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Mineralogical Characteristics of Natural Semiconducting Minerals in Danxia Red Layers of Lang Mountain, Xinning, Hunan Province, China
XIAO Yuxiong, LI Yanzhang, DING Hongrui, LI Yan, LU Anhuai
Acta Scientiarum Naturalium Universitatis Pekinensis 2019, 55 (
5
): 915-924. DOI:
10.13209/j.0479-8023.2019.065
Abstract
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1041
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After fieldwork, metallic minerals in the samples collected from the red layers of Danxia located in
Lang mountain, Xinning, Hunan province, were characterized by complementary methods, including Polarizing
Optical Microscope (POM), Environmental Scanning Electron Microscopy (ESEM), Energy Dispersive X-ray
analysis (EDX), High Resolution Transmission Electron Microscopy (HRTEM), Electron Probe Micro-Analysis
(EPMA), micro-area X-Ray Diffraction (XRD), micro-Raman spectra (μ-Raman), and X-ray fluorescence (XRF),
either by in situ analysis or powder analysis. The dominant natural semiconducting minerals from the red layers of
Danxia were hematite and anatase. In addition, the contents of iron and titanium in the red layers were 2.8 times
and 2.4 times higher than that of the non-red layers, respectively. Mineralogical investigation revealed that the
majority of Fe/Ti oxides were presented like cementating coarse silicate minerals (feldspar, quartz and biotite),
suggesting these Fe/Ti oxides were formed exogenically after weathering and eluviation of Fe and Ti-bearing
silicate minerals (ilmenite and biotite). Semiconducting properties exhibited by exogenic hematite and anatase in
the red layers of Danxia can provide fundamental information to further study the photocatalytic properties and
environmental effects of the Danxia red layers, and to understand the interrelationship between the Cretaceous
oceanic red bed and continental red bed on the Earth’s surface.
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Feasibility of Measuring Nitrite with Semiconductor Laser
WU Feng;HAO Ruixia;JIANG Yuan;YANG Shiqin;LU Anhuai
Acta Scientiarum Naturalium Universitatis Pekinensis DOI:
10.13209/j.0479-8023.2015.068
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Study on the Preparation of Low Cost Organoclay from Low-Level Ca-bentonite
ZHOU Jiangong,LU Anhuai,WANG Changqiu
Acta Scientiarum Naturalium Universitatis Pekinensis
Abstract
(
593
)
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The organic bentonites were prepared with the low-level Ca-bentonites obtained from Jianping, Liaoning province. By means of orthogonal experiment, the optimal conditions of organic bentonites preparation are 20 g natural bentonite, 6.25 g CTMAB, 150 mL water, stirring time 3 hours, and standing time 2 days. XRD shows d(001) value of modified bentonite has increased from 1.5286 nm to 2.1567 nm, TG-DTA, and FT-IR prove organic modifiers have entered into the interlayers of the bentonites. A hydrophobic and lipophilic analysis of the modified bentonites was made. By one time modified technics, the traditional technics of organoclay preparation only by cation exchange reaction of Na-montorillonite with quaternary ammonium salt organic cation (HDTMA) are innovated and the cost of the organoclay preparation is greatly reduced.
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Mineralogical Characteristics Study of Natural Cryptomelane in the Xialei Manganese Deposit, Guangxi
ZHAO Dongjun,LU Anhuai,WANG Lijuan,ZHENG Xishen,LIU Rui,GUO Yanjun
Acta Scientiarum Naturalium Universitatis Pekinensis
Abstract
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934
)
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In the supergene zones of Xialei manganese deposit in Guangxi, south China, there is abundant resource of natural cryptomelane, which is well known as a manganese oxide octahedral molecular sieve having a well-defined 2*2 tunnel structure (OMS-2) with K
+
situated in tunnel positions. This study was focused on the occurrence characteristics of the cryptomelane-bearing ores and the mineralogical characteristics of natural cryptomelane. The morphology, chemical and structure features of natural cryptomelane were characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalyzer(EPMA), energy dispersive spectrometer (EDS) and X-ray fluorescence(XRF). The morphology of the natural cryptomelane crystals via SEM showed short prismatic, needle-like and fibrous shapes with the diameters varying from few nanometers to hundreds nanometres. The MnO
2
content was by and large over 90% and K
2
O ranged from 2.52 to 4.37wt%. However, the composition resulted from EDS revealed a higher content of K, 3.37 - 4.17wt%. The XRD of the samples agreed with a monoclinic cryptomelane and the cell parameters were given as
a
= 9.956nm,
b
= 2.870nm,
c
= 9.706nm and
β
= 90.95°. The phase transformation temperature of the natural cryptomelane was about 635.5℃ examined by TGA and DTA and the cryptomelane was changed to bixbyite at a higher temperature. These studies reveal the significant features of cryptomelane for the potential application in the environmental materials science.
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Classification and Framework Features of Tunnel Structure Minerals
LIU Yingxin,QIN Shan,LIU Rui,LU Anhuai
Acta Scientiarum Naturalium Universitatis Pekinensis
Abstract
(
812
)
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The definition and classification of tunnel structure minerals are prop osed. The framework characteristics for typical tunnel structure minerals are described in detail, such as natrolite, laumontite, phillipsite, chabazite, mordenite, palygorskite, sepiolite, beryl, hemimorphite, pyrolusite, ramsdellite, cryptomelane, psilomelane, todorokite, manganite, cacoxenite, beryllonite and patite, which belong to silicate, manganese oxide and hydroxide minerals and phosphate respectively. The effects of surface absorption, tunnel structure and catalytic reaction, which were applied in the field of harnessing contamination and remedying environment, are also discussed. The tunnel minerals will play important roles in the future development of the exploitation of environmental properties, chemical and microbial modifications as well as synthetic tunnel structure minerals.
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Powder X-ray Study on Perovskites in the System of Ca
1-
x
Sr
x
TiO
3
(0≤
x
≤1)
QIN Shan,LU Anhuai,WU Xiang
Acta Scientiarum Naturalium Universitatis Pekinensis
Abstract
(
714
)
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The structures of perovskites in the system CaTiO
3
-SrTiO
3
were measured and refined at room temperature by X-ray powder diffraction. The sequence of phase transitions for Ca
1-
x
Sr
x
TiO
3
(0≤
x
≤1), found with increasing Sr content, is orthorhombic
Pbnm
, orthorhombic
Bmmb
, tetragonal
I4/mcm
and cubic
Pm3m
. The boundaries of phase transitions are at
x
=0.45(5)for
Pbnm
-
Bmmb
,
x
=0.65(5) for
Bmmb
-
I4/mcm
and
x
=0.92(2) for
Pm3m
, respectively.
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