As well-known, the addition of seed crystal, especially active seed crystal, is usually favorable for restraining the formation of new nuclei and promoting the growth of crystalline grains during crystallization. A series of experiments have been made using active APT crystal prepared under special conditions as seeds. It can be seen that with the same experimental conditions, the apparent density of APT crystal made by seed crystal is coarser than that produced without seed crystal.

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Puring the crystallization of APT crystals, temperature has double effects on APT crystals. On the one hand, rising temperature will increase the growth rate of the crystalline grains, and help to make coarse grain APT. On the other hand, higher temperature will lead to rapid volatilization of NH3 and cause the over- saturation of the solution ,and a large amount of nuclei were formed. In this case coarse grain crystals can not be obtained. Therefore , it is necessary to find out which effect on APT crystals plays a dominant role in the crystallization process of APT.

Solution with different initial concentrations of (NH4)2WO4 were used for studying the influence of temperature on the apparent density and FSSS size. The results show the apparent density and FSSS size increase obviously with the raising of temperature, and APT crystals with an density more than 1.8g/m-3 and a FSSS size more than 32 um are obtained at temperature higher than 90℃. This is because at higher temperature, the activity of the active center on the surface of crystalline grains increases, and the rate of nucleating is slower than that of crystal growing. It was clearly observed through a microscope that the APT crystals made at higher temperature are coarser than that obtained at lower temperature.

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The concentration of WO3 directly influences the over –saturation of the solution which has an important effect upon both the speed of nucleation and crystal growth. It is show that the higher the concentration of WO3, the larger the over-saturation of the solution, the smaller the APT crystal obtained. We have observed with microscope that the crystal obtained of WO3 has three shapes agglomerates of small cubic particles; needle crystals and tabular –like. This is because in the high over-saturation (NH4)2WO3 aqueous, the supply of APT solute for APT crystalline grains growing is uneven, so that on the active centers of the crystal-edges and the crystal pinpoints, there are more chances to receive APT solute for growing rapidly. Therefore, the needle crystals and tabular-like crystals are formed easily.

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Once upon a time well, beginners chose nice brass darts! It is strongly recommended that buy tungsten darts in the marketing darts.

The reason one is that tungsten darts is a long-lasting tungsten dart. Now it become better, you will often run into darts The third is stuck before. Because the same metal with each other, absolutely and scraping to, you will be to continue to wear. For those of tungsten is much more durable than brass I will last longer.

The reason two that shape is rich. In the current darts world, choices are rich because of the overwhelming mainstream people of tungsten. I will be easier to find what suits your feeling.

Tungsten darts are thinner ,it can make for brass darts that would have been absolutely made thick large in relation to specific gravity, is often get in the way when you aim the same location. This is the story of a millimeter Once in diameter, but you have actually throw the moment affect large difference.

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