When {HEAD ~ Al contents} increased above about 2 wt %, it was necessary to heat rapidly in order to achieve {TAIL ~ high density} 
When { HEAD ~ Al contents } increased above about 2 wt % , it was necessary to heat rapidly in order to achieve { TAIL ~ high density }
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL