Guobo Yang,Baoqiang Xu,Heli Wan,Fengkang Wang,Bin Yang,Zhijun Wang
The compound CaCl2plays a significant role in the process of direct calciothermic reduction of Ti2O3to prepare porous titanium. In this paper, the effect of CaCl2on reduction products by calciothermic reduction of Ti2O3was investigated. Results show that the distribution of CaCl2in reduction preform influences particle size and morphology differences in reduction products both on the surface and the inside. The CaCl2is transferred to the surface of the Ti2O3preform due to its volatilization before and throughout reduction. The content of CaCl2in the surface zone of Ti2O3preform is significantly higher than that in the interior during the reduction process, contributing to the formation of large Ti particles with a smooth shape on the surface, and small Ti particles with inherited morphology of Ti2O3inside. More CaCl2causes the aggregation of Ti particles to form large Ti particles which are advantageous as they connect and form a more solid porous titanium structure. The presence of a small amount of CaCl2in the interior also results in the coexistence of small Ti and CaO particles, forming a loose structure with uniform distribution.Keywords:CaCl2;calciothermic reduction;Ti2O3;microstructure;morphology;Ti particles
Zhijun Wang,Baoqiang Xu,Jia Yang,Bin Yang,Heng Xiong,Guobo Yang,Fengkang Wang
A route is present for preparing porous titanium scaffolds with open and interconnected pore morphology through calcium thermal in-situ reduction of TiO precursor. Titanium and dioxide titanium powders, with ammonium carbonate as the space holder, were used to prepare porous precursor whose main phase is TiO by a sintering process. Then calcium vapor was conduced to reduce the precursor and CaO was removed by leaching to obtain porous titanium structures. The morphology, pore structure, phase analysis of porous titanium precursor and porous titanium scaffolds were investigated by means of XRD, SEM and EDS. The porosity was observed by Archimedes method. By this route, the porous titanium with multi-gradient pore sizes ranging from a few microns to several hundred microns was formed. The porous titanium is of multi-gradient pore size distribution of 100 μm bigger, 10 μm∼100 μm and 10 μm smaller. The micro-pores on the pore walls increases connectivity between the macro-pores throughout the porous titanium interior. The porous titanium obtained by this method has a porosity of 50–65% and a titanium content more than 99%.
The lunar regolith can be utilized as raw materials for constructing lunar bases through the fabrication of lunar cement. However, the low CaO content in lunar regolith presents a challenge for producing silicate cement. This study explores enriching CaO in NEU-1 lunar soil simulant by calciothermic reduction. Non-isothermal differential scanning calorimetry analysis indicated that calcium reacted with Fe 2 O 3 , SiO 2 , and Al 2 O 3 at approximately 808°C, 816°C, and 826°C, respectively. The reaction ratios were 1.1, 1.6, and 0.8, with apparent activation energies of 941.6 kJ/mol, 965.17 kJ/mol, and 547.28 kJ/mol. The products obtained from the calciothermic reduction of lunar soil simulant were CaO, Ca 2 Si, and AlFe, as analyzed by X-ray diffraction. Increasing the temperature was found to be beneficial to the reaction process, and a suitable reaction temperature of 850°C was determined. X-ray photoelectron spectroscopy analysis showed that the reduction percentages of SiO 2 and Al 2 O 3 were 93.01% and 91.04%, respectively, at 850°C for 30 min. The CaO content in the product obtained by calciothermic reduction was 50.65%, which could be further increased to 81.16% after crude purification, and the CaO yield was 82.57%. These results demonstrated that the process has a significant CaO enrichment effect.
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