Water-resistant organic thermoelectric generator with >10μW output

Flexible p–n thermoelectric generator(TEG)technology has rapidly advanced with power enhancement and size reduction.To achieve a stable power supply and highly efficient energy conversion,absolute chemical stability of n-type materials is essential to ensuring large temperature differences between device terminals and ambient stability.With the aim of improving the long-term stability of the n-type operation of carbon nanotubes(CNTs)in air and water,this study uses cationic surfactants,such as octylene-1,8-bis(dimethyldodecylammonium bromide)(12-8-12),a gemini surfactant,to stabilize the nanotubes in a coating,which retains the n-doped state for more than 28 days after exposure to air and water in experiments.TEGs with 10 p-n units of 12-8-12/CNT(n-type)and sodium dodecylbenzene sulfonate/CNT(p-type)layers are manufactured,and their water stability is evaluated.The initial maximum output of 16.1μW(75 K temperature difference)is retained after water immersion for 40 days without using a sealant to prevent TEG module degradation.The excellent stability of these CNT-based TEGs makes them suitable for underwater applications,such as battery-free health monitoring and information gathering systems,and facilitates the development of soft electronics.

Discrimination conditions and process of water-resistant key strata

Water-preservation mining is one of the most important parts of the ‘Green Mining' technology system,which can realize the effective regulation of groundwater resources by controlling strata movement,changing passive prevention and governance of water disasters to active conservation and utilization of groundwater resources and thus obtaining coal and water simultaneously in mining.The concept of water-resistant key strata further enriches the content of the key stratum theory and provides a theoretical basis for water-preservation mining.In order to realize the idea of water-resistant key strata as a guideline in the design of water-preservation mining and engineering applications,the conditions for discrimination in the process of water-resistant key strata,we have presented a mechanical model,as well as its corresponding computer program,based on a large number of theoretical analyses and field measurements,as well as on a comprehensive consideration of the position,structural stability and seepage stability of key strata.Practical engineering applications indicate that this discrimination method and its corresponding computer program on water-resistant key strata are accurate and reliable and can satisfy the actual design needs of water-preservation mining and thus have instructional importance for water-preservation mining in mining areas lacking water.

Relationship between water inrush from coal seam floors and main roof weighting

A water-resistant key strata model of a goaf floor prior to main roof weighting was developed to explore the relationship between water inrush from the floor and main roof weighting. The stress distribution,broken characteristics, and the risk area for water inrush of the water-resistant key strata were analysed using elastic thin plate theory. The formula of the maximum water pressure tolerated by the waterresistant key strata was deduced. The effects of the caved load of the goaf, the goaf size prior to main roof weighting, the advancing distance of the workface or weighting step, and the thickness of the waterresistant key strata on the breaking and instability of the water-resistant key strata were analysed.The results indicate that the water inrush from the floor can be predicted and prevented by controlling the initial or periodic weighting step with measures such as artificial forced caving, thus achieving safe mining conditions above confined aquifers. The findings provide an important theoretical basis for determining water inrush from the floor when mining above confined aquifers.

Chemical Modification of Cassava Starch by Transesterification Using Vegetable Oil/Aluminum Chloride

Chemical modification of cassava starch by transesterification of a vegetable oil(palm kernel oil)using aluminum chloride as a Lewis acid catalyst was achieved under relatively mild conditions(temperature 60–110°C;atmospheric pressure).The reaction was carried out without any additional solvent.The modified starch was characterized by degree of substitution(DS),FTIR,X-ray diffraction and thermal analysis.DS of 0.09 to 0.53 were obtained.The cassava starch presented an X-ray diffraction pattern of a type A starch.X-ray analyses showed that the reaction did not significantly affect the crystallinity of starch.The modified starch films(MStF)adsorbed less water than the reference native starch film(NStF)at all the relative humidities investigated.The MStF were also less soluble in water.The tensile tests showed an increase of the strength and a decrease of the flexibility of MStF compared to the reference NStF.The results showed that this chemical route could be used to increase the water resistance of starch-based materials.

