| 查看: 814 | 回复: 3 | ||
| 当前只显示满足指定条件的回帖，点击这里查看本话题的所有回帖 | ||
youpengxuan木虫 (正式写手)
小鱼虫
|
[求助]
急求大神翻译
|
|
|
Platinum Particle Size Distribution from TEM, EXAFS,and Hydrogen Chemisorption The experimental results obtained with hydrogen chemisorption, EXAFS, and TEM analysis (see Table 4) and the modeling results for A(size) (Figs. 7A and 7B), NPt–Pt(size) (Fig. 8), and D(size) (Fig. 9) were used to calculate the average particle size and the average number of atoms per particle for a few selected samples. For the catalysts for which TEM did not reveal or hardly revealed the presence of large platinum particles (4–9 nm)(Pt/NaY), this calculation was done by combining the experimental EXAFS NPt–Pt numbers (Table 4) with the NPt–Pt (size) function (Fig. 8) and the A(size) function (Fig. 7A). The results are presented in Table 5. For the zeolite catalysts calcined at 1±C/min TEM revealed the presence of large particles. The mass fraction TEM of the particles in the size distribution as determined by TEM is calculated by estimating the mass of the particles using their size and the modeled atom size function, A(size). From the particle size distributions (Figs. 5A, 5B), applied loading, and relation between the first-shell coordination number and particle size (Fig. 8), the average coordination number of the particles observed by TEM (NPt–Pt TEM) for both catalysts is calculated to be 11.3. With this number and using Eq. [3], the average coordination number of the mass fraction of platinum particles of catalyst Pt/NaY (1.1–IE–1) <2 nm (NPt–Pt not detected with TEM) is found to be 6.7 [.1=0:95/ ￡ .6:9–0:05 ￡ 11:3/], and for catalyst Pt/HUSY( 1.05–IE–1) this coordination number is found to be 7.5 [.1=0:92/￡.7:8-0:08 ￡ 11:3/]. The corresponding average size and number of atoms per particle as given in Table 5 were calculated by combining these calculated coordination numbers with the NPt–Pt (size) function (Fig. 8) and the A(size) function (Fig. 7A) derived from the modeled particles. The accuracy of the EXAFS coordination numbers used to calculate the average particle size is 10%. This statistical error is included in the sizes listed in Table 5. The weight factor in the averaging of the coordination number over all particles is the fraction of platinum atoms of a given coordination. Because the number of atoms per particle increases with approximately r 3 and the coordination number of the particles strongly depends on their size (Fig. 8), the larger particles in a size distribution dominate the average EXAFS coordination number. The deduced average particle size from EXAFS analysis of a (narrow) particle size distribution is therefore a volume average of the particle size distribution and an overestimation of the diameter average of the particle size distribution. On the other hand TEM cannot be used to detect Pt particles smaller than 2 nm. A combination of TEM and EXAFS is a powerful method to detect bimodal particle size distributions. A schematic presentation is given in Fig. 10 of the size range (nm/number of atoms per particle) where EXAFS and TEM have to be used to determine particle size accurately. |
回复此楼» 猜你喜欢
博士读完未来一定会好吗
已经有21人回复
-
导师想让我从独立一作变成了共一第一
已经有5人回复
-
到新单位后，换了新的研究方向，没有团队，持续积累2区以上论文，能申请到面上吗
已经有11人回复
-
读博
已经有4人回复
-
JMPT 期刊投稿流程
已经有4人回复
-
心脉受损
已经有5人回复
-
Springer期刊投稿求助
已经有4人回复
-
小论文投稿
已经有3人回复
-
Bioresource Technology期刊，第一次返修的时候被退回好几次了
已经有9人回复
-
申请2026年博士
已经有6人回复
lihl910807
木虫 (著名写手)
真强必胜: 屏蔽内容, 禁止Google等机器翻译，下次违规罚。。。 2014-10-31 14:55:14
|
本帖内容被屏蔽 |
3楼2014-10-30 23:13:56