【作者】 苏华枝；

【导师】 吴建青；

【作者基本信息】 华南理工大学 ， 材料学， 2013， 博士

【摘要】 二氧化钛（TiO₂）具有活性高、稳定性好、无毒和成本低等优点，是目前研究最为广泛的光催化剂之一。负载型TiO₂是实现其应用的有效途径，但由于TiO₂本身能分解有机物，所以不能直接将其通过高分子材料粘合而负载到其它材料上。采用适当的固定化方法将TiO₂固定在玻璃、陶瓷和金属等基材表面，是实现其光催化性能的关键。利用TiO₂的光催化活性和光诱导亲水性，可制备具有抗菌除臭、净化空气和自清洁功能的光催化陶瓷。但是光催化活性（低煅烧温度下较好）和涂层附着力（高煅烧温度下较好）之间的矛盾是制约其实际应用的主要原因。本论文对锐钛矿型TiO₂的高温稳定条件与制备及其在陶瓷上的应用进行了比较深入的研究，创新性地提出利用磷酸钛在釉中的分解反应实现在高温烧结条件下制备TiO₂光催化陶瓷的目标。SiO₂^3-改性和PO₄改性是提高纳米锐钛矿型TiO₂粉体热稳定性的有效途径。通过溶胶-凝胶法引入SiO₂、浸渍法或机械混合法引入KH₂PO₄和水解沉淀法引入磷酸都能使TiO₂的相变起始温度由550℃提高到950℃以上。通过掺入碳酸盐和硅酸盐研究氧化物对TiO₂晶相结构的影响。结果表明：在低温时，Li₂O、Na₂O、K₂O、MgO、CaO、ZnO、BaO、B₂O₃、Al₂O₃等陶瓷常用成分对锐钛矿相晶粒长大和TiO₂相变主要起到阻碍作用。将TiO₂与釉料混合，研究TiO₂在釉中的相变行为。结果表明：水解法制备的TiO₂粉体和Degussa P25TiO₂粉体在釉中的相变发生温度和相变完成温度都分别低于釉的始熔温度和熔融温度，而在熔融石英粉中的相变与它们单独时差异不大。低共熔液相是破坏锐钛矿相热稳定性的主要原因。SiO₂改性和5wt%KH₂PO₄改性的TiO₂在熔融石英粉和釉中的相变与纯的TiO₂相似。相比KH₂PO₄改性的TiO₂，磷酸改性的TiO₂在釉中具有更好的热稳定性。当用P/Ti摩尔比为1:2的磷酸改性TiO₂涂覆在陶瓷釉面上制备光催化陶瓷时，底釉和烧成制度对釉面表层中的TiO₂晶相结构影响不大，但对釉面的表面形貌和光催化活性具有重要的影响。此外，提高烧成温度，有利于提高涂层的光泽度和耐磨性，但会导致光催化性能和光诱导亲水性能下降。分别将3种不同P/Ti摩尔比的磷酸钛前驱体与低温熔块（G2）混合并在不同温度下快速烧成。3种情况下都有TiO₂生成，但TiO₂的相变行为不一样。当摩尔比为1:1时，1000℃下TiO₂大部分为锐钛矿相，只有少量的金红石相。不同摩尔比的磷酸钛与Na₂CO₃的分解反应过程各不一样，当摩尔比为1:1时TiO₂主要存在于初级分解产物，而当摩尔比为2:1和4:1时TiO₂主要存在于次级分解产物。显微结构分析表明：磷酸盐对TiO₂颗粒具有一定的粘附作用，这有效地阻碍了TiO₂颗粒间的接触并对其相变起到抑制的作用。磷酸钛与Na⁺的反应可视为磷酸钛与釉反应的前期，当烧成温度达到液相产生的温度时，磷酸钛与Na⁺反应生成的磷酸钛类化合物会被液相熔融并析出TiO₂。磷酸根对初级分解得到的TiO₂的相变具有更好的抑制作用。将P/Ti摩尔比为1:1的磷酸钛前驱体涂覆在陶瓷釉面上并在1000℃下快速烧成，结果表明：直接涂覆在低温釉面上（C2）会导致TiO₂颗粒被玻璃相覆盖，而直接涂覆在高温釉面上（C4）又会导致磷酸钛与釉反应不足使得釉层表面致密化不高。采用在高温釉面上预先涂覆一层薄的低温釉层可避免上述问题。当涂层在1000℃保温3min快速烧成时，尺寸范围为70¹30nm的锐钛矿TiO₂颗粒牢固地嵌入在涂层表面。所得涂层表面致密化程度高，光泽度达到77.8%，附着力为5B级，铅笔擦伤硬度＞6H，其质量非常接近普通陶瓷釉面。UV光照5h后MO降解率达到97%，UV光照12h后水的接触角降低到9.9°。通过磷酸钛在釉中的分解实现了TiO₂光催化陶瓷的高温烧结制备。更多还原

