This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decompos...This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters ; their pseudo-active energy Ea; and that the top-temperature of decom-position Tp decreases gently in the scope of micron-sized diameter, but decreases sharply when the average di-ameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reac-tions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both Ea and Tp to decline sharply with the decrease of the average diameter of nano-particles.展开更多
Pt/Ti bottom electrodes were fabricated on SiO2/Si substrates by magnetron dual-facingtarget sputtering system. Lead zirconate titanate（PZT） thin films were deposited on Pt/Ti/SiO2/Si substrates by radio frequency ...Pt/Ti bottom electrodes were fabricated on SiO2/Si substrates by magnetron dual-facingtarget sputtering system. Lead zirconate titanate（PZT） thin films were deposited on Pt/Ti/SiO2/Si substrates by radio frequency （RF） magnetron sputtering system. The thickness of PZT thin films which were deposited for 5 h was about 800 nm. XRD spectra show that PZT thin films deposited in Ar ambience and rapid-thermal-annealed for 20 min at 700 ℃ have good crystallization behavior and perovskite structure. AFM micrographs show that mean diameter of crystallites is 70 nm and surface structures of PZT thin films are uniform and dense. Raw mean, root mean square roughness and mean roughness of PZT thin films are 34..357 rim, 2. 479 nm and 1. 954 nm respectively. As test frequency is 1 kHz, dielectric constant of PZT thin films is 327.5. Electric hysteresis loop shows that coercive field strength, residual polarization strength and spontaneous polarization strength of PZT thin films are 50 kV/cm, 10μC/cm^2 and 13μC/cm^2 respectively.展开更多
文摘目的评价载银(Ag)或锌(Zn)的介孔钙硅纳米粒子(mesoporous calcium-silicate nanoparticles,MCSNs)和聚己内酯(poly-ε-caprolactone,PCL)的复合材料的理化性能、体外生物活性及促进成骨能力。方法通过加热熔融法制备PCL-MCSNs、PCL-Zn-MCSNs、PCL-Ag-MCSNs和PCL-Ag-Zn-MCSNs(Ag与Zn物质的量比为1∶1),表征其表面形貌、机械性能和体外降解性能。复合材料与根尖乳头干细胞(stem cell from the apical papilla,SCAP)共培养,观察其表面的细胞附着和羟磷灰石晶体(hydroxyapatite,HA)形成情况。通过CCK-8法、碱性磷酸酶(ALP)活性测定和茜素红染色,评价材料的细胞毒性和促进体外成骨效果。结果所有复合材料的表面平整均匀,PCL-MCSNs的压缩强度最高,为3.05 MPa。PCL-Zn-MCSNs的表面HA形成最多、降解最快、表面附着的细胞密度最高,细胞粘附性最好。除PCL-Ag-MCSNs和PCL-Ag-Zn-MCSNs外,其他实验组都能促进细胞增殖,ALP活性升高,产生的钙化结节含量均高于PCL,其中PCL-Zn-MCSNs显著高于其他组(P<0.05)。结论PCL和载银或锌的MCSNs的复合材料具有良好的机械性能和降解性能,但细胞粘附性、细胞增殖性、ALP活性和钙化结节形成能力随Zn含量增加而增强,提示含Zn的该类型复合材料的体外生物活性良好,在促成牙/成骨方面有着优越的潜能,有望成为新型的口腔颌面骨缺损的修复材料。
文摘This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters ; their pseudo-active energy Ea; and that the top-temperature of decom-position Tp decreases gently in the scope of micron-sized diameter, but decreases sharply when the average di-ameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reac-tions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both Ea and Tp to decline sharply with the decrease of the average diameter of nano-particles.
文摘Pt/Ti bottom electrodes were fabricated on SiO2/Si substrates by magnetron dual-facingtarget sputtering system. Lead zirconate titanate（PZT） thin films were deposited on Pt/Ti/SiO2/Si substrates by radio frequency （RF） magnetron sputtering system. The thickness of PZT thin films which were deposited for 5 h was about 800 nm. XRD spectra show that PZT thin films deposited in Ar ambience and rapid-thermal-annealed for 20 min at 700 ℃ have good crystallization behavior and perovskite structure. AFM micrographs show that mean diameter of crystallites is 70 nm and surface structures of PZT thin films are uniform and dense. Raw mean, root mean square roughness and mean roughness of PZT thin films are 34..357 rim, 2. 479 nm and 1. 954 nm respectively. As test frequency is 1 kHz, dielectric constant of PZT thin films is 327.5. Electric hysteresis loop shows that coercive field strength, residual polarization strength and spontaneous polarization strength of PZT thin films are 50 kV/cm, 10μC/cm^2 and 13μC/cm^2 respectively.
