【正文】
for preliminary glassmaking. The blastfurnace slag is formed in the processes of pig iron manufacture from iron ore, contains bustion residue of coke, fluxes of limestone or serpentine, and other materials. If the molten slag was cooled quickly by highpressure water, fine grain glass of vitreous Ca–Al–Mg silicate can be formed [10]. This suggests the blastfurnace slag can be used as a glass source to make sintered glass–ceramics and vitrifying raw materials at hightemperature step can be omitted. The free glass surfaces are preferable sites for devitrification and thus crystallization may occur without any nucleating agent. Therefore, the finely ground slag powder can used as the main ponent of parent glass. Comparing with the two sintered methods mentioned above, a remarkable advantage of the present study is absent of vitrification step because of the using of blastfurnace slag. Thus a low energy cost and manufacture simplicity can be expected. However, in our previous studies glass–ceramics prepared with pure blastfurnace slag show poor properties [11]. Therefore, some sintering additives are needed. In this study, we show when using blastfurnace slag to prepare glass–ceramics by a conventional ceramics route, if suitable amount of potashfeldspar is added. Glass–ceramics with high microhardness andbending strength as well as lower water absorption can be obtained. 2. Experimental procedure The slag (provided by Anyang iron Corporation of China) was pulverized by ball milling for about 24 h (size in the range of 10–20 mm), and then blended with 5–10 wt% potash feldspar powder. The mixtures were ball milling for 2 h. We use K5, K8 and K10 to denote the weight percent of potash feldspar in the samples. The process used in our study is illustrated in Fig. 1. The blended powders were uniaxially pressed in a steel die at room temperature, using a hydraulic pressure of 40–60 MP a without any binder. The obtained green bodies were sintered in air at nucleation temperature of 720–760℃ and crystallization temperature of 800–900℃ for different times (from 20 to 60 min), with heating rates of 2–5 ℃ /min, followed by a hightemperature treatment at 1200℃ The blended powders were examined by differential scanning calorimetr