Daming Zhuang

Improved Crystallization of Perovskite Films by Optimized Solvent Annealing for High Efficiency Solar Cell

Organic-inorganic halide perovskite-based thin film solar cells show excellent light-to-power conversion efficiency. The high performance for the devices requires the preparation of well-crystallized perovskite absorbers. In this paper, we used the postannealing process to treat the perovskite films under different solvent vapors and observed that the solvent vapors have a strong effect on the film growth. A model regarding the perovskite film growth was proposed as well. Intensive characterizations including scanning electron microscopy, electrochemical impedance spectroscopy, and admittance spectroscopy allowed us to attribute the improved performance to reduced recombination loss and defect density. Solar cell based on the DMSO-treated films delivered a power conversion efficiency of over 13% with negligible photocurrent hysteresis.

Toughening and reinforcing alumina matrix composite with single-wall carbon nanotubes

The authors report an efficient way of incorporating single-wall carbon nanotubes (SWNTs) into alumina matrix with strong interfaces by heterocoagulation. The fracture toughness of SWNTs/Al2O3 composite reaches 6.40±0.3MPam1∕2, which is twice as high as that of unreinforced alumina. The flexure strength of the composite also increases by 20%. The main toughening mechanism is crack bridging of SWNTs, and SWNT pullout takes effect also.

Low-temperature, solution processed metal sulfide as an electron transport layer for efficient planar perovskite solar cells

Organic–inorganic halide perovskites possess excellent chemical, optical, and electronic properties that make them attractive for next-generation solar cells. In this paper, we introduce all-low-temperature processed perovskite solar cells using metal sulfide as an electron transport layer. First, we evaluated the alignment of energy levels at the perovskite/metal sulfide layer interface. The properties of metal sulfide and the perovskite layer, as well as the corresponding device performance, were then investigated. Using a CdS layer as an electron transport layer, we have achieved a maximum power conversion efficiency of 11.2% under reverse scans. The successful use of the CdS layer in perovskite solar cells likely would create new pathways and opportunities for the advancement of device design.

Microstructure of iron sulfide layer as solid lubrication coating produced by low-temperature ion sulfurization

Abstract FeS is an excellent solid lubricant due to its hexagonal structure, low shear strength, and high melting point. A new low-temperature ion sulfurization technology was developed to produce a sulfide layer of varying thickness on AISI 1045 and AISI 52100 steels. It has many advantages compared with the electrolytic process. Metallography, an SEM equipped for energy-dispersive X-ray spectroscopy, and X-ray spectroscopy, and X-ray diffraction were used to examine the microstructure of sulfide layers and their structural depth-profiles. The results showed that the sulfide layer was loose and porous, and no transition layer was found between it and the substrate. The sulfide layer was composed of iron sulfide and substrate phases. The former included mainly FeS and FeS 2 . On the top of the sulfide layer, only FeS 2 appeared. FeS was found to become more abundantly with increasing depth below the surface, whereas FeS 2 was found in greater quantities in thicker sulfide layers.

Microstructure and tribological properties of sulphide coating produced by ion sulphuration

Abstract Based on the principle of ion-nitriding a new ion sulphuration technique was developed. Its basic process and advantages compared with the traditional electrolytic method were described. The sulphuration coating was formed mainly by a chemical conversion, not only by a diffusion process. Its thickness was generally in the range of several to several tenth micrometers. X-ray diffraction, SEM, and EDAX were employed to analyze the microstructure, morphology, and composition of sulphide coating. The results showed that the sulphide coating was mainly composed of FeS with layered hexagonal lattice as well as a certain amount of FeS 2 . So that it showed a pretty good solid lubrication behavior. The tribological properties of ion sulphuration coatings on the 52100 and 1045 steel substrates were tested on SRV and Amseler testing machines. It can be found from the testing results that the sulphide coating can significantly decrease the friction coefficient and increase the wear resistance of materials. The mechanism was discussed in detail based on the microanalyses of sulphide coating as well.

Preparation of diamond films by hot filament chemical vapor deposition and nucleation by carbon nanotubes

Preparation of diamond films by hot filament chemical vapor deposition (HF-CVD) and nucleation of carbon nanotubes on diamond films were investigated. The optimum parameters for preparing diamond film were explored. Diamond films of high quality were deposited on silicon substrates seeded with carbon nanotubes as nucleation precursors. Diamond grains grew essentially perfectly with no congregation occurring during long depositions. The effect of the quality of the carbon nanotubes on the character of the deposited diamond are discussed.

