Characterization of two-phase nickel aluminides produced by pressure-assisted combustion synthesis

Two-phase (B2+L1₂) nickel aluminide intermetallic compounds were synthesized by the pressure-assisted volume combustion synthesis (CS). The production and characterization of the samples containing NiAl+Ni₃Al were investigated. Aluminum (99% pure, 15 μm) and carbonyl nickel (99.8 pure, 4-7 μm) powders were used. The production of intermetallic compound was carried out at 1050 °C under 150 MPa uniaxial pressure in open air atmosphere in an electrical resistance furnace for 60 min. The formation temperature of intermetallic compound was determined by differential scanning calorimeter (DSC) analysis, and exothermic temperature of powder mixture was determined as 653 °C. The characterization of samples was confirmed by optical microscope, SEM and XRD analysis. It was observed that the structure of compound has very low porosity and the formation of NiAl was completed successfully. The relative density of test materials measured according to Archimedes’ principle was 98.04%. The microhardness of test materials was about 351 HVN₁.     

Pressureless sintering and characterization of cordierite/ZrO2 composites

Cordierite/ZrO₂ composites with 5 to 25 wt% ZrO₂ were fabricated by conventional powder mixing and pressureless sintering method. Their densification behavior, microstructure, mechanical and thermal properties were studied. By dispersing 25 wt% (9.57 vol%) ZrO₂, densified cordierite/ZrO₂ composite with a relative density of 98.5% was obtained at an optimum sintering condition of 1440 °C and 2 h. ZrO₂ particles were homogenously dispersed within matrix grains and at the grain boundaries. The intragranular particles were finer than 100 nm and the intergranular particles were coarser. Both fracture strength and toughness could be enhanced more than two times higher, compare to those of monolithic cordierite, by dispersing 25 wt% ZrO₂ into the cordierite matrix. The toughening mechanism in the present composites was mainly attributed to martensitic transformation due to ZrO₂ dispersion. Electronic Publication     

纳米Fe2O3对镁铬耐火材料烧结及力学性能的影响

在镁铬耐火材料中添加纳米Fe2O3,研究了它对镁铬耐火材料烧结性能与常温力学性能的影响.结果发现,在相同的工艺条件下,加入1%(外加)的纳米Fe2O3即可使镁铬砖的烧成温度降低150℃左右,并在相同烧成温度下能使试样的常温抗折强度和耐压强度大幅度提高.分析认为,在镁铬耐火材料中添加少量纳米级Fe2O3,可促进MgO-FeO固溶体中Cr3+和Al3+含量的提高,增强镁铬砖的直接结合程度,从而提高其力学性能.     

一种新型悬臂棒条筛的设计与应用

介绍了一种新型悬臂棒条筛分机械,论述了其结构、工作原理和技术特性。从理论和实践两方面论证了它的结构、处理能力、筛分效率、返矿率都明显优于普通悬臂棒条筛分机械,可广泛应用于高炉槽下烧结矿的筛分作业。     

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     

Phase composition and properties of solid solutions of GdFeO3–GdInO3 bulks

Solid solutions of the GdFeO₃–GdInO₃ system were prepared at 1550 °C by ceramic powder processing. The formulated composition was Gd(Fe_1−xIn_x)O₃ (GFI) with the indium contents at x = 0, 0.25, 0.5, 0.75, and 1.0. A stable phase of Gd(Fe_1/3In_2/3)O₃ in our system was identified by X-ray diffraction and phase composition analysis. Multi-phase morphologies were observed for GFI bulks with x = 0.5 and 0.75. Dielectric and electrical properties of the GFI bulks were investigated. The addition of 25% In³⁺ in GdFeO₃ had an obvious enhancement in polarization and led to an elevated resonance frequency. Dielectric properties of GFI bulks except GdInO₃ were strongly dependent upon the test frequency, which corresponded to the response of polarization mechanism. GdInO₃ displayed as a stable dielectric, which was frequency- and temperature-insensitive. GdInO₃ was thermally activated and became leaky until above 600 °C.     

Characterization of sintered coal fly ashes

Çan, Çatala?z?, Seyitömer and Af?in-Elbistan thermal power plant fly ashes were used to investigate the sintering behavior of fly ashes. For this purpose, coal fly ash samples were sintered to form ceramic materials without the addition of any inorganic additives or organic binders. In sample preparation, 1.5 g of fly ash was mixed in a mortar with water. Fly ash samples were uniaxially pressed at 40 MPa to achieve a reasonable strength. The powder compacts were sintered in air. X-ray diffraction analysis revealed that quartz (SiO₂), mullite (Al₆Si₂O₁₃), anorthite (CaAl₂Si₂O₈), gehlenite (Ca₂Al₂SiO₇) and wollastonite (CaSiO₃) phases occurred in the sintered samples. Scanning electron microscopy investigations were conducted on the sintered coal fly ash samples to investigate the microstructural evolution of the samples. Different crystalline structures were observed in the sintered samples. The sintered samples were obtained having high density, low water adsorption and porosity values. Higher Al₂O₃ + SiO₂ contents caused to better properties in the sintered materials.     

The effect of the addition of chemical materials on the sintering of biomass ash

In this work the use of chemical materials (additives) in order to reduce the biomass ash sintering tendency is investigated. A total of seven additives (kaolin, limestone, lime, dolomite, calcined dolomite, ophite and alumina) and silica utilised as reference material were mixed in different proportions with the ash of five different biomasses, and then a laboratory sintering test was performed on the mixtures to determine the effect of the additives on the sintering. The biomasses studied in this work were: thistle biomass, brassica carinata biomass, barley straw, almond shell and orujillo (olive oil extraction residue). The sintering decrease among the additives was studied using X-ray diffraction.Kaolin, lime, calcined dolomite and ophite are proved to be suitable to reduce the biomass sintering in all the considered cases. Dolomite, limestone and, particularly, the tabular alumina, offer poorer results. The dilution of the biomass ash is considered the main process involved in the decrease of the sintering for most of the additives, with the exception of kaolin whose chemical reactions could be more important than the dilution effect.     

影响拟薄水铝石烘干系统产能的成因分析及其改进措施

本文针对拟薄水铝石生产线中的关键环节—烘干系统的设备产能问题进行了分析和技术改造,收到了较好的效果,并为同类生产企业及今后改、扩建工作提供了有益的借鉴。