翻译论文 nanointerface.doc

（张颖彧）3.2 CHEMICAL CHARACTERIZATION 3.2.1 CHARACTERIZATION USING FOURIER TRANSFORMED INFRA-RED (FTIR) 3.1 化学表征3.2.1 应用傅氏转换红外线光谱分析仪进行表征A Nicolet NEXUS 470-ESP FTIR spectrometer was employed to take the spectra of both the particles themselves and the associated composites samples. To investigate the nature of the particles before incorporation into a composite, the particles were compressed into pellets approximately 0.8 mm in thickness, and, for composite measurements, laminar samples of approximately 1 mm thickness were used. 应用一台美国Nicolet的NEXUS 470 - ESP的红外光谱仪来获取颗粒本身以及相关的复合材料样品的光谱。为了研究混入复合材料以前的颗粒的性质，我们将颗粒压缩成大约0.8mm厚的大颗粒，同时，我们将复合材料制成1mm厚的薄片状样品。Figure 11 shows the FTIR spectra for (a) the nanoparticles and (b) the microparticles. The sharp band at 3747 cm-1, present only in nanoparticles, is attributed to isolated silanols and the broad absorption band around 3500 cm-1(more pronounced in the microparticle sample) has been assigned to the (OH) stretching vibration of surface hydroxyl groups involved in hydrogen bonds with water molecules and with adjacent silanol groups 35. The band at 1630 cm-1corresponding to the (OH) bending vibration of adsorbed water molecules, decreased for nanoparticles. Based on the above results, changes in the surface silanol structure for particles of two different sizes can be illustrated in Figure 12. For relatively large particles, most of the silanol groups are hydrogen-bonded to each other and this imparts some polarity to those silanol groups (Figure 12a). For particles of nanoscale diameter, the high surface curvature increases the distance between the silanol groups preventing hydrogen bonding between them (Figure 12b). 36. 图11显示的是傅氏转换红外线光谱分析仪测得的（a）纳米粒子和（b）微粒子的光谱。只有在纳米粒子中才会在3747cm-1处出现急剧升高的光谱带，这是由于孤立的硅羟基和在3500cm-1处宽吸收谱带（在微粒子样本中更为突出）已被分配到在水分子和相邻的硅羟基中的表面羟基（OH）的伸缩振动中。【35】在1630cm-1处的谱带与吸收了水分子的纳米粒子的弯曲振动相一致，在纳米粒子中减少。基于以上的结论，我们可以用图12来阐述两种不同尺寸粒子中的表面羟基结构的变化。相对来说比较大的粒子中大多数的硅羟基是通过氢键相互连接的，并且这赋予了硅羟基一些极性（图12a）。对于纳米直径的颗粒来说，高表面曲率增加了硅羟基间的距离同时阻止了硅羟基间氢键的形成（图12b）。【36】图11. 傅氏转换红外线光谱分析仪 二氧化硅粉末表面的红外光谱.a， 纳米级；b，微米级。图12. 两种不同尺寸粒子的示意图，a，微米级；b，纳米级。 大尺寸粒子硅羟基中距离最近的O和H间拥有氢键；而在纳米尺寸的粒子间不存在这种氢键。3.2.2 CHARACTERIZATION USING ELECTRON PARAMAGNETIC RESONANCE (EPR)3.2.2 应用电子顺磁共振进行表征（EPR）The Electron Paramagnetic Resonance (EPR) spectra show evidence of changes in the interface chemistry due to composite processing. The microwave magnetic field component perpendicular to the direction of the field causes EPR transitions when the microwave quantum energy, h (where is the frequency and h is Planks constant), is equal to the Zeeman energy splitting gH of two energy states (M = and M = - ), i.e. h = gH. The parameter g (called Landes g factor) is the spectroscopic splitting factor representing the nature of the unpaired electron and is the unit of magnetic moment called the Bohr magneton 37, 38. Each type of unpaired electron is identified with the appropriate g factor obtained from the resonance condition as g = (h/)(/H). All the powdered silica samples and composites (cryo-crushed) were measured using a Bruker ER 042 EPR spectrometer. The g value calibration was done before and after the measurement using dpph, which has g value of 2.0039 (the g value for a free electron is 2.0023). All the curves presented for the analysis are the derivative of microwave absorption at 9.77 GHz plotted as a function of the applied magnetic field and are normalized for comparison. In the case of powder samples containing anisotropic defects, as is the case here, the spectra become quite complicated in appearance. 电子顺磁共振谱给出了由于复合过程引起界面化学变化的证据。微波磁场分量垂直于磁场方向导致当微波能量剧增时引起EPR的量子跃迁，h(是频率，h是普朗克常量)，等于两种能级（M=1/2和M=-1/2）的赛曼能量分割gH，即h= gH。参量（叫做朗德因子）是波谱分裂因子，表示不配对电子的性质，为电子磁矩的自然单位，称波尔兹子【37，38】。每种不配对电子的g因子因共振情况的不同不同，即g=(h/)( /H)。所有经干燥而成粉末的二氧化硅样品和混合粉末（低温粉碎）都应用布鲁克ER 042 EPR 谱仪进行测量。在测量之前及测量之后都需用二苯基苦基酰肼对g值进行校准，得到g值等于2.0039（自由电子的g值为2.0023）。分析中用的所有曲线都是在9.77GHz处微波吸收所衍生出来的，标记为应用磁场，同时也是为了规范化比较。由于粉末状式样存在各向异性的缺点，由于这个原因，光谱看上去非常复杂。Figure 13 shows the EPR spectra for micro and nanosilica powders dried at 195 C. The peak shown by nanoparticles (Figure 13a) is “well defined”,whereas in the spectra for micro particles (Figure 13b), thespecies responsible for the peak is broader and not “well defined”, and of lower intensity. The term “well defined” here implies that, in the case of nanoparticles, most of the radical centers have the same crystallographic environment. For the microparticles, however, the environments of the radicals are more diverse. The positions of upper and lower bound extrema, at g values of 2.28 and 2.09 respectively, strongly suggest that the responsible species for the spectra are diatomic oxygen (O-2). The surface treated nanoparticles have an EPR signature similar to microparticles. The magnitude of the spectra, which are proportional to the number of radicals, increases when the particles are incorporated into the polymer (Figure 14). This is true for all particles. Table 3 shows the peak signal height of particles alone and of the 5% loaded composite. The signal is normalized with respect to power and sensitivity of equipment, but not to the volume fraction of particles (composites have 5 wt% of particles). Although the resurgence of oxygen radicals is lower for surface-treatednanosilica fillers compared with untreated nanosilica fillers, the trend of increasing oxygen radicals is evident. 图13是微粒和纳米二氧化硅粉末在195下干燥后的EPR谱图。纳米粒子（图13a）的峰值是“明确界定”，然而微粒子（图13b）的谱图中，峰值的种类较宽泛，没有“明确界定”，且峰值较低。这里“明确界定”这个词指的是，就纳米颗粒来讲，大多数的自由基中间体都拥有相同的晶