. This kinetic approach enables us to predict the rate constant and consequently, the energy consumption for the mechanochemical treatment. The predictability of these parameters will encourage the further application of mechanochemical reaction in the field of POPs treatment.     

Mechanochemical synthesis and characterization of TiB2 and VB2 nanopowders

A novel method for the synthesis of transition-metal boride nanopowder has been developed using a mechanochemical reaction between LiBH₄, LiH and transition-metal chloride (TiCl₃ and VCl₃) by high energy ball milling. This method successfully produces TiB₂ and VB₂ particles dispersed within a soluble LiCl matrix. Subsequent washing with distilled water, ethanol and acetone to remove the LiCl matrix phase yields TiB₂ and VB₂ nanopowders of 15-60 nm particle size. From the X-ray diffraction patterns and high resolution transmission electron microscopy image, it is found that each particle is polycrystalline consisting of 3-5 nm crystallites. Neither particle nor crystallite size are increased significantly after heating at 680 °C.     

衍射透镜的色散分析

基于标量衍射理论，本文分析了衍射透镜的色差，首次得出了计算其色散的数学表达式。结果表明，衍射透镜的色散包两个部分：材料色散和波长色散，二者所占的比例随孔径值的不同而变化。     

炭黑分散性质的研究

本文以十二烷基苯磺酸钠、十二醇硫酸钠、乙醇、氯仿、蒸馏水等做分散剂,分析了炭黑分散时间和温度等影响因素,用扫描探针显微镜DFM模式观察炭黑粒子分散情况。实验结果表明观察炭黑单个粒子用蒸馏水做分散剂最好,随着分散时间的增加,分散效果越来越好,3h最佳,当分散4h之后分散效果趋向稳定。烷基分散剂、醇基分散剂、烷基和醇基复配分散剂的炭黑形貌图比较,可知加入烷基和醇基复配分散剂有利于炭黑分散,但是不利于炭黑粒子的观察。     

等离子体天线中波的色散关系的研究

本文研究了同轴对称表面波沿等离子体柱轴向传播的色散关系,由此得到的波矢说明了当频率小于等离子体频率时,电磁波沿等离子体柱的传播类似于电磁波沿金属介质交界面上的传播,传播速度接近于光速.因此可以使用等离子体代替金属用来构成最基本的天线振子.     

纳米红色硒粉在乙二醇介质中的分散工艺研究

针对含纳米红色硒粉抗菌保健不锈钢餐具的开发问题,为制备高分散性和悬浮稳定性的纳米硒粉,本文在测定纳米硒粉在乙二醇介质中pH-zeta电位图的基础上,选用CTAB、PVP、PEG-2000和Span80四种表面活性剂,采用吸光度测试、沉降实验研究了纳米硒粉在乙二醇介质中的分散工艺及其悬浮稳定性,并探讨了不同表面活性剂的分散机理。结果表明,在最佳配比下的CTAB与具有空间位阻稳定机理PVP和PEG-2000的复合分散体系的分散效果明显好于单分散剂,其中,PVP与CTAB的复合分散比最佳单分散剂CTAB的分散效果提升了105%;推荐纳米硒粉在乙二醇中的分散工艺为:在pH=6、3%(质量比)CTAB+3%PVP复配分散,分散时间为10 min,该工艺下分散的纳米硒粒子静置60天的沉降率仅为0.7%。红外测试表明,CTAB在纳米硒粉表面为物理吸附,PVP、PEG-2000和Span80则为化学吸附。