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hellen7256木蟲 (小有名氣)
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[求助]
求助翻譯一段英文文獻。
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The representative geopolymerization product was fabricated through alkaline- or alkali-silicate-activated metakaolin, which has a wide range of compositions represented by M2O-mAl2O3-nSiO2, where (usually) m ≈ 1, 2 ≤ n ≤ 6, and M represents one or more alkali metals. To obtain geopolymers with a low Si/Al ratio and to overcome the disadvantages associated with the use of impure raw materials; amorphous Al2O3-SiO2 powder was first prepared through a sol-gel method in accordance with chemical compositions that were specifically designed in our work. The composition of the geopolymers is similar to that of the NaA zeolites when n = 2 and M = Na [15-16]. During this fabrication process, sodium silicate was used as an alkali activator (SiO2:Na2O molar ratio = 1.0), and the molar ratio of SiO2 in the synthetic powders to that of the sodium silicate was 1:1. Therefore, the chemical composition of the resulting geopolymers was Al2O3-2SiO2-Na2O. The zeolite crystal structure was obtained through the hydrothermal processing of Al2O3-2SiO2-Na2O at 90ºC for 6 h. The XRD patterns and the MAS NMR spectra of the calcined Al2O3-SiO2 powders, the chemosynthetic Al2O3-2SiO2-Na2O geopolymers, and the hydrothermal samples are presented in Fig. 2. Traditional alkali-based geopolymers typically exhibit one “hump” centered at approximately 26.0° to 29.0° (2θ) in their XRD patterns [17-19]. However, the XRD pattern of the as-prepared Al2O3-2SiO2-Na2O geopolymer has one “hump” centered at approximately 28.5°, which indicates a trend of crystallization. The HRTEM results from the analysis of the Al2O3-2SiO2-Na2O geopolymer confirm the existence of nanoscale ordered structures within the amorphous geopolymer gel [15-16]. After the hydrothermal process, the XRD results indicate that the majority of the Al2O3-2SiO2-Na2O geopolymers transformed into NaA zeolite crystals with good crystallinity (see Fig. 2a). The most important observation from our results is that the crystalline zeolite seeds already exist in a solid geopolymer gel. Key evidence supporting this conclusion was also obtained from the MAS NMR spectra. |
金蟲 (著名寫手)
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典型的地質(zhì)聚合產(chǎn)物是通過堿性的-或堿金屬-硅酸鹽-活化的偏高嶺土制造的,這種偏高嶺土具有寬泛的組分,表示為M2O-mAl2O3-nSiO2,式中(通常)m≈1, 2≤n≤6, M代表一種或多種堿金屬。為了獲得具有較小Si/鋁比的地質(zhì)聚合物并為了克服使用不純的原料所帶來的缺點;首先,按照我們研究當中明確地設(shè)計的化學(xué)成分通過溶膠-凝膠法制備了非晶形Al2O3-SiO2粉末。當n=2并且M=Na時這種地質(zhì)聚合物的組分與NaA分子篩相似[15-16]。在這種制造過程當中,硅酸鈉作為一種堿金屬活化劑( SiO2:Na2O摩爾比=1.0)使用并且合成的粉末中的SiO2對硅酸鈉的摩爾比為1:1。因此形成的地質(zhì)聚合物的化學(xué)成分為Al2O3 - 2SiO2 - Na2O。這種分子篩晶體結(jié)構(gòu)是通過Al2O3-2SiO2-Na2O于90℃熱液作用6小時而獲得的。 焙燒的Al2O3-SiO2粉末、化學(xué)合成的Al2O3-2SiO2-Na2O地質(zhì)聚合物和熱液樣品的X射線衍射圖和MAS NMR譜圖如圖2所示。 在X射線衍射圖中,傳統(tǒng)的堿基地質(zhì)聚合物表現(xiàn)出典型的一個"駝峰",其中心大約在26.0°到29.0°(2θ)[17-19]。 然而,所制備的Al2O3 - 2SiO2 - Na2O地質(zhì)聚合物的X射線衍射圖具有一個"駝峰",其中心大約在28.5°處,這表明一種結(jié)晶的趨勢。 Al2O3-2SiO2-Na2O地質(zhì)聚合物的高分辨率透射電子顯微鏡分析結(jié)果證實在非晶形地質(zhì)聚合物凝膠之內(nèi)存在納米級有序結(jié)構(gòu)[15-16]。 熱液作用之后,X射線衍射結(jié)果顯示大多數(shù)Al2O3-2SiO2-Na2O地質(zhì)聚合物轉(zhuǎn)化成具有良好的結(jié)晶度的NaA分子篩結(jié)晶(詳見圖2a)。 從我們的結(jié)果當中最重要的發(fā)現(xiàn)是結(jié)晶分子篩種子已經(jīng)存在于固體地質(zhì)聚合物凝膠之中。 還由魔角旋轉(zhuǎn)核磁共振譜圖中得到了支撐這種結(jié)論的關(guān)鍵證據(jù)。 |
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