Experimental study on thermal and mechanical properties of tailings-based cemented paste backfill with CaCl_(2)·6H_(2)O/expanded vermiculite shape stabilized phase change materials

CaCl_(2)·6H_(2)O/expanded vermiculite shape stabilized phase change materials(CEV)was prepared by atmospheric impregnation method.Using gold mine tailings as aggregate of cemented paste backfill(CPB)material,the CPB with CEV added was prepared,and the specific heat capacity,thermal conductivity,and uniaxial compressive strength(UCS)of CPB with different cement-tailing ratios and CEV addition ratios were tested,the influence of the above variables on the thermal and mechanical properties of CPB was analyzed.The results show that the maximum encapsulation capacity of expanded vermiculite for CaCl_(2)·6H_(2)O is about 60%,and the melting and solidification enthalpies of CEV can reach 98.87 J/g and 97.56 J/g,respectively.For the CPB without CEV,the specific heat capacity,thermal conductivity,and UCS decrease with the decrease of cement-tailing ratio.For the CPB with CEV added,with the increase of CEV addition ratio,the specific heat capacity increases significantly,and the sensible heat storage capacity and latent heat storage capacity can be increased by at least 10.74%and 218.97%respectively after adding 12%CEV.However,the addition of CEV leads to the increase of pores,and the thermal conductivity and UCS both decrease with the increase of CEV addition.When cement-tailing ratio is 1:8 and 6%,9%,and 12%of CEV are added,the 28-days UCS of CPB is less than 1 MPa.Considering the heat storage capacity and cost price of backfill,the recommended proportion scheme of CPB material presents cement-tailing ratio of 1:6 and 12%CEV,and the most recommended heat storage/release temperature cycle range of CPB with added CEV is from 20 to 40℃.This work can provide theoretical basis for the utilization of heat storage backfill in green mines.

Stabilized multifunctional phase change materials based on carbonized Cu-coated melamine foam/reduced graphene oxide framework for multiple energy conversion and storage

The leakage of organic phase change materials(OPCMs)at temperatures above their melting point severely limits their large-scale application.The introduction of porous supports has been identified as an efficient leakageproofing method.In this study,a novel carbonized Cu-coated melamine foam(MF)/reduced graphene oxide(rGO)framework(MF/rGO/Cu-C)is constructed as a support for fabricating stabilized multifunctional OPCMs.MF serves as the supporting material,while rGO and Cu act as functional reinforcements.As a thermal energy storage material,polyethylene glycol(PEG)is encapsulated into MF/rGO/Cu-C through a vacuum-assisted impregnation method to obtain PEG@MF/rGO/Cu-C composite with excellent comprehensive performance.PEG@MF/rGO/Cu-C exhibits high phase change enthalpies of 148.3 J g^(-1)(melting)and 143.9 J g^(-1)(crystallization),corresponding to a high energy storage capability of 92.7%.Simultaneously,MF/rGO/Cu-C endues the composite with an enhanced thermal conductivity of 0.4621Wm^(-1) K^(-1),which increases by 463%compared to that of PEG@MF.Furthermore,PEG@MF/rGO/Cu-C displays great light-to-thermal and electric-to-thermal conversion capabilities,thermal cycle stability,light-tothermal cycle stability,and shape stability,showing promising application prospects in different aspects.

A field experimental study of lignin sand stabilizing material(LSSM) extracted from spent-liquor of straw pulping paper mills

A new technique was introduced for sand stabilization and re-vegetation by use of lignin sand stabilizing material(LSSM). LSSM is a reconstructed organic compound with lignin as the most dominant component from the extracts of black-liquor issued by straw pulp paper mills. Unlike the polyvinyl acetate or foamed asphalt commonly used for dune stabilization, the new material is plant-friendly and can be used with virescence actions simultaneously. The field experimental study was conducted since 2001 in China's Northwest Ningxia Hui Autonomous Region and has been proved that LSSM is effective in stabilizing the fugitive dunes, making the arenaceous plants survive and the bare dune vegetative. The advisable solution concentration is 2% and the optimal field spraying quantity is 2 5 L/m^2 The soil nutrients of the stabilized and greened dune, such as organic matter, available phosphorous and total nitrogen are all increased compared with the control treatment, which is certainly helpful to the growth of arenaceous plants. The technique is worthwhile to be popularized because it is provided not only a new method for desertification control but also an outlet for cleaning contaminants issued from the straw paper mills.

