合理垂直烧结速度的研究

通过考查气流速度的变化研究垂直烧结速度随烧结过程的变化规律。结果表明:垂直烧结速度并非固定不变,而是随着烧结过程的逐步进行发生显著变化;点火保温后,随烧结物理化学反应的进行,燃烧带逐渐形成并变宽且产生过湿现象,导致料层的透气性显著变差,烧结速度显著下降,直至约25 min后过湿层完全消失,透气性变好,烧结速度迅速上升。根据垂直烧结速度变化规律,通过改变负压烧结,进行烧结速度优化实验,结果表明:在保持转鼓强度及成品率基本不变的情况下,将垂直烧结速度由20.08 mm/min提高到21.82 mm/min,利用系数由1.401 t/(m2-h)提高到1.587 t/(m2-h)。     

Nd掺杂的Bi4Ti3O12变温X射线衍射分析

利用变温X射线衍射技术，在预烧过程中分析了Nd掺杂Bi4Ti3O12后生成Bi3.15Nd0.85Ti3O12（BNT）相的形成过程以及微结构的变化．实验观察到以30℃／min的升温速率，BNT相在700℃时开始形成，其衍射峰强度随温度的继续升高而增强，衍射峰半高宽随烧结时间延长而减小．X射线衍射分析结果表明，在900℃恒温条件下，烧结约2h，可形成单一的BNT相．     

Modification of a three-way catalyst washcoat by aging: A study along the longitudinal axis

This work reports the research carried out by studying aliquots extracted at different axial coordinates from Three Way Catalyst (TWC) monoliths aged under real traffic conditions. Our study focused on the catalytic properties and on several chemical and physical effects caused in the Front and Rear monolith washcoat surfaces by vehicle aging after 60,000 km. Regarding the catalytic properties, all the used aliquots showed poorer activity than their corresponding fresh counterparts. The strongest deactivation was detected for NO and hydrocarbon conversion. CO conversion was less affected and the Rear monolith was as deactivated as the Front one. The characterisation techniques (TXRF, N₂ adsorption-desorption isotherms, XRD and H₂-TPR) detected - (i) the deposition of P, Zn and Pb; (ii) the formation of CePO₄ on account of the Ce from the washcoat; (iii) thermal sintering; (iv) inhibition of the reducibility of Ce oxides - as the main effects brought about by vehicle aging conditions. The deactivation observed at the beginning of the Front monolith was the result of a combination of the former effects. When moving downstream to higher axial coordinates, Pb accumulation and the loss of specific area appeared to be the only probable sources of deactivation.     

Y2O3薄膜处理对3Cr25Ni7N合金的抗高温氧化性能的影响

采用电沉积-热解法在3Cr25Ni7N合金表面制备了Y2O3薄膜,并研究了薄膜处理对合金在1000℃空气中的抗高温氧化性能的影响。氧化动力学曲线、SEM及XRD分析结果表明,Y2O3薄膜处理使合金表面氧化膜以尖晶石结构为主,氧化膜致密,有效地抑制了Cr2O3的挥发反应,且氧化膜与基体的附着性好,因此合金在高温下的抗氧化性能得到提高,这与氧化钇薄膜在较低温度下抗高温氧化性能提高的机制是不同的。在不同温度下,Y2O3薄膜处理均可以有效提高合金的抗高温氧化性能。     

Polymer melting and polymer powder sintering by thermal analysis

Sintering of polymeric powders is a peculiar characteristic of many processing technologies, including rotational moulding and selective laser sintering (SLS). During polymer sintering, viscosity reduction in the melt state promotes densification of polymer powders, through a double stage mechanism, involving powder coalescence and bubble removal. In particular, sintering of semi-crystalline polymers is strongly influenced by the melting behaviour. Nevertheless, melting itself in absence of pressure is not necessarily accompanied by powder sintering, unless low viscosities are achieved. In this work, the melting and sintering behaviour of recycled high density polyethylene (rHDPE) have been analysed through differential scanning calorimetry (DSC) and Thermomechanical Analysis (TMA). Efficient models capable of describing the melting temperature distribution and rate of sintering of rHDPE powders have been developed, highlighting the inherent differences between the two distinct processes. This revised version was published online in July 2006 with corrections to the Cover Date.     

