POSS containing hyperbranched polymers as precursors for magnetic Co@C-SiOx ceramic nanocomposites with good sinter-resistant properties and high ceramic yield

For the first time, POSS and cobalt containing hyperbranched polymer (HP2-Co) was synthesized via a convenient A2+B3 strategy for solid-state pyrolysis to generate magnetoceramics. For comparison, its analogue (HP1-Co) without...

Effect of Si-SiC Additives on Properties of Tap Hole Clay

Non-water taphole clay was prepared by using high alumina ((Al2O3)>85%,Particle Size is 3~1, ≤1 mm),coke, clay, kyanite, Ferrosilicon Nitride Powder and Corundum powder, adding more 15% tar as the binder and Si-SiC (0,4%,8%,12%) to replace Ferrosilicon Nitride. Specimens with dimensions of φ50mm × 50mm and 125mm × 25mm × 25mm were prepared under a uniaxial pressure of 5MPa. The microstructure, high temperature bending strength (600oC,800 oC,1000 oC,1200 oC,1400 oC) and apparent porosity and sinter ability of the tap hole clay were studied. The influence of the substitution content of Si-SiC of the tap hole Clay was also investigated. The results showed that the high temperature bending strength of the samples decreased with the increasing of Si-SiC and apparent porosity almost no changing, but it could still met the need of the actual requirement. The Si-SiC substitution content within 5% of the tap hole clay has also good performance. Through the analysis of the microscopic structure of the tap hole clay, the tap hole clay with Si-SiC has good sinter ability.

Preparing MIM Feedstocks for Bio-Applications Using an Agar-Based Binder

The present study aims to prepare feedstocks for MIM (Metal Injection Molding) where the metal powders are 316L stainless steel powders (SS). The master objective is to compare the performance of a biodegradable binder with a commercial one based on polyolefins. Different challenges must be overcome in SS injection molding, as follows: to decrease binder/carbon content in feedstocks; to decrease carbon contamination during debinding and sintering; to avoid the formation of chromium carbide and presence of precipitation-free zones; to avoid the grain growth during sintering and to reduce the feedstock price. The optimization of the feedstocks was performed using a torque rheometry technique. Feedstocks of coated and uncoated SS powders mixed with an agar-based binder were used to produce sound parts. A feedstock constituted by SS powders mixed with a high quality commercial binder was the standard. SS with agar-based on feedstocks can admit solids content similar to those based on the commercial binder (62 vol.%). For similar powder content, the sinters resulting from feedstocks with the agar-based binder shows a lower quantity of solid solution of carbon and chromium carbides, absence of precipitation-free zones than commercial feedstocks and good sinter soundness. Coating powders with nanocrystalline stainless steel contribute to control grain growth during debinding and sintering.

Sintering of β-Si3N4 Powder Prepared by Self-Propagating High-Temperature Synthesis (SHS)

Sintering of the Self-Propagating High-Temperature Synthesis (SHS) of β-Si3N4 powder with 6.67 wt.% Y2O3 and 3.33 wt.% Al2O3 as sintering additives has been emphatically investigated using hot-press sintering process. The relative density of hot-pressed β-Si3N4 reached near to the full densification (99.43%) at 1700°C. The similar micrographs with self-reinforcing rod-like β-Si3N4 grains forming an interlocking structure were observed. The better mechanical properties of hot-pressed Si3N4, such as the hardness (16.73GPa), fracture toughness (5.72 MPa·m1/2) and bending strength (611.72MPa) values, were obtained at 1700°C. The results indicate that good sinter ability can be obtained with the cheaply SHS of silicon nitride powder for preparing silicon nitride materials, which will make the cost of silicon nitride materials lowered.