4 nitrogen change 3 silicon / the preparation of pottery and porcelain of SiC(N) accept Mi Fuxiang and function research
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Nitrogen of foreword of Css" Type=text/css Rel=stylesheet>1 changes silicon (Si3N4) pottery and porcelain is data of a kind of high-powered project pottery and porcelain, a large number of application receive in the domain such as mechanical, chemical industry, the sources of energy, war industry, but its taller brittleness restricted his to use range greatly. Carborundum (SiC) pottery and porcelain also has good high temperature strength, fight oxidisability, wearability, corrosion resistance to wait, but its inferior room temperature intensity and tenacity inadequacy also make its application is restricted. To improve the performance characteristics of project pottery and porcelain, people was developed fill oneself strong, add grain or fiber to fill strong, brilliant must add pliable but strong to wait for material preparation engineering technology, but the taking buildup, effect that add pliable but strong is more finite. In recent years, people introduces accept rice idea technology of preparation of project pottery and porcelain, make material of pottery and porcelain increases, the technology that add pliable but strong obtained striking progress. Japanese Xin Yuanhao is first-class the person takes the lead in regarding pottery and porcelain of class of rice of dispersion addition in a subtle way as matrix grain of pottery and porcelain of accept rice class in, preparation gave pottery and porcelain of accept Mi Fuxiang, obtained the very good buildup, result that add pliable but strong. Because accept rice grain fills to add effect of craft of pliable but strong by force apparent, operation handy, cost is inferior, because this has wide applied perspective. Current, si3N4 pottery and porcelain adds the research of technology of pliable but strong to basically center at two respects: ① raises tenacity of material of pottery and porcelain through microstructure design, raise density of material of pottery and porcelain and purity namely through reducing matter content of porosity, control: The brilliant to material of pottery and porcelain, grain dimension, development is complete degree undertakes controlling: Have reasonable adjusting control character to the size of crystal boundary, material: The amount to vitreous photograph, property, distributing, condition undertake controlling, have the microstructure of optimal tenacity in order to obtain. ② is begun on afore-mentioned foundations " crystal boundary project " research. This research adds grain of SiC of accept rice class through be in powder of pottery and porcelain of micron class Si3N4, preparation gave data of pottery and porcelain of Si3N4/SiC(N) accept Mi Fuxiang, undertook experimenting study to preparation craft and material function. Powder of pottery and porcelain of Si3N4 of 2 material preparation uses Shanghai material institute to change the commodity powder that legal system takes with Si pink nitrogen, its granuality D50<0.
5µm, among them α - Si3N4 appearance content > 93%(quality mark, similarly hereinafter) , azotic content > 37% , <0 of free Si content.
5% , the others is β - Si3N4 photograph. The purity of pink of agglomeration auxiliary Y2O3, Al2O3, WC, TiC is 99.
9% . Purity of ground rice of accept of dispersion photograph SiC > 95% , average size is 0.
02µm. When preparation sample, it is base material with Si3N4 pink, join SiC accept ground rice (the accretion of different recipe is measured it is respectively 0% , 5% , 10% , 15% , 30%) . Mix all sorts of pink makings by the recipe, after dispersing through supersonic vibration, put alcohol ball is added to grind 48 hours inside ball mill (grind bead to be Al2O3) , make powdery makings mixes adequately to be refined equably. The ball is ground after finishing, take out, the drying inside park oven, undertake screening via 100 eye sieve again, get fine and pulverous. Suppress undertakes powder in tool set machine (for easily drawing of patterns, need to change boracic pulverous) with nitrogen in besmear of wall of black lead model, undertake agglomeration inside furnace of hot pressing of vacuum high temperature next (agglomeration principle) . Furnace of hot pressing of vacuum high temperature should first vacuumize, next slow warm up to firing temperature, the firing temperature of pure Si3N4 is 1850 ℃ , pressure is 30MPa, heat preservation 60min: The firing temperature that adds recipe of SiC accept ground rice is 1750 ℃ , pressure is 30MPa, heat preservation 30min. The sample after agglomeration (flat cylinder of grey black of Ø45 × 6mm) after cooling along with furnace, take out. The microstructure of the ceramics of Si3N4/SiC accept Mi Fuxiang that makes. 3 function test is cut of semifinished product of board shape test specimen 4 × the test piece of 5 × 30(mm3) , used at 3 o'clock respectively observation of organization of bend test, metallographic, hardness detects, the experiment such as fracture toughness test. With HVS-1000 Digital Microhardness Tester microscopical sclerometer check those who measure test piece is microscopical hardness, carry on one's shoulder of place to load is 100g. In AKASHI(AVK-A) diamond pyramid hardness plan the fracture toughness that goes up to measure test piece with check of tiny impress law, carry on one's shoulder of place to load is 3kg. Detect is measure: ? ⑴ of ァ of You of Wa of stew in shallow water of Juan of v/LIT all over the ground drops arrogant of Guo Mei gets dizzy ⒕ of Gui know well enlighten of Xuan of T of mansion of of Gao of form of model ㄓ of of cervine Juan Yu is disrelished catch light dregs of rice rare ?9.
