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991.
Toshihiko Myojo Takako Oyabu Kenichiro Nishi Chikara Kadoya Isamu Tanaka Mariko Ono-Ogasawara Hirokazu Sakae Tadashi Shirai 《Journal of nanoparticle research》2009,11(1):91-99
Mass production of some kinds of carbon nanotubes (CNT) is now imminent, but little is known about the risk associated with
their exposure. It is important to assess the propensity of the CNT to release particles into air for its risk assessment.
In this study, we conducted aerosolization of a multi-walled CNT (MWCNT) to assess several aerosol measuring instruments.
A Palas RBG-1000 aerosol generator applied mechanical stress to the MWCNT by a rotating brush at feed rates ranging from 2
to 20 mm/h, which the MWCNT was fed to a two-component fluidized bed. The fluidized bed aerosol generator was used to disperse
the MWCNT aerosol once more. We monitored the generated MWCNT aerosol concentrations based on number, area, and mass using
a condensation particle counter and nanoparticle surface area monitor. Also we quantified carbon mass in MWCNT aerosol samples
by a carbon monitor. The shape of aerosolized MWCNT fibers was observed by a scanning electron microscope (SEM). The MWCNT
was well dispersed by our system. We found isolated MWCNT fibers in the aerosols by SEM and the count median lengths of MWCNT
fibers were 4–6 μm. The MWCNT was quantified by the carbon monitor with a modified condition based on the NIOSH analytical
manual. The MWCNT aerosol concentration (EC mass base) was 4 mg/m3 at 2 mm/h in this study. 相似文献
992.
A. K. Mahapatra 《Journal of nanoparticle research》2009,11(2):467-475
CdS nanotubes with wall thickness comparable to excitonic diameter of the bulk material are synthesized by a chemical route.
A change in experimental conditions result in formation of nanowires, and well-separated nanoparticles. The diameter and wall
thickness of nanotubes measured to be 14.4 ± 6.1 and 4.7 ± 2.2 nm, respectively. A large number of CdS nanocrystallites having
wurzite structure constitute these nanotubes. These nanotubes show high energy shifting of optical absorption and photoluminescence
peak positions, compared to its bulk value, due to quantum confinement effect. It is proposed that nucleation and growth of
bubbles and particles in the chemical reaction, and their kinetics and interactions are responsible for the formation of nanotubes. 相似文献
993.
采用密度泛函方法对铜原子在有限长(5,5)椅型单壁碳纳米管的吸附行为进行了研究.计算结果表明,铜原子吸附在管外壁要比吸附在管内壁能量上更为有利,在管外壁碳原子顶位吸附最佳,属于明显的化学吸附.且用前线轨道理论对其成键特性进行了分析,表明在顶位吸附时主要由铜原子的4s轨道电子与碳纳米管中耦合的σ-π键形成新的σ键.此外还对比计算了两种典型位置电子密度,发现顶位吸附的成键中有更大的电子云重叠.进一步表明在某些情况下铜碳原子可以成键.
关键词:
碳纳米管
铜原子
成键特性 相似文献
994.
将碳纳米管与纳米Al2O3-TiO2陶瓷粉末超声共混制备了碳纳米管/纳米Al2O3-TiO2复合粉末,测试了复合粉末在2—18GHz波段的电磁参数.研究表明:随着碳纳米管质量分数的增加,碳纳米管/纳米Al2O3-TiO2复合粉末的复介电常数和损耗角不断增大.当碳纳米管质量分数和厚度增加时,复合粉末对电磁波的反射率峰值先增加后减小,而谐振频率不断向低频移动.采用微弧等离子喷涂制备了7wt%碳纳米管/纳米Al2O3-TiO2复合吸波涂层,当厚度为1.5mm时,涂层最小反射率为-24.0dB,当厚度为2.0mm时,涂层小于-10dB的频带宽为3.60GHz,当温度为500℃高温时,1.0mm厚的涂层最小高温反射率为-12.2dB,小于-10dB频带宽为2.0GHz.复合涂层的实际厚度D与理论厚度d呈线关系:d=0.898D+0.515.
关键词:
等离子喷涂
碳纳米管
2O3-TiO2')" href="#">纳米Al2O3-TiO2
吸波性能 相似文献
995.