【Abstract】 Titanium dioxide （TiO₂） has been widely investigated as a heterogeneous photocatalystsince1972, due to its excellent functionality, long-term stability, low cost, and nontoxicity.Photocatalytic ceramics are expected to play a significant role in air purification andself-cleaning against growing environmental problems utilizing its photocatalytic activity andphotoinduced hydrophilicity. However, the metastable anatase phase tends to transform intostable rutile phase upon heating. Thermal stability of anatase TiO₂is lower when coated on theglazed ceramic surface compared to the powder alone due to the negative influence ofthe glaze.Therefore, to find a compromise between photoactivity （best at the lower firing temperature）and coating adhesion（best inhigher firing temperature） is the main goalofpractical applicationof photocatalytic ceramics. In this research, highly thermal stable anatase TiO₂powders weresynthesized and applied in ceramics. A novel method has been developed for the first time togenerate TiO₂from the decomposition reaction of titanium phosphate in the glaze.The anatase-to-rutile phase transformation is significantly inhibited by SiO₂orPO3-4modification. The phase transformationstart temperature ofTiO₂increases from550℃toabove950℃when SiO₂was introduced by the sol-gel process, KH₂PO₄was doped byimpregnation technology or mechanical mixing method, and phosphoric acid was introducedby hydrolysis precipitation method.Carbonates and silicates were doped inorder to investigatethe role ofoxides inthe crystalstructure of TiO₂. The results reveal that the common components of ceramic, such as Li2O,Na2O, K2O, MgO, CaO, ZnO, BaO, B2O3, and Al2O3,mainly have inhibitory effects to thegrowth of anatase and the phase transformation of TiO₂.The mixtures of TiO₂and glaze were obtained for the investigation of the phasetransformation of TiO₂in glazes. The results suggest that the start and finish phasetransformation temperatures of TiO₂synthesized by hydrolysis method and Degussa P25TiO₂in glazes are close to the softening temperature and sphere temperature of the glazes,respectively. However, the phase transformation behaviors of TiO₂in fused silica are similar tothat of alone. The eutectic liquid is essential for the phase transformation behavior of anataseTiO₂in glaze. The phase transformation behaviors of SiO₂-modified TiO₂and5wt%KH₂PO₄-modified TiO₂in fused silica and glazes are similar to that of pure TiO₂. TiO₂modified by phosphoric acid has a higher thermal stability in glazes than that ofKH₂PO₄-modified TiO₂.Photocatalytic ceramics were prepared by spin-coating phosphoric acid modified TiO₂ with a P/Ti molar ratio of1:2on the surface of glazed ceramics. Underglaze and firing systemhave little effects on the crystal structure of TiO₂on the surface of glaze layer, but have greateffects on the surface morphology and photoactivity. In addition, the improvement of firingtemperature is favorable for the gloss and abrasion resistance, but unfavorable forphotocatalytic activity and photoinduced hydrophilicity.Three titanium phosphate precursors with different P/Ti molar ratios were respectivelymixed with a low temperature frit （G2） and rapidly firing at different temperatures. TiO₂isfound in all three cases, but undergoes different phase transformation behaviors. The anatasephase is stable up to1000℃when titanium phosphate precursor with a P/Ti molar ratio of1:1is used. The reaction between titanium phosphate and sodium carbonate is related to the P/Timolar ratio of titanium phosphate and the relative amount of sodium carbonate. TiO₂is mainlypresent as the primary decomposition product in the case of P/Ti molar ratio of1:1, but mainlythe secondary decomposition product in the case of P/Ti molar ratio of2:1and4:1. From themicroscopic analysis, phosphate compound has a certainadsorptioncapacity for TiO₂particles,whicheffectivelyprevents the contact ofTiO₂particles and inhibits the phase transformationofTiO₂. The reaction process of titanium phosphate and sodium carbonate under the meltingtemperature of glaze can be regarded as an earlier stage of the sintering process of titaniumphosphate and glaze. On further heating, titanium phosphate compounds dissolve in the liquid,so that precipitation of TiO₂occurs. The inhibiting effect of phosphate on the anatase-to-rutilephase transformation is more significant for the primary TiO₂than that of secondary TiO₂.Photocatalytic ceramics were prepared by spin-coating titanium phosphate precursor witha P/Ti molar ratio of1:1onthe surface ofglazed ceramics and rapidly sintering at1000℃. TiO₂particles are covered by the matrix if directly coated on the low temperature glaze （C2）,whereas TiO₂particles are immobilizing on the surface of glaze with low densification ifdirectly coated on the high temperature glaze （C4）. The problem can be avoided by previouslycoating a thin G2layer on the surface of C4. Anatase TiO₂particles with a size range of about70-130nm are firmly embedded on the coating when rapidly sintered at1000℃for3min. Thedensified coating has a high gloss of77.8%, a good adhesion of rank5B, and a high pencilscratchhardness over6H, which has a veryclose qualityas compared to the surface ofordinaryglazed ceramics. Photocatalytic degradationofMO accomplishes97%after5hUV irradiation, and water contact angle ofthe surface decreases dramatically to9.9°after12h UV irradiation.High temperature sintering preparation of photocatalytic ceramics is achieved by thedecomposition of titanium phosphate in the glaze.更多还原