The Effect of Different Doping Methods of Sintering Aids on the Barium Titanate Based X7R Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 83-86 ◽  
Author(s):  
C. Ma ◽  
X.H. Wang ◽  
R.Z. Chen ◽  
Long Tu Li ◽  
Zhi Lun Gui
Keyword(s):  
Rare Earth ◽  
Dielectric Loss ◽  
Barium Titanate ◽  
Low Temperature ◽  
Rare Earth Oxide ◽  
Sintering Aids ◽  
Sintering Properties ◽  
Relationship Of ◽  
The Relationship

The barium titanate based X7R ceramics, which are doped with rare earth oxide, Nb2O5, Co3O4 and ZnO-B2O3, could be sintered at a rather low temperature to satisfy the X7R requirements with good permittivity and dielectric loss. In this paper, different doping methods of sintering aids have been used to prepare X7R BaTiO3 ceramics. Samples were sintered at a low temperature and the relationship of doping methods and sintering properties has been concluded.

Effects of Rare Earth Oxides on the Microstructure and the Mechanical Properties of High-Purity Alumina Ceramics Sintered at Low Temperature

2008 ◽  
Vol 368-372 ◽  
pp. 694-696
Author(s):  
Feng Sun ◽  
Ting Yan Tian ◽  
Wei Ru Zhang ◽  
Bo Chen
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
Low Temperature ◽  
High Purity ◽  
Rare Earth Oxide ◽  
Transgranular Fracture ◽  
Alumina Ceramics ◽  
Sintering Aids ◽  
Compact Structure ◽  
Main Fracture

High-purity alumina ceramics were prepared by sintering at low temperature, using rare earth oxide Y2O3 and Tm2O3 as sintering aids. Adding the mixture of Y2O3 and Tm2O3 in the alumina powders can effectively improve the sintering ability and mechanical properties. The mixture, Y2O3+Tm2O3, can restrain the grains growth, fine the grain size, make the grain uniform and finally help to form compact structure. The transgranular fracture was the main fracture mode. It was found the relative density of alumina ceramics with 0.3wt% Y2O3 and Tm2O3, sintered at 1620°C for 3hrs, can be over 99.2% and the strength, toughness and microhardness reach 533.1MPa, 4.9MPa⋅m1/2 and 17.2GPa, respectively.

Effect of B4C Content on Densification Behavior of SiC-B4C Ceramics

2014 ◽  
Vol 997 ◽  
pp. 454-456
Author(s):  
Yun Long Zhang ◽  
Yu Min Zhang ◽  
Ming Hu ◽  
Xiao Gang Song
Keyword(s):  
Rare Earth ◽  
Rare Earth Oxide ◽  
Gas Pressure ◽  
Volume Shrinkage ◽  
Densification Behavior ◽  
Sintering Aids ◽  
Phase Constitution ◽  
Sintering Additives ◽  
Multi Phase ◽  
Gas Pressure Sintering

The SiC-B4C multi-phase ceramics was fabricated by gas-pressure sintering technology. The rare-earth oxide Al2O3combined with Er2O3/SiO2was served as sintering aids. The results were shown that the combination of Al2O3/Er2O3/SiO2sintering additives were effective for densification of SiC-B4C multi-phase ceramics. The influence of B4C content on the phase constitution, microstructure and densification behavior of the SiC-B4C multi-phase ceramics were detailed. The lose weight and volume shrinkage rate of SiC-B4C multi-phase ceramics had similar evolvement trend when B4C content increased. Keywords: Gas-Pressure Sintering, SiC-B4C multi-phase ceramics, densification behavior.

