Microstructure and Characterization of Capric-stearic Acid/Modified Expanded Vermiculite Thermal Storage Composites

In order to improve the thermal storage capacity of expanded vermiculite(EV) based formstable composite PCM(FS-PCM) via organic modification of EV, first, EV was modified with a sodium stearate(Na St) as surface modifier, and organic EV(OEV) with hydrophobicity and higher adsorption capacity for fatty acid was obtained. A novel capric-stearic acid eutectic(CA-SA)/OEV FS-PCM with high thermal storage capacity was then developed. OEV and CA-SA/OEV were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC), thermal gravimetry(TG), and thermal cycling test. Results showed that OEV has obvious hydrophobicity and a higher adsorption capacity for fatty acid. Its adsorption ratio has increased by 48.71% compared with that of EV. CA-SA/OEV possesses high thermal storage density(112.52 J/g), suitable melting temperature(20.49 ℃), good chemical compatibility, excellent thermal stability and reliability, indicating great application potential for building energy efficiency. Moreover, organic modification of inorganic matrix may offer novel options for improving its adsorption capacity for organic PCMs and increasing heat storage capacity of corresponding FS-PCMs.     

放电等离子合成Ti3AlC2/TiB2复合材料的研究

采用放电等离子烧结工艺成功地制备了Ti3AlC2/TiB2复合材料.研究表明:在1 250 ℃,30 MPa压力和保温8 min下烧结,可以得到相对密度达98%以上的致密Ti3AlC2/TiB2块体材料;在Ti3AlC2中添加TiB2能大幅度提高材料性能,Ti3AlC2/TiB2复合材料Vickers硬度随TiB2掺量的增加而增大,最大可达到10.4 GPa;当TiB2体积含量为10%时,复合材料的最大的抗弯强度为696 MPa,断裂韧性为6.6 MPa·m1/2.     

弥散强化铜基复合材料的研究现状与展望

弥散强化铜(DSC)合金因为有一系列优良的性能而逐渐成为很多领域中不可替代的结构功能材料,常用的增强相一般有Al2O3,WC和TiB2,最近,又有一种新的Ti3SiC2陶瓷被用来作为增强相.本文对几种复合材料分别做了介绍,分析了研制弥散强化铜基复合材料中的一些问题,还对该材料的应用进行了展望.     

Preparation of Ti_3SiC_2 with Aluminum by Means of Spark Plasma Sintering

1　ＩｎｔｒｏｄｕｃｔｉｏｎＴｉｔａｎｉｕｍｓｉｌｉｃｏｎｃａｒｂｉｄｅ (Ｔｉ3ＳｉＣ2 )ｉｓａｌａｙｅｒｅｄｈｅｘａｇｏｎａｌｍａｔｅｒｉａｌｗｈｅｒｅｉｎｅｖｅｒｙｔｈｒｅｅｌａｙｅｒｓｏｆｎｅａｒ ｃｌｏｓｅ ｐａｃｋｅｄｌａｙｅｒｓｏｆＴｉａｒｅｓｅｐａｒａｔｅｄｂｙａｌａｙｅｒｏｆｐｕｒｅＳｉ,ｔｈｅＣａｔｏｍｏｃｃｕｐｉｅｓａｌｌｔｈｅｏｃｔａｈｅｄｒａｌｓｉｔｅｓｂｅｔｗｅｅｎｔｈｅＴｉａｔｏｍｓ[1,2 ] .Ｔｉ3ＳｉＣ2 ｈａｓａｎｕｍｂｅｒｏｆｅｘｃｅｐｔｉｏｎａｌｐｒｏｐｅｒｔｉｅｓ[3- 8…     

热压TiAl/Ti2AlC复合材料的相形成规律

采取原位热压方法，利用Ti、Al、TiC为原料合成了TiAl／Ti2AlC复合材料。通过X衍射图谱，分析了从600℃到1300℃该合成过程的相形成规律。Ti、Al、TiC的反应大致可分为2个阶段：900℃之前，Ti和Al反应生成TiAl金属化合物；900℃之后，TiAl金属间化合物和TiC反应并合成致密TiAl／Ti：AlC复合材料。讨论了这2个阶段的反应机及烧结产物的微观结构特点。     

Ti3AlC2陶瓷材料的制备及性能研究

新型层状陶瓷材料Ti3AlC2结合了金属和陶瓷的许多优异性质，既具有与金属相似的良好的导热、导电性，良好的可加工性，相对柔软，抗热震性好，可塑性变形等；同时又具有与陶瓷相似的抗氧化、耐腐蚀、耐高温等特性；并且还有很好的自润滑性和超低摩擦系数，被认为在许多领域有着广泛的应用前景。     

高早强粉煤灰水泥的探索研究

本文通过试验，探索出一种新型的不含Ｋ＋、Ｎａ＋、Ｃｌ－等有害离子的外加剂，直接掺入粉煤灰水泥中使用，能促使粉煤灰活性较快发挥，显著提高粉煤灰水泥强度，尤其是早期强度。且不会对水泥混凝土造成不良影响。     

放电等离子烧结工艺制备Ti2A1C材料的研究

以元素粉钛、铝、碳为原料,采用放电等离子烧结工艺在1100℃的温度下成功地制备了高纯、致密Ti2AlC材料.合成材料的X-射线衍射(XRD)和扫描电镜(SEM)分析的结果表明:多晶体Ti2AlC形貌为板状结晶,晶粒大小平均约为20μm,厚度在3～5μm.     

Numerical simulation on heat transfer enhancement of phase change thermal storage devices for low-middle temperature

Using Ba(OH)_2·8H_2O as phase change material(PCM) and water as heat transfer fluid(HTF),we numerically simulated annular finned-tube heat exchangers.In order to measure and analyze the impact of parameters in the heating/cooling process,temperature changes of different monitoring points,fin widths,and fin pitches as key parameters were considered and applied.The experimental results show that the heat exchange process can be divided into three stages within a certain time.The faster heat transfer rate is associated with the greater temperature difference between PCM and HTF.Furthermore,fins width and pitch affect dramatically the heat charging/discharging rate.The large fins width or small fins pitch is beneficial for extending the heat exchange surface,leading to improve heat transfer efficiency.     

磷石膏对硅酸盐水泥凝结时间的影响

将不同形态的磷和氟直接加入水泥中,研究水泥凝结时间的变化。通过分别粉磨或预处理磷石膏的方法来改善磷石膏对水泥的缓凝作用。结果表明:磷石膏对硅酸盐水泥的缓凝作用主要是由其中的可溶磷和氟造成的,难溶磷和氟的影响很小,可溶磷中以HPO42-对水泥的缓凝作用最强。分别粉磨、800℃煅烧或2%生石灰中和磷石膏,均能改善磷石膏对水泥的缓凝作用。