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youpengxuan木蟲 (正式寫手)
小魚蟲
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[求助]
急求大神翻譯
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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. |
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2樓2014-10-30 21:42:42
lihl910807
木蟲 (著名寫手)
真強(qiáng)必勝: 屏蔽內(nèi)容, 禁止Google等機(jī)器翻譯，下次違規(guī)罰。。。 2014-10-31 14:55:14
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3樓2014-10-30 23:13:56
chenbaishan
銅蟲 (小有名氣)
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通過TEM（透射電鏡）、EXAFS（擴(kuò)展x射線吸收精細(xì)結(jié)構(gòu)）以及氫原子吸附得到的Pt顆粒的粒度分布 通過氫原子吸附、EXAFS以及TEM分析（見表4）得到的實(shí)驗(yàn)結(jié)果以及A（尺寸）（圖7A和7B），NPt-Pt（尺寸）（圖8）和D（尺寸）（圖9）被用來計算平均粒度以及選定的幾個樣品的每個顆粒的平均原子數(shù)。 因?yàn)門EM并沒有反映或很難反映出大的pt顆粒（4-9nm）（Pt/NaY）催化劑，這個估算是通過結(jié)合實(shí)驗(yàn)EXAFS NPt-Pt數(shù)量（表4）和NPt-Pt（尺寸）函數(shù)（圖8）以及A（尺寸）函數(shù)（圖7A）來完成的。結(jié)果在表5中呈現(xiàn)了。 TEM反映出了在1±C/min下煅燒的沸石催化劑有大顆粒的存在。通過TEM測定的顆粒的尺寸分布的質(zhì)量分?jǐn)?shù)是用它們的尺寸和原子尺寸函數(shù)A（尺寸）建模來估算顆粒質(zhì)量來判定的。從顆粒尺寸分布（圖5A，5B），外加載荷以及第一外形同等數(shù)量和顆粒尺寸（圖8）可以得到，兩種催化劑通過TEM（NPt-Pt TEM）觀察到的同等顆粒平均數(shù)量計算結(jié)果是11.3。這個數(shù)據(jù)結(jié)合使用Eq，催化劑Pt/NaY(1.1–IE–1) <2 nm (TEM下NPt–Pt沒探測到)中的Pt顆粒的質(zhì)量分?jǐn)?shù)的同等數(shù)目被發(fā)現(xiàn)是6.4[.1=0:95/ ￡ .6:9–0:05 ￡ 11:3/]，對催化劑Pt/HUSY( 1.05–IE–1)來說同等數(shù)目是7.5 [.1=0:92/￡.7:8-0:08 ￡ 11:3/]。通過結(jié)合NPt-Pt（尺寸）函數(shù)（圖8）以及源于粒子建模得到的A（尺寸）函數(shù)（圖7A）估算的相當(dāng)?shù)臄?shù)量得到相當(dāng)?shù)钠骄叽绾皖w粒平均原子數(shù)如表5所示。 用來估算平均顆粒尺寸的EXAFS相當(dāng)數(shù)量的準(zhǔn)度是10%.這個錯誤統(tǒng)計在表5中的尺寸數(shù)據(jù)中包含了。在所有顆粒的相當(dāng)平均重量系數(shù)是給定相當(dāng)?shù)腜t原子的一部分。因?yàn)槊總�顆粒的原子數(shù)大約隨著r的增加呈3次關(guān)系，并且顆粒的相當(dāng)數(shù)量與尺寸密切相關(guān)（圖8）,粒度分布中大的顆粒支配著EXAFS的平均相當(dāng)數(shù)量。通過EXAFS分析的（窄的）顆粒尺寸分布推斷出的平均顆粒尺寸因此是顆粒尺寸分布的平均體積，而且是對顆粒尺寸分布的平均直徑的過高估計。另一方面，TEM不能被用來探測尺寸小于2nm的Pt顆粒。TEM和EXAFS的結(jié)合是用來探測顆粒尺寸分布的雙峰曲線的強(qiáng)力手段。圖10的圖示給出了在EXAFS和TEM不得不被用來準(zhǔn)確確定顆粒尺寸的情況下的粒度范圍（nm/每個顆粒的原子數(shù)）。 我試著翻譯的哈，非常粗糙，一方面急著吃飯，另一方面水平有限，等等看別人有沒有更靠譜的翻譯咯~  |
4樓2014-11-21 17:44:35
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