Multi-walled carbon nanotubes (MWCNTs), dispersed in suspensions consisting mainly of individual tubes, were used for intratracheal instillation and inhalation studies. Rats intratracheally received a dose of 0.2 mg, or 1 mg of MWCNTs and were sacrificed from 3 days to 6 months. MWCNTs induced a pulmonary inflammation, as evidenced by a transient neutrophil response in the low-dose groups, and presence of small granulomatous lesion and persistent neutrophil infiltration in the high-dose groups. In the inhalation study, rats were exposed to 0.37 mg/m(3) aerosols of well-dispersed MWCNTs (>70% of MWCNTs were individual fibers) for 4 weeks, and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. The inhalation exposures delivered less amounts of MWCNTs into the lungs, and therefore less pulmonary inflammation responses was observed, as compared to intratracheal instillation. The results of our study show that well-dispersed MWCNT can produce pulmonary lesions, including inflammation.

In order to investigate the pulmonary toxicity of titanium dioxide (TiO2) nanoparticles, we performed an intratracheal instillation study with rats of well-dispersed TiO2 nanoparticles and examined the pulmonary inflammation and histopathological changes in the lung. Wistar Hannover rats were intratracheally administered 0.2 mg (0.66 mg/kg) and 1.0 mg (3.3 mg/kg) of well-dispersed TiO2 nanoparticles (P90; diameter of agglomerates: 25 nm), then the pulmonary inflammation responses were examined from 3 days to 6 months after the instillation, and the pathological features were examined up to 24 months. Transient inflammation and the upregulation of chemokines in the broncho-alveolar lavage fluid were observed for 1 month. No respiratory tumors or severe fibrosis were observed during the recovery time. These data suggest that transient inflammation induced by TiO2 may not lead to chronic, irreversible legions in the lung, and that TiO2 nanoparticles may not have a high potential for lung disorder.

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The influence of complex dopants including donor and acceptor ions on microstructure and electrical properties of PZT (Zr/Ti = 53/47) ceramics was investigated. The prepared PZT ceramics modified with complex soft dopants, La +3 and Nb +5 , showed that the piezoelectric properties were enhanced and stable with the compositional variations, which made it possible to establish the higher reliability and reproducibility of the piezoelectric performances. For 1.0 mol% La and 1.2 mol% Nb doped composition, the maximum value, k P = 0.66, was obtained. Unlike single element doping, the complex doping of both the donor and acceptor ions caused various compensation effects for the piezoelectric properties of the PZT ceramics. The improved piezoelectric properties, i.e., enhanced Q m with remaining higher k p , were obtained in the PZT composition complexly doped with La +3 and Fe +3 . For 1.0 mol% La and 2.0 mol% Fe doped PZT composition, relatively high Q m and k p values of 580 and 0.53, respectively, were obtained. It was also shown that the PZT composition had the rather lowered dielectric constant, ε r = 800, and considerably low loss, tanδ = 0.003. By changing the dopants compositions, the properties can also be tailored over wider range.