The Grinding Efficiency of Sialon Ceramics

实验室研磨当然磨料物质用于制备均匀粉末样品或粒度减小目的在研究领域是重要的，如陶瓷，玻璃，冶金，药品和地质。这样做的方法是通过使用高能量行星磨机。

Image Credits: International Syalons

These mills consist of a bowl and cover containing a number of grinding balls. The sample is ground (either wet or dry) through impact and friction of the balls with each other and with the inside surface of the bowl. As a result of the high energy of the balls (they can reach a centrifugal force of approximately 20 times gravitational acceleration) there is a severe burden put on the grinding media, particularly when grinding very hard abrasive substances. Thus, in order to limit contamination (which for many applications is very important) the grinding media should possess certain fundamental properties. These are high hardness coupled with excellent wear resistance (to limit contamination through abrasion), chemical inertness (to avoid a chemical reaction between the grinding media and the sample) and high purity. These requirements have restricted the number of candidate materials suitable for this application. They include agate (a naturally occurring form of silica), zirconia, alumina, tungsten carbide and hardened steel.

The majority of使用的研磨材料是陶欧洲杯足球竞彩瓷的, which as a class of materials are generally characterized by their high hardness and chemical inertness. They have the added advantage that they are free from significant amounts of metallic impurities, which is often an important consideration when preparing a sample for chemical analysis. A recently developed ceramic, Syalon 101, also has these highly desirable properties but coupled with its proven success in other applications demanding wear resistance, it is a material worthy of consideration as a high energy grinding material.

目的

The purpose of this investigation was to compare the wear resistance and grinding efficiency of Syalon 101 to conventional materials used as grinding media for the high energy grinding of abrasive substances. The materials chosen for comparison were agate, zirconia (ZrO₂）和碳化钨（WC）。这些材料以及欧洲杯足球竞彩Syalon 101涵盖了广泛的物理性质。希望有些扣除可以做到尽可能多的材料属性对于最佳高能量研磨是重要的。

实验

在Fritcech“Pulverisette 5”（P5）实验室行星磨机和Fritsch“Pulisette 7”（P7）行星微型磨机上进行研​​磨实验。使用Syalon 101，玛瑙和氧化锆研磨介质进行P5的实验，而P7上的那些是使用Syalon 101和碳化钨介质进行的。

To compare the wear resistance of the four chosen grinding media materials, the weight loss of the grinding bowls, the bowl covers and the grinding balls were measured after the wet (in water) grinding of three abrasive samples for up to 1 hour. The samples chosen were a coarse beta-silicon carbide (SiC), a sintered crushed alumina (Al₂O₃) and a basalt stone. Of particular note is the extreme hardness of these materials which will severely test the grinding media materials. The weight losses were measured at time intervals of 5, 15, 30 and 60 minutes. At the same time, an indication of grinding efficiency was determined by measuring the particle size of the samples after each tome interval, beginning with 15 minutes.

The two configurations of balls used with the P5 were chosen to study the affect of ball size on wear resistance and grinding efficiency. Each combination of experimental configuration and grinding media material was used for each of three grinding samples. The particle size measurements were done using the Fritsch “Analysette 22” Laser Particle Sizer.

Results

Grinding Tests on the “Pulverisette 5”

For comparative purposes the results for the weight losses from the grinding balls will be used since they are the greatest and therefore the most accurate. However, it can be seen that the weight losses for the bowls and covers generally follow the same pattern. It is immediately obvious that in all cases the weight losses from the Syalon 101 grinding media are significantly less than those for zirconia and agate. For example, after 1 hour grinding of SiC the 20mm diameter Syalon 101 balls lost 2.52g compared to 14.57g for zirconia and 14.37g for the agate. Thus Syalon 101 is nearly 6 times more wear resistant than both the zirconia and agate. Indeed, this pattern is repeated throughout with Syalon 101 typically being between 5 and 10 times more wear resistant, although in certain cases when grinding the less hard alumina and basalt samples the wear resistance is much greater than this.

