title: [Influence of MgO and TiO2 on mechanical properties of zirconia toughened alumina ceramics formed by gel-casting technique].
abstract: OBJECTIVE
  The objective of this study is to investigate the influence of mechanical properties and sintering performance by adding 5% weight percentage aids to nano-compound zirconia toughened alumina (ZTA) ceramics.
  
  
  METHODS
  Micrometer Al2O3 and nanometer ZrO2 (quality ratio 4:1) were used to get 55% volume percentage slurry. Magnesium oxide and titanium oxide were taken as aids which were 5% weight percentage of the Al2O3 and ZrO2 powder. Five groups (number 0, 1, 2, 3, 4 group) were divided according to different proportion of aids. After gel-casting, the porcelain pieces were sintered at 1150, 1200, 1300, 1400, 1450, 1500, 1600 degrees C for 2 hours. Static three-point flexure strength, line shrinkage, relative density were measured and scanning electron microscopy (SEM) was used to observe section.
  
  
  RESULTS
  Number 1 (MgO 1%, TiO2 4%) group had the highest bending strength. It was (401.78+/-19.50) MPa after sintering at 1600 degrees C for 2 hours and was higher than 0 group (380.64+/-44.50) MPa. Bending strength became lower than 0 group when MgO was more than 2% or more than that weight percentage of ZTA powder. When MgO content was higher than 2% or more than that weight percentage, there was no difference in relative density raising rate between each sintering assistants groups. When the sintering temperature was higher than 1200 degrees C, all groups showed obvious line-shrinkage and the groups which contained sintering assistants were all was higher than 0 group.
  
  
  CONCLUSIONS
  Adding MgO and TiO2 aids from 1% to 4% weight percentage of ZTA will promote fritting and increase ZTA nano-compound ceramics mechanical properties. Adding 2% MgO aids or more than that weight percent will has no obvious help to increase the relative density raising rate of ZTA nano-compound ceramics and will degrade the mechanical properties of ZTA nano-compound ceramics.
authors.affiliation: Dept. of Prosthodontics, School and Hospital of Stomatology, Wenzhou Medical College, Wenzhou 325027, China.
authors.forename: Si-Qian
authors.initials: SQ
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Ruo-Xi
authors.initials: RX
authors.lastname: Du
authors.forename: Da-Feng
authors.initials: DF
authors.lastname: Zhang
authors.forename: Chuan-Tong
authors.initials: CT
authors.lastname: Liu
authors.forename: Jian-Feng
authors.initials: JF
authors.lastname: Ma
mesh_terms: D000537:Aluminum Oxide; D003776:Dental Porcelain; D008855:Microscopy, Electron, Scanning; D013696:Temperature; D014025:Titanium; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; C009495:titanium dioxide; D015040:Zirconium; D014025:Titanium; D000537:Aluminum Oxide; C028541:zirconium oxide