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When slowly loading in the static state: HKR C / 2 ∝ (2) () 2 / CC K dEH H  ∝⋅  (3) Observing the indentation pattern of the glass by SEM, it is found that the crack number on the material surface is smaller than 10 percent, the critical depth of the indentation should meet: 2 C c KE d HH ξ   =   (4) ξ is the material coefficient.
The grain sizes of dressing oilstone are #200 and #400, and the dressing wheel speed is 35.3m/s and dressing depth 10µm/pass.
Grain size of wheel is #270.
Fig.2 Common grinding （ap=8μm） Fig.3 Ultrasonic grinding（ap=8μm） The index of the material performance value The index of the material performance value The Vickers hardness [Gpa] The elasticity modulus [Gpa] The bending strength [Mpa] The fracture toughness [Mpa.m 1/2] The density [g/cm 3] 11 200 1150 9 6.2 The Poisson's ratio [v] The coefficient of thermal conductivity [W/m⋅K] The grain size of material [nm] 0.27 10 60 Fig.4 The brittle grinding surface of nano- Fig.5 The ductile grinding surface of nano- ZrO2 ceramics (Common ap=12μm) ZrO2 ceramics (Ultrasonic ap=20μm) Fig.6 AFM photo- of the brittle grinding Fig.7 AFM photo- of the ductile grinding surface of nano-ZrO2 ceramics surface nano-ZrO2 ceramics (Common ap=12μm) (Ultrasonic ap=20μm) According to the test results, the critical
On the other hand, because of the random distribution and the stress diversity of the mass nanoparticles in grains, the quadric deflection and the bifurcation occur to the transgranular crack, which consume the energy of cracking expansion and increase the expansion route and the difficulty.

Luo et al. [6] reported the microstructure development and b-Si3N4 grain growth forming can controlled by used high oxynitride glass with Y3+ that effected on increasing the elevated temperature properties of Si3N4.
Bi2O3 remains in the sintered material by forming a highly viscous glass phase located at grain boundaries and enhances the fracture toughness of the glass phase lead to Si3N4 specimens has a high strength at high temperatures.
After drying by hot air oven at 80 ºC for 24 h and screening through a sieve (number 100 mesh).
At the sintering temperature lower than 1650 ºC as Figure 2 (a), (b), (e) and (f) the average grain size was smaller and porous surface could be observed in these specimens.
At the sintering temperature as 1650ºC, specimens of Si3N4 ceramics under ambient gas have more elongated β- Si3N4 grains than specimens of Si3N4 ceramics sintered under 1 MPa gas pressure, corresponding to XRD pattern Figure 1.

In this experiment, a certain number of lead oxide ceramics were processed by conventional method in order to make a contrast with the samples made by microwave method.
The comparison of three samples’ grain shows that Method Two sample has the minimal grain size.
Method One sample has poor hardness and larger grain size because the pellet buried in silicon carbide powder has asymmetric heat conduction by direct contact with silicon carbide powder, which leads excessive grains growing in one side against the other.

Long term research shows that the improvement of properties of alloys on intermetallic FeAl phase matrix can be achieved by a proper selection of the contents of aluminum, addition of chromium and alloy micro-additions, mainly zirconium and boron, separation of strengthening phases, controlling the surface conditions and grain structure, as well as the maintenance of appropriate process parameters [3].
Corrosion products in the form of oxides on the surface appear partly as fine needles as well as grains (Fig. 2b).
The morphology of the scale arisen on the surface of the sample after oxidation at 1100°C had a form of grains (Fig. 3b).
At a temperature of 1000°C scale morphology is characterized by the oxides in the form of fine needle but also a small number of them take the form of clods, which is a transient state between the oxidation at a temperature of 1100°C, at which the oxides appear only in the shape of grains.

The mechanical properties of these materials depend on their composition and microstructure, especially on the grain size of the carbide phase.
The average grain size and size distribution have the critical effect on hardness, strength, wear resistance and so on [6].
However certain number of elongated particles is also seen.
Misra, Grain boundary segregation of phosphorus in iron-vanadium alloys, Acta Mater. 44 (1996) 4367-73
Kear, Synthesis and characterization of submicron vanadium and chromium carbide grain growth inhibitors, Adv.