激光烧结陶瓷粉末成形零件的研究

实验研究了Ａｌ２Ｏ３陶瓷粉末的激光烧结过程,介绍了激光烧结实验装置,分析了烧结参数对烧结过程的影响,得到了激光烧结的Ａｌ２Ｏ３陶瓷零件。所设计的实验装置的结构简单,可满足实验要求。     

Self-strengthening and high temperature sintering in binder-free silicon nitride

A thermal strengthening process, which occurs during low-temperature heating of binder-free silicon nitride, has been investigated using simultaneous thermal analysis, dilatometry and FTIR and shown to occur in separate stages over clearly identifiable temperatures. Reactions which give the strengthening are the loss of physically and chemically combined water and the decomposition of ammonium carbonate and various hydrosilicates. Compacts have bend strengths of 8–10 MPa after strengthening at 500°C and 30–34 MPa after strengthening at 900°C. High-temperature dilatometry shows several stages of sintering. The maximum rate occurs at 1800°C with shrinkage commencing at 1450°C. Densities of 98.3% theoretical are obtained on heating to 1900°C.     

添加RE—USY分子筛后海泡石的水热热压成型研究

本文采用水热热压技术研究了海泡石中添加RE-USY分子筛的固化成型条件,同时以XRD、SEM、IR对固化体的结构变化以及表面酸性进行了测定.实验结果表明,在海泡石中添加Y型沸石分子筛容易制成具有一定强度的固化体.成型后,海泡石和分子筛的原有骨架结构保持不变.成型后的固化体含B酸和L酸中心,但B酸酸量较固化前减少,而L酸量增加.     

Dense Sphene-type Solid Electrolyte Through Rapid Sintering for Solid-state Lithium Metal Battery

The sphene-type solid electrolyte with high ionic conductivity has been designed for solid-state lithium metal battery. However, the practical applications of solid electrolytes are still suffered by the low relative density and long sintering time of tens of hours with large energy consumption. Here, we introduced the spark plasma sintering technology for fabricating the sphene-type Li_1.125Ta_0.875Zr_0.125SiO₅ solid electrolyte. The dense electrolyte pellet with high relative density of ca. 97.4% and ionic conductivity of ca. 1.44×10^-5 S/cm at 30℃ can be obtained by spark plasma sintering process within the extremely short time of only ca. 0.1 h. Also the solid electrolyte provides stable electrochemical window of ca. 6.0 V(vs. Li⁺/Li) and high electrochemical interface stability toward Li metal anode. With the enhanced interfacial contacts between electrodes and electrolyte pellet by the in-situ formed polymer electrolyte, the solid-state lithium metal battery with LiFePO₄ cathode can deliver the initial discharge capacity of ca. 154 mA·h/g at 0.1 C and the reversible capacity of ca. 132 mA·h/g after 70 cycles with high Coulombic efficiency of 99.5% at 55℃. Therefore, this study demonstrates a rapid and energy efficient sintering strategy for fabricating the solid electrolyte with dense structure and high ionic conductivity that can be practically applied in solid-state lithium metal batteries with high energy densities and safeties.     

Sm2O3掺杂CeO2纳米粉体的烧结动力学

对Sm2O3掺杂CeO2纳米粉体的烧结性能进行了研究, 得出等速烧结过程中试样的线收缩率、密度、气孔率随烧结温度的变化规律, 它们随烧结温度的变化均呈"S"型曲线关系, 利用非线性回归了等速烧结过程动力学方程. 结果表明, Sm2O3掺杂CeO2纳米粉体的烧结过程分为3个阶段, 当烧结温度低于1000 ℃时, 线收缩率与密度变化较小, 处于烧结的初期; 在1000～1400 ℃时, 随着烧结温度的升高, 线收缩率与体积密度急剧增大, 材料开始烧结并致密化; 当烧结温度高于1400 ℃时, 线收缩率与体积密度趋于一恒定值, 材料已经致密化. 由归一化速率方程可知, 在T=1225 ℃时, 材料的烧结致密化速率最大.