The load to load of 4N(3kg) 15 seconds, hit an impress, measure crack length and impress diagonal length. Use next formula calculable give fracture toughness (apply to tenacity crackle of poorer surface of hemicycle of pottery and porcelain) : KIC/(Ha½)=0.
In 203(c/a)-3/2 type, KIC is toughness factor, h is value of diamond pyramid hardness, 2a is length of diagonal of impress of diamond pyramid hardness (Mm) , 2c is crack length (Mm) . Be opposite with lens of report of HITACHI S-570 scanning the fracture surface after bend test undertook SEM observes at 3 o'clock. Choice sample is enchased in bakelite pink, observation face burnish, polish, get lens area, after undertaking cankerous in mixed liquor of hydrofluoric acid, nitric acid, undertake constituent observation on scanning report lens and take a picture. Measure opposite density and hole rate with catchment law. With diffraction of ray of Rigakv Geigerflex X appearance undertakes X ray diffraction is analysed, in order to decide the photograph in material is comprised. To Si3N4/SiC accept rice the function of sample of answer photograph pottery and porcelain checks a result to see next tables. Constituent of result of test of function of pottery and porcelain of Mi Fuxiang of watch Si3N4/SiC accept (%) is opposite density (%) hole is led (M½) of · of KIC(3kg)(MPa of fracture toughness of Bb(MPa) of %) bending strength σ is microscopical hardness (Ⅰ of HV) recipe Si3N4SiCY2O3Al2O3WC+TiC 795331099.
740.
2565516.
202116.
17 Ⅱ 7410331099.
730.
2716407.
202036.
17 Ⅲ 6915331099.
880.
1127508.
502436.
17 Ⅳ 5430331099.
400.
5747005.
102496.
1794033099.
100.
6115005.
613004 analysises and discuss 4.
1 mechanical function and fracture surface analysis add grain of SiC accept rice in Si3N4 hind, can drop firing temperature significantly, shorten agglomeration time, and agglomeration hind is compound of pottery and porcelain send density to rise greatly, index of each mechanical function also improves other significantly, press recipe Ⅲ among them (the sample hole that grain of SiC accept rice adds a quantity to be 15%) preparation leads lowest, bending strength, microscopical hardness, fracture toughness is highest. Because the recipe is medium it is certain to was joined pink of proportional WC, TiC, because sample of these a few kinds of recipes all is had relatively Gao Xianwei hardness (HV2000 ～ 2500) , can regard cutting of production high speed as cutting tool and mould await select material to expect. When to load (when 3kg) , the sample of a few kinds of recipes that added grain of SiC accept rice all shows taller fracture toughness (5.
1 ～ 8.
