Research on preparation and related properties of macro-micro porous mullite ceramic skeletons via twice pore-forming technology.

A lot of solid waste coal gangue is produced every year in the process of coal mining and coal washing, which poses a great threat to human health. How to deal with coal gangue properly is still a serious problem. In this study the macro-micro composite porous mullite ceramic skeletons were successfully prepared using solid waste coal gangue and α-Al2O3 as main raw materials via twice pore-forming technology. The main phase composition of the porous ceramic skeletons was mullite tested by X-ray Diffractometer (XRD). The morphology and microstructure of the porous ceramic skeletons were analyzed by Scanning Electron Microscope (SEM). The results show that the microstructure of porous ceramic skeletons was mainly composed of mullite whiskers. With the increase of sintering temperature from 1200 °C to 1350 °C, the maximum length of mullite whiskers grew up from 2.68 µm to 8.10 µm and their average length grew up from 0.78 µm to 2.98 µm. The maximum compressive strength of the porous ceramic skeletons with 30 PPI and 45 PPI were 1.25 MPa and 1.54 MPa tested by Universal Testing Machine (UTM) at the sintering temperature of 1250 °C, respectively. The linear shrinkage, bulk density and pore stem density of the porous ceramic skeletons became larger with the rising of sintering temperatures from 1150 °C to 1350 °C. However, the corresponding performance values of 45 PPI porous ceramic skeletons were greater than that of 30 PPI at the same sintering temperature. The prepared porous ceramic skeletons will be used in ceramic-metal wear-resistant composites for the later research and the study provides a new idea for coal gangue on the comprehensive utilization with high added value and brings both good environmental and economic benefits.

Physical simulation of the influence of the original rock strength on the compaction characteristics of caving rock in longwall goaf.

The compaction characteristics of broken rock in a caving zone have a significant impact on the movement law of overburden and the prediction of surface subsidence. The mechanical properties of the broken rock were clearly affected by the original rock strength of the roof. Based on the similarity theory, the 'quartz sand-gypsum-lime-water' mixed material was used to make similar samples of original rocks with different strengths, and the compaction mechanical behaviour of broken loose rock masses with different original rock strengths was studied. The results show that (i) the greater the original rock strength of broken rock, the shorter the initial compaction stage, the earlier the transition and stable compaction stages and the lower the degree of compaction; (ii) the initial deformation modulus and ultimate axial strain had a linear relationship with the original strength of the broken rock; and (iii) under different axial pressures, the deformation modulus increased with the increasing original rock strength of the broken rock. The tangent modulus and axial stress change approximately linearly, the secant modulus and stress change linearly, and the tangent modulus and secant modulus exhibit an exponential/hyperbolic relationship with the strain. The research results have high engineering application value for using numerical method to predict the mechanical behaviour of roof rock mass with different strength in coal mining and analysing the surface subsidence.

Overcoming Perovskite Corrosion and De-Doping Through Chemical Binding of Halogen Bonds Toward Efficient and Stable Perovskite Solar Cells.

4-tert-butylpyridine (TBP) is an indispensable additive for the hole transport layer in highly efficient perovskite solar cells (PSCs), while it can induce corrosion decomposition of perovskites and de-doping effect of spiro-OMeTAD, which present huge challenge for the stability of PSCs. Herein, halogen bonds provided by 1,4-diiodotetrafluorobenzene (1,4-DITFB) are employed to bond with TBP, simultaneously preventing perovskite decomposition and eliminating de-doping effect of oxidized spiro-OMeTAD. Various characterizations have proved strong chemical interaction forms between 1,4-DITFB and TBP. With the incorporation of halogen bonds, perovskite film can maintain initial morphology, crystal structure, and light absorbance; meanwhile, the spiro-OMeTAD film shows a relatively stable conductivity with good charge transport property. Accordingly, the device with TBP complex exhibits significantly enhanced stability in N2 atmosphere or humidity environment. Furthermore, a champion power conversion efficiency of 23.03% is obtained since perovskite is no longer damaged by TBP during device preparation. This strategy overcomes the shortcomings of TBP in n-i-p PSCs community and enhances the application potential of spiro-OMeTAD in fabricating efficient and stable PSCs.

Low-cost and easily prepared interface layer towards efficient and negligible hysteresis perovskite solar cells.

Matched energy level alignment and minimal non-radiative recombination at the buried perovskite/charge transport material interface are essential for efficient electron transfer and highly-efficient perovskite solar cells (PSCs). Herein, we develop a facile and feasible method by inserting Cesium(I) Bis(trifluoromethanesulfonyl)imide (CsTFSI) interlayer to fabricate high performance PSCs with negligible hysteresis. With CsTFSI modification, tin oxide displays less trap density, improved electrical conductivity and better energy level alignment with perovskite, leading to a considerable increase in power conversion efficiency (PCE). Consequently, the champion target device presents a PCE of 22.05%, much higher than that of the control device (19.93%). Our work provides an effective and simple strategy for the modification of perovskite buried interface to obtain highly efficient PSCs.

Effect of Acetylated SEBS/PP for Potential HVDC Cable Insulation.

