Laboratory test on moisture adsorption-desorption of wall paintings at Mogao Grottoes, China

Abstract

Polymer-sorted high-density carbon nanotube (CNT) arrays have shown great potential to extend the silicon-based Moore's law. Imaging the CNT arrays on insulators like SiO2/Si using low-voltage scanning electron microscopy (LVSEM) to acquire array information like the alignment, density, and distribution of residual polymers is necessary. Such a task remains challenging due to the nanoscale CNT body (1-2 nm in diameter), nanoscale tube-to-tube separation (1-10 nm), the broadening of the apparent diameter, and the complex image contrast caused by the insulating substrate and polymer residues. In this study, the imaging mechanism for this system is investigated. Two methods are developed to separate the three dominant contrasts, i.e. topographic contrast, charge contrast, and material contrast, by selecting the take-off angle and energy of the emitted electrons as enabled by changing the working distance or the deceleration voltage. The contrast formation and separation mechanism is further confirmed by the dynamic contrast evolution due to the electron-beam-induced deposition of amorphous carbon. The contrast separation method is further applied to an individual CNT, reducing its apparent diameter from 36 nm to 6 nm. This result hints at the potential for LVSEM to count the density exceeding 150 CNTs/µm of CNT arrays. Finally, a comparative study of LVSEM and transmission electron microscopy confirms the failure of LVSEM to resolve CNTs in a bundle. The results suggest that the density of CNT arrays may be underestimated in reported SEM data. The proposed method can serve as a useful tool for further study and application of arrayed CNTs.

The Compression Behavior of Undisturbed and Compacted Loess Under the Controlling of Total Suction and Injected Solutions

“…Meanwhile, the sodium sulfate in soil would form hydrated crystals in the process of humidity increasing. It lead to the expansion of soil and the reduction of compressibility (Zhang et al, 2012;Langlet et al, 2013).…”

“…In the process of environmental humidity change, their phase transform played a key role in the structure of loess. In recent years, many studies had obtained the variation rule of NaCl crystal deliquescence under environmental humidity changing (Zhang et al, 2012;Langlet et al, 2013). As shown in Figure 12, the deliquescence relative humidity (DRH) divided the deliquescence process of NaCl into two stages.…”

Study on Strength and Permeability of Silt Soils Improving by Tung Oil and Sticky Rice Juice

“…In China, many immoveable historical earthen sites are facing severe threat due to the natural environment and human activities, such as shrinkage, cracking, collapse, and erosion [1,2]. According to air humidity or soil water content, the historical earthen sites are commonly divided into dry or moist earthen sites at present [3].…”

Paint adsorption on walls: I. Fractal-Stochastic model

“…The application of paints on walls is essential for the protection of these surfaces and the conservation of residential structures. It is also applied to other kinds of products like plasters [1,2]. Covering power depends on paint composition and the pigment used [3], as well as on the porosity and roughness of the surface to be protected.…”