粉煤灰改性瓷砖背胶性能研究

研究了粉煤灰改性瓷砖背胶在不同龄期、环境条件下的拉伸粘接强度。研究结果表明:粉煤灰的加入可很好地改善瓷砖背胶耐水、冻融和热老化性能;但改性后的瓷砖背胶在浸水及冻融条件下较标准养护条件下的拉伸粘接强度有所下降,热老化条件下的拉伸粘接强度明显提高,且各环境条件下瓷砖背胶的拉伸粘接强度随着龄期的增长而减小。通过SEM(扫描电镜)分析,粉煤灰的加入使得瓷砖背胶固化后絮状生成物明显增多,尤其在热老化条件下界面处形成更为致密的网状结构;但浸水及冻融条件下聚合物膜发生溶胀和冻胀,界面结构较标准养护条件下疏松,导致拉伸粘接强度下降。

STUDIES ON TUNG OIL COATED REGENERATED CELLULOSE FILMS WITH WATERRESISTANCE

Regenerated cellulose films with water-resistance were obtained by an improved method ofpreparing cellulose cuoxam solution from pulps of agricultural wastes (linters, wheat straw, reedand Bamao). Experimental results showed that the mechanical properties of both the dry. and wetfilms were excellent. Data from IR, SEM and tensile strength measurements implied that thesignificant improvement of water-resistance of the films was due to the cohesion between the thinTung oil covers with hydrophobicity and the regenerated cellulose films. The films werecompletely biodegraded after being buried in soil for 100 days. The transmittance of the filmsderived from linter and reed in visible band range were 80-90%.

Natural polypeptides treat pollution complex： Moistureresistant multi-functional protein nanofabrics for sustainable air filtration

Development of ＂green＂ multi-functional air filters with features such as excellent filtration efficiency eco-friendliness, and environmental stability are critically required to address the increasing concerns of polluted air. Natural proteins, such as soy protein and gelatin, are attractive candidates as multi-functional air-filtration materials owing to the rich functional groups; however, these bio-materials are vulnerable to moisture, which limits their broad application in practice. In this work, a hydrophobic protein of zein derived from abundant corn is modified for the first time to produce high-performance nanofilters via electrospinning. The zein nanofabrics are fabricated with the aid of a non-toxic solvent and co-electrospinning agent, poly（ethylene oxide）. The results reveal that the zein-based nanofabrics show high efficiency for the simultaneous removal of particulate matters of different sizes ranging from 0.1 to 10 btm （〉 99.5%） and certain gaseous toxic chemicals （〉 70%）. In addition, the zein nanofabrics show excellent moisture-resistance and good adhesion to the cellulose paper towel used as the air-filter substrate. This study demonstrates that nanofabrics based on hydrophobic natural proteins such as zein are promising materials for developing multi-functional ＂green＂ air filters.

Model test of the mechanism underpinning water-and-mud inrush disasters during tunnel excavation in sandstone and slate interbedded Presinian strata

Water-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata.Disaster prediction and prevention rely in part on realistic modeling and observation of the disaster process,as well as the identification and examination of the underlying mechanisms.Based on the geological conditions and the historical records of the Xinping Tunnel on the China–Laos Railway,an engineering geological model of the water-and-mud inrush was established.A physical model test that accurately reproduced water-and-mud inrush during tunnel excavation in sandstone and slate interbedded strata was also carried out.Then,testing was conducted that examined the stress and strain,seepage pressure,and high-leakage flow of the surrounding rock.The results indicated that the water-and-mud inrush proceeded through three stages:seepage stage,high-leakage flow stage,and attenuation stage.In essence,the disaster was a catastrophic process,during which the water-resistant stratum was reduced to a critical safety thickness,a water-inrush channel formed,and the water-resistant stratum gradually failed under the influence of excavation unloading and in situ stress–seepage coupling.Parameters such as the stress and strain,seepage pressure,and flow of the surrounding rock had evident stage-related features during water-and-mud inrush,and their variation indicated the formation,development,and evolution of the disaster.As the tunnel face advanced,the trend of the stress–strain curve of the surrounding rock shifted from sluggish to rapid in its speed of increase.The characteristics of strain energy density revealed the erosion and weakening effect of groundwater on the surrounding rock.The seepage pressure and the thickness of the water-resistant stratum had a positive linear relationship,and the flow and thickness a negative linear relationship.There was a pivotal point at which the seepage pressure changed from high to low and the flow shifted from low to high.The thickness of the water-resistant stratum corresponding to the pivotal point was deemed the critical safety thickness.

Exploration of sea anemone-inspired high-performance biomaterials with enhanced antioxidant activity

Antioxidant biomaterials have attracted much attention in various biomedical fields because of their effective inhibition and elimination of reactive oxygen species(ROS)in pathological tissues.However,the difficulty in ensuring biocompatibility,biodegradability and bioavailability of antioxidant materials has limited their further development.Novel bioavailable antioxidant materials that are derived from natural resources are urgently needed.Here,an integrated multi-omics method was applied to fabricate antioxidant biomaterials.A key cysteine-rich thrombospondin-1 type Ⅰ repeat-like(TSRL)protein was efficiently discovered from among 1262 adhesive components and then used to create a recombinant protein with a yield of 500 mg L^(-1).The biocompatible TSRL protein was able to self-assