结合系统对刚玉质浇注料显微结构及性能的影响

以板状刚玉骨料和细粉为主要原料,分别以硅微粉、Al2O3-SiO2凝胶粉和铝酸钙水泥为结合剂,制备了3组不同结合系统的刚玉质浇注料,研究了浇注料经不同温度热处理后的物相变化及物理性能,采用X射线衍射及扫描电镜技术研究了其相组成和显微结构特征。结果表明,以硅微粉为结合剂的浇注料在1100℃时有莫来石晶核析出;继续升温,莫来石长大并出现液相。以凝胶粉为结合剂的浇注料在1100℃时出现方石英,不利于莫来石的生成。以铝酸钙水泥为结合剂的浇注料经1500℃处理后,水泥矿物转化为六铝酸钙（CaO·6Al2O3,CA6）相,这种呈片状的CA6相在基质结构内部交叉穿插,有利于提高浇注料的高温抗折强度和抗热震性能。     

水泥对刚玉-尖晶石浇注料抗侵蚀性影响研究

以板状刚玉为骨料,电熔白刚玉、电熔尖晶石、Al2O3微粉和纯铝酸钙水泥为基质,研究了纯铝酸钙水泥加入量对刚玉-尖晶石浇注料抗侵蚀性能的影响.结果表明:纯铝酸钙水泥加入量为4%时,浇注料的侵蚀、渗透指数最大,抗渣侵蚀性能最差;水泥含量≥6%时抗渣侵蚀、渗透指数明显下降,抗渣性逐渐改善.水泥加入量影响浇注料的抗侵蚀性能主要与基质中的物相组成和显微结构有关.随水泥加入量的增加,水泥中的CaO与Al2O3反应形成六铝酸钙,基质中刚玉的含量减少;渣中的CaO与刚玉颗粒反应形成六铝酸钙,产生体积膨胀堵塞气孔,抑制了渣的渗透,使得抗渣侵蚀性能得到改善.     

刚玉质泵送浇注料流变性的研究

采用浇注料流变仪(IBB Rheometer V1．0)研究了微粉对湿式泵送喷射刚玉质浇注料流变性的影响．结果表明：浇注料的流变行为呈宾汉姆流体特征；随Al2O3微粉／SiO2微粉比例中SiO2微粉含量的增加，浇注料的流变性得到显著改善．即：在不同的剪切速度下，浇注料的扭矩、剪切粘度和流动阻力下降，用水量减少，自流值提高．当Al2O3微粉／SiO2微粉比例小于50／50后浇注料具有较好流变性，适合于泵送施工．     

γ-Al2O3对刚玉浇注料中温性能的影响

以刚玉质浇注料为研究对象,将基质中的α-A12O3细粉部分用γ-Al2O3代替,观察对浇注料中温下力学性能的影响.制备γ-Al2O3含量分别为0%、2%、4%、6%(wt%)试样,尺寸宽高长为40 mm×40 mm×160 mm.将获得的试样在中温1100 ℃保温处理3小时后,测量试样的线变化率、抗折强度、显气孔率、体...     

链状纳米碳酸钙的制备

用间歇鼓泡碳化法制备了链状纳米CaCO3,用pH计和电导仪对碳化反应跟踪检测 ,对其形成机理进行了分析 ,实现了对链状CaCO3的粒度控制。考察了碳化反应过程中pH值、电导率和反应物质量分数、反应温度、CO2 气体流等因素对产品粒径和形态的影响。结果表明 ,碳化反应过程中 pH值和电导率都有一个快速下降阶段。其中电导率有两个下降回复过程。Ca(OH) 2 质量分数、CO2 流量的增大、反应温度升高都会使反应速率和晶核生长速率变大。反应温度控制在 30℃左右 ,Ca(OH) 2 质量分数为 1 0 %左右 ,在一定范围内CO2 流量越大所得晶体结构越好     

影响纳米碳酸钙性能的制备方法研究进展

碳酸钙作为一种工业上来源众多、用途广泛的无机材料,其纳米级的尺寸更扩展了它的应用潜力.综述了不同制备工艺对碳酸钙形貌、尺寸造成的影响,以及晶型控制剂在制备特殊形貌碳酸钙时的作用.单一的添加剂较难得到均匀、特定形貌的产品,探究复合添加剂的使用具有广阔的发展前景.在碳酸钙制备方法的基础上,阐述了表面改性方法和原理,同时对表...     

纳米碳酸钙作为液压油添加剂的摩擦学性能

纳米碳酸钙是一种重要的工业原料,用途广泛.它作为一种生活中常见易得的化合物,所以碳酸钙作为液压油的添加剂具有十分广泛的研究意义.为了研究纳米碳酸钙颗粒作为润滑油添加剂的润滑摩擦学性能,充分发挥其抗磨减摩效果,采用CFT-1型材料性能测试仪对比研究了不同载荷下不同含量的纳米碳酸钙粒子作为液压油添加剂的摩擦学性能.数据3,不同含量的纳米碳酸钙作为液压油添加剂的抗磨减摩性能不同.重载荷下的数据比较稳定.纳米碳酸钙在一定程度上可以提高液压油的抗磨减摩性能,这是由于在磨痕表面形成了一层保护膜,起到了良好的抗磨减震效果.     

表面改性对纳米碳酸钙界面性质的影响

采用铝锆偶联剂对纳米碳酸钙进行表面改性.借助傅里叶红外光谱（FT-IR）、X射线衍射分析（XRD）、投射电镜（TEM）对改性前后的纳米碳酸钙的表面结构进行表征.FT-IR分析表明,铝锆偶联剂以化学键合和物理吸附的方式在纳米碳酸钙的表面形成吸附层,粒子表面存在羧基等等有机官能团的红外吸收特征.XRD分析证明,改性纳米碳酸钙保持原样品完整的体相结构,为方解石型纳米微晶.TEM分析显示,改性纳米碳酸钙呈立方体,平均粒径大约70 nm.通过颗粒粒度分布和表观粘度测量,对纳米碳酸钙的改性效果进行评价.实验表明,未改性纳米碳酸钙在水中存在明显的团聚现象,而铝锆偶联剂改性后的纳米碳酸钙的分散情况得到很大改善,颗粒粒度分布在70～100 nm之间,低剪切速率下的表观黏度大为降低,这为纳米碳酸钙在纸张涂料中的应用创造有利条件.     

蓝晶石对低水泥浇注料性能的影响

通过蓝晶石对低水泥浇注料性能影响的研究，表明蓝晶石莫来石化伴随的体积膨胀在补偿浇注料烧结的体积收缩的同时，存在降低其强度的不利影响；蓝晶石在较低温度上出现液相促进烧结的同时也将降低其高温性能。因此，在不同温度下使用的耐火浇注料中加入不同的适量蓝晶石才能在提高浇注料的高温体积稳定性和强度的同时不降低其荷重软化温度。     

纳米碳酸钙对回收丙烯腈-丁二烯-苯乙烯共聚物性能的影响

利用熔融共混方法制备出纳米碳酸钙/回收丙烯腈-丁二烯-苯乙烯复合材料,采用偶联剂对纳米碳酸钙表面改性,或加入增容剂马来酸酐接枝(丙烯腈/苯乙烯)共聚物(AS-g-MAH),得到力学性能较好的纳米碳酸钙/回收丙烯腈-丁二烯-苯乙烯复合材料.研究了纳米碳酸钙含量、偶联剂、增容剂AS-g-MAH对回收丙烯腈-丁二烯-苯乙烯(ABS)力学性能的影响.实验结果表明:与新料ABS相比,回收的ABS性能有所下降.纳米碳酸钙含量为ABS质量的2%,硅烷偶联剂含量为纳米碳酸钙质量的5%,或增容剂AS-g-MAH为纳米碳酸钙质量的2%时,回收ABS的力学性能最佳.扫描电镜显示加入增容剂AS-g-MAH后,纳米碳酸钙粒子能均匀混合在回收ABS中,且粒径分布较窄,分散性好;无增容剂时有纳米碳酸钙团聚粒子出现.     

结合剂对Al2O3-SiC—C质铁沟浇注料性能的影响

研究了铝酸钙水泥、铝酸钙水泥／SiO2微粉、α—Al2O3微粉以及α—Al2O3微粉／SiO2微粉4种结合剂对Al2O3一SiC-C质浇注料性能的影响。结果表明,加入α—Al2O3微粉结合剂的材料性能最好,可以获得性能良好的铁沟浇注料。     

高铝浇注料高温耐磨性影响因素的研究

利用新研制的高温耐磨实验设备,以高铝浇注料为原料,研究了水泥加入量（3%、6%、9%）、热处理温度（6001、000、1 200℃）和临界粒度（5、8、15 mm）对材料高温耐磨性的影响。结果表明,随着水泥含量的增加,试样的磨损体积在常温和1 000℃下逐渐减小,1 200℃时略有增大。采用-ρAl2O3微粉代替铝酸钙水泥作结合剂,两者的耐磨性在各试验温度下差别不大。试样经不同温度热处理后,其磨损量随着试验温度的变化趋势是相似的,即磨损量随着试验温度的升高而降低;经6001、000℃处理后的试样,各试验温度下其磨损量均较小,但经1 200℃处理后的试样,其磨损量稍大一些。温度为1 000℃时,浇注料的磨损量随着临界粒度的增大而降低;1 200℃时,浇注料磨损量随着临界粒度的增大变化不大。     

聚醚偶联剂改性碳酸钙及CaCO_3/PP复合材料的性能

自制了偶联剂四氢呋喃均聚醚(PTHF),并用其对轻质碳酸钙表面进行处理,将处理后的碳酸钙填充到聚丙烯塑料中,探讨了新型改性剂对复合材料力学性能的影响。结果表明,四氢呋喃均聚醚能够使碳酸钙的吸油值降低到22%,接触角降低到68.6°。改性后的碳酸钙填充进聚丙烯,能在一定程度上缓解拉伸强度的下降趋势,使复合材料的断裂伸长率达到28.47%、冲击强度达到6.7kJ/m2。SEM观察四氢呋喃均聚醚添加前后复合材料的断面形态,表明碳酸钙在聚丙烯中分散良好。     

Heat mass transfer model of fouling process of calcium carbonate on heat transfer surface

A new heat mass transfer model was developed to predict the fouling process of calcium carbonate on heat transfer surface. The model took into account not only the crystallization fouling but also the particle fouling which was formed on the heat transfer surface by the suspension particles of calcium carbonate in the supersaturated solution. Based on experimental results of the fouling process, the deposition and removal rates of the mixing fouling were expressed. Furthermore, the coupling effect of temperature with the fouling process was considered in the physics model. As a result the fouling resistance varying with time was obtained to describe the fouling process and the prediction was compared with experimental data under same conditions. The results showed that the present model could give a good prediction of fouling process, and the deviation was less than 15% of the experimental data in most cases. The new model is credible to predict the fouling process. Supported by the National Basic Research Program of China (“973”Project) (Grant No. G2000026304) and the Beijing Municipal Elitist Cultivation Project (Grant No. 20061D0501500186)     

Effect of matrix composition on physical properties of Al<Subscript>3</Subscript>CON in-situ reaction reinforced corundum composite