Relationship of basal plane and prismatic stacking faults in GaN to low temperature photoluminescence peaks at ∼3.4 eV and ∼3.2 eV

2004 ◽  
Vol 831 ◽  
Author(s):  
J. Bai ◽  
M. Dudley ◽  
L. Chen ◽  
B. J. Skromme ◽  
P. J. Hartlieb ◽  
...  
Keyword(s):  
Low Temperature ◽  
Thin Layer ◽  
Basal Plane ◽  
Stacking Faults ◽  
Structural Defects ◽  
Cubic Phase ◽  
Bulk Crystals ◽  
Relationship Of ◽  
The Relationship ◽  
Low Temperature Photoluminescence

ABSTRACTThe relationship between the optical properties and microstructure of GaN is of great interest due to the important optical and electronic applications of this material. Several different studies have been reported attempting to link the low temperature photoluminescence (PL) peak at ∼3.4 eV to the presence of various microstructural defects. However, no clear systematic studies have been reported establishing such a link for the PL peak observed at ∼3.2 eV. In this paper, we present evidence linking the ∼3.4 eV PL peak to the presence of a thin layer of cubic phase associated with basal plane stacking faults (BSF). This relationship is mainly established by studying a series of ammonothermally-grown GaN bulk crystals. The existence and strength of the ∼3.4 eV peak are found to be related to the I2 type BSF (RI2=1/3<1>) observed in these samples. To investigate the relationship between the ∼3.2 eV peak and structural defects, a series of GaN epilayers grown on either SiC or sapphire (of various off-cut angles) was investigated by TEM and PL spectroscopy. Samples grown on 3.5° off-cut SiC and 5° and 9° off-cut sapphire substrates exhibit PL peaks near ∼3.2 and ∼3.4 eV, which are absent in the on-axis SiC and sapphire cases. TEM shows that the former group of samples has defect configurations consisting of prismatic stacking faults (PSFs) folding back and forth between two different {1120} planes connected by stair rod dislocations, which in turn fold onto to I1 type BSFs again with stair rod dislocations at the fault intersections. The ∼3.2 eV PL peaks are proposed to possibly arise from transitions involving the PSFs and the stair rods associated with their mutual intersections and their intersections with the BSFs. The ∼3.4 eV peak is again attributed to the thin layer of cubic phase associated with the I1 type BSF (three bilayers as opposed to four bilayers for the I2 type BSF).

Study on Low Temperature Sintering Behaviour of CaO-B2O3-SiO2 Glass Ceramics

2010 ◽  
Vol 150-151 ◽  
pp. 350-353
Author(s):  
Peng Fei Wei ◽  
Hong Qing Zhou ◽  
Hai Kui Zhu ◽  
Bin Dai ◽  
Jie Wang
Keyword(s):  
Low Temperature ◽  
Glass Ceramics ◽  
Sintered Sample ◽  
Sintered Glass ◽  
Powder Characteristics ◽  
Sintering Properties ◽  
Median Particle ◽  
Materials Used ◽  
Sintering Behaviour ◽  
The Relationship

CaO-B2O3-SiO2 glass ceramics were prepared by powders of different particle sizes. The relationship between CBS powder characteristics and structures was studied by XRD and SEM, and the effect of powder characteristics on sintering properties, dielectric properties at 10GHz, thermal properties (CTE) were investigated to obtain low-temperature sintered glass ceramics. The results showed that the median particle size of glass powders reduced, sintered temperature and apparent porosity decreased. But at the same time, bulk density and thermal expansivity increased. The sample with the powders of D50=2.34μm could be sintered at 850 with the density about 2.615g•cm-3 and the water absorption about 0.16%. Having a dielectric constant of 6.16 and a dielectric loss of 1.9×10-3 at 9.98GHz, the sintered sample could satisfy the requirements of the substrate materials used in LTCC in some fields.

Electrical Conductivity of Molten DyCl3-NaCl and DyCl3-KCl Systems: An Approach to Structural Interpretations of Rare Earth Chloride Melts

2017 ◽  
Vol 72 (12) ◽  
pp. 1105-1112
Author(s):  
Yasuhiko Iwadate ◽  
Takahiro Ohkubo
Keyword(s):  
Rare Earth ◽  
Type Equation ◽  
Structural Features ◽  
Rare Earth Chloride ◽  
Chloride Melts ◽  
Electrical Conductivities ◽  
Increasing Temperature ◽  
Melt Composition ◽  
Relationship Of ◽  
The Relationship

