Key Engineering Materials Vol. 519

Abstract: With powerful security and reliability of storage, the SFAM that is visibly different from the technology of storage fuel oil by the empty container adsorbs storage fuel oil by the adsorption material. Using reticular polyurethane foam to adsorb gasoline, is the application of the SFAM technology. In order to promote the development of the SFAM technology, the article analyzes the research status of the basic theory and the related theory at home and abroad of the fuel oil adsorption storage.

Abstract: The influence of La2O3 on the phase and microstructure evaluation and mechanical properties of La2O3-Al2O3 ceramics sintered with 2.45 GHz microwave energy was investigated. The results showed that La2O3 could densify the pure alumina with a lower sintering temperature and a short sintering time. La2O3 reacted with Al2O3 to form LaAl11O18 completely and the amount of LaAl11O18 increased with the increasing content of La2O3, distributing at the Al2O3 grain boundaries. The specimen doped with 10 vol.% and 15 vol.% La2O3 sintered at 1500 °C exhibited plenty of columnar grains with draw ratio about 1:4. The existence of columnar grains enhanced the microhardness and fracture toughness of La2O3-Al2O3 ceramics.

Abstract: Objective. To investigate the flexure strengths and elastic modulus of four types of dental fiber posts. Methods. The flexure strengths of ParaPost Taper Lux, Tenax Fiber White, Luxa Post and Rebilda Post fiber post were measured. The rupture modes were analyzed with SEM. Results. There was no significant difference between ParaPost Taper Lux (591.47±35.15MPa) and Rebilda Post (614.67±58.36MPa) in flexure strength (P>0.05), and Tenax Fiber White (846.62±71.15MPa) had significantly higher flexure strength than the other groups. There was no significant difference between Tenax Fiber White (23.93±2.14GPa) and Luxa Post (22.67±1.39GPa) in elastic modulus (P>0.05), and Tenax Fiber White and Luxa Post had significantly lower elastic modulus than other groups. It could be observed by transverse SEM that the combine of fiber and resin was even and compact and plenty of resin fragment adhered to the surface of fiber in Tenax Fiber White group, multitudinous cracks were observed by lengthwise SEM. Conclusion. The flexural properties and rupture modes of four kinds of dental fiber posts were significantly different.

Abstract: This research investigated the effect of sintering temperature on the physical properties and bending strength of zirconia toughened ceramic (ZTC). 3mol% yttria-stabilized zirconia compacts were prepared by dry press method and then sintered with different final sintering temperature: 1490°C, 1530°C, 1570°C and 1610°C respectively. The physical properties and three-point bending strength were measured. The results of the test indicated that the density and shrinkage of ZTC increased along with the rise of sintering temperature, while the surface porosity of the samples decreased. The curve of flexural strength is indicated the variolation tendency of falling after rising, being the maximum at 1570°C. The results of this experiment showed that the best sintering temperature of yttria-stabilized zirconia was showed at 1570°C in terms of physical properties and bending strength among the selected temperature range.

Abstract: Abstract. This paper investigated the Cf/SiC ceramic matrix composites. By utilizing different interfacial treatment processes to prepare carbon-fiber preform, the preform was then densified by infiltration and pyrolysis(PIP) with polycarbosilan/xylene solution as precursor, and the Cf/SiC ceramic matrix composite specimens were fabricated. Mechanical tests such as bending test and fracture toughness were performed for Cf/SiC samples. The results show that the interfacial bonding strength in the sample with high-temperature treatment process was improved due to removing surface sizing. The samples which were treated up to 1400°C exhibited the highest three-point flexural strength, up to 595MPa; The samples which were treated up to 1400°C and deposited by pyrolytic carbon(PyC) coating shows the highest fracture toughness value which was 20.70MPa•m1/2.

Abstract: Silicon nitride (Si₃N₄) ceramic foam was prepared from water-based Si₃N₄ slurries via protein coagulation casting method with egg white protein as the foam agent. The open porosity of the as-fabricated ceramic foams was close to 80%, and the compressive strength was about 20 MPa. Further, the content of sintering additive on the phase composition, pore structure and pore size distribution were investigated. Results indicate that with the increasing of sintering aids, more windows appear on the wall of pore and the average size increases. Moreover, Pore size distribution of as-fabricated ceramic not only changes with sintering additive addition but also varies with pore size.

Abstract: Porous zirconium dioxide (ZrO2) ceramics has been widely used in biomedicine, heat-insulation and piezoelectric actuators. In this study, a kind of porous ZrO2 ceramics with the gradient porosity and pore sizes was designed to be a composite lamellar material. The porosity and pore size change regularly through the thickness of the layers. This porous lamellar zirconic material has been prepared by the solid state reaction consisting of yttria-stabilized zirconia (YSZ) and stearic acid (SA) powders. The porosity and pore size can be tuned by the addition of SA. The mechanical properties of the graded porous ZrO2 have been studied in detail. The results show that the mechanical characteristics of the gradient porous ZrO2 can be controlled by changing the porosity and pore size.

Abstract: Zirconia fiber body was prepared with Extrude-extracting, using zirconium slurry made of partial stabilized Zirconia ultra-fine powder. The result shows that，acetone is the first choice as extraction agent because of its notable effect of water extraction on zirconium slurry. The Zirconia fiber body, which length is over 2 centimeters and solid content is more than 98% ( weight percent ), can be prepared while the range of solid fraction in slurry is in 36 vol％～49vol％, with addition less than 1% ammonium polyacrylic acid, the extrusion force is range in 1641.5 Pa～6566.2 Pa. The solidfication mechanism transformation from slurry streamlet to fiber body is particle caking, result in water being extracted by aceton and static repulsion force falling as powder surface electronmotive force being reduced, when zirconium slurry extruded into solvent with low dielectric constant. Difference of velocity distribution of slurry passing through spinneret orifice and very small surface tension between slurry and extraction agent cause coarseness occurred on the fiber body surface.

Abstract: In order to research the characteristic of flow drag reduction on large area super-hydrophobic surface, we have been designed a new processing technology to construct a micro-nano structure super-hydrophobic surfaces which formed by surface nanometer fly ash cenosphere. The experimental result of the flow drag reduction tested on macro-scale channel in laminar flow is very well, and the maximum drag reduction is 25.6%.

Abstract: Through this experiment, we try to determine the initial melting temperature of Vita Alpha porcelain powder and observe micro-structural changes of it. To determine softening temperature point, the powder of Vita Alpha has been sintered at 600°C, 700°C, 800°C and 900°C after mixed with sintering water. It was evaluated through direct observation in combination with scanning electron microscopy (SEM) and differential thermal analysis (DTA). Results shows that with sintering temperature increased, Vita Alpha veneering porcelain was enhanced gradually and the sintering degree was also improved. Sintering at 600°C, the powder was still in original state. But at 700°C the grain size and translucency were both increasing and grain boundaries cannot be clearly distinguished, which means the initial integration. When sintering temperature is at 900°C, Vita Alpha porcelain has been a translucent uniform material. In terms of DTA result, there are no significant endothermic and exothermic peaks in the softening, melting and crystallizing process of Vita Alpha powder. It indicates no significant thermal effect can be found, which infers that Vita Alpha porcelain powder contains a large number of ceramic components, rather than mainly of glass composition. Therefore, the conclusion is initial melting temperature of Vita Alpha porcelain powder is higher than 600°C, less than 700°C. With sintering temperature increased, Vita Alpha porcelain was gradually enhanced. There is no significant thermal effect in the softening, melting and crystallizing process, which indicates that Vita Alpha powder contains a large number of ceramic components, rather than mainly of glass composition.