School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo, Japan.
Appl Spectrosc. 2012 Jun;66(6):665-72. doi: 10.1366/11-06428.
This paper demonstrates the potential of near-infrared (NIR) electronic spectroscopy in nondestructive monitoring of a chemical reaction of inorganic functional material. For this purpose NIR spectra in the 12,000-4000 cm(-1) region were measured for high reflective green-black (HRGB) pigments (Co(0.5)Mg(0.5)Fe(0.5)Al(1.5)O(4)) calcined at 1000, 1100, and 1200 °C and pigments with the same components as HRGB but calcined at different temperatures (500-900 °C) (hereafter, called "Pigments A") . NIR spectra of their components such as Co(3)O(4), MgO, Fe(2)O(3), and Al(2)O(3) were also measured. The NIR spectra of Pigments A show two major broad bands. One arises from a (4)A(2)→(4)T(1) (T(h)) d-d transition of Co(II) in the 9000-6000 cm(-1) region. The other band in the 12,000-9000 cm(-1) region is assigned to a foot of the charge-transfer (CT) band of Fe(2)O(3). The Co(II) band contains three component bands that are characteristic of a spinel structure. A shoulder arising from (A(1-x)B(x))(Th)(A(x)B(2-x))(Oh)O(4) (A≡Co, Mg, B≡Fe, Al; inverse spinel structure) emerges near 5900 cm(-1) in the spectra of Pigments A calcined in the temperature range of 700-900 °C, indicating that the Pigments A calcined in this temperature range assume an inverse spinel structure. When the calcination temperature is above 1000 °C, the final product, HRGB, is produced. This is confirmed from the fact that HRGB shows peaks characteristic of a spinel structure that have different wavenumbers from those of the corresponding peaks of Pigments A. Wide-angle X-ray diffraction (WAXD) patterns were also measured for HRGB, Pigments A, and their components. Based on the NIR and WAXD data we investigated calcination-temperature-dependent crystal structural changes of the components. We also developed partial least squares (PLS) calibration models for the 9000-6000 cm(-1) region of the NIR spectra of HRGB and Pigments A. The score plot of latent variable (LV) 2 of the calibration model for calcination temperature demonstrates clearly the existence of an intermediate of the calcination reaction, which may be (A(1-x)B(x))(Th)(A(x)B(2-x))(Oh)O(4) (A≡Co, Mg, B≡Fe, Al).
本文展示了近红外（NIR）电子光谱在无机功能材料化学反应无损监测中的潜力。为此，我们测量了在 12,000-4000 cm(-1) 区域内高反射绿黑色（HRGB）颜料（Co(0.5)Mg(0.5)Fe(0.5)Al(1.5)O(4)）在 1000、1100 和 1200°C 下煅烧以及具有相同成分但在不同温度（500-900°C）下煅烧的颜料（以下称为“颜料 A”）的近红外光谱。还测量了它们的成分（如 Co(3)O(4)、MgO、Fe(2)O(3)和 Al(2)O(3)）的近红外光谱。颜料 A 的近红外光谱显示出两个主要的宽带。一个源于 Co(II)在 9000-6000 cm(-1) 区域的 (4)A(2)→(4)T(1)（T(h)）d-d 跃迁。另一个在 12,000-9000 cm(-1) 区域的带归因于 Fe(2)O(3)的电荷转移（CT）带的底部。Co(II)带包含三个特征于尖晶石结构的组成带。在 700-900°C 范围内煅烧的颜料 A 的光谱中，在 5900 cm(-1) 附近出现一个源于 (A(1-x)B(x))(Th)(A(x)B(2-x))(Oh)O(4)（A≡Co、Mg、B≡Fe、Al；反尖晶石结构）的肩峰，表明在该温度范围内煅烧的颜料 A 呈反尖晶石结构。当煅烧温度高于 1000°C 时，生成最终产物 HRGB。这从 HRGB 显示出与颜料 A 的对应峰具有不同波数的尖晶石结构特征峰这一事实得到证实。还测量了 HRGB、颜料 A 及其成分的广角 X 射线衍射（WAXD）图谱。基于 NIR 和 WAXD 数据，我们研究了成分的煅烧温度依赖性晶体结构变化。我们还为 HRGB 和颜料 A 的近红外光谱的 9000-6000 cm(-1) 区域开发了部分最小二乘（PLS）校准模型。校准模型的潜在变量（LV）2 的得分图清楚地表明了煅烧反应中间产物的存在，该中间产物可能是 (A(1-x)B(x))(Th)(A(x)B(2-x))(Oh)O(4)（A≡Co、Mg、B≡Fe、Al）。
