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Erosion Behavior of Silicon Nitride with Graded Microstructure Dae-Soon Lim 1,a, Jong-In Park1,b, Dong-Phill Lim 1,c, Byung-Dong Han 2,d, Dong-Soo Park2,e 1 Department of Material Science and Engineering, Korea University, 1, 5-ga, Anam-dong, sungbuk-gu, Seoul 136-701, Korea 2 Ceramic Materials Group, KIMM, 66 Sangnam-dong, Chang-Won, Kyong-Nam, Korea a dslim@korea.ac.kr, bmaru203@hanmail.net, cnoonimp@empal.com, d cera72@kmail.kimm.re.kr, epds1590@kmail.kimm.re.kr Keywords: Graded microstructure, Erosion, Silicon nitride, Oxidation, Carbothermal reduction Abstract Silicon nitride has been considered as candidate tribological material due to their excellent mechanical and thermal properties.
Introduction Silicon nitride is a potentially useful material for tribological applications due to its outstanding properties such as high strength, high hardness, chemical resistance, and thermal stability [1 - 3].
Gogotsi et al concluded that the oxidation of silicon nitride based ceramics could affect the materials response to mechanical stresses as ,for example, cracking[ 10 ].
It implied that oxidation could affect the eorison rate of silicon nitride.
This study also shows that these factors influence erosion rate differently with temperature and number of impact by erodent particles.

Polymer/TiO2 nanocomposite films have good mechanical, electrical and thermal property, which are applied to electrical engineering and microelectronic technique field extensively.
Under the condition of high heat it still has outstanding dielectric properties, mechanical properties, corrosion resistance and performance under low temperature.
Although the traditional insulation materials have special properties, it can't provide long-term protection by corona discharge in the practical application, eventually leading to breakdown [5-8].
References [1] Chiang P C,Wang W T,T sai M H,et al.Physical and Mechanical Properties of Polyimide/titania Hybrid Films[J].Thin Solid Films,2004,447-448:359-364
Synthesis an Optical Properties of Polyimide-silica Hybrid Thin Films[J].Chem.Mater.,2002,14:4242-4248

Mullite whiskers can be used for metal matrix composite and ceramic matrix composites to enhance the mechanical properties of materials.
Using scanning electron microscopic to observe the morphology of sintered products and EDS to characterize phase composition, and measure the thermal barrier properties of products. 3.
Thus, orthogonal experiments ultimately selectes the addition of fluoride is 10:1.5, 10:2.0 and 10:2.5. 3.3 Orthogonal experiment In conjunction with all the above experiments suggest that the major factors to affect mullite whiskers thermal barrier materials generated are particle size of raw-material, heating rate and the ratio of addition.
Based on these three factors, each of these factors to consider three levels, the orthogonal experimental of three factor and three levels has been done, and the orthogonal experiments are shown in Table 2 and Table 3.
Structureand properties of mullite a review [J].

The mechanical properties and frost resistance of these mixtures were discussed concerning the results obtained for concrete without aggregate substitution.
Deterioration due to freeze-thawing cycles (F&T cycles) is a severe problem affecting concrete structures' durability.
This indicates that LWA affects the mechanical properties negatively and no positive effects of self-curing were observed in terms of strengths and dynamic modulus of elasticity.
This contradicts the conventional understanding of water's role in developing mechanical properties.
Subsequent experiments in our ongoing research revealed that achieving a positive effect on mechanical properties from soaked LWA required a water-to-cement ratio of 0.20.

With the impact of rainfall, the water content of gravel soil increases, and the water table changes, this eventually affects the mechanical properties of gravel soils.
On the one hand the water reduces the mechanical strength of high slope slide surface, on the other hand the weight of slope body increased.
Owing to its large sized sample, large-scale direct shear apparatus can keep a greater extent graded gravel soil properties and weaken the size effect, which leads to a more accurate result of the gravel soil strength.
Conclusions Through indoor large direct shear experiment test under different water content on gravel soil at the new city of Badong County, we can come to the following conclusions: The mechanical characteristics of grave slope body will be affected as its soil water content gradually increases along with the increase of rainfall.
The large-scale direct shear test and analysis further shows that the influence of water content and gradation are greater than any other factors.

