【正文】 s, but has yet to be discovered since then. The mineral with the same chemical position as CZ, but in the monoclinic crystal system, is baddeleyite. Cubic Zirconia ? Cubic zirconia has a hardness of on Moh39。s when Swarovski amp。t until the 197039。s modulus – ability to be polished to a superior surface finish – lower hardness 下圖為三種晶型的單位晶胞結(jié)構(gòu) ： ZrO2 三種晶胞參數(shù) 晶型 溫度 0C a b c ? 單斜 30 99o18′ 四方 1393 立方 2400 ZrO2結(jié)構(gòu)特征 純 ZrO2 在不同溫度下具有單斜 （ m） 、 四方 （ t） 、 立方 (c)三種不同晶型 ， 晶型轉(zhuǎn)化式為： 11700C 23700C 27150C 單斜相 四方相 立方相 液相 Stabilized zirconia ? FSZ fully stabilized zirconia ? PSZ partially stabilized zirconia ? TZP tetragonal zirconia polycrystalline ? stabilizer CaO MgO Y2O3 CeO2 To produce colored cubic zirconia, the following oxides can be added to achieve the following colors. Oxide Colors Produced Cerium oxide red, orange, yellow Copper oxide yellow, amber, brown Iron oxide yellow, amber, brown Nickel oxide yellow, amber, brown Praseodymium oxide yellow, amber, brown Titanium oxide yellow, amber, brown Erbium oxide pink Europium oxide pink Holmium oxide pink Chromium oxide green Manganese oxide green Vanadium oxide green Cobalt oxide lilac, violet Manganese oxide lilac, violet Neodymium oxide lilac, violet Excess yttrium oxide blue, green Cubic Zirconia history ? Cubic Zirconia was discovered in its natural state in 1937 by two German mineralogists, von Stackelberg and Chudoba. It was in a highly metamict zircon given to them by . Anderson. The zircon contained tiny crystals that were determined to be the cubic form of zirconium oxide by xray diffraction. The two mineralogists thought so little of their discovery that they did not even give it a name。 C. This has lead to applications in oxygen sensors and high temperature fuel cells. Typical characteristics ? High temperature capabilty up to 2400176。 Slip Casting Powder Pressing Process Filling Mould Compaction Green part ejected then sintered What is Gelcasting? ?Developed at the Oak Ridge National Laboratory ?Colloidal ceramic forming process ?Insitu polymerization of a monomer solution ?Polymer holds together the “green” ceramic part ?Developed with Alumina, can be used with all engineering ceramics Why Gelcasting? ? Form plex shape ceramics for applications such as high temperature turbines ? Increase quality of manufacturing ? Lower manufacturing costs Oak Ridge National Laboratory Gelcasting System ? Aqueous system ? Used Hydroxymethylacrylamide as monomer – Relatively low toxicity ? Darvan C dispersant ? AZIP (Azobis dihydrochloride) activator ? Alumina (Al2O3) – Chosen because of low sintering temperature Hotpressed slip casting ? flow chart ? 主要用于形狀復(fù)雜 精細(xì)而小巧的產(chǎn)品 原料粉 石蠟、油酸 加熱攪拌 快攪拌 慢攪拌 熱壓注成型 排蠟 高溫 燒成 The properties of alumina ceramics ? 主要性能指標(biāo) ： ? 體積密度 ≥ (g/cm3） ? 抗折強(qiáng)度 ≥ 280 （ MPa） ? 線膨脹系數(shù) （ 10–6mm/℃ ） ? 20∽500℃ (∽7) 20∽800℃ (∽8) ? 介電常 1MH220℃ 9∽10 10GH220℃ 9∽10 ? 擊穿強(qiáng)度（ Kv/mm） 15 The properties of alumina ceramics(continued) ? 化學(xué)穩(wěn)定性（ mg/cm2） 1:9Hcl ≤7 10%NaOH ≤ ? 介質(zhì)損耗角正切值（ 104） 1MH220℃ ≤4 10GH220℃ ≤10 ? 體積電阻率 （ ） 25℃ 8 1014 Microstructures of alumina Saffil Al2O3 Fibre Alumina platelets Alumina continuous fiber 99% Al2O3 Su=3000 MPa E = 400 Gpa ?= g/cm3 Ceramic Composite Armor Projectil eOuter hard s k inC eram ic D is c on t inuou sI nnerductiles k i nPers onn elandEquipm entCe ramic Arm or Syst emCeramic Armor ? Ceramic armor systems are used to protect military personnel and equipment. ? Advantage: low density of the material can lead to weight efficient armor systems. ? Typical ceramic materials used in armor systems include alumina, boron carbide, silicon carbide, and titanium diboride. ? The ceramic material is discontinuous and is sandwiched between a more ductile outer and inner skin. ? The outer skin must be hard enough to shatter the projectile. Ceramic Armor ? Most of the impact energy is absorbed by the fracturing of the ceramic and any remaining kiic energy is absorbed by the inner skin, that also serves to contain the fragments of the ceramic and the projectile preventing severe impact with the personnel/equipment being protected. ? CF uses alumina ceramic/Kevlar posite system in sheets about 20mm thick and having a bulk density of about g/cm3 to protect key areas of Hercules aircraft (cockpit crew/instruments and loadmaster station). ? This lightweight solution provided an efficient and removable/replaceable armor system. Similar systems used on APC’s 3 Zirconia ZrO2 ceramics ? to zirconia ? zirconium。此外激光加工及超聲波加工研磨及拋光的方法亦可采用。通常采用由粗到細(xì)磨料逐級(jí)磨削，最終表面拋光。由于氧化鋁陶瓷材料硬度較高，需用更硬的研磨拋光磚材料對(duì)其作精加工。 Processes of alumina ceramics (continued) ? 四 精加工與封裝工序： 有些氧化鋁陶瓷材料在完成燒結(jié)后，尚需進(jìn)行精加工。因此，目前一些高附加值氧化鋁陶瓷產(chǎn)品或國防軍工需用的特殊零部件、如陶瓷軸承、反射鏡、核燃料及槍管等制品、場(chǎng)采用熱等靜壓燒成方法。由于結(jié)構(gòu)均勻，材料性能比冷壓燒結(jié)提高３０～５０％。連續(xù)熱壓燒結(jié)雖然提高產(chǎn)量，但設(shè)備和模具費(fèi)用太高，此外由于軸向受熱，制品長度受到限制。 燒成使用的設(shè)備是電爐。 Processes of alumina ceramics (continued) ? 三 燒成技術(shù)： 將顆粒狀陶瓷坯體致密化并形成固體材料的技術(shù)方法叫燒結(jié)