Anti-scuffing properties of ion sulfide layers on three hard steels

Abstract In order to improve the anti-scuffing properties of steels, a new low temperature ion sulfuration technology was utilized to modify the surfaces of high speed steel, die steel and plain carbon steel. Sulfide layers, dominated by FeS phase, were produced on the surfaces of the three steels. The anti-scuffing and tribological properties of the sulfide layers were investigated on a ball-on-disc friction and wear test rig of QP-100 model under oil lubrication. Scanning electron microscope (SEM) equipped with EDX and X-ray diffraction (XRD) were employed to analyze the morphologies of cross-section and scuffing surfaces of sulfide layers, as well as the surface phase structures. Scanning auger microprobe (SAM) and X-ray photoelectron spectroscope (XPS) were used to detect the element variation with depth and the valence states of boundary lubrication films of scuffing surfaces, respectively. The results showed that the anti-scuffing and tribological properties of all sulfurized steels were improved remarkably. The anti-scuffing and tribological properties decreased in the order of high speed steel—die steel—plain carbon steel. The difference in anti-scuffing and tribological properties of different steels was mainly determined by the hardness, microstructure and corrosion resistance of substrate.

Effect of the substrate state on the microstructure and tribological properties of sulphide layer on 1045 steel

Sulphide layers were produced on 1045 steel substrates of five different states: as quenched, quenched and tempered at different temperature, and annealed, respectively, by low temperature ion sulphurization technology. The effect of substrate hardness on the microstructure and tribological properties of sulphide layer was studied by SEM equipped with EDX, XRD and a reciprocating wear tester. Increasing defect density of substrate could probably result in thicker layer, but the surface morphology, composition, and structure of sulphide layer were unchanged greatly. No transition layer was found between the sulphide layer and substrate. The sulphide layer showed an obviously friction-reducing effect. The friction coefficient of sulphide layer was independent of the substrate, but its endurance life could be extended on a harder substrate. The wear-resistance of sulphurized surface was improved because the sulphide layer could effectively protect it from adhesion and strain fatigue. However, the decomposition and regeneration of iron sulphide due to friction heat in the friction process could have a certain corrosive effect on the surface. The wear volume of sulphurized surface was increased on the contrary if the sulphide layer was thicker and its endurance life was longer.

Chemical vapor infiltration tailored hierarchical porous CNTs/C composite spheres fabricated by freeze casting and their adsorption properties

Carbon nanotubes (CNTs) are one of the most promising candidates as adsorbents in many fields due to their unique structural characteristics. In this paper, hierarchical porous CNTs/carbon (CNTs/C) composite spheres were prepared and their strength and adsorption of vitamin B12 (VB12) were investigated. The initial porous CNT spheres were fabricated by freeze casting followed by freeze drying. Afterwards, the primary porous CNT spheres were further reinforced and tailored by chemical vapor infiltration (CVI) and steam activation. Consequently, the composite CNTs/C spheres with hierarchical porous structure and high strength were successfully fabricated. SEM and polarized light microscopy observations showed that, in addition to macro-sized radial through-pores in the spheres, many micro-sized pores were distributed uniformly in the wall of the radial tunnel-like through-pores. Mercury porosimetry and BET tests indicated that the width of the radial lamellar channels was about 5–15 μm, and the average diameter of the mesopores was about 3.8 nm. Adsorption of VB12 for these hierarchical porous CNTs/C spheres could reach 51.48 mg g−1, which is about 3.7 and 3.4 times those of traditional activated carbon beads and macroporous resin beads, respectively.

Field emission behavior of aligned carbon nanofiber arrays

Aligned carbon nanofiber arrays are synthesized on plain silicon surface by thermal decomposition of propylene with Ni film as the catalyst at 600°C. These arrays consist of carbon nanofibers with uniform diameters and heights, standing vertically on the substrate. TEM examinations show that carbon nanofibers have unique layer structure. These arrays also show excellent field emission properties comparable to those of carbon nanotubes during subsequent testing.