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北京石油化工學院2026年研究生招生接收調劑公告

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寶MMC

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7. Synthesis of Mesoporous CrN. Mesoporous CrN was synthesized using a method similar to one we reported previously. 35 The XRD patterns for the washed nitride product of the ammonolysis of K2Cr2O7 at 700 °C for 8 h, CrN, can be seen in Figure 1a; this ﬁgure conﬁrms the phase purity of the ammonolysis product. The CrN crystallizes in the space group Fm3̅m with a reﬁned lattice parameter of a = 4.1430(2) Å as shown in Figure 1b. The CrN products from ammonolysis at 700 °C show relatively broad diffraction peaks due to the small crystalline domain sizes. The EDX result of the CrN product shows no K peak, which suggests the possible K-containing byproducts have been washed out by DI water. The PXRD reﬁnement of the product obtained shows that the average nitride crystalline domain size is 29 nm. SEM and TEM images were used to observe the surface morphology of the binary nitride products. Figure 2a and b shows SEM images of the CrN, with pores on the scale of 5−10 nm.
8. Chemical, Surface Area, and Conductivity Properties. It is expected that nitrides produced from the ammonolysis of oxides contain residual amounts of oxygen. 21,39 The ammonolysis products of single phase CrN show that the CrN contained <2 wt % oxygen by elemental analysis. The oxide surface layer is most likely from surface hydrolysis due to air exposure of the nitride product produced by ammonolysis. Thus, the oxygen content in the interior of the CrN grains is likely to be lower than that found by elemental analysis. The BET surface area of a 451 mg sample prepared from K2Cr2O7 at 700 °C was 72 m2/g (see Figure 3). The average pore sizes ranged from 10 to 20 nm. There is some microporosity (pore diameter ≤2 nm) that accounts for 1.9 m2/g of the surface area and a total micropore volume of 3 × 10−2 cm3/g. As discussed in the paper reporting the synthesis of metal (oxy)nitrides from Zn-containing oxides, the mesoporosity obtained is a feature of the bulk material and not just porosity induced at the surfaces of the original crystalline oxide grains. 34 The electrical conductivity of mesoporous CrN powder compressed at 35 bar was 54 S/cm, which is about 1 order of magnitude higher than the reported conductivity of carbon-based supports under similar conditions (∼4 S/cm). 40 A reported value for bulk, rocksalt CrN electrical conductivity is 1.1 × 10 3 S/cm. 41 Thus, the conductivity of the compressed mesoporous CrN powder is approximately 2 orders of magnitude lower than that of the bulk material, presumably due to both the porosity and the weak particle−particle contacts at low pressure.

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寶MMC: 金幣+40, 翻譯EPI+1, ★★★很有幫助, 超級感謝！ 2013-12-01 21:43:20

7。介孔氮化鉻的合成。介孔氮化鉻合成使用了我們以前的報告的類似方法。 35圖1a可以看到重鉻酸鉀在700℃下8小時的氨解洗滌氮化產物------氮化鉻的X射線衍射圖譜，該圖證實了氨解產物的相純度。氮化鉻結晶空間群Fm3m中精確的晶格參數(shù)為：a =4.1430（2）埃，如圖1b。氮化鉻產品在700℃下氨解，由于小的結晶域尺寸顯示出相對寬的衍射峰。氮化鉻產品的EDX結果沒有K峰，表明可能K-副產品都被去離子水沖走了。產物的PXRD精確化顯示氮化物結晶體平均尺寸為29納米。用SEM和TEM圖像來觀察二元氮化物產品的表面形貌。圖2a和b顯示了CrN的SEM圖像，有5-10納米大小的孔。
8�；瘜W結構，表面積和導電性能。氧化物氨解生成氮化物預期含有殘留氧。 21,39經元素分析，單相氮化鉻的氨解產物表明氮化鉻含有<2％（重量）的氧。由于通過氨解作用所產生的氮化物產物暴露于空氣中，氧化表面層是最有可能從表面水解。因此，在氮化鉻顆粒內部的氧含量可能比通過元素分析發(fā)現(xiàn)的更低。一個451毫克從重鉻酸鉀在700℃下制備的樣品BET表面積為72平方米/克（參見圖3）。孔徑平均范圍為10至20nm。有一些表面積1.9平方米/克和總微孔體積微孔3×10-2立方厘米/克微孔（孔徑≤2納米）。正如本文報道的從含Zn的氧化物合成金屬（氧）氮化物所討論的，中孔為主體材料的一個特征，不僅僅是原始結晶氧化物顆粒表面引起的孔隙。 34在35巴壓縮的中孔性CrN粉末的電導率為54秒/厘米，比已報道的相似條件碳載體的電導率（〜4的S /厘米）高一個數(shù)量級。 40零星的報告值，巖鹽的CrN電導率為1.1×103 S / cm。 41因而，壓縮的介孔氮化鉻粉末的導電率比該應用較少的材料低約2個數(shù)量級，這可能是由于低壓力條件下兩者的孔隙和顆粒與顆粒的接觸較弱。

低一個數(shù)量級為小10倍。

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