X射线衍射仪在材料科学中的应用外文翻译资料

Keywords:

Ceramics

Phase transformation

In situ XRD

Red mud

hematite, residual quartz, and generated pyroxene formed the skeleton phase in ceramics during high temperature sintering. Formation of more pyroxene in ceramics improved the bending strength (115.88 MPa for ceramic sample #1). Slow cooling was beneficial to precipitate more pyroxene and less anorthite during sintering. This research is of special interest for the utilization of red mud in ceramics. 2019 Published by Elsevier B.V.

a r t i c l e

i n f o

a b s t r a c t

Article history:

Received 17 September 2018

Received in revised form 19 December 2018

Accepted 3 January 2019

Available online 9 January 2019

The sintering mechanism of novel SiO₂-Al₂O₃-CaO-MgO ceramics obtained from red mud was studied using two batches of ceramics mixed with 50 wt% red mud. The sintering behavior and mechanical properties were studied, and crystal evolution was investigated using X-ray diffraction (XRD), especially in situ XRD. Results showed that anorthite with Na -solidification played the role of flux to reduce the optimal sintering temperature of ceramics by about 50 C (1080 C for ceramic sample #2), whereas

1. Introduction

Red mud (RM) is a byproduct of the digestion of bauxite ores for alumina production, and is a major industrial solid waste and potential pollutant. Every year, approximately 120 million tons of RM are discharged globally [1]. In recent years, many studies have proposed different approaches for the reuse of red mud. For example, RM was used as a raw material for preparing environmental materials [2] and radio-opaque materials [3], and also as a secondary source for extracting iron, titanium dioxide, and alumina [4]. However, apart from building materials, other applications of red mud consume only limited amounts of it. Several studies have been reported on the utilization of red mud for cement [5] and clay ceramics [6]. However, high Na₂O and CaO contents of RM are harmful and limit its usage in cement and clay ceramics, respectively.

Based on the previous research on ceramics with high CaO content derived from steel slag [7], SiO₂-Al₂O₃-CaO-MgO (10 wt%) ceramics were prepared from RM by our research group, and the Na -solidification behavior of these novel ceramics was studied [8]. The results showed that ceramics with 50 wt% RM had lower sintering temperature and excellent properties. Pyroxene and anorthite were found to be the main phases of the novel ceramics. The anorthite phase had better ability for Na -solidification than

pyroxene. However, the sintering mechanism of SiO₂-Al₂O₃-CaOMgO ceramics derived from RM has not been investigated yet. In this paper, the sintering mechanism was studied using in situ Xray diffraction (XRD) to investigate the effects of different phases on the sintering process, and the effects of cooling rate on phase precipitation.

1. Experimental

2.1. Materials

The raw materials were RM, pyrophyllite, talcum, shale and quartz. Talcum and pyrophyllite were obtained from Shandong province, and the others were obtained from Guizhou province in China. Based on experimental result [9] (low SiO₂/Al₂O₃ ratio is favorable for the formation of Si-O-Al band) and SiO₂-Al₂O₃-CaOMgO phase diagram [10], sample #2 was designed through replacement of talc in sample #1 in our previous report [8] by pyrophyllite with high Al₂O₃ content to ensure the formation of more anorthite. Both samples #1 and #2 had 50 wt% RM in the raw material mixture. The designed compositions of the ceramics are shown in Table 1, which were tested using XRF analysis. The ceramic green samples were prepared by the same method

Sample

SiO₂

Al2O3

CaO

MgO

K₂O

Fe2O3

TiO₂

Na₂O

#1 [8]

49.75

11.95

10.69

6.25

2.54

10.11

3.11

4.21

#2

53.08

14.27

10.04

0.78

2.95

10.15

3.14

4.24