Cheepborisutikul Siraphat Jan, Ogawa Makoto
School of Energy Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), 555 Moo 1 Payupnai, Wangchan, Rayong 21210, Thailand.
Inorg Chem. 2023 Jul 31;62(30):12166-12174. doi: 10.1021/acs.inorgchem.3c01904. Epub 2023 Jul 18.
Anatase/silica core/shell particles were prepared by the hydrolysis and condensation of tetraethyl orthosilicate on anatase particles with the sizes of 9, 22, and 111 nm, respectively. The thickness of the silica layer was designed from ca. 3 to 14 nm by repeating the coating procedure on anatase with a particle size of 22 nm. By the heat treatment at 1000 °C, though the pristine anatase particles transformed to rutile, anatase remained for the silica-coated particles. Anatase particles (111 nm) transformed to rutile upon heating at 1100 °C, while the transformation was not observed for the smaller particles (9 and 22 nm). With the increase of the silica thickness to 14 nm, anatase did not transform to rutile even after heating at 1150 °C, while resulting in varied compositions of anatase and rutile after heating at 1200 °C. The crystal growth of anatase and rutile was also suppressed for the silica-coated particles compared with that seen for pristine anatase. Thus, the thermal transformation and crystal growth of titania were controlled by the coating with silica, and the effects were shown to affect the coating.
锐钛矿/二氧化硅核壳颗粒是通过原硅酸四乙酯在分别为9、22和111nm尺寸的锐钛矿颗粒上进行水解和缩合制备的。通过在粒径为22nm的锐钛矿颗粒上重复包覆过程，将二氧化硅层的厚度设计为约3至14nm。通过在1000℃下进行热处理，尽管原始锐钛矿颗粒转变为金红石，但包覆二氧化硅的颗粒仍保留锐钛矿相。锐钛矿颗粒（111nm）在1100℃加热时转变为金红石，而较小颗粒（9和22nm）未观察到这种转变。随着二氧化硅厚度增加到14nm，即使在1150℃加热后锐钛矿也未转变为金红石，而在1200℃加热后会产生锐钛矿和金红石的不同组成。与原始锐钛矿相比，包覆二氧化硅的颗粒中锐钛矿和金红石的晶体生长也受到抑制。因此，二氧化钛的热转变和晶体生长通过二氧化硅包覆得以控制，并且这些效应显示出会影响包覆情况。
