MgAlON结合镁质和尖晶石质材料的烧结性能

以镁砂或尖晶石为骨料,以Al-Al2O3 -MgO混合粉为基质料,采用氮化烧结法制成MgAlON结合镁质和尖晶石质复合材料,研究了烧成温度和基质料中Al2O3、Al比 (质量比,下同 )和Al2O3、MgO比对试样烧结性能的影响。研究表明:以尖晶石为骨料的试样的烧结致密化程度随烧成温度的升高而提高,但以镁砂为骨料的试样在 1400℃时烧结致密化程度最差;随着基质料中Al2O3、Al比的提高,以镁砂为骨料的试样的烧结致密化程度基本上呈增加趋势,以尖晶石为骨料的试样的烧结致密化程度则基本上呈下降趋势;当基质料中Al2O3、MgO比为 2. 33时,以镁砂为骨料的试样的烧结致密化程度最差,而以尖晶石为骨料的试样的烧结致密化程度随着基质料中Al2O3、MgO比的提高而降低。     

放电等离子烧结合成单相MgAlON材料

以氮化铝、富铝镁铝尖晶石和氧化铝为原料 ,用放电等离子烧结 (SPS)技术合成了单相MgAlON,研究了其显微结构 ,并与用传统的无压烧结 (PLS)技术制备的单相MgAlON材料在显微结构和断裂行为上做了比较。结果表明 :用SPS法在 170 0℃保温 1min的条件下合成出的单相MgAlON材料 ,显微结构比用PLS法合成的更加均匀致密 ,且晶粒细小 ;前者的断裂模式主要是穿晶断裂 ,后者的断裂模式则主要是沿晶断裂。     

矾土基MgAlON复合材料的制备及性能研究

选用登封轻烧矾土(Al2O3含量为85wt％)、电熔镁铝尖晶石、高纯电熔镁砂、Al粉和少量的活性材料氮化气氛下制备矾土基MgAlON复合材料,考察了MgAlON含量及烧成温度对制备矾土基MgAlON复合材料性能的影响.结果表明:随着MgAlON加入量的增加,显气孔率、线变化率及增重率逐渐增大,材料体积密度逐渐减少,常温抗折强度呈上升趋势;随着烧成温度的提高,试样的体积密度略有减小,显气孔率增大,常温抗折强度逐渐增大,1500℃下氮化烧成的制品性能最好;矾土基MgAlON复合镁铝尖晶石材料比矾土基MgAlON复合镁质材料密度大,强度高,氮化效果好.     

反应烧结法制备MgAlON的合成机理及烧结行为的研究

通过对以Al2 O3、MgO和AlN为起始原料 ,在氮气气氛中反应烧结合成MgAlON材料合成机理的研究发现 :在 12 0 0℃以前 ,MgO与Al2 O3反应生成镁铝尖晶石 ,此后 ,随着温度的升高 ,Al2O3不断向所形成的尖晶石中固溶 ;在 130 0℃以前 ,AlN基本上不参与反应 ,而在更高的温度下 ,AlN开始向尖晶石中固溶形成MgAlON ,约在 15 5 0℃时形成单一的MgAlON相。用热膨胀仪检测了试样的线变化率随温度和时间的变化 ,用最小二乘法回归分析了试样线变化率的实验数据 ,并根据烧结理论对MgAlON材料烧结初期的动力学进行了探讨。结果表明 ,MgAlON材料烧结初期的烧结机理以体积扩散为主     

MgAlON对碳结合制品性能的影响

采用合成MgAlON部分或全部取代铝碳砖和铝镁碳砖中的基质部分 ,并测试其对材料密度、强度、抗氧化性和抗渣性能的影响。结果表明 :在铝碳和铝镁碳耐火制品中加入MgAlON后 ,体积密度上升 ,耐压强度提高 ,抗氧化性能改善 ,抗渣性能略有降低但仍保持较好水平     

放电等离子烧结超快速合成MgAlON尖晶石的研究

本文以MgO、AlN及Al2O3为原料，研究了采用放电等离子烧结技术合成MgAlON尖晶石的机理。并成功地实现了MgAlON陶瓷的超快速制备。研究结果表明，MgAlON的合成机理为：在1200℃以前，MgO和Al2O，首先反应形成尖晶石，该尖晶石是一中间体。随着烧结温度的升高(1300℃以上)，AlN开始向中间体中固溶形成MgAlON。研究表明，采用放电等离子烧结技术，在1600℃保温5min及在1700℃保温1min的条件下即可获得致密的单相MgAlON陶瓷。     

添加剂对MgAlON材料抗氧化性能的影响

MgAlON材料较易被氧化 ,研究了几种抗氧化剂的作用。结果表明 :B4 C和SiC的效果最好 ,它们氧化后分别生成B2 O3、SiO2 及其化合物 ,填充于材料气孔 ,起着保护作用 ,使得MgAlON材料的氧化性质由连续性变成保护性     

MgO与ZrSiO_4反应烧结机理研究

应用ＳＥＭ方法观察了ＭｇＯ与ＺｒＳｉＯ_４的反应烧结机理。结果表明,随着ＺｒｓｉＯ_４的分解,ＳｉＯ_２呈不定形态向外扩散,与ＭｇＯ反应生成Ｍｇ_２ＳｉＯ_４,原来的锆英石颗粒中只留下了ＺｒＯ_２,同时ＭｇＯ向ＺｒＯ_２方向移动,与ＺｒＯ_２形成有限固溶体;反应产物之一ＺｒＯ_２大部分聚集成集合体,也有一部分分布比较均匀。     

