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Shallow Trench Isolation CMP
Published in Ungyu Paik, Jea-Gun Park, Nanoparticle Engineering for Chemical-Mechanical Planarization, 2019
Cerium carbonate was used as a precursor to synthesize two types of ceria powder. The primary grain size of the polycrystalline ceria abrasives was controlled by employing a calcination process for 4 h with two calcination temperatures of 700°C and 800°C. The secondary particle size of the abrasives was controlled by crushing the powders by using a laboratory-scale air jet mill and a wet ball mill. The ceria powders were crushed by wet mechanical milling for several hours to reduce their secondary particle sizes to the target size of 130 nm, after initial mechanical dry jet milling for several hours to reduce the size to 300 nm. The ceria abrasives were then dispersed in deionized water and stabilized by adding 100 ppm of a commercially available dispersant (PMAA), along with 1 wt% of ammonium salt (Mw = 10,000; Darvan C, R.T. Vanderbilt, USA) as another dispersant of the abrasive particles. We also added an anionic organic additive (PAA; Polysciences, USA) at a concentration of up to 0.80 wt%, with one of three molecular weights (Mw = 30,000, 50,000, and 90,000). Each suspension was twice subjected to ultrasonic treatment for 15 min to break down agglomerates and promote mixing. An ice bath was used to control the temperature of the suspension during the ultrasonic treatment. The suspension was aged for 12 h at room temperature with a wrist-action shaker and subjected to ultrasonic treatment for an additional 15 min prior to use. The solid content was initially controlled to 5 wt% of ceria powder in the suspension. We then diluted each slurry with deionized water to produce a final ceria abrasive concentration of 1 wt%. Each slurry’s pH was adjusted to the range of 6.0 to 7.0 by adding an alkaline agent. Table 3.3 lists the slurry characteristics, including the slurry pH, the different PAA pH values with the three molecular weights, and the experimental conditions during synthesis.
Novel Inorganic and Metal Nanoparticles Prepared by Inverse Microemulsion
Published in Victor M. Starov, Nanoscience, 2010
The existence of the remaining precursor in the samples is due to the incomplete reaction between cerium carbonate and sodium hydroxide. This would be due to a relatively low preparation temperature that is difficult to control in a mechanical milling process. Therefore, to investigate the effect of temperature on the phase and crystal growth of cerium dioxide synthesized by the mechanochemical method, the samples are annealed at different temperatures.
Effect of rare earth oxides on the formation of gaseous products from low rank coal pyrolysis
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Lingkun Rong, Baolu Cui, Yin Qu, Jialei Sun, Fengjun Jia, Wenxiu Li, Mo Chu, Wanzhong Yin
The LRC used in this study is from Ordos area, Inner Mongolia, China. First, the coal (3–0.1 mm) was demineralized via acid treatment to minimize the effect of other mineral matters (Liu et al. 2004; Song et al. 2020), and then the demineralized coal was dried for 1 h under the condition (150°C, 20 kPa). The dried demineralized coal is marked as DE, and the proximate and ultimate analyses of DE and raw coal are presented in Table 1. The moisture of dried coal is significantly reduced, which may be related to negative pressure drying (NPD). NPD causes partial coal pyrolysis to produce tar, and the tar condenses in the pores of the coal particles during cooling, which effectively prevents the reabsorption of moisture. CeO2 and La2O3 were selected and added to DE (the addition amount was 10 wt%) separately to prepare another two coal samples, which were named DE-Ce and DE-La, respectively. CeO2 and La2O3 were prepared via calcination of the analytical pure cerium carbonate and lanthanum carbonate powder (<0.074 mm) at 1000°C. After calcination, CeO2 was stored into air-tighten plastic bags in a desiccator; while La2O3 was used immediately after preparation because it can easily absorb CO2 and water to form other chemicals.
Effect of rare earth oxides on the formation of semi-char from low-rank coal pyrolysis: a comparative study based on X-ray diffraction and Raman analysis
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Lingkun Rong, Yi Yang, Dahu Li, Xiaoping Wang, Fengjun Jia, Jie Wang
The LRC used in this study was obtained from Hongce Coal Mine located in Ordos, Inner Mongolia, China. First, the coal (<0.35 mm) was demineralized via acid treatment to minimize the effect of other mineral matters (less than 1% in total), following the method reported elsewhere (Rong et al. 2015). CeO2 and La2O3 were prepared via calcination of the pure cerium carbonate and lanthanum carbonate powder (<0.074 mm) in muffle furnace at 1000°C. After calcination, CeO2 was stored into air-tighten plastic bags in a desiccator as backup; while La2O3 was used immediately after preparation because it can easily absorb the carbon dioxide and water from the air and form other chemicals.
Acceleration effects of rare earths on salt bath nitriding: diffusion kinetics and first-principles calculations
Published in Surface Engineering, 2021
Chang Du, Jin Zhang, Le Zhang, Yong Lian, Mengsha Fang
Two kinds of nitridation baths were prepared, one with the nitride salt and one with the nitride salt and 2 wt-% of the rare earth salt. The nitride salt with Product ID N-A was made by Chengdu Surface Metal Technology Co., Ltd in China. The major constituents of the salt were NaCNO, K2CO3 and a small amount of other substances; the ratio of sodium to potassium was 1:1; and the concentration of CNO− was 34–38%. The rare earth salt was mainly composed of cerium carbonate (≥46 wt-%) and cerium oxide (≥53 wt-%). An oxidation bath (Product ID C–C) from Chengdu Surface Metal Technology Co., Ltd. was also prepared to remove cyanide from the surface of the samples after nitridation.