Abstract: Spherical impact indentation tests with different impact angles (90°, 60°, 45°, and 30°) was carried out to understand the effect of impact angles on damage degree of cement clinker. A linear rail which can adjust angle to alter impact velocity was used to guide the slipping impact head to impact the sample. The different steel wedge was used to change the impact angle. It is found that the area of damage surface for cement clinker is most serious the peak impact force for surface damage decreases but the contact indentation becomes longer with decreasing impact angle when the impact angle is 45°. Under almost the same impact velocity, the smaller the impact angle, the higher the impulse, the longer contact time, and the peak impact force of 45° is maximum.
Abstract: This paper presents a preliminary exploration in tribological property and dynamic elastic/plastic behavior of cement composite material at micro- and nano- scale. Pastes were prepared by pure cement clinker with water-to-cement ratio of 0.3 and 0.4. For comparison, a polymer-based clinker composite was also introduced. Nano-scratch test was carried out to study the scratch process. Different constituents were identified by penetration depth value. Based on this identification, the coefficient of friction and elastic deformation status were analyzed. Substrate effect was found when refers to the coefficient of friction of hard clinker particles embedded in soft matrix. An H/E ratio dependent elastic/plastic behavior was also revealed for cement composite. The results confirm the nano-scratch test as a promising method for cement composite investigation; however, some important attributes of this type of material, including the complexity of multi-phase structure and the viscous effect, need to be taken into account in experimental analysis and practical application.
Abstract: To study whether the veneering technique will have an impact on zirconia grain and the bonding type and relationship on interface between zirconia and veneer porcelain. Materials and methods: After sintered, zirconia was annealed for 15 minute to finish the phase transition from m to t.4 types of veneer porcelains were sintered and observed with SEM (scanning electron microscopy) and TEM (transmission electron microscopy). Results: With etching time extending, it appeared that many materials loosed and corrosional pit deepened, enlarged in the veneer porcelain, which made crystallize structure move into veneering surface. Composition of interface mainly was amorphous glass matrix and zirconia. Energy spectrum analysis showed that there was no remnant glass composition in the zirconia side departing from interface. SEM showed that crystal in veneering side did not participate interface bonding. Conclusion: The interface between 4 types of veneer porcelains and zirconia bonded well. Veneering sintering technique didn’t change lattice structure of zirconia, which still was tetragonal structure. The specific bonding property of interface still remained to be analyzed further to determine.
Abstract: Laminated glass and photovoltaic laminated glass are widely used in architecture. The interfacial bonding strengths between poly(vinyl butyral) (PVB) and glass were investigated by the cross-bonding method from room temperature to -50 °C. The loading speed was 5 mm/min, and the cooling speed was about 0.5 °C/min. The testing sample was hold at each temperature for half an hour. It was revealed that the testing temperature had great effect on the bonding strength. At room temperature, the tensile bonding strength was 11.49 MPa and the shear bonding strength was 6.61 MPa. With the temperature decreased from RT to -50 °C, the tensile bonding strength was decreased by 66.81%, but the shear bonding strength was increased by 212.16%. From RT to -30 °C, the change rates of the tensile and shear bonding strength bonding strength were 65.57% and 172.68% respectively, only 3.61% and 14.48% from -30 °C to -50 °C. The mechanism for the bonding strength depended on testing temperatures from RT to -50 °C was also discussed.
