Environment-friendly High Efficiency CH3NH3PbI3 Perovskite Solar Cells Fabricated by Green Antisolvent Method

Green antisolvents propyl acetate and isooctane can promote the nucleation of PbI2 particles and provide the heterogeneous nucleation site of perovskite crystal, so as to promote the rapid growth of perovskite crystal. The films treated with propyl acetate and propylene glycol methyl ether have larger grains and lower root-mean-square value (RMS) than those treated with chlorobenzene. The full coverage perovskite films with uniform grain size which is closer to the exciton diffusion length of perovskite can be obtained. Compared with the CH3NH3PbI3 perovskite solar cells treated with chlorobenzene (power conversion efficiency (PCE) is 17.86%), the best efficiency of the devices treated with propylene glycol methyl ether is 21.60%, which is improved by 21%, which has certain reference value and guiding significance for researchers to obtain environment-friendly high-quality perovskite solar cells in the future.

Grain refinement of commercially pure aluminum with addition of Ti and Zr elements based on crystallography orientation

The edge-to-edge matching (E2EM) model and electron back-scatter diffraction (EBSD) technique are used to explore the grain refinement mechanism of commercially pure Al through the addition of Ti and Zr elements. EBSD results show that there are favorable crystallography orientation relationships (ORs) between both Al3Ti and Al3Zr particles with α-Al matrix. Due to these ORs Al3Ti and Al3Zr particles act as the heterogeneous nucleation site during solidification nucleation of Al–Ti and Al–Zr alloys, respectively. Furthermore, both Al3Ti and Al3Zr particles have small values of interplanar spacing mismatch and interatomic spacing misfit with respect to α-Al matrix by using E2EM. It shows that micro-addition of Ti and Zr element is efficient heterogeneous nucleation refiner in commercial purity Al or Al alloys. Besides, there may be some other mechanisms in grain refinement of Al alloys with addition of Ti grain refiner.

Microstructural Stability of Ti based Composites Fabricated by Spark Plasma Sintering

In our previous study, the effects of TiC heterogeneous nucleation site particles on formability and microstructure of additive manufactured (AMed) Ti-6Al-4V products were studied. It was found that the addition of TiC particles decreased the grain size of primary β phase in AMed Ti-6Al-4V samples, since TiC particles act as heterogeneous nucleation sites. It is also found that the density of AMed Ti-6Al-4V samples could be increased by addition of TiC particles. It is expected that solid-state β-grain growth by the high temperature thermal cycles associated with layer-by-layer manufacturing can be suppressed by the pinning effect of TiC heterogeneous nucleation site particles. In this study, the pinning effect of heterogeneous nucleation site particles on microstructure of Ti at elevated temperatures is studied. For this purpose, Ti-0.3vol%TiC samples fabricated by spark plasma sintering (SPS) are used as the model materials, and microstructure and hardness of the samples heat treated at elevated temperatures are studied.

Review, Role of L12 Modified (Al1−xMex)3Ti Intermetallic Compounds on Heterogeneous Nucleation of Alpha Aluminum Grains

Al3Ti intermetallic compound with the tetragonal D022 structure undergoes a phase transformation to the high-symmetry L12 cubic structure by addition of third elements, Me. The lattice constants of some L12 modified (Al1−xMex)3Ti intermetallic compounds are closed to that of alpha aluminum. Therefore, it is expected that the addition of L12 modified (Al1−xMex)3Ti intermetallic compound particles show good grain refining performance of cast aluminum. In this paper, our recent results on novel refines containing heterogeneous nucleation site particles of L12 modified (Al1−xMex)3Ti intermetallic compounds have been reviewed.

Complex Precipitates of TiN-MCx in GCr15 Bearing Steel

Nitride and carbide are the second phases which play an important role in the performance of bearing steel, and their precipitation behavior is complicated. In this study, TiN-MCxprecipitations in GCr15 bearing steels were obtained by non-aqueous electrolysis, and their precipitation mechanisms were studied. TiN is the effective heterogeneous nucleation site for Fe7C3 and Fe3C; therefore, MCxcan precipitate on the surface of TiN easily. The chemistry component of MCx consists of M3C and M7C3 (M = Fe, Cr, Mn) and Cr3C2. TiN-MCx with high TiN volume fraction, TiN forms in early stage of solidification, and MCx precipitates on TiN surface after TiN engulfed by the solidification advancing front. TiN-MCx with low TiN volume fraction, TiN and MCx form in late stage of solidification, TiN can not grow sufficiently and is covered by numerous precipitated MCxparticles.

Complex Precipitates of TiN-MCx in GCr15 Bearing Steel

Nitride and carbide are the second phases which play an important role in the performance of bearing steel, and their precipitation behavior is complicated. In this study, TiN-MCx precipitations in GCr15 bearing steels were obtained by non-aqueous electrolysis, and their precipitation mechanisms were studied. TiN is the effective heterogeneous nucleation site for Fe7C3 and Fe3C, therefore, MCx can precipitate on the surface of TiN easily, its chemistry component consists of M3C and M7C3 (M = Fe, Cr, Mn) and Cr3C2. TiN-MCx with high TiN volume fraction, TiN forms in early stage of solidification, and MCx precipitates on TiN surface after TiN engulfed by the solidification advancing front. TiN-MCx with low TiN volume fraction, TiN and MCx form in late stage of solidification, TiN can not grow sufficiently and is covered by a large number of precipitated MCx particles.

Effect of Manganese Sulphide Size on the Precipitation of Tin Heterogeneous Nucleation in as-Cast Steel

Tramp elements in steels such as tin have been thought harmful because of the hot brittleness at grain boundaries and will be enriched in new steels because of difficulty of removal. It has been an important and difficult matter for metallurgist to use these elements. In the present paper, the as-cast steel containing high concentration of tin is prepared in laboratory and tin precipitates at the manganese sulphide inclusions have been found. A theoretical model is established to calculate the size of manganese sulphide inclusions acted as the heterogeneous nucleation site of tin precipitation. The results show that the inclusions with the smaller contact angle between tin precipitate is more advantageous to be the nucleus of tin heterogeneous nucleation. In this experiment, the manganese sulphide inclusions whose size is 2~4 μm in diameter can act as the nuclei of the nucleation of tin precipitation.

Precipitation Behavior of Cd in Al-5wt.%Cu Based Alloy during Solidification

The precipitation behavior of Cd in an Al-5wt.%Cu based alloy during solidification were investigated, using scanning electron microscopy (SEM) and transmission electron microscope (TEM) observations. It has been found that a novel phase (Al4Cu) is observed except α-Al, θ-Al2Cu, T-Al12CuMn2 phases of Al-5wt.%Cu based alloy during solidification. This phase, with chemical element similar to Al2Cu, was present as closed hexagonal structure, which distributed dispersedly at the edge of grain boundary and adjacent to Al2Cu phase. Moreover, it has the same crystal structure with Cd and satisfies the lattice matching principle, which makes it suitable for the heterogeneous nucleation site for precipitation of Cd.