Blending thermoplastic elastomers into polypropylene (PP) can make it have great potential for high-voltage direct current (HVDC) cable insulation by improving its toughness. However, when a large amount of thermoplastic elastomer is blended, the electrical strength of PP will be decreased consequently, which cannot meet the electrical requirements of HVDC cables. To solve this problem, in this paper, the inherent structure of thermoplastic elastomer SEBS was used to construct acetophenone structural units on its benzene ring through Friedel-Crafts acylation, making it a voltage stabilizer that can enhance the electrical strength of the polymer. The DC electrical insulation properties and mechanical properties of acetylated SEBS (Ac-SEBS)/PP were investigated in this paper. The results showed that by doping 30% Ac-SEBS into PP, the acetophenone structural unit on Ac-SEBS remarkably increased the DC breakdown field strength of SEBS/PP by absorbing high-energy electrons. When the degree of acetylation reached 4.6%, the DC breakdown field strength of Ac-SEBS/ PP increased by 22.4% and was a little higher than that of PP. Ac-SEBS, with high electron affinity, is also able to reduce carrier mobility through electron capture, resulting in lower conductivity currents in SEBS/PP and suppressing space charge accumulation to a certain extent, which enhances the insulation properties. Besides, the highly flexible Ac-SEBS can maintain the toughening effect of SEBS, resulting in a remarkable increase in the tensile strength and elongation at the break of PP. Therefore, Ac-SEBS/PP blends possess excellent insulation properties and mechanical properties simultaneously, which are promising as insulation materials for HVDC cables.

Recent Progress of Inverted Perovskite Solar Cells with a Modified PEDOT:PSS Hole Transport Layer.

Organic-inorganic hybrid perovskite solar cells (PSCs) has achieved the power conversion efficiency (PCE) of 25.2% in the last 10 years, and the PCE of inverted PSCs has reached >22%. The rapid enhancement has partly benefited from the employment of suitable hole transport layers. Especially, poly(3,4-ethenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most widely used polymer hole transport materials in inverted PSCs, because of its high optical transparency in the visible region and low-temperature processing condition. However, the PCE and stability of PSCs based on pristine PEDOT:PSS are far from satisfactory, which are ascribed to low fitness between PEDOT:PSS and perovskite materials, in terms of work function, conductivity, film growth, and hydrophobicity. This paper summaries recent progress regarding to modifying/remedy the drawbacks of PEDOT:PSS to improve the PCE and stability. The systematically understanding of the mechanism of modified PEDOT:PSS and various characteristic methods are summarized here. This Review has the potential to guide the development of PSCs based on commercial PEDOT:PSS.

Overcoming intrinsic defects of the hole transport layer with optimized carbon nanorods for perovskite solar cells.

To overcome the intrinsic chemical-reduction-activity of highly p-doped PEDOT:PSS and improve the open-circuit voltage (Voc) of planar inverted perovskite solar cells, a kind of oxidized carbon nanorods (OCNRs) is developed by a ball-milling/chemical-oxidation method and incorporated into PEDOT:PSS hole transport layer (HTL). The incorporation of OCNRs can increase the work function of the PEDOT:PSS layer, which avoids the energy-level mismatch between the PEDOT:PSS HTL and the HOMO level of the CH3NH3PbI3 perovskite layer, leading to a relatively high Voc of 1.01 V (vs. 0.92 V for the PEDOT:PSS device). Moreover, the introduction of OCNRs into the PEDOT:PSS HTL increases the grain size and uniformity of the perovskite layer, accompanied by the improved charge transport ability. As a result, the fill factor of perovskite solar cells is increased from 75.4% to 81.7%, and the best power conversion efficiency of 19.02% is achieved.

Developing 1D Sb-Embedded Carbon Nanorods to Improve Efficiency and Stability of Inverted Planar Perovskite Solar Cells.

To overcome the zigzag pathway transport of the electron diffusion process and eliminate the surface trap states of phenyl-C61-butyric acid methyl ester (PCBM) nanofilms in inverted perovskite solar cells, novel 1D N-type doped carbon nanorods (CNRs) are developed by a stibonium (Sb) auxiliary ball milling method and introduced into the PCBM film to prepare the PCBM:Sb-CNRs hybrid transport layer. In this way, the N-type doped Sb-CNRs can extend the built-in electric field between CH3 NH3 PbI3 and PCBM to facilitate the separation of electron/hole pairs. The discontinuous band with the built-in potential in the PCBM/Sb-CNRs heterojunction can boost interfacial charge redistribution and promote electrons diffusion from PCBM to electrode through 1D Sb-CNRs network. As a result, the high device efficiency of 19.26% with enhanced air stability and little hysteresis are achieved. This work demonstrates a simple strategy to improve the efficiency and stability of perovskite photovoltaic devices using low-cost carbon nanomaterials.

[Morphologic changes in the life cycle of Cytophaga hutchinsonii].

OBJECTIVE: To study the morphological changes of Cytophaga hutchinsonii cell during its life circle. METHODS: Cytophaga hutchinsonii cell was observed under light microscope, fluorescence microscope and scanning electron microscope. The nucleoids in the cell were stained with fluorescent dye Hoechst33342 and examined by fluorescence microscopy. RESULTS: We discovered that under starvation conditions, the long, flexible rod cell of Cytophaga hutchinsonii would bend and turn into circular cell. The circular cell failed to produce carboxymethyl cellulase. Some of the circular cells might further wind around and turn into tiny spherical cells. The tiny spherical cell similar to the microcyst of sporocytophaga could germ into long flexible rods again under certain circumstances. When growing cultures to logarithmic phase of cell growth, Cytophaga hutchinsonii cell with three nucleoids in it was occasionally observed, which indicated that the two strands of DNA might act differently in the initiation of DNA replication. CONCLUSION: This is the first detailed description of the formation process of circular cell and tiny spherical cell in the life circle of Cytophaga hutchinsonii. The result will help to further reveal the relation between morphologic change and cellulose degradation ability of the strain.