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Effect of Acetic Acid on the Structure and Crystallization of Mg...
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Effect of Acetic Acid on the Structure and Crystallization of MgO Prepared by Chemical Precipitation,王维,乔学亮,The influence of acetic acid on the structure and crystallization of MgO prepared by a chemical precipitation process was investigated in this work. The as-synthesized precursors a
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- 1 -
Effect of Acetic Acid on the Structure and Crystallization of
MgO Prepared by Chemical Precipitation
1
Wang Wei, Qiao Xueliang
*
, Chen Jianguo
State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University
of Science and Technology, Wuhan, Hubei, P.R. China (430074)
E-mail:wjiawei_2002@163.com
Abstract
The influence of acetic acid on the structure and crystallization of MgO prepared by a chemical
precipitation process was investigated in this work. The as-synthesized precursors and MgO powders
were characterized by using X-ray powder diffraction (XRD), Fourier-transformed infrared
spectroscopy (FT-IR), and differential thermal analysis (DTA). Compared to the samples without using
acetic acid, the addition of acetic acid as a chemical modifier in the precursor solution could yield a
bidentate coordination compound of carboxyl groups, which significantly lower the transition
temperature from Mg(OH)
2
to MgO, signifying faster the crystallization of MgO.
Keywords: Crystallization; Chemical precipitation; Magnesium compounds; Oxides
1. Introduction
Magnesium oxide (MgO) has been attracting both fundamental and application studies [1, 2]
as a very important metal oxide for use in catalysis [3, 4], toxic waste remediation [5, 6],
antibacterial materials [7, 8], or as an additive in refractory, paint and superconductor products [9,
10]. There are many methods reported in literature for synthesis of MgO, such as sol-gel, chemical
precipitation, hydrothermal method and chemical vapor deposition (CVD). Due to the advantages
of technical simplicity, low manufacturing cost and high reproducibility, the chemical
precipitation is one of the most popular methods. However, a sharp pH change is usually taken
place in the reaction system, when the precipitating agent (ammonium hydroxide or other alkaline
compounds) is added to the Mg
2+
ion solution. Consequently, the as-obtained MgO products
usually exhibit relatively large and varied grain sizes, inhomogeneous morphologies, and low
surface areas, all of which are disadvantageous for their use in applications.
Recently, acetic acid has been successfully used as a stabilizing agent against hydrolysis and/or
precipitation for metal organic systems [11, 12]. Hong et al. [13] have investigated the influence
of acetic acid treatment on the crystallization behavior of alkoxide sol-gel derived MgO. They
confirmed the addition of acetic acid enhanced the stability of the alkoxide against precipitation,
and lowered the crystallization temperature of MgO gel powder as well thin film. Hayashi et al.
[14] used acetic acid as a chemical modifier to control the hydrolysis and condensation reaction of
zirconium alkoxide, and they found acetic acid coordinated to a zirconium alkoxide to form a
stable bidentate chelating compound if molar ratio of acetic acid to zirconium alkoxide was less
than two. These reports are mainly with regard to alkoxides in the sol-gel process, while the
modification effect of acetic acid on MgO prepared by chemical precipitation has not been
investigated.
In the present work, acetic acid was used as a chemical modifier to synthesize MgO via a
chemical precipitation procedure using magnesium nitrate hexahydrate and ammonia hydroxide as
starting materials. The effect of acetic acid on the structure and crystallization of as-synthesized
MgO was investigated using X-ray powder diffraction (XRD), Fourier transformed infrared
spectroscopy (FT-IR), and differential thermal analysis (DTA) by comparing to the samples
1
Specialized Research Fund for the Doctoral Program of Higher Education of China (20050487011) and the
Project of Tackling the Key Problem of Science and Technology of Hubei Province (2006AA101C46).
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