烟火药中Mg+H_2O与MgO+H_2O反应的竞争机理研究

为了明确氧化镁在含镁烟火药中作为安定剂的作用机理,对镁/水反应和氧化镁/水反应的竞争机理进行了研究。采用密度泛函B3LYP/6-311++G(d,p)方法优化反应路径中各驻点的几何构型,分析其电子结构并计算振动频率,确定过渡态和中间体,得到两种反应的反应势能曲线。对比发现氧化镁与水会先发生反应,在长贮中起到保护镁粉的作用。     

聚丙烯纤维和氧化镁在面板混凝土中的应用

洪家渡水电站面板堆石坝属200 m级高面板坝,面板混凝土的防裂技术是一个重要的研究课题.洪家渡大坝面板混凝土配合比设计的基本思路是在满足设计要求的强度、耐久性及良好的施工和易性的前提下,重点考虑其抗渗防裂问题.经过大量的试验论证之后,采用了在混凝土中掺加聚丙烯纤维和轻烧氧化镁的方法.已完工的一期面板到目前为止仅发现10条小于0.2 mm的细微裂缝,大大低于同类坝型的水平.聚丙烯纤维和轻烧氧化镁双掺技术的应用,在面板混凝土的防裂中发挥了明显的作用.     

石灰卤水法制备氧化镁核心工段的流程设计

建立在充分试验和研究所取得的成果基础上 ,文章对石灰卤水法制备氧化镁的关键工序的设计进行了阐述     

Effect of magnesia on structure, degradability and in vitro bioactivity of CaO-MgO-P2O5-SiO2 system ceramics

CaO-MgO-P₂O₅-SiO₂ system ceramics with various magnesia contents (0, 5, 10 and 20 mol%) were successfully prepared by sintering the sol-gel-derived powder compacts. The ceramic degradation was evaluated through the weight loss in the tris-(hydroxymethyl)-aminomethane and hydrochloric acid (Tris-HCl) buffer solution, and their ability to form apatite was determined by soaking in simulated body fluid (SBF). Results indicated that the ceramics structure was greatly influenced by magnesia contents. New crystal phases of Ca₂MgSi₂O₇ and SiO₂ were formed when magnesia was added and with an increase of magnesia concentration the phase of Ca₂MgSi₂O₇ increased with a simultaneous decline of β-CaSiO₃. In addition, studies showed that magnesia played an important role in affecting the degradability and apatite forming ability of CaO-MgO-P₂O₅-SiO₂ system ceramics. It is observed that with increasing magnesia concentration, the ceramic degradability gradually decreased and the formation of apatite on samples was delayed.     

中间包镁质干式料用结合剂的研究

首先将电熔镁砂(≤0.088 mm)分别与低温结合剂(分别为沥青、蔗糖、石蜡、松香、酚醛树脂)和中温结合剂(分别为三聚磷酸钠、九水硅酸钠、六水氯化镁、硼酸、十水硼砂和硼酸盐玻璃)按95∶5的质量比混练均匀,以120 MPa的压力干压成型为36 mm×36 mm的试样,分别在300℃2 h、1 000℃3 h、1 450℃3 h、1 500℃3 h和1 600℃3 h条件下热处理后测量其显气孔率、体积密度和耐压强度,以评价这些结合剂的结合性能和促烧结性能,并评价了其环保性;然后,在上述试验的基础上分别采用沥青-硼酸盐玻璃、松香-硼酸盐玻璃和酚醛树脂-硼酸盐玻璃3种复合结合剂按镁质干式料的配方制备成镁质干式料试样,分别在200℃2 h、1 100℃3 h和1 500℃3 h条件下热处理,测量试样热处理后的永久线变化率、显气孔率、体积密度和耐压强度等常温物理性能。结果表明:采用酚醛树脂、沥青和松香为结合剂时,镁质材料300℃2 h热处理后的耐压强度较高;而采用硼酸、十水硼砂和硼酸盐玻璃为结合剂时,镁质材料1 000℃3 h热处理后的耐压强度较高,硼酸和硼酸盐玻璃能明显促进镁质材料的高温烧结;使用5%松香-4%硼酸盐玻璃作为复合结合剂制备的镁质干式料具有较好的常温物理性能和环境友好性。     