60% white corundum used for aggregate, 5% aluminium powder for fixed additions and 35% various additives for matrix were prepared for specimens 1#,2#,3#. They were mixed uniformly with the suitable resin as a binder and pressed under pressure of 315 ton forging press, then dried at 200℃ for 24 h. Effects of various additives on 1500 ℃×2 h creep properties of Al3CON reinforced corundum composite were researched. The experimenal results show that creep coefficients of specimens 1#,2#,3# at 1500 ℃×2 h are 1.4×10^- 4, -9.4×10^-4, -22.6×10^-4, respectively. Crushing strength of the slide plate added with suitable additive A after fired at 1500 ℃ ×3 h reaches to 225 MPa, the creep rate is positive all the time from 0% to 0.014% at 1500 ℃ for 2 h. The microstructure result analysis shows that reinforced phases of Al3CON fiber composite have been formed after fired with Al powder in coke at high temperatures for specimen 1#, and the strength of the composite is increased. The hot modulus of rupture is up to 59 MPa at 1400 ℃ and the RUL is obviously higher than that at 1700 ℃. Its service life is two times as that of Al2O3-C slide plate when used in the process of pouring steel. The mechanism of creep rate resistance of the composites can be discovered by means of SEM and EDAX analysis. It is concluded that the active Al3CON and Al2O3 multiphases that were formed by N2 in gas, C, Al and Al2O3 inside the matrix of the composites during in-situ reaction,which gives the composites outstanding creep rate resistance for the dense zone resuiting from Al3CON oxidation that inhibits contraction at the high temperature. Besides, the matrix will turn into the multiphase with high refractoriness, N content and its Al3CON reinforced fiber will further increase accordingly. In addition, Al3CON formed by Al2O3 and C, Al in the matrix with N2 in gas will inhibit the creep rate and also greatly improve the creep rate resistance of the composites.     

Preparation and characterization of three-dimensional chrysanthemun flower-like calcium carbonate

Calcium carbonate with three-dimensional chrysanthemun flower-like structure was successfully prepared from calcium chloride and sodium carbonate ethanol/water mixed solution by a simple precipitation method,using trisodium citrate as crystal modifier.The experimental results show that the three-dimensional structure of chrysanthemun flower-like calcium carbonate is built up with several symmetrical micrometer multi-layer petals arranged around the multi-layer pancake-liked center,and the micrometer center and petals are assemblied by a large number of nanometer spherical particles with size 10-20 nm.It is found that the amount of trisodium citrate,the ethanol volume content has an important influence on the formation of this morphology.A possible mechanism is proposed to explain the formation of three-dimensional chrysanthemun flower-like calcium carbonate according the results.Scanning electron microscopy(SEM),X-ray powder diffraction(XRD),flourier transform infrared spectroscopy(FT-IR),thermogravimety analysis(TG),transmission electron microscopy(TEM) equipped with energy-dispersive X-ray(EDX),and selected area electron diffraction(SAED) were used to characterize the crystals.     

不同品种碳酸钙填充PVC性能的研究

为了考察不同品种碳酸钙对PVC/CaCO3复合材料性能的影响,采用双螺杆挤出机挤出造粒、注塑机注塑成型,通过万能试验机和简支梁冲击试验机检测其力学性能,使用SEM观察断面微观形貌.结果表明:纳米钙和包覆钙的填充效果最好,分别使PVC的拉伸强度增加19%和17%,PVC的无缺口冲击强度增加4倍以上,分别达54.05和51.67kJ/m2;PVC的缺口冲击强度增加3倍左右,分别达28.94和22.59kJ/m2;复合钙的填充效果居中,重钙和轻钙最差.多种CaCO3填充PVC后,PVC原来平整的颗粒轮廓发生了变化,纳米钙和包覆钙形成了大量高低不平而圆润的表面,重钙和轻钙形成较多的裂纹和空穴.     

Effect of boron addition on the microstructure and stress-rupture properties of directionally solidified superalloys

This study is focused on the effect of boron addition, in the range of 0.0007wt% to 0.03wt%, on the microstructure and stress-rupture properties of a directionally solidified superalloy. With increasing boron content in the as-cast alloys, there is an increase in the fraction of the γ′/γ eutectic and block borides precipitate around the γ′/γ eutectic. At a high boron content of 0.03wt%, there is precipitation of lamellar borides. Upon heat treatment, fine block borides tend to precipitate at grain boundaries with increasing boron content. Overall, the rupture life of the directionally solidified superalloy is significantly improved with the addition of nominal content of boron. However, the rupture life decreases when the boron content exceeds 0.03wt%.