Experimental study on pressure resistance performance of the plastic housing for the underwater robot system
The underwater housing is used to protect the electronic parts of the underwater robot system from water and pressure. The housing made of a metal material is widely used, but the weight is heavy and the price is expensive. So in recent years the housing of plastic material that is inexpensive and lightweight is being used in shallow water depth. In this paper, we have obtained the pressure resistance performance in several plastic housing specimens by the high pressure experiments. In the experiments result, we know the pressure resistance performance of the oil filled housing specimen better than other specimens.
Hybrid pressure-tolerant electronics
When working in deep-sea environments, the ambient pressure of the water column causes special design effort on the integration of electronic components for robotic structures. Until recently, electronic modules required housings which allowed the use of electronics at pressure conditions like they are on land. These housings increased the costs and the dimensions of the overall system as those modules are bulky and expensive to manufacture. Other ways have to be taken when designing miniaturized components. A hybrid approach between pressure tolerant systems design and pressure hulls enables the realization of miniaturized and cost-effective components for deep-sea.
MAS-NMR spectroscopy studies in the setting reaction of glass ionomer cements.
OBJECTIVES
The main objective is the characterisation of the setting reaction in glass ionomer cements based on experimental ionomer glasses with different fluorine content and a commercial glass ionomer cement liquid by using 13C CP/MAS-NMR, 29Si, 27Al and 31P MAS-NMR spectroscopy in order to receive information specifically about the cross-linking process.


METHODS
Different fluorine containing glass compositions based on 4.5SiO2-3Al2O3-1.5P2O5-(5-z)CaO-zCaF(2) where z=0-3, were mixed with a commercially available polymer liquid to form glass ionomer cements. The cements were subjected to 27Al, 13C CP/MAS, 29Si, and 31P MAS-NMR analysis.


RESULTS
The 27Al spectra showed clearly the formation of six-fold coordinate Al(VI), that may crosslink the carboxyl groups in the poly-acid molecules. A shift towards to more positive values of the carboxyl peak in the 13C CP/MAS-NMR spectra showed clearly the proton dissociation of the carboxyl groups. A shift towards more negative values was observed in the 29Si MAS-NMR spectra, suggesting formation of hydrated silica gel and consequently formation of additional Si-O-Si bonds. 31P MAS-NMR spectra also reflected changes in the coordination state around a PO4(3-) tetrahedron. Increasing the fluorine content of the glasses resulted generally in increased reactivity during setting, due to promoting cross-linking and repolymerisation of the silicate phase, followed by clear changes in the MAS-NMR spectra.


CONCLUSIONS
The cross-linking process during the setting reaction of glass ionomer cements can be followed by MAS-NMR spectroscopy observing the conversion of Al(IV) to Al(VI). The acid base setting reaction is completed in 1 day and no further significant changes in the MAS-NMR spectra can be observed. Further study is required in order to understand the role of phosphorus.