Effects of La2O3 on the viscosity of copper smelting slag and corrosion resistance of magnesia refractory bricks

The rotating method is carried out to investigate the effects of La₂O₃ content (0–4 wt%) on the viscosity of copper smelting slag at high temperatures, the apparent activation energy is evaluated according to the Arrhenius equation and the structural characterization of this quenched slag is characterized by Raman spectroscopy. Meanwhile, the corrosion resistance of copper smelting slag with different content of La₂O₃ on magnesia refractory bricks is researched by employing a static crucible method. The experimental results show that the viscosity of copper smelting slag decreased with the La₂O₃ ratio increases from 0 to 3 wt% in a certain temperature range, which is because La₂O₃ simplifies the structural units of [SiO₄] tetrahedral groups. However, the melt viscosity increases after add 4 wt% La₂O₃, the reason is that more La₂O₃ addition improves the structural compactness of [SiO₄] tetrahedral groups in the molten slag due to the strong accumulation effect of La³⁺. Observation of the corroded samples found that the corroded magnesia refractory brick has a lower penetration index when the copper smelting slag with the content of 4 wt% La₂O₃. Therefore, the copper smelting slag containing 4 wt% La₂O₃ has a higher viscosity, and thus impeded the penetration behavior of copper smelting slag on magnesia refractory bricks.     

The deactivation study of Co–Ru–Zr catalyst depending on supports in the dry reforming of carbon dioxide

Carbon dioxide reforming of methane was performed over Co–Ru–Zr catalyst (0.4 wt% Ru added, calcined at 400 °C) with different supports (SiO₂, γ-Al₂O₃ and MgO) in order to study their deactivation. The Co–Ru–Zr/γ-Al₂O₃ showed the highest activity at first, but severe deactivation was observed due to carbon deposition. Co–Ru–Zr/MgO exhibited low activity because of its low specific surface area. However, the high conversions could be obtained in Co–Ru–Zr/SiO₂, and activity was kept almost constantly for 500 h reaction. The characteristics of the catalysts, before and after the reaction, were investigated employing BET, XRD, TPR, TGA-DTA and TEM.     

Clean fuel-magnesia bonded coal briquetting

Benefaction from coal fines as solid fuel in Turkey is very much important for economical development. Beneficiation from washed coal fines in the industry using solid fuel at lump size and in the municipal areas as an household solid fuel may be only provided by hot briquetting of the coal fines. The most practical common way of that benefication from coal fines in our country have been hot binding by sulfite liquor–sulfite liquor-melas and lime mixtures. Harmful the flue content of sulfite liquor-melas may only be eliminated by lime, a type of solid additive. However, cold bonded briquettes produced from coal fines are environmentally free. Just ash contents of these briquettes increase at a certain degree and heat content of them decrease at a certain extent. By using magnesia binder showed in this study, Tunçbilek lignite fines have been briquetted by cold and hot briquetting techniques. The qualities of briquettes produced by cold binders were compared with to those produced by other hot binding methods As a result, magnesia binder showed the similar characteristics with those of the briquettes produced by only cold bonded gypsum. Use of magnesite mixture and gypsum just as only cold binder was not suitable for the requirements from the coal briquettes to be used as solid fuels, particularly from household fuels, but just only as cold additive should be used.     

基质组成对Al2O3-MgO质钢包浇注料物理性能的影响

在Al_2O_3-MgO质钢包浇注料基质内引入不同配比的镁砂细粉、SiO_2微粉及预合成尖晶石细粉,固定MgO的总量约为5%(质量分数,下同),制成不同试样;研究各试样分别在400℃、800℃、1100℃、1400℃及1600℃处理3h后的物理性能以及随着温度升高而发生的物相变化。结果表明加入预合成尖晶石细粉的试样由于没有太多的膨胀反应及液相,其显气孔率、线变化率及热态抗折强度等物理性能相对较好;基质中反应生成的尖晶石、CA6以及CA6晶粒的长大会对浇注料的显气孔率及线变化率起到不利影响;基质中加入0.5%SiO_2微粉的试样,由于在高温下产生较多液相,使其在1400℃时的高温抗折强度发生明显下降,但对控制浇注料的高温膨胀还是有贡献的。