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[求助] 帮忙翻译化学文献中的英文英译汉7-8

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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