相对于时间的所有介质材料的重量损失通常在铣削的早期阶段中最大，即铣削的前欧洲杯足球竞彩15分钟。例如，使用配置1铣削SiC，在前15分钟内发生大约50％的总重量损失。这可以通过以下事实来解释，即在粉碎最初粗糙的材料时涉及更有磨损。欧洲杯足球竞彩

两个球尺寸遭受相似的磨损量，20mm球通常由于较大的碰撞而导致稍微接受。

粒度测量的结果显示磨削球密度对铣削效率的影响。在所有情况下，媒体较重的媒体在给定的时间里更好地研磨。例如，使用20mm球与氧化锆和Syalon 101（图3）分别使用20mm球（图3）的D50值（即50％下尺寸的粒径）30分钟分别为8.08μm和13.16μm。这是由于较重的球具有更大的冲击能量。还可以看出，介质密度的效果更加明显，较难的样品较难。

The effect of milling ball size on milling efficiency can also be seen. For example, the d90 values for the SiC milled for 30 minutes using 20mm and 30mm Syalon 101 balls are 35.03µm and 47.25µm respectively. It should be noted however, that when crushing initially very coarse materials, for example the sintered alumina, for the 20mm balls it took 30 minutes before the sample was ground sufficiently such that a particle size measurement could be made, whereas with the 30mm balls this could be done within 15 minutes. This was true for all the media materials.

Grinding Tests on the “Pulverisette 7”

与“Pulverisette 5”的结果一样，Syalon 101研磨介质显示比碳化钨（WC）显着较低的磨损。通常，Syalon显示比WC减轻少于5至15倍。

The WC is more effective than Syalon 101 when grinding very hard samples such as silicon carbide, although for the longer milling times (i.e. 60 minutes) the particle size distributions are almost identical.

应该注意的是，Syalon 101介质不会研磨烧结氧化铝样品。在这款小型磨机中只有15毫米球，Syalon没有足够的能量来压碎非常坚硬，大的肿块。

When grinding a relatively soft material like basalt the Syalon 101 was more effective than WC. For example, for 60 minutes milling the Syalon resulted in d50 of 2.76µm compared to 3.47µm for the WC. This is contrary to what we have seen for the heavier grinding media in the other trials and is thought to be a re-sintering effect due to the intense impact forces on the soft basalt from the high energy WC balls. Thus, WC would not be recommended for grinding softer materials, particularly for longer grinding times.

Summary and Conclusions

Measuring and comparing the weight loss of several grinding media materials after grinding an abrasive sample is a simple but effective method for ranking the materials with respect to their abrasion resistance. Also, by measuring the particle size distribution of the samples after grinding, an appreciation of the grinding efficiency could be gauged. These methods were used to compareSyalon 101, zirconia, agate and tungsten carbide grinding media。

已经表明，对于所研究的所有实验条件，Syalon 101显示比其他三种材料更大的耐磨性，并且通常在5至10倍之间，Syalon对于下部线束样品更明显的优点。欧洲杯足球竞彩

已经发现研磨效率依赖几件事。首先，介质的密度越大（并且因此研磨球的重量）在给定时间内将样品较好。这是具有更大冲击能量的较重球的结果。然而，如果需要相对粗糙的样品（即大于30μm），则更轻的介质材料（Syalon 101和玛瑙）表现和较重的材料。欧洲杯足球竞彩对于更柔软的样品，密度的效果也降低。事实上，观察到，当非常重的介质（WC）用于相对柔软的样品（玄武岩）时，粒度实际上可以由于重振方法而实际增加。

希望通过将这些结果与研磨介质材料的物理性质相关联，可以识别最佳高能磨削的重要性。欧洲杯足球竞彩然而，没有观察到真正的模式，特别是关于耐磨性。例如，尽管Syalon氧化锆和WC都具有非常相似的硬度值，但Syalon 101显示出明显更好的耐磨性。此外，虽然玛瑙不太困难，但它显示出对氧化锆的非常相似的耐磨性。关于研磨效率，可以得出结论，更高密度介质更有效，特别是对于短铣削时间和非常硬的样品。但是，这是牺牲更大的污染。

总体而言，我们得出结论，伊拉松101拥有耐磨性和研磨效率的最佳组合。尽管可能需要较长的铣削时间来实现所需的粒度，但是通过显着降低的磨损来抵消。

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