| Abstract: Due to their good durability and compatibility, calcium oxalate, hydroxyapatite, and calcium carbonate have been extensively studied as coating materials for the conservation of limestone relics in recent years. In this paper, the characteristics, preparation methods, and practical applications of the protective films composed of the above materials are reviewed. In terms of acid resistance of the materials, calcium oxalate is the best, then hydroxy- apatite and calcium carbonate is number three. However, from the point of compatibility between limestone relics and protective materials, the law is the opposite. That is, calcium carbonate is the best, next comes hydroxyapatite, follows by calcium oxalate. Generally, inorganic calcium protective films can be prepared by both chemical and biological methods. Specifically, calcium oxalate and hydroxyapatite protective films can be obtained by the chemical reaction between limestones or their weathering crust and protectants such as oxalic acid, phosphoric acid, and their derivatives. The preparation conditions including the concentration, temperature, pH, and functional additives of the protectant are vital to the protective performance of the films. The calcium carbonate protective film, however, can be prepared by both chemical and biological methods. The former involves the carbonation reaction of all kinds of calcium precursors with carbon dioxide in the air. Carbon dioxide or carbonate ions, however, can be produced by bacteria or fungi, which can combine with calcium cations to form calcium carbonate deposition film. Calcium oxalate, hydroxyapatite, and calcium carbonate films began to be used in the surface protection of limestone relics around the world. Nevertheless, in practical operation, the preparation of the protective films with satisfying performance is still challenging, especially for the immovable stone relics with irregular shapes. So, greater efforts in the research of protective materials and technologies are still necessary in the future. |
| 杨富巍,严景臣,蒋伊洁,李婷,郭姝钰,张坤,刘妍.无机钙材料在石灰岩文物表面防护中的应用[J].无机化学学报,2023,39(7):1209-1222. |
