欧美人妻精品一区二区三区99,中文字幕日韩精品内射,精品国产综合成人亚洲区,久久香蕉国产线熟妇人妻

In recent years, the production technology of ultra-fine grain cemented carbide has developed rapidly, especially in the key technology of preparing ultra-fine grain WC powder, where the competition is very fierce. Many promising methods have emerged, some of which have reached the level of practical application. However, there are few reports in domestic literature, especially on basic theories or regularity research. In the process of developing the preparation technology of ultra-fine grain WC powder, this paper deeply investigates the influence of the particle size of carbon black powder on the carbon content of WC powder under different carbonization temperatures when using ultra-fine (0.35 μm) tungsten powder.

 

The Influence of Carbon Black Particle Size on the Carbon Content of WC Powder 2

Experimental Content and Method

Test Materials of WC powder

(1) Ultra-fine tungsten powder: The ultra-fine tungsten powder is prepared by the ultrasonic spray pyrolysis method from ultra-fine WO? powder, which is generally amorphous with an average particle size of 25~30 nm. It is reduced by hydrogen at a medium temperature (750~780℃) to obtain tungsten powder with an average particle size of ≤0.35μm (BET particle size).

(2) Carbon black powder: Carbon black powder is produced by two methods: one is by cracking ethane and propane (at 850℃) and then subjected to high-energy ball milling for different periods to produce carbon black powders with average particle sizes of 0.1 and 0.3 μm, respectively; the other is from activated carbon powder with an original particle size of 100~200μm, which is subjected to high-energy ball milling for different periods to produce carbon black powders with average particle sizes of 0.8 and 4.5 μm, respectively.

Experimental Method

Using ultra-fine tungsten powder with the same particle size (0.35 μm) and four different particle sizes (0.1, 0.3, 0.8, 4.5 μm) of carbon black powder, the carbon is blended according to the reaction formula W+C=WC (with an additional loss of 0.1%). The mixture is ball milled for 1.5 hours in a conventional ball mill with a ball-to-material ratio of 1:1. The heat-resistant stainless steel boat containing the mixed material is placed in a stainless steel tube furnace and carbonized under a hydrogen atmosphere. The holding time is 40 minutes for all. In the temperature range of 830~1300℃, the carbonized material is taken out at different temperatures, cooled, and then removed from the furnace. Subsequently, XRD phase analysis and chemical analysis are conducted to determine the total carbon and free carbon, and the amount of combined carbon in WC is calculated. Finally, the quantitative relationship between the particle size of carbon black powder and the phase composition and combined carbon content of WC powder under different carbonization temperatures can be plotted.

 

Test Results and Discussion

Figure 1 shows the effect of carbon black powder with different particle sizes carbonized at different temperatures on the combined carbon content of WC powder. Curve 1 in Figure 1 represents the relationship between carbonization temperature and the combined carbon content of WC powder when using ultra-fine carbon black powder with a particle size of 0.1 μm. As can be seen from Figure 1, when using 0.1 μm ultra-fine carbon black, the combined carbon content of WC powder can reach 5.8% (by mass), which is equivalent to 95% of the theoretical content, at a very low carbonization temperature (850℃). When the temperature is greater than 950℃, the carbon content of WC powder can reach the theoretical content. This result indicates that the carbonization reaction can be completed at a low temperature when using ultra-fine tungsten powder in conjunction with ultra-fine carbon black powder. This phenomenon suggests that the ultra-fine W powder particles are carbonized before they undergo significant aggregation and growth.

The Influence of Carbon Black Particle Size on the Carbon Content of WC Powder 3
At this temperature, as the particle size of the carbon black used increases, the combined carbon content in WC powder rapidly decreases. For example, as shown in Curve 2 of Figure 1, when using 0.3 μm carbon black at 950℃ with the same holding time of 40 minutes, the combined carbon content of WC powder only reaches 5.2% (by mass). XRD analysis indicates that there is still significant W?C in the WC powder, as shown in Figure 2. The free carbon phase was not detected due to its low content. The combined carbon content in WC powder can only reach the theoretical value when the temperature is increased to 1060℃. Its complete carbonization temperature is about 130℃ higher than that of the 0.1 μm carbon black.

The Influence of Carbon Black Particle Size on the Carbon Content of WC Powder 4

When using 0.8 μm carbon black, as shown in Curve 3 of Figure 1, at 950℃ with a holding time of 40 minutes, the combined carbon content of WC is only 3.18% (by mass). XRD analysis indicates that in addition to the obvious W?C phase, there is also significant free carbon present in the WC powder, as shown in Figure 3. The combined carbon content in WC powder can only reach the theoretical value when the carbonization temperature is increased to 1230℃. The temperature required for complete carbonization has increased significantly.
The reason for this phenomenon is that when the carbon content ratio is constant, the finer the carbon black particle size, the easier it is to mix uniformly with W powder particles, increasing the contact area between them. Undoubtedly, fine-grained carbon black will accelerate the carbonization rate. Moreover, the finer the carbon black particle size, the more its specific surface area and the number of active carbon atoms on the surface increase dramatically. Thus, the carbonization reaction rate between carbon and tungsten accelerates, and the complete carbonization temperature decreases with the decrease of carbon black particle size.

WC powder

Conclusions

(1) When the particle size of ultra-fine W powder is the same (≤0.35μm), the combined carbon content in WC powder decreases significantly with the increase of the carbon black particle size at a certain temperature.
(2) When the particle size of carbon black is constant, the content of combined carbon increases with the rise of carbonization temperature.

Bir cevap yaz?n

E-posta hesab?n?z yay?mlanmayacak. Gerekli alanlar * ile i?aretlenmi?lerdir

日韩精品诱惑一区?区三区| 大鸡巴插美女小逼逼| 韩美国男人叉女人| 美女的粉嫩小逼视频特写| 日韩午夜免费av在线| 日本欧美中文字幕| 欧美 日韩 国产 自拍| 大鸡巴插入骚穴在线观看| 嗯嗯好硬好大啊老公| 性爱大鸡吧喷水视频| 欧美日韩一区二区成人在线| 骚逼被操视频拳交| 国奴精品毛片av一区二区三区| 国产裸模大尺度私拍视频| 日韩精品高清在线| 欧美日韩精品视频在线第一区| 欧美精品国产一区二区在线观看| 大鸡巴日大鸡巴在线观看| 美女穿黑丝被大鸡巴猛操| 中国三级片在线视频| 天天躁久久躁中文字字幕| 无码社区在线观看| 女人张开腿让男人捅个爽| av人摸人人人澡人人超| 美女被操的流水AV| 成人高清在线播放一区二区三区| 日韩美女一区二区三区香蕉视频| 爆操大奶子美女视频| 久久久国产系列丝袜熟女| 综合伊人久久在一二三区| 无码人妻免费一区二区三区| 东京热无码AV一区二区三区| 一区二区三区四区五六区| 午夜性福福利视频一区二区三区| 亚洲AV无码一区二区三区系列| 黄色软件大屌怒戳粉嫩小穴| 亚洲激情无码视频| 国产精品亚洲综合av| 波多野结衣高潮尿喷| 欧美真人性爱视频| 日韩一区二区三区夜色视频|