耐火材料的MgAlON晶须结合

RH脱气炉用无铬化的方镁石-尖晶石-Al不烧砖具有优越的力学特性和抗渣渗透性,在极其苛刻的使用条件下成功取代传统的镁铬砖。与传统的陶瓷结合不同的是,方镁石-尖晶石-Al不烧砖使用后呈现微米级柱状MgAlON晶须相互交织、浓密网状分布的结合基质。为建立和完善晶须结合的概念,归纳了耐火材料中晶须结合的特征,晶须形成的机制和条件,晶须增强和晶须结合的不同之处。     

MgAlON结合耐火材料的氧化动力学研究

借助于微量热天平 ,通过非等温氧化实验和在不同温度下进行等温氧化实验 ,研究了MgA lON结合耐火材料的氧化行为和氧化动力学。研究结果表明 ,MgAlON结合刚玉耐火材料比MgAlON结合尖晶石耐火材料易于氧化。MgAlON结合尖晶石耐火材料的氧化规律为化学反应速度控制阶段 -混合控速阶段 -扩散速度控制阶段。而MgAlON结合刚玉耐火材料试样的氧化规律为化学反应速控-扩散速控。     

Sintering high-purity fusions of MgO and MgO·Al2O3

Conclusions The porosity and strength of specimens of fused MgO obtained by induction smelting in cold crucibles and having 1% impurities is significantly increased by the addition of 1% CeO₂, 5% ZrO₂, and 20% of the vibromilled component plus 5% Y₂O₃. An addition of 5% Y₂O₃ has the greatest effect on the sintering characteristics of the MgO·Al₂O₃ specimens. A significant improvement in the characteristics of the materials is observed with an increase in the pressing pressure of the specimens from 100 to 200 MPa.Translated from Ogneupory, No. 3, pp. 54–56, March, 1981.     

Experimental Analysis of Sintering of MgO Compacts

Experimental sintering studies On undoped and cao-doped Mgo powder compacts in Static air and flowing Water Vapor atmospheres were conducted at 1230° to 1600°C. Corresponding microstructural changes of specimens during sintering were examined by scanning electron microscopy. Kinetic and microstructural data were analyzed to determine sintering mechanisms during the initial and intermediate stages of sintering.     

MgO-MgAl2O4-MgAlON系复合材料的制备及性能研究

分别以60%(w)的电熔镁砂或(和)电熔镁铝尖晶石为骨料,以40%(w)的Al-Al2O3-MgO混合粉(采用Al粉、活性α-Al2O3和MgO粉按质量比4∶9∶1混合)为基质料,在N2气氛中于1500℃6h反应烧结制备了MgO-MgAlON、MgO-MgAl2O4-MgAlON和MgAl2O4-MgAlON三种复合材料,并研究了材料的烧结性能、高温力学性能、物相组成以及显微结构。结果表明在本试验范围内,3种材料的烧结性能相差不大,1500℃氮化烧成后均达到致密烧结状态;材料的HMOR-T曲线属于I类曲线,且热态抗折强度(≤1400℃)均高于常温强度,强度峰值的对应温度均为1200℃。所制备的3种复合材料相比较,MgAl2O4-MgAlON复合材料的综合性能最优。     

Sintering of MgO made from MgCl2

Conclusions The production parameters for a densely sintered magnesite powders made from MgO obtained from the thermal decomposition of MgCl₂ have been established. It is shown that the mechanical activation of MgO can be carried out in a vibromill for 10–20 min with an addition of a surface-active material (distillery waste or C₇-C₉ (fatty acids).Under pilot-plant conditions, using the process which has been developed, we obtained an MgO briquette of apparent density 3.20–3.33 g/cm³, an open porosity of 1.6–4.6%, and a MgO concentration of 97.9%. The magnesite and magnesite-chrome articles based on this briquette have excellent properties.Deceased.Translated from Ogneupory, No. 7, pp. 41–45, July, 1979.     

Structural Rearrangement During the Sintering of MgO

MgO compacts were sintered from 900° to 1395°C in dry argon and in argon with 2.3 kPa of water vapor. The surface area and pore size distributions measured by mercury porosimetry showed large changes during the first minute of sintering, indicating that rearrangement instead of coalescence of small particles is the controlling process in the early stage. Rearrangement was found to be temperature-dependent and to extend through the initial stage of sintering.     

Sintering and characterization of flyash-based mullite with MgO addition

Mullite ceramics were fabricated at relatively low sintering temperatures (1500-1550 °C) from recycled flyash and bauxite with MgO addition as raw materials. The densification behavior was investigated as function of magnesia content and sintering temperature. The results of thermal analysis, bulk density and pore structure indicate that MgO addition effectively promoted sintering, especially above 1450 °C. Due to the presence of large interlocked elongated mullite crystals above 1450 °C, associated with enhanced densification, an improvement in mechanical strength was obtained for the samples containing magnesia. The addition of magnesia slightly decreases the LTEC at 1300 °C due to the formation of low-expansion α-cordierite, but slightly increases the LTEC above 1400 °C due to the formation of high expansion corundum and MgAl₂O₄ spinel.     

Effect of Minor Additions on Sintering of MgO

Fourteen selected metal ions were added to magnesium basic carbonate, and the MgO obtained after calcining was fired at various temperatures to determine the effect of the additives on the sintering behavior. The magnesia without additives showed rapid increase in density with firing temperature near 1200° C. The majority of the additives caused increased density, at a given firing treatment, but some were without effect and one (Cr) dramatically inhibited sintering in certain percentages. It is believed that most of the additives which aided sintering did so by entering into the magnesia lattice and creating defects, although at least one (V) clearly promoted sintering by liquid formation.