Preparation and Assessment of Superhydrophobic Organic-Inorganic Hybrid Coatings for Conservation of Yungang Grottoes
- PDF / 305,125 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 74 Downloads / 182 Views
Preparation and Assessment of Superhydrophobic Organic-Inorganic Hybrid Coatings for Conservation of Yungang Grottoes Shipeng Tian1, Shaojun Liu1,2, Feng Gao2,3, Min Fan4, and Jianguang Ren5 1
Division of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen, 518055, China State Key Laboratory for Powder Metallurgy, Central South University, Changsha, 410083, China 3 Chinese Academy of Cultural Heritage, Beijing, 100029, China 4 Baiyun Cultural Heritage Conservation Engineering Co. Ltd., Guangzhou, 510540, China 5 Yungang Grottoes Research Institute, Datong, 037006, China 2
ABSTRACT Yungang Grottoes in Shanxi, China, which represent outstanding example of Chinese outdoor immovable stone artifacts, are precious world cultural heritage. In the present study, the preparation and assessment of superhydrophobic hybrid coatings with photocatalytic activity on the sandstone substrate collected from Yungang were explored preliminarily. The protection efficiency of coating is investigated by measuring the water-stone contact angles, water vapor permeability, water absorption, and resistance to acid and salt corrosion. Results show that the superhydrophobic organic-inorganic hybrid coatings with photocatalytic and self-cleaning properties are highly suitable for the conservation of stone monuments. INTRODUCTION Condensed water is the most important weathering and decay factor for stone monuments, which can cause stone deterioration through cycles of freezing and thawing inside the pores of the stone or by intraporous crystallization of salts transferred by water [1]. Water repellent coatings are of importance as surface coatings for the conservation of stone monuments [2]. It is well known that the enhanced water repellency of superhydrophobic (SH) coatings (water contact angle>150°) is attributed to the combination of the hierarchical micrometer- and nanometer-sized rough surfaces and low surface energy components [3]. Recently, superhydrophobic coatings have been suggested as promising materials for surface protection of outdoor stone monuments [4-5]. Several properties are necessary for coatings in the conservation of stone monuments, such as good coagulation between grains to restore its strength, permeability for water vapor, hydrophobicity to hinder the penetration of water, and good resistance to acid and salt corrosion. While conventional organic, such as, TEOS, increases the cohesion of the grains of decayed stone, the gel obtained from TEOS results in the cracks and dense fragments of gel inside the stone during the drying [6]. Cracks occur as a result of differential capillary pressure produced within the gel pores. Recently, nanoparticles have been added to enlarge gel network pore radius inside the gel and reduce the capillary pressure [7]. Biodeterioration usually is a secondary degradation process following the initial deteriorating effects of inorganic agents [8]. The use of oxide photocatalysts has been considered as an effective strategy for removing low-leve
Data Loading...