996.
通过分子动力学方法模拟了在碳纳米管内填充一定数目的半导体元素硅形成碳纳米管-硅纳米线复合结构的过程,并采用Lindemann指数研究了这种复合结构的热稳定性.计算结果表明,当考虑碳纳米管和硅纳米线轴向方向的周期性边界条件之后,在C(13,0)和C (14,0)碳纳米管内能够形成亚稳结构的硅纳米线Si16NW和Si20NW,从而获得一种碳纳米管-硅纳米线的新型复合结构.通过计算这种复合结构的Lindemann指数,可以看到由于碳纳米管的保护作用,碳纳米管包裹的硅纳
关键词:
复合结构
纳米线
碳纳米管
分子动力学 相似文献
997.
D. Seifert F. Langenhorst H. Chiron 《Journal of magnetism and magnetic materials》2009,321(24):4045-4051
Single-phase M-type hexagonal ferrites Sr1−xLaxFe12O19 (0≤x≤1) were prepared by a ceramic route. The stability limits of the ferrite phases were determined with a combination of various microscopy techniques, electron-probe micro-analysis, powder X-ray diffraction and thermal analysis. SrFe12O19 (x=0) is stable up to 1420 °C, whereas LaFe12O19 (x=1) exists between 1360 and 1400 °C only. The lattice parameters of Sr1−xLaxFe12O19 exhibit a linear variation with x, i.e. a0 slightly increases and c0 decreases with x, leading to a decrease of the unit cell volume with x. The saturation magnetization at T=5 K decreases with increasing La concentration. Room temperature Mössbauer analysis shows that the Fe3+/Fe2+ valence change occurs in the 2a sites for the whole composition range. 相似文献
998.
Temperature dependent ultrasonic properties of aluminium nitride 总被引:1,自引:0,他引:1
Hexagonal wurtzite structured aluminium nitride has been characterized by the theoretical calculation of ultrasonic attenuation, ultrasonic velocity, higher order elastic constants, thermal relaxation time, acoustic coupling constants and other related parameters in temperature range 200-800 K for wave propagation along the unique axis of the crystal. Higher order elastic constants of AlN at different temperatures are calculated using Lennard-Jones potential for the determination of ultrasonic attenuation. A decrease in ultrasonic velocity with temperature has been predicted, which is caused by reduction in higher order elastic constants with temperature. The temperature dependent ultrasonic properties have been discussed in correlation with higher order elastic constants, thermal relaxation time, thermal conductivity, acoustic coupling constants and thermal energy density. Anomalous behaviour of the attenuation is found at 400 K. On the basis of attenuation, the ductility and performance of AlN have been studied. 相似文献
999.
采用多层工艺和光刻方法在玻璃衬底上加工了亚微米级金叉指型超微带电极阵列(IDA),IDA电极的宽度为362nm,电极表面位于沟槽内。实验表明,所加工的IDA电极可作为生物和化学传感器的一次性超微基体电极。采用电聚合的方法将葡萄糖氧化酶(GOD)和吡咯(PPy)固定于IDA电极,该修饰电极可作为葡萄糖传感器。采用该葡萄糖传感器对磷酸钾缓冲溶液(pH7.0)中的葡萄糖浓度进行了比对测量,在2.0-7.0mmol/L的浓度范围内,传感器的响应时间为10s;灵敏度为14.6nA/(mmol/L),相关系数为0.999。 相似文献
1000.
以改进方法合成的B-ZSM-5分子筛为母体,采用气固相法合成了Ti-ZSM-5分子筛,并以XRD,FT-IR,UV-Vis,XRF,SEM,ICP-AES和MAS NMR等手段对B-ZSM-5和Ti-ZSM-5进行了表征,考察了Ti-ZSM-5对苯酚羟基化反应的催化性能. 结果表明,合成B-ZSM-5时的前期低温晶化有助于晶粒的减小; 以其为母体制备的Ti-ZSM-5对苯酚羟基化反应具有优异的催化性能. 在n(PhOH)/n(H2O2)=3,n(Me2CO)/n(PhOH)=2.7,m(cat)/m(PhOH)=5%,T=353 K和t=6 h的反应条件下,苯酚转化率可达20%以上. 相似文献