Sepiolite powder was hydrothermally solidified into a cemented, designed to function both in humidity regulation and volatile organic compound (VOC) removal. The solidification process mimicked the cementation of sedimentary rocks. The formation of the calcium aluminium silicate hydrate (C-A-S-H) or Al-tobermorite enhanced the strength (maximum flexural strength >17 MPa) and improved the porosity of the solidified materials. Due to the low temperature of hydrothermal solidification (≤473.15 K), most sepiolite remained in the matrix of the solidified specimens. The cemented sepiolite aggregate shows outstanding humidity-regulating performance (moisture adsorption of 430 g m–2), and the synergistic effects of the residual sepiolite and neoformed Al-tobermorite exerted a positive influence on the humidity regulation performance of the material. Similarly to the behaviour of sepiolite, the solidified material also displayed good formaldehyde-removal capacity (60–68%). The pore dimensions controlled the humidity regulation and formaldehyde removal. The humidity regulation depends on the mesopores, which originate mainly from both the original sepiolite and the neoformed C-A-S-H phases and Al-tobermorite, while the formaldehyde removal depends on the micropores from the original sepiolite in the matrix. As such, the cemented sepiolite aggregate might be hydrothermally synthesized and might be used to improve the comfort and safety of indoor environments for human beings.
Diatomaceous
earth (DE)-based material and amine-functionalized
poly(vinyl chloride) (Amino-PVC)/DE composite have been hydrothermally
synthesized at low temperature (≤200 °C)
to remove formaldehyde (HCHO) indoors. The synthetic materials acquired
high strength up to 18 MPa due to a newly formed C–S–H
gel and tobermorite within the matrix. Moreover, the DE-based material
possessed higher HCHO adsorption capacity than raw DE, indicating
that HCHO adsorption could be promoted synergistically by both the
residual DE and the newly formed C–S–H gel. To further
improve the adsorption, Amino-PVC was introduced to modify the DE-based
material and the novel Amino-PVC/DE composite demonstrated superior
adsorption capability. Its maximum HCHO removal rate increased from
75 up to 90%. Furthermore, the desorption testing was conducted to
verify the stability of HCHO adsorption, and HCHO desorption rates
of both DE-based material and Amino-PVC composite were very low, only
1.5 and 2.9%, respectively. The lower HCHO desorption rate of the
Amino-PVC/DE composite might result from the chemisorption between
Amino-PVC and HCHO verified by the kinetic study.
The goal of this study is to develop a miniaturized artificial muscle in which a tiny compressor can be installed. Pneumatic actuators, such as pneumatic artificial rubber muscles (PARMs), have been widely used in many industrial and robotic research applications because they are compact and lightweight. However, the compressors driving such actuators are relatively large. To solve this problem, the authors have been researching soft actuators driven by gas-liquid phase changes (GLPCs).
In this study, a fixed chamber containing a constantan heater and fluorocarbon was used to generate pressure instead of a compressor. The pressure generation caused by the GLPC was confirmed, and a PARM contraction experiment was then conducted. Additionally, a PI control system was built to test the step and frequency responses of the actuator. A frequency response of up to 4.0 Hz was determined, and the corner frequency was found to be approximately 1.5 Hz.
The size of the actuator was reduced by removing the chamber and installing the heater in the rubber muscle. A PARM driving experiment was conducted, and the performance of the PARM was evaluated. The miniaturized actuator consumes less power than the original actuator.
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