Development of a Soil Stabilizer for Road Subgrade Based on Original Phosphogypsum

The research used industrial by-products original phosphogypsum(PG)as the main raw material,slag(SG)and Portland cement(PC)as auxiliary materials,and the optimal additive amount was determined according to the compressive strength value of the sample.Comprehensively evaluate the water resistance and volume stability of the samples,and determine the best formula for new roadbed stabilized materials.The results showed that when the weight ratio of PG,slag and cement was OPG:SG:PC=6:3:1,and mixed with 5%micro silica fume(MSF)and 3‰hydroxypropyl methyl cellulose(HPMC),the sample’s comprehensive performance was the best,specifically,the sample’s compressive strength in 60 days reached 28.8 MPa,the softening coefficient reached 0.9,and the expansion rate was stable at about−0.2%.In addition,the mechanism of action of enhancers MSF and HPMC was analyzed according to use Vicat device,X-ray diffractometer and scanning electron microscope.The best formula SP3GH3 has the best curing effect on soil.The 28-day unconfined compressive strength(UCS)of the sample reached 2.4 MPa,the expansion rate was less than 0.09%,and the water stability coefficient was above 0.79,which was higher than that of the samples cured by traditional cement and lime during the same period.

A Mini Review: Can Graphene Be a Novel Material for Perovskite Solar Cell Applications?

Perovskite solar cells(PSCs) have raised research interest in scientific community because their power conversion efficiency is comparable to that of traditional commercial solar cells(i.e., amorphous Si, GaAs,and CdTe). Apart from that, PSCs are lightweight, are flexible, and have low production costs. Recently, graphene has been used as a novel material for PSC applications due to its excellent optical, electrical, and mechanical properties. The hydrophobic nature of graphene surface can provide protection against air moisture from the surrounding medium, which can improve the lifetime of devices. Herein, we review recent developments in the use of graphene for PSC applications as a conductive electrode,carrier transporting material, and stabilizer material. By exploring the application of graphene in PSCs, a new class of strategies can be developed to improve the device performance and stability before it can be commercialized in the photovoltaic market in the near future.

INSTABILITY AND DISPERSIVITY OF WAVE PROPAGATION ININELASTIC SATURATED/UNSATURATED POROUS MEDIA

A model based on the Biot theory for simulating coupled hydro-dynamic behavior in saturated-unsaturated porous media was utilized with integration of the inertial coupling effect between the solid-fluid phases of the media into the model. Stationary instability and dispersivity of wave propagation in the media in one-dimensional problem were analyzed. The effects of the following factors on stationary, instability and dispersivity were discussed. They are the viscous and inertial couplings between the solid and the fluid phases, compressibility of the mixture composed of solid grains and pore fluid, the degree of saturation, visco-plastic (rate dependent inelastic) constitutive behavior of the solid skeleton under high strain rate. results and conclusion obtained by the present work will provide some bases or clues for overcoming the difficulties in numerical modelling of wave propagation in the media subjected to strong and shock loading.

Thermal Cycling Stability of Mg-25Al-15Zn-14Cu PCM

Thermal cycling tests of repeated melting/freezing processes were performed to check the thermal stability of Mg-25Al-15Zn-14 Cu alloy as phase change thermal storage material（PCM）. Latent heat storage capacity and phase transition temperature of the PCMs were determined by differential scanning calorimetry（DSC） technique as a function of repeated thermal cycles such as 0, 100, 200, and 1000. The present work also comprised the investigation of the density and microstructure of Mg-25Al-15Zn-14 Cu alloy before and after thermal cycles by using the hydrostatic method and optical microscopy（OM）, X-ray diffraction（XRD）, and electron probe microanalysis（EPMA）, respectively. The results show that the melting temperature of alloy after 1000 thermal cycles is 415.1 ℃ and the latent heat value is 190.4 J/g. Compared with the original alloy, the phase transition temperature will increase by 1.87% and the value of phase change latent heat will decrease by 7.35%, which are in a suitable range. Therefore, Mg-25Al-15Zn-14 Cu alloy has a good thermal reliability in terms of the change in its thermal properties with respect to thermal cycling for 1000, and can be used for a middle-temperature thermal storage utility.

The Stabilizing Role of Material Structure in Scientific Practice

Knowledge of the environment is essential for the survival of organisms; but those organisms have to have the capacity to stabilize such knowledge. The aim of this article is to analyze the various strategies for stabilizing human knowledge, with a special focus on its material anchors and their interactions with other stabilization means. In particular, I consider how such stabilization is reflected in scientific activity and practice, and what its repercussions are for the models of science that have dominated the philosophical landscape of the 20th century. My starting hypothesis will be that the role of material anchors in stabilizing conceptual blends is analogous to that of technology in grounding scientific knowledge. The framework I adopt with regard to conceptualization is that of Fauconnier and Turner （2002） on conceptual blends. Just as technology intervenes in scientific practice in conjunction with conceptual elements, so do material anchors, which conjoin other non-material strategies of knowledge stabilization. Endowing knowledge with a material basis may be understood firstly as an element （sometimes a key element） for representing knowledge and offering an explanation, and secondly as a way of providing a scientific hypothesis with empirical grounding. It is this second sense that connects with scientific experimentation and the use of instruments and technology.

