Yihang Zhou

Towers, as monumental structures with profound cultural and religious significance, have been constructed throughout Chinese history. These buildings are now undergoing natural deterioration and anthropogenic damage, making detailed material studies essential for their conservation. Technical analysis of ancient bricks not only reveals historical manufacturing techniques but also helps in the evaluation of seismic performance, thereby providing vital information for the protection and restoration of ancient towers. This study investigated bricks from 13 ancient towers located in Shaanxi and Sichuan Provinces, China, particularly within the Guanzhong Basin, spanning approximately a millennium from the Sui to the Ming Dynasties. Utilizing techniques like SEM, XRF and XRD, we analyzed the microstructure and composition of the bricks to provide reference data for historical research and future restoration. The results indicate that regional variations had a significantly greater influence on the bricks than temporal changes during this period. Bricks from Shaanxi’s ancient towers exhibit higher Ca content and a more porous, loose microstructure compared to those from Sichuan’s towers. These characteristics merit careful consideration when assessing the weathering resistance of these historic towers and planning future conservation and restoration efforts.

Outdoor stone relics, including inscriptions, statues, temple grottoes, etc., are continuously subjected to natural weathering and air pollutants. Those made of marbles and other carbonate rocks are particularly vulnerable to acid rains, which can be protected by acid-resistant coatings. A novel method to prepare enamel-like hydroxyapatite coating on marble surfaces is presented in this paper and analyzed using optical microscopy, a scanning electronic microscope, grazing incident X-ray diffraction, and nano-indentation. The described coating is composed of tightly arranged hydroxyapatite nanorods, perpendicular to the marble substrate, with a thickness of 3–5 μm. Not only does the coating exhibit high acid resistance, it also has considerably higher elastic modulus and hardness compared to that synthesized by the well-known diammonium phosphate (DAP) method owing to the wellarranged microstructure. Consequently, the enamel-like hydroxyapatite coating would probably be more effective and durable for marble protection than the existing calcium phosphate coating.

Dehydration is the principal conservation process for waterlogged archaeological wood (WAW), with the aim of preventing shrinkage and cracking. For well-preserved WAW, shrinkage mainly takes place when the moisture content is below the fiber saturation point. Here, we conduct a new trial using ionic liquid as a dimensional stabilizer to maintain a stable swollen state of WAW. Molecular dynamics simulation (MD), shrinkage measurement, Fourier transform infrared spectroscopy (FTIR), and dynamic vapor sorption (DVS) were adopted to investigate the interactions and effects of 1-Butyl-3-methylimidazolium chloride ([Bmim][Cl]) on WAW (Dipterocarpaceae Dipterocarpus sp. with a maximum moisture content of 80.3%) in comparison with the conventional material polyethylene glycol (PEG). The results show that [Bmim][Cl] and its water mixtures have a comparable or slightly greater ability to swell amorphous cellulose than does water at room temperature, while crystalline cellulose is left intact. The samples treated with [Bmim][Cl] show less shrinkage than the PEG 300- and PEG 2000-treated samples at all tested concentrations after air-drying. The best dimension control was achieved by 40 wt% [Bmim][Cl], with volumetric shrinkage reduced from 5.03% to 0.47%. DVS analysis reveals that [Bmim][Cl] reduces moisture contents at moderate and low relative humidity (<80%) when the concentration is at or below 20 wt%, which suggests that good dimensional stability was not achieved by simply preserving the moisture content but possibly through the interaction of the ionic liquid with the wood polymers.

Recent excavation of the elephant ivories at the Sanxingdui site of the Shang Dynasty in Sichuan, China brings attention to the burnt features of the ivories. However, burnt ivories cannot be assessed by the same criteria established for burnt bones because of the differences in the ways that the two materials respond to heat. This study examines differences in the phase transition characteristics of ivory and bone, and confirms that the threshold temperature of the alteration in ivories is lower than that in bones. In our analysis, elephant ivories and bovine bones burnt at the temperatures between 200 and 1000 °C in oxidizing or reducing atmosphere are prepared and comparatively investigated by attenuated total reflection Fourier transform infrared spectroscopy. The results show that the transformation from magnesium-substituted hydroxyapatite (Mg-HAp) to magnesium-substituted β-tricalcium phosphate in ivory dentin takes place at the temperature as low as 800 °C, while β-tricalcium phosphate is not observed in bovine bones burnt at 1000 °C or below mainly because of the different magnesium contents. Due to the destruction of Mg-HAp at 800 °C in ivories, cyanamidapatite that could form in bones burnt under reducing atmosphere is absent in burnt ivories. With reference to the experimental burnt ivories, archaeological burnt ivories from the Sanxingdui site can now be clearly determined to be burnt unevenly at temperatures up to around 800 °C. This study may provide further information for archaeological research on ivories from the Sanxingdui site and identification of burnt bioapatite materials in other archaeological findings.

The ancient lacquer films excavated from Dongshan Han tomb M6 of the Western Han Dynasty in Taiyuan City, Shanxi, China, were found sensitive to pH variation. This paper aims to demonstrate the pH-dependent warping behaviors of the ancient lacquer film and discuss their mechanism. The samples were analyzed by surface analytical techniques including attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry. The results suggest that the outer layer of the lacquer film is more oxidized than the inner layer and contains more carboxylates, with calcium ions and possibly ammonium cations as counter ions. The carboxylates are speculated to be formed by oxidative cleavages in the urushiol side chains and hydrolysis of glycerides of drying oils. The shrinkage and swelling of the lacquer film can be regulated by the type of cations (H⁺, Ca²⁺, Na⁺) of carboxylates through hydrogen bonds, coordination bonds and static forces. Due to the higher content of carboxylates in the outer part, it shrinks more at low pH causing warping outward and swells more at high pH causing warping inward. This paper may provide an important reference for pH control and help resolve the warping problem during conservation or restoration of ancient lacquerware.