In the stage of nugget growth and mechanical collapse, the growth of the molten nugget and mechanical collapse continue to cause resistance to decrease beyond the peak.
The discrepancy cause the force from the liquid nugget (due to the internal pressure in a liquid expansion and other factors) exceed than the effective electrode force that is a portion of the electrode force.
Although surface expulsion may not affect the strength of the joint if it is limited to the surface, it severely affects surface quality and electrode life.
The risk of expulsion is especially high in resistance spot welding between aluminum alloy and steel because of the very dynamic and unstable characters of the process, which is related to the application of a high current in a short welding time, and the intrinsic electrical, thermal, metallurgical and mechanical properties of aluminum alloy.
References [1] RF Qiu, S Satonaka, C Iwamoto, Mechanical properties and microstructures of magnesium alloy AZ31B joint fabricated by resistance spot welding with cover plates, Science and Technology of Welding and Joining. 14(2009) 691-697

In the binary bismuth chalcogenide family, Bi–Te based and Pb–Te based [5, 6] materials showed the best TE properties at room and middle temperatures, respectively.
However, complex substitution and interstitial Cu atoms make the crystal structures of Cu3.21Bi4.79S9 highly complex and disordered [8], hence, better TE properties are expected for this material.
Hence, a parameter thermoelectric power factor (S2σ) was calculated to estimate the actual improvement in thermoelectric properties (Fig. 5).
Li, Enhanced thermoelectric properties of bismuth sulfide polycrystals prepared by mechanical alloying and spark plasma sintering, Journal of Solid State Chemistry, 181 (2008) 3278-3282
Cava, Structures and thermoelectric properties of the infinitely adaptive series (Bi 2) m (Bi 2 Te 3) n, Physical Review B, 75 (2007) 195203

The research work indicates that the activating flux will be used in more welding process to obtain deep weld penetration, high productivity, low deformation and excellent joint mechanical properties. 0 Introduction Activating flux is to decrease surface tension of the interface and change interface properties and conditions of the system[1].
Activating flux has been applied in welding field to improve weld quality through the influence on droplet and the surface properties of molten pool.
Weld productivity has been improved obviously by A-TIG, meanwhile, there are little change in the properties of weld metal[2, 3].
Thus the combination properties could satisfy the correlation standard requirements.
The contraction degree of arc has depended on two factors: one has been the binding force between steam particles and electrons; the other has been the dissociation temperature of steam substance.

It was also worth trying other metals as matrix material so as to see the differences among mechanical properties.
After these factors had been considered, it was tin that was chosen as the matrix metal owing to its low melting point (232°C) and good fluidity.
Most problems arose in connection with aluminium matrix specimens as its wettability properties are worse than the wettability properties of other metals.
General conclusions are that double composites improve the mechanical properties of products yet, unfortunately, at the same time the moulding parameters become changed too.
Valle et al: On the role of brittle interfacial phases on the mechanical properties of carbon fibre-reinforced Al-based matrix composites, Mater.

Because of their poor machinability, it is very difficult to machine Ti-6Al-4V alloy with traditional mechanical cutting [1].
Fonda et al. used EDM technology to machine Ti-6Al-4V alloy to examine the effect of thermal and electrical properties on the productivity[1].
The essential steps include identifying the factors that are to be included in the study and determining the factor levels.
Table 5 and Table 6 show that the Voltage is most significant process parameters affecting the multiple machining responses.
The voltage affecting Material removal rate and Electrode wear ratio with nearly 58% of contribution ratio and the duty factor has almost a 21% contribution.