Probably you cannot directly connect the tubing to the quartz. A good option is a union made from Teflon, with O-rings at both ends, those O-rings made from Kel-F (a rubbery Teflon). Please be aware that quartz (really fused silica, not quartz) is a perfect light guide, so it passes IR heat on long distances - if a glassblower is working on a 1-meter long rod, a cigarette can be lit at the other end of that rod. Therefore, water cooling may be necessary on fittings attached to a heated quartz tube. Surprisingly, the same applies (to a lesser degree) to ceramic alumina tubes.
Dr Tuan:Tq but now im using PTFE,TEFLON which can withstand up to 1500 deg c,but surprisingly outlet tubing for gasses in the microwave melt and cause fire in the microwave.So i have no idea what is wrong and what factor cause fire in the microwave.if teflon is not suitable then i wonder why the inlet tube which i use the same tubing does not burn?
Mr Jerry:here i attached to u the picture of the reactor and tubing inside the microwave.i have no idea why got fire during heating eventhough i have purge N2 gas .
Your source of information on 1500 oC allegedly being Teflon's thermal resistance is grossly incorrect. At 1500 oC iron melts, it is a white-hot temperature. Wikipedia gives 327 oC as the Teflon's melting point, but in my opinion Teflon starts decomposing (slowly) below 300 oC. You probably need to make your quartz tube MUCH longer, so that the points of connections to Teflon are much cooler than 300 oC. Either the furnace should be of "through" type, or both quartz/Teflon ports need to be at the same end of the quartz.
TQ for the feedback, but at the mean time, i already have that size of quartz tube, besides, the teflon/ptfe i bought supposedly can withstand high T based on the specification given to me.but mybe i need to find other material other than this one. btw tq for the suggestion =)
Regarding a microwave heating for pyrolysis, it is reason to arrange all the tubing parts of quartz glass pyrolysis reactor (I think it is a lab scale) beyond the microwave radiation area, allowing and using so way all the convenient constructive materials for that, even allowing some of ex-panding the reactor design in length (or height).