Bond Strength of the Sn-Ti-Ⅹ Ternary Active Solders on Sialon Ceramic

The bond strength of the Sn based ternary active solders,Sn-5Ti with various contents of Ag,Cu,In, Ni or AI on sialon ceramic was investigated by the ceramic/ceramic joint joining.The bond strength of Sn-STi (about 80 MPa) may increase to 90-100 MPa by small addition of Ag or Cu (about 5-10%).A little Ni (about 1-3%) in the solder is slightly beneficial,but too more Ni (more than 5%) is harmful.Small addition of In is trivial,but too more In is detrimental.On the other hand,small addi- tion of AI in the active solder decreases greatly the bond strength of the solder,therefore it is very harmful.In discussion,three suggestions for selection of the third element to increase the bond strength of the soft solders on ceramic,i.e.with a high surface energy,benefiting to wetting on ce- ramic and strengthening the soft solder itself,have been made.

Preliminary Study on Combining K2O-Al2O3-SiO2 System Dental Glass Ceramic with Al2O3 Ceramic

Relationship between K2O-Al2O3-SiO2 system dental glass ceramics and Al2O3 ceramics was investigated. 4 groups of glass ceramic with the same components but different thickness（0.8, 1.2, 1.6, and 2.0 mm） were sintered on Al2O3 base ceramics according to the same thermal treatment system of leucite micro-crystallization reported in previous literatures. The products of each group were analyzed by polarizing microscope, X-ray diffractometer, and an INSTRON material testing machine. Under the thermal treatment system, leucite crystals were formed in samples of each group, and dispersed evenly. Meanwhile, the compressive strengths of group 3 and group 4 were higher than those of group 1 and group 2. Samples of group 3 showed better mechanical properties than others. The conclusions are drawn that Leucite crystals can be controlled in K2O-Al2O3-SiO2 system glass ceramic-Al2O3 ceramic composite material, and the thickness of glass ceramic has a notable influence on the compressive strength of this ceramic composite material.

Basic Properties of Concrete Incorporating Recycled Ceramic Aggregate and Ultra-fine Sand

Recycled ceramic mixed sand（RCMS） was obtained by partially replacing ultra-fine sand with recycled ceramic coarse sand（RCCS）. The effects of RCCS replacement rate on the apparent density, workability, compressive strength and splitting tensile strength of recycled ceramic concrete（RCC） were investigated. In addition, the relationship between the water-cement ratio and compressive strength of RCC was also studied. The experimental results indicate that the reusing of recycled ceramic aggregate can improve the cohesiveness and water retentiveness of fresh concrete and benefit the mechanical properties development. When the RCCS replacement rate is not less than 40%, the mechanical properties of RCC are superior to those of the reference concrete. Moreover, when recycled ceramic medium sand was completely used as fine aggregate, the maximum increase in both compressive strength and splitting tensile strength were obtained, comparing with those of reference concrete, the increment ratio was 19.85% and 32.73%, respectively. The microscopic analysis shows that the using of recycled ceramic aggregate can meliorate distinctly the structure of the interfacial transition zone（ITZ） and increase the compaction degree of cement paste. Furthermore, an expression of the compressive strength of RCC and the cement-water ratio is regressed and gains a good linear relativity. It is an effective way to recycle waste ceramic, and the consumption of recycled ceramic aggregate could reach from 26.9% to 47.6% of the total weight of aggregate in producing concrete.

Ceramic membrane separation technique for washing nano-sized ceramic powder precursors

Washing using ceramic micro-filtration membranes was studied in the preparation of nano-sized TiO2 and A1203 powder precursors obtained by wet chemical methods. The key parameters for the washing process, such as operation pressure, cross-flow velocity, and slurry concentration, were examined and optimized. The shape and size of particles influenced the structure of the filter cake, leading to different permeation flux for different systems. The results demonstrated that washing using ceramic membranes is superior to the traditional plate-and-frame filtration and could be considered an advanced technique for ultra-fine powder preparation by wet-chemical method.

Prosthetic Impingement in Total Hip Arthroplasty—The Trigger for Adverse Wear

Development of total hip arthroplasty (THA) now spans more than 5 decades encompassing combinations of metal-on-metal (MOM), ceramic-on-metal (COM), metal-on-plastic (MOP), ceramic-on-plastic (COM), and ceramic-on-ceramic (COC). In every arena of extensive technical development, there exists a data set that when viewed in isolation seemed of little import, but when assembled in-toto may produce a generational shift in perception. Our review focused on two such THA events. Firstly, COC retrieval studies (1999-2001) noted habitual wear patterns on heads and peripheral wear stripes, along with femoral-neck impingement, and ceramic surfaces stained gray by metal debris. These COC data indicated THA risks included, 1) cup edge-loading (E/L) on heads producing “stripe wear”, 2) component impingement releasing metal particles resulting in 3) tissues contaminated by metal debris. A corresponding MOM impingement-debris mechanism was only perceived by Howie (2005) in a McKee-Farrar retrieval study. Our anticipation at LLUMC was that MOM retrievals would provide superior wear details to those seen on COC retrievals. We noted stripe wear in the polar zone of CoCr heads and basal stripes in the non-wear areas. The basal-polar stripe combinations were found in all MOM retrievals. Basal-polar stripe combinations followed cup-rim profiles in our LLUMC simulations of prosthetic impingement. LPUH videos demonstrated the formation of stripe wear in functional-standing and functional-sitting postures for both impingement and subluxation episodes using THA and RA designs. The stripes on CoCr heads revealed the large scratches we now term “microgrooves”. Microgroove width varied from 40 - 400 um with 100 um being typical. The longitudinal striations in microgrooves, the raised jagged lips, scratches with shallow entry and exit termini, were all indicative of a classic 3rd-body wear mechanism. The THA impingement simulations denoted four sites of edge-loading, i.e. neck-E/L, inferior cup-E/L, superior cup-E/l and head-E/L, and ingress of Ti64 particles as a contaminating-roughness effect. Individual MOM cases referred to LLUMC demonstrated dramatic evidence of neck notching. At one end of the debris spectrum, a Ti64-notch model predicting a 6 mm3 annual wear-rate represented the release of 5700 particles of 126 um-size (approximating daily release of 16 particles). At the other end of the spectrum, if metal particles were crushed between MOM surfaces to the equivalent nanometer size found in tissues, our notch model represented approximately 22-trillion Ti64 particles annually deposited in tissues. The anatomical THA models represented in LPUH videos demonstrated that even 1-degree of head subluxation from a rigid cup created a cup “lift-off” scenario (CLO) that would open a gap of 250 - 400 microns between femoral head and cup. This would void all lubrication potential and focus the total hip-joint force along the beveled cup rim, i.e. stripe wear. It is therefore interesting that MOM impingement/debris predictions by Howie et al. have not been confirmed until now or discussed in contemporary literature. Therefore, this review of 50 years of THA data demonstrated that hip impingement was always the trigger for adverse wear and that metal-backed cups represent the potential for release of metal debris at extremes of functional standing and sitting postures.