Mixed with SiO2, TiO2 crystal structure becomes more stable, with smaller grain size and SiO2 highly dispersed in the matrix.
Incorporation of F ions has little effect on the TiO2 crystal structure, but can effectively reduce the grain size and improve the photocatalytic efficiency.
There are two different chemical states for the interaction of F with TiO2 grain: one is the adsorption of F ions onto TiO2 particles with TiOF2[11], and the other is Ti-F [12,13] with F instead of oxygen incorporated into the TiO2 crystal lattice and combined with Ti.
Compared with TiO2 nanowires, SiO2/TiO2 nanowires have smaller grain size.
F-/SiO2/ TiO2 nanowires have higher photocatalytic activity than F-/TiO2 and SiO2/TiO2 nanowires, due to the increase of electron-hole number and oxidation or reduction potential.

It can be seen that the average size of crystal grain in Table 1 Aluminizing Composition of Agent � Al2O3 (wt%) Al (wt%) NH4Cl (wt%) Cecl3 (wt%) Agent 1 96 2 2 0 Agent 2 95.5 2 2 0.5 matrix is 300-500µm much coarser than crystal grain in aluminized layers which is 80-100µm.
The interface aluminizing in agent 1 is flat, the interface aluminizing in agent 2 is undulation, and these small grains in aluminized layers near the interface are bulged in matrix.
The depth and aluminum content of aluminized layer which aluminizing in agent 2 are higher than in agent 1 is because that when aluminizing in agent 2, the chemical reaction within Al, CeCl3 and NH4Cl as follows: NH4Cl→NH3+HCl; 6HCl+2Al→2AlCl3+3H2; AlCl3→[Al3+]+3[Cl- ]; CeCl3→[Ce 3+]+3[Cl- ] At the early stage of aluminizing, [Ce 3+] is infiltrated into substrate along grain boundary.
(3) A large number of nanosize Al2O3 particles are dispersed in strengthen layer

In the present study, a scalable production method was used to acquire satisfactorily dispersed spinel nano-powders, which were then fabricated into fully compact and fine grain transparent magnesium-aluminum spinel ceramics with LiF as the sintering aid.
Researchers have developed a number of techniques for high purity ultrafine spinel powder, including high temperature solid phase method, gel solid phase reaction, homogeneous precipitation, co-precipitation, supercritical method, freeze-drying alkoxide method, hydrothermal method, Evaporation decomposition from solution, combustion synthesis, etc.[5-13].
During the sintering process, wholly sphere- like micro grains are helpful to convert into fully compact items, even without the presence of the sintering aid.
It is found that grain size of 3-300nm is preferred for the highly transparent spinel ceramics.
Bi-metal alkoxide method and sol-gel process are used in preparing magnesium aluminum spinel powders, which can be purer than 99.95%wt, with nano-size evenly distributed grains.

Formation and Mechanical Properties of Mg-Cu-Al-Gd Bulk Metallic Glass Composites Yiming Wang, Lijing Zheng*, Shujie Pang School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China Fund Project: Fok Ying Tung Education Foundation (Grant Number: 114014) and the Aviation Science Foundation of China (Grant No. 2007ZF51063) Resume of author: Yiming Wang, Female, birth year:1985, Master Candidate *Corresponding author: zhenglijing@buaa.edu.cn Keywords: Mg-based metallic glass, composite, microstructure, mechanical properties Abstract: The effect of Al addition to Mg65Cu25Gd10 glassy alloy on the microstructure, thermal properties and mechanical properties were investigated.
The Mg65Cu25Gd10 alloy shows homogenous contrast with no crystalline grains, indicating its glassy single-phase state.
However, for the Al containing alloys, crystalline grains are emerged in the amorphous matrix.
The grain size varies from 20 to 60µm in the Mg65Cu25-xAlxGd10 (x=1-5 at. %) glass composites.
Nevertheless, the Mg65Cu18Al7Gd10 alloy exhibits a large amount of slender crystallites of about 5 µm in length dispersed homogeneously in the glassy matrix and only a few bulk grains can be found, which is significantly different from the other Mg65Cu25-xAlxGd10 composites.

The factors stabilizing deformed austenite are: 1) enhanced resistance to shear of a deformed grain refined austenite; 2) retardation of carbon diffusion, the greater redistribution of carbon between the phases needed for bainite transformation in higher cooling rate austenite.
As the cooling rate increased, the size of the ferrite grain size was decreased.
When the cooling rate is higher than 20˚Cs-1, the change of ferrite grain size is small.
Coupling Fig.2 and Fig.3, when the cooling rate is lower than 20˚Cs-1, the yield strength (570～650MPa) is relatively low although the ferrite grain is fine.
For low cooling rate specimen, the amount of the precipitates is small, and for the higher cooling rate specimen, a large number of extremely tiny Ti compound precipitates are observed in Fig.4, particularly for the UFC process.