Polycarbosilane-derived silicon carbide MEMS component fabricated by slip casting with SU8 micro mold
In this paper, we describe a new production method for microscale silicon carbide (SiC) ceramics parts. Slip casting with SU8 micro mold was carried out for the fabrication of a three-dimensional SiC MEMS component, which was made from polycarbosilane (PCS) precursor-derived SiC nano powder. SiC nano powder was mixed with a PCS solution. The slips were then cast into SU8 micro mold made on porous tungsten carbide (WC) plate. Firing at 1273 K was conducted for SU8 evaporation and PCS pyrolysis. We have succeeded in producing microscale SiC ceramics gears using the “μ slip casting” technique.
New curing method for polycarbosilane with unsaturated hydrocarbons and application to thermally stable SiC fibre
Abstract A new curing method, chemical vapour curing (CVC), for polycarbosilane with unsaturated hydrocarbon vapours was developed. The SiC fibre with low oxygen content was prepared by CVC method and had excellent mechanical properties and higher thermal stability in comparison to the SiCO fibre prepared by oxidation-curing. Particles on the surface of SiC fibre were deposited by heat-treatment at about 1500°C. The deposit which was caused by carbothermal reduction in the fibre decreased the strength of the fibre. The CVC method was applied to SiTiCO fibre. However, the thermal stability of the fibre was little improved.
Comparison of the effects of dopamine, isoproterenol, norepinephrine and bradykinin on canine renal and femoral blood flow.
The effects of arterial injections of dopamine on femoral and renal blood flow were compared with those of isoproterenol, norepinephrine and bradykinin after POB pretreatment. Dopamine was found to have a vasodilator action on the hind limb, which was antagonized by pronethalol and DCI. The potency of dopamine as a femoral vasodilating agent was very low compared to that of isoproterenol. In contrast, dopamine caused renal vasodilation by a qualitatively different mechanism, as indicated by a higher relative potency within the series of adrenergic agonists and the lack of antagonism by selective beta adrenergic blockade. This property cannot be attributed to conversion of dopamine to tetrahydropapaveroline which causes renal vasodilation by a beta adrenergic mechanism. Also, the metabolism of dopamine to norepinephrine,3,4-dihydroxyphenylacetic acid or 3-methoxy-4-hydroxyphenylethylamine is not the basis for this property. Furthermore, the renal vasodilation was not antagonized by atropine or eliminated by reserpine pretreatment. The ability of dopamine to dilate the renal vascular bed without producing a qualitatively similar direct effect on the femoral vascular bed sets it apart from agents such as papaverine and the nitrites. The physiologic significance of the renal vascular effects of dopamine remains to be determined.