Tuning the Dimensionality of Nano Ca(OH)₂ with Surfactants for Wall Painting Consolidation

Abstract

As an effective conservation material for wall paintings, ancient paper, and stone artifacts, nano Ca(OH)2 has been studied for more than two decades. However, the synthesis methods are expensive, complex, time‐consuming, or require considerable energy. To tackle the issue, we report, in this study, a facile, large‐scale, time saving, and economical method for synthesizing nano Ca(OH)2 (∼90 nm) at room temperature. This is achieved by controlling crystal growth of Ca(OH)2 at the (1‾010 ) facet (vertical direction) and (0001) facet (horizontal direction) with simultaneous addition of octyl phenyl polyoxyethylene ether (OPPE) and dimethylformamide (DMF) in the reaction. Density functional theory (DFT) calculations revealed that the crystal dimensionality tuning is caused by attaching OPPE to the (0001) facet and DMF to the (1‾010 ) facet of Ca(OH)2. Experimental results showed that the synthesized nano Ca(OH)2 has higher stability and carbonation degree than commercial Ca(OH)2 and was used for consolidating a 1300‐year‐old tomb painting, which is a very important, precious, and heavily damaged national treasure of China. The results demonstrate that the nano Ca(OH)2 shows excellent penetration into the painting, considerably improves the strength of the painting, and has no side effects on the color, pore distribution, and porosity of the painting. Our work will significantly facilitate the industrial production of nano Ca(OH)2 and its application in cultural heritage conservation.

Polydopamine-Modified Nanolime with High Kinetic Stability in Water for the Consolidation of Stone Relics

“…In Figure 2a (red and black lines), peaks of 2θ at 18.2, 28.8, 34.2, 47.2, 50.8, 54.5, 62.8, 64.5, 71.9, and 12.2°correspond to the (001), (100), ( 101), ( 102), (110), ( 111), ( 200), ( 201), (103), and (202) lattice planes of Ca(OH) 2 (PDF card 44-1481), demonstrating that the component of as-synthesized materials is Ca(OH) 2 . 27 Additionally, after introducing PDA, all the diffraction peaks are broadened. According to calculation of Debye−Scherrer formula (determined by the above lattice planes), the average sizes of NL and PDA@NL are 37.7 and 11.8 nm, respectively, suggesting that the presence of PDA may inhibit the growth of Ca(OH) 2 crystals.…”

“…The synthesis of NL is according to our previous work. 27 Briefly, at room temperature, CaCl 2 •2H 2 O was dissolved in DMF and OPPE to obtain CaCl 2 solution. NaOH was dissolved in deionized water to obtain NaOH solution, which then was poured into CaCl 2 solution.…”

“…31 The cutoff energy for the plane waves was 400 eV, and the atomic core region was described by PAW pseudopotentials. 27,32 The gamma point was used to integrate the Brillouin zone, and dipole correction along the Z-direction was also added. 33 Gaussian function with molecularly optimized double-zeta polarized basis sets (MOLOPT-DZVP) was used for expanding the wave function of Ca 3s 2 3p 6 4s 2 , H 1s 2 , C 2s 2 2p 2 , O 2s 2 2p 4 , and N 2s 2 2p 3 electrons.…”

“…The synthesis of NL is according to our previous work . Briefly, at room temperature, CaCl 2 ·2H 2 O was dissolved in DMF and OPPE to obtain CaCl 2 solution.…”

“…All calculations are performed with the Vienna ab initio package (VASP). , The total energy and forces were calculated within the framework of DFT, using the PBE exchange–correlation functional, with the dispersion interaction corrected by the D3 scheme . The cutoff energy for the plane waves was 400 eV, and the atomic core region was described by PAW pseudopotentials. , The gamma point was used to integrate the Brillouin zone, and dipole correction along the Z -direction was also added . Gaussian function with molecularly optimized double-zeta polarized basis sets (MOLOPT-DZVP) was used for expanding the wave function of Ca 3s 2 3p 6 4s 2 , H 1s 2 , C 2s 2 2p 2 , O 2s 2 2p 4 , and N 2s 2 2p 3 electrons.…”