AbstractElectrical conductivities (κs) of molten DyCl3-NaCl and DyCl3-KCl systems were estimated by measuring the impedances of each mixture melt at any temperature and/or frequency. The molar volumes (Vms) were measured by dilatometry and represented as a polynomial empirical equation of temperature and composition. Due to both the properties, the molar conductivities (Λms) were calculated and their temperature and/or composition dependences were discussed from the standpoint of structural features as well. The κs increased curvilinearly with increasing temperature across the whole composition ranges. This trend was also applied to the Λms which was fitted by an Arrhenius-type equation. The relationship of Λms with melt composition was studied and the Λms were found to decrease with increasing composition of DyCl3. These findings were interpreted based on the results of structural science so far reported, and finally, the relationship between Λms and the structures of pure rare earth chloride melts was discussed.

Surface Modification of Magnesium with Rare Earth Conversion Films for Biomedical Protection

2007 ◽  
Vol 546-549 ◽  
pp. 601-604 ◽  
Author(s):  
Jia Cheng Gao ◽  
Yan Xue ◽  
Li Ying Qiao ◽  
Yong Wang ◽  
Yan Zhang
Keyword(s):  
Corrosion Resistance ◽  
Rare Earth ◽  
Metabolic Process ◽  
The Body ◽  
Surface Microstructure ◽  
Corrosion Properties ◽  
Corrosion Rates ◽  
Protective Films ◽  
Relationship Of ◽  
The Relationship

The specific gravity and elastic modulus of magnesium alloys are similar to that of human bone. Magnesium is one of the most important elements in the human body and plays a key role in the metabolic process. But the application of magnesium is seriously limited as a biomaterial since it corrodes easily in the physiological environment of the body. In order to reduce the corrosion, we developed protective films using rare earth (RE) conversion processing. The surface of magnesium samples was modified by contact with different rare-earth salt solutions; then the samples were dipped in SBF to test their corrosion resistance. The change of mass and the pH of the solutions were measured continuously using an electronic scale and a pH micrometer. The surface microstructure of the samples was observed by XRD and metallomicroscope. Corrosion rates of the samples in SBF were determined using Taffier curve. The preliminary results show that the conversion treatment with CeCl3 or Y(NO3)3 can improve the corrosion resistance of magnesium in SBF. The relationship of the RE salts concentration and the corrosion properties were studied,the best combination of parameters was determined, and the formation mechanism of rare-earth conversion film has been also elaborated.

scholarly journals STUDY ON TEMPERATURE FIELD OF ASYMMETRIC LARGE-SPAN ARCH SHEDS UNDER LOW-TEMPERATURE ENVIRONMENT

2020 ◽  
pp. 239-248
Author(s):  
Kai Zhou ◽  
Zhiwei Meng ◽  
Jialin Hou ◽  
Min Wei ◽  
Tianguo Jin ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Wind Speed ◽  
Low Temperature ◽  
Storage Capacity ◽  
Heat Storage ◽  
Large Span ◽  
Distribution Uniformity ◽  
Relationship Of ◽  
The Relationship ◽  
Better Than

In order to improve the effective sunshine time, heat storage capacity and temperature distribution uniformity of traditional arch shed under low temperature, this paper designed a large-span arch shed which has larger sunny side span and east-west orientation. According to the numerical and measured data, it is concluded that the heat storage capacity and temperature distribution of asymmetrical arch shed are better than those of symmetrical arch shed within a certain range of the ratio between sunny and shaded side. After that, ten different asymmetric arch sheds were designed. It is concluded that the structure of 11+9 m along north-south direction has the best heat storage capacity. Besides that, the analysis of outside wind speed and opening size of top vent were carried out. It is found that the outside wind and top vent can effectively promote convection and exchange of the air, and then achieve the purpose of reducing the temperature. At the end of this paper, in order to identify the relationship of temperature with the structure of arch shed, outside wind speed, and opening size of top vent, a mathematical model was built based on response surface methodology, which would provide theoretical guidance for the design of arch sheds.

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