Incorporation Of Alumina Research Articles

Combustion of polyethylene filled with metallic hydroxides and crosslinkable polyethylene

Incorporation of magnesium hydroxide and alumina trihydrate into polyethylene confers good fire retardancy together with excellent smoke suppressant characteristics without evolution of toxic or corrosive decomposition products originating from the filler phase. However, the total impact energies ( E t ) of the polymer decreased dramatically upon addition of these metallic hydroxide fillers. These limitations can be overcome by adding silane crosslinkable polyethylene (SCPC) copolymer to polyethylene/metallic hydroxide samples and/or treating the SCPC-containing samples with boiling water, which gives a dramatic improvement in E t , combined with further improvement in fire retardancy properties and smoke suppressant characteristics. Further investigations indicated that the gel contents of SCPC-containing samples increased significantly with the amounts of SCPC added and the treatment times in boiling water. These results suggested that crosslinking of SCPC in polyethylene/metallic hydroxide samples can significantly improve the flame retardant, smoke suppressant and impact properties of these samples.

The strengthening mechanism of a magnesia core ceramic

A high-expansion core material containin magnesia and forsterite may be used to make all-ceramic dental crowns with porcelain-fused-to-metal body porcelains. The purpose of this study was to investigate the strengthening mechanism for the magnesia core material. Six batches of the magnesia core material were made by reacting magnesia with a silica glass with holding times ranging from 17 to 120 min. The flexural strength was measured using three-point loading according to the ISO specification for dental ceramics. The forsterite content was measured using quantitative x-ray diffraction. A statistically significant correlation was found between the forsterite content and flexural strength. The proposed mechanism for strengthening is the precipitation of fine forsterite crystals in the glass matrix surrounding unreacted magnesia. Longer reaction times produced more dissolution of magnesia and subsequent precipitation of forsterite. This method results in a new strengthening mechanism for dental ceramics which have previously relied on the incorporation of alumina, leucite or ceramic whiskers.

Studies on the mechanism and kinetics of the oxidation of copper sulphide—II oxidation of copper sulphide mixed with alumina in a fluidised bed

The kinetics and mechanism of the oxidation of cupric sulphide mixed with ignited alumina have been studied in a fluidised bed. Incorporation of alumina has been found necessary to maintain uniform and continued fluidisation. The product distribution as well as the mechanism of oxidation in the presence of alumina in a fluidised bed is completely different from that in a fixed bed of pure copper sulphide (reported in Part I). The reaction is no longer autocatalytic and copper sulphate, instead of cuprous oxide (formed in the fixed bed), was the main solid product. Both of the following two rate-expressions represent the kinetics of oxidation quite satisfactorily: ▪Tthe correspondence between the two equations has been established. The role of alumina in altering the mechanism of the oxidation of cupric sulphide has also been discussed.

Effect of Residual Compressive Stress in a Hotel-China Glaze on Some Physical Durability Properties of the Glaze

The resistance of a hotel-china glaze to fracture by impact was improved by increasing the residual compressive stresses in the glaze. Increases in residual compressive stresses were developed, for laboratory convenience, by increasing the coefficient of expansion of the body by the incorporation of alumina in the body.