Durability Properties of Materials and Mixture Composition of Bitumen Stabilized Materials

Bitumen Stabilized Materials (BSMs) are widely recognized as environmentally friendly through significantly reduced energy consumption,reduced emissions and reuse of high percentage of RAP and recycled pavement materials. In order for these materials to be cost effective,their life-cycle performance needs to be proven. Durability of BSMs is a long-term phenomena that requires consideration during mix design. Time is very important variable for performance consideration under field conditions. The factors that influence durability and long-term performance of BSMs include the mineral aggregates,binder and mixture compositions. In this study,the important,but less understood aspects of durability properties of BSMs were investigated. These include wear and tear of mineral aggregates,age-hardening of binder (foamed bitumen and bitumen emulsion) and moisture susceptibility of typical mix composition. The wear and tear was investigated using Durability Mill Index (DMI) test,binder ageing was investigated for short and long-term effect,and moisture susceptibility was investigated by pulsing water pressures using new device i.e. moisture induction simulation test (MIST). The accelerated moisture conditioning simulates field conditions whereafter retained shear properties are evaluated. The results found that durability of mineral aggregates is significantly influences by the type and nature of mineral composition. The ageing of binder occurred in both short and long-term conditions,with short-term effects being dominating the foamed bitumen properties during laboratory production. Moisture susceptibility is significantly influenced by the mix compositions of aggregates blends with and without RAP,with different bitumen binder types (foamed bitumen or bitumen emulsion) and active filler type (cement or lime) and contents. The evaluation and ranking of mixes which are resistant and susceptible to moisture damage was done using retained cohesion (RC) after dry and wet monotonic triaxial testing.

Appending triphenyltriazine to 1,10-phenanthroline: a robust electron-transport material for stable organic light-emitting diodes

There has been an increasing demand for high-performance and cost-effective organic electron-transport materials for organic light-emitting diodes （OLEDs）. In this contribution, we present a simple compound 3-（3-（4,6-diphenyl-l,3,5-triazin-2-yl）phenyl）-1,10-phenanthroline through the facile Pd-catalyzed coupling of a triphenyltriazine boronic ester with 3-hromo-1,10-phenanthroline. It shows a high Tg of 112℃. The ultraviolet photoelectron spectroscopy measurements reveal a deep HOMO level of -6.5 eV. The LUMO level is derived as -3.0 eV, based on the optical bandgap. The low-temperature solid-state phosphorescent spectrum gives a triplet energy of -2.36eV. n-Doping with 8-hydroxyquinolatolithium （Liq, 1：1） leads to considerably improved electron mobility of 5.2 × 10 -6 -5.8 × 10 -5 cm2 v-1 S-1 at E=（2-5） × 10 5Vcm -1, in contrast with the triarylphosphine oxide- phenantroline molecular conjugate we reported previously. It has been shown that through optimizing the device structure and hence suppressing polaron-exciton annihilation, introducing this single Liq-doped electron-transport layer could offer high-efficiency and stable phosphorescent OLEDs.

Improved performance and air stability of perovskite solar cells based on low-cost organic hole-transporting material X60 by incorporating its dicationic salt

The development of an efficient, stable, and low-cost hole-transporting material (HTM) is of great significance for perovskite solar cells (PSCs) from future commercialization point of view. Herein, we specifically synthesize a dicationic salt of X60 termed X60(TFSI)2, and adopt it as an effective and stable "doping" agent to replace the previously used lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) for the low-cost organic HTM X60 in PSCs. The incorporation of this dicationic salt significantly increases the hole conductivity of X60 by two orders of magnitude from 10-6 to 10-4 S cm-1. The dramatic enhancement of the conductivity leads to an impressive power conversion efficiency (PCE) of 19.0% measured at 1 sun illumination (100 mW cm-2, AM 1.5 G), which is comparable to that of the device doped with LiTFSI (19.3%) under an identical condition. More strikingly, by replacing LiTFSI, the PSC devices incorporating X60(TFSI)2 also show an excellent long-term durability under ambient atmosphere for 30 days, mainly due to the hydrophobic nature of the X60(TFSI)2 doped HTM layer,which can effectively prevent the moisture destroying the perovskite layer. The present work paves the way for the development of highly efficient, stable, and low-cost HTM for potential commercialization of PSCs.