Abstract: Objective: To investigate the effects of different surface treatments on the microstructural and crystallographic changes of dental 3Y-TZP ceramics. Methods: 21 pieces of zirconia specimens (15 ´ 15 ´ 1.5 mm) were prepared and divided into 7 groups: control group; grinding group; polishing group; sandblasting group; sandblasting + veneer porcelain sintering group; sandblasting + veneer porcelain sintering twice group and sandblasting + annealing group. The crystal structure of specimen was monitored by X-ray diffraction (XRD) before morphological observation with scanning electron microscope. Results: monoclinic phase increased after grinding while decreased little after polishing, bigger phase change presented after sandblasting compared with decreased phase change induced by veneer porcelain sintering; annealing eradicated the surface m phase. Grinding produced coarse scratches on the surface of samples with removal of surface particles; after grinding and polishing to 7 um level, the surface particles were removed massively, and the surface became smooth with remaining scare scratches and substantial micro cracks. Sandblasting removed scratches near completely producing coarse and irregular surface of samples. Conclusions: Grinding, sandblasting and polishing could produce the transition of Zirconia Ceramic surface from t to m phase. It is better to use heat treatment after mechanical treatment to reverse the changed surface phase.
Abstract: The objective of this study was to investigate the mechanical properties of yttrium- stabilized tetragonal zirconia (Y-TZP) ceramics after different surface treatments. Cercon Smart Ceramics samples were divided into groups: (1) bland control (no treatment), (2) hand grinding, (3) Al2O3 air-abration, (4) irradiation with 200mJ Er:YAG laser. Tensile bond strength, shear bond strength and flexural strength were evaluated after 24h storage at 37°C. Each group had 10 samples for different test. Data were evaluated using ANOVA analysis (α=0.05). Laser and air-abration achieved higher tensile and shear bond strength when air-abration presented the best flexural strength. Surface modifications significantly increased the mechanical properties of the Y-TZP ceramics.
Abstract: To evaluate the erosion of various engineering materials subject to cavitation in laboratory, a ultrasonic vibratory apparatus (UVA-1) is designed and manufactured according to ASTM G 32-06. The principle and setup of the UVA-1 are briefed. Some utilities of this apparatus are listed with several good examples.
Abstract: CNx films were deposited on YG8 carbide alloy (WC+8%Co) substrates by DC or RF magnetron sputtering. The composition, bonding state, adhesion, and tribological behavior of CNx films were researched. X-ray Photoelectron spectroscopy results showed that C-N, C=N and C≡N bond existed in CNx films. RF magnetron sputtering is in favor of the bonding of C and N, the adhesion and the wear resistance of CNx films. DC magnetron sputtering is in favor of lubricating ability of CNx films. Substrate bias has some effect on the bonding of C and N, the adhesion of the films, decrease of adhesive wear and the friction coefficient of films.
Abstract: Solid particle erosion wear behavior of 3YSZ ceramics were performed by self-designed sand blasting type high-temperature solid particle erosion wear equipment, using 36# corundum as abrasive particles. 3YSZ ceramics were pressureless sintered in air atmosphere at 1500°C for 3h. The fracture toughness and Vickers hardness could achieve 10.3 MPa•m1/2 and 12.8 GPa, respectively. The effect of temperature (25°C, 400°C, 600°C, 800°C, 1000°C) and the total weight of the abrasive particles (300g, 900g, 1800g) at room temperature on the erosion wear of 3YSZ ceramic were investigated. The volume erosion rate raised and developed a nonlinear dependence on the weight of corundum abrasive particles at room temperature. The slope of the curve decreased gradually. At elevated temperature, volume erosion rate increased as the temperature went up. Nonlinear fitting presents the relationship between the volume erosion rate of 3YSZ ceramics and the corresponding temperature. Plastic deformation is the major erosion mechanism at room temperature when the weight of corundum particles was 300g and 900g. Minor chipping instead of it when the temperature grew up to 400 and 600°C or the corundum particles was as much as 1800g at 25°C. When 3YSZ targets were eroded at 800°C and 1000°C, the material removal are mainly attributed to lateral cracks for an ideally brittle material. Crack propagation is the controlling factor of volume erosion rate.
Abstract: Nano-sized 8mol% MgO-PSZ powder was prepared via coprecipitation, Afterwards, the prepared powders were characterized by XRD and SEM technologies. The results clearly demonstrate that the calcined temperature can be feasible for the MgO-ZrO2 composite, crystal structure and particle size.