5MPa · M½) . Among them the fracture toughness value of recipe Ⅱ and recipe Ⅲ sample is highest, making clear these two kinds of recipes is the better prescription that add pliable but strong. When checking fracture toughness show micro-crack picture. Visible, of pure Si3N4 microscopical crack length is the longest, as the addition of content of grain of SiC accept rice, crack length shortens gradually, it is when content of grain of SiC accept rice 15% when crack length is the shortest. By the test the result is knowable, accept rice grain is added to be able to improve the mechanical performance of material substantially in matrix of material of pottery and porcelain, its add effect of pliable but strong apparent excel adds micron grain, this shows its are had unlike micron the buildup of material of compound pottery and porcelain, mechanism that add pliable but strong. Sample of pottery and porcelain of Si3N4/SiC accept Mi Fuxiang fights the photograph of SEM fracture surface that curves an experiment. Visible, the SiC accept ground rice that adds as a result of recipe Ⅰ is less, because this pliable but strong turns the result poorer, si3N4 grain is bulky and inhomogenous, rupture the form is broken away from in great quantities for grain, fracture surface still ruptures for edge brilliant, section is uneven, after presenting a bigger insular state steps leading up to a house and grain to break away from empty. Visible, right amount add SiC accept ground rice to be helpful for β - Si3N4 development is the strong record grain that distributings equably, the crackle when rupturing has more deflexion and bifurcate, make material tenacity rises, its action mechanism is the SiC accept that capacity of high strenth, tall hardness, high stretch standard adds in Si3N4 matrix after rice grain, the grain of SiC accept rice of dispersion can bear stress and generation micro-crack, prevent a wrong exercise or produce a hammer to plunge into action, make of crackle expand produce deflexion or bend, patulous path is more tortuous, add effect of pliable but strong to arriving since base material thereby. Because matrix grain is refined as the addition of content of SiC accept ground rice, when because this is become,SiC accept ground rice adds excess, β - Si3N4 criterion to growth of state waiting for an axis, make pliable but strong changes the effect to drop. Appearance of form of analytic fracture surface is knowable, break fission to be pottery and porcelain of Si3N4/SiC accept Mi Fuxiang from the edge brilliant of pure Si3N4 pottery and porcelain the main effect mechanism that wearing brilliant to rupture may be the aggrandizement that add pliable but strong. Rupture the change of mode (from micron compound pottery and porcelain gives priority to pottery and porcelain of accept Mi Fuxiang with wearing brilliant to rupture with rupturing along brilliant) by inside the main reason that brilliant mechanism and crystal boundary mechanism considers as a change function of material of pottery and porcelain jointly, can conclude from this, of accept rice grain introduce patulous to crackle process to have outstanding effect, join Namidi 2 photographs are brought about happen wear brilliant to rupture sure it is the result that joint action turns infirmly inside crystal boundary aggrandizement and brilliant. 4.
2The Si3N4/SiC offer that the photograph of pottery and porcelain of Si3N4/SiC accept Mi Fuxiang constitutes 4 kinds of recipes the X ray diffraction of sample of Mi Fuxiang pottery and porcelain pursues. Knowable, increase of content gradually as ground rice of accept of the SiC in base material, α - the content of Si3N4 increases subsequently, make clear block up of grain of SiC accept rice α - Si3N4 to β - Si3N4 is changed. 5 conclusion are right amount in Si3N4 matrix add pottery and porcelain of photograph of Mifu of accept of Si3N4/SiC of preparation of grain of SiC accept rice to be able to drop firing temperature significantly, those who raise the pottery and porcelain after agglomeration is compact degree. Because the WC+TiC white of 10% was joined in the recipe, because this sample is had relatively Gao Xianwei hardness (HV2000 above) , can regard high speed cutting as cutting tool and mould await select material to expect, but material function still needs to be optimized further. Those who join grain of SiC accept rice and firing temperature reduce the mechanical performance that can improve data of pottery and porcelain significantly. As the addition of content of SiC accept ground rice, matrix organization is refined gradually, generate even and petty columnar brilliant. Achieve 10% ～ when content of SiC accept ground rice 15% when, compound pottery and porcelain has highest intensity and bigger tenacity: Increase when content of SiC accept ground rice 30% when, the microcosmic organization of compound pottery and porcelain is thick any crystalline substance waiting for an axis, its intensity and tenacity drop somewhat. Expression of appearance of form of sample fracture surface ruptures for typical brittleness. Break fission to be pottery and porcelain of Si3N4/SiC accept Mi Fuxiang from the edge brilliant of pure Si3N4 pottery and porcelain the main mechanism that wearing brilliant to rupture may be action of the aggrandizement that add pliable but strong. The raises grain of rice of accept of main ascribe SiC to cause crackle of fracture toughness of answer photograph pottery and porcelain is most advanced slant fold reach patulous distance to lengthen. CNC Milling