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.     

氟化物对低温烧结氧化镁陶瓷的影响

研究了添加不同种类氟化物的氧化镁陶瓷的各种烧结条件和显微结构.实验发现:添加MgF2可以在相对低的温度下显著提升制品的致密度并促进晶粒的生长,说明采用MgF2可以实现低温烧结MgO.这说明MgO-MgF2体系中烧结驱动力即总界面自由能随着粒子总表面积的不断降低而降低.     

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.     

Intensified Sintering of Lithium Aluminosilicate Ceramics

Experimental data are presented showing that the sintering of lithium aluminosilicate-based glass ceramics, produced by ceramic technology, can be accelerated by adding 0.1 – 0.7% Cr₂O₃, without detriment to the product quality.     

MgAlON及MgAlON结合MgO材料烧结性能研究

以电熔镁砂细粉和颗粒、煅烧α-Al2O3微粉及金属铝粉为原料,在高纯氮气中烧成制备MgAlON及MgAlON结合MgO材料,并研究了化学反应引起的体积膨胀、氧化物挥发和保温温度(1450、1550、1650℃)对MgAlON及MgAlON结合MgO材料烧结的影响。结果表明:(1)在烧成过程中,形成过渡相MgAl2O4是引起MgAlON和MgAlON结合MgO试样体积膨胀的主要原因;(2)在低氧分压和高温条件下,MgAlON和MgAlON结合MgO试样的质量损失主要是由MgO挥发引起的;(3)对于MgAlON试样,高温(≥1550℃)烧成时显著的体积收缩使试样具有较高的密度和高强度;(4)对于MgAlON结合MgO试样,高温(≥1450℃)烧成时显著的体积膨胀和MgO大量挥发导致了试样的低密度和低强度。     

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 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.     

Influence of Light Calcining Hydration of Magnesite on MgO Sintering

Sintered magnesia clinker(also called sintered MgO) was prepared with Mg(OH)2(prepared by light calcining hydration of magnesite) and magnesite as starting materials,respectively,by the technical process:light calcining(850 ℃ 1 h) → grinding → molding → firing(1 600 ℃ 3 h).The morphology and structure of light calcined MgO powders prepared with magnesite or Mg(OH)2 were analyzed by XRD,SEM and FT-IR.The sinterability and microstructure of sintered magnesia prepared with magnesite or Mg(OH)2 were researched....     

多种外加剂对红柱石制品烧结性能影响的研究

研究了多种外加剂对红柱石原料烧结性能的影响，分析了其作用机理。结果表明：加入氧化镁可明显促进红柱石的烧结，在高温阶段其作用更加明显，但其质量分数必须严格控制，不宜超过2％。添加氧化钛也可促进红柱石的烧结，其质量分数应该控制在4％以内。而添加氧化铬和氧化锆则不利于红柱石的烧结。     

MgO烧结助剂对氧化铝多孔陶瓷结构和性能的影响

以叔丁醇为溶剂,采用凝胶注模成型工艺于1 500℃保温2 h烧结制备出高气孔率、高强度、低热导率氧化铝多孔陶瓷。研究了氧化镁烧结助剂对氧化铝多孔陶瓷气孔率、气孔尺寸及分布、耐压强度和室温热导率的影响。结果表明:当氧化镁添加量从0.5%(质量分数)增加到2.0%时,气孔率的变化范围为64.65%~73.28%;气孔尺寸分布均匀,平均孔径为0.91~1.30μm;加入Mg O后,陶瓷具有较高的耐压强度,介于14.1~36.2 MPa之间,室温热导率[最低可达0.55 W/(m?K)]比相应的致密陶瓷[室温热导率约为30 W/(m?K)]低2个数量级左右。     

Microstructural Development during Sintering of Lithium Fluoride

Measurements are reported of the influences of temperature, green density, and pore network breakup on the densification, grain growth, and pore volume distribution in LiF compacts. As long as most of the pore volume remained open to the compact perimeter, the ratio of the rate of densification to the rate of grain growth was higher than that sometimes reported for copper or typical oxides. Plots of the logarithm of densification rates versus sintered density for LiF are approximately linear during intermediate-stage sintering, like those for some oxides. But the plots for LiF are unlike those of the oxides in that, for LiF, densification rates measured at different temperatures converge near the density at which half the pore volume is isolated from Hg intrusion. Calculations suggest that further densification of the LiF compacts is blocked because air trapped in isolated pores becomes sufficiently compressed to balance the sintering stress.     

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.     

Microwave-Assisted Synthesis and Sintering of NZP Compounds

We have identified the high microwave susceptibility of the sodium di-hydrogen phosphate monohydrate (NHPM), NH₂PO₄·H₂O. This acid phosphate of sodium can be heated to >900°C when exposed to 2.45 GHz microwave radiation. Using NHPM and microwave energy, a novel single-step synthesis of many important crystalline NZP compounds has been accomplished in a very short time. Interestingly, the combination of microwaves and nonstoichiometric oxide precursors for the preparation of NZP materials is found to reduce the reaction temperatures and enhance the reaction kinetics further. The microwave synthesis method is found to be simple and fast, minimizing the loss of volatile chemical species from the reaction. A microwave-assisted procedure for the rapid sintering of NZP compounds has also been demonstrated. Densification (>97%) has been achieved in <30 min at sintering temperature much lower than normally required in conventional processes. Finer microstructure and better densification are the main advantages of the microwave sintering in this study.     

Studies in Lithium Oxide Systems: X, Lithium Phosphate Compounds

As a preliminary to the investigation of the ternary systems Li₂O-B₂O₃-P₂O₅ and Li₂O-SiO₂-P₂O₅ the existence of the previously reported lithium ortho-, pyro-, and metaphosphate compounds was confirmed. A rapid, reversible inversion takes place in Li₄P₂O₇ at 630°C. New data on the melting points, optical properties, and X-ray diffraction patterns of each of the compounds were obtained.     

The Effect of Ferrous Compounds on Sintering of Clay Mixtures under Decreased Pressure of Firing Medium

It is demonstrated that when clays mixtures are fired under decreased pressure, ferrous compounds intensely transform into active forms due to the reducing type of gaseous medium. At the same time the mechanism of modification transformations changes, which contributes to improving the physicomechanical properties of products obtained.__________Translated from Steklo i Keramika, No. 2, pp. 13 – 16, February, 2005.     

Sintering of Ultra-High-Purity Alumina Doped Simultaneously with MgO and FeO

The use of ultra-high-purity powder processing and multiple solid-solution additive doping has been evaluated as an effective approach for the fabrication of alumina ceramics. MgO was found to inhibit grain growth more strongly in very pure powders because of its stronger solute drag effect. The degree of inhibition was severe enough to render grain growth insensitive to porosity. By diminishing the dragging influence of pores on grain-boundary motion, MgO guards against abnormal grain growth due to inhomogeneous densification. FeO acted singly in alumina to promote grain growth more than densification. FeO was not, therefore, an effective sintering additive for undoped alumina. FeO did, however, Ceramic benefit the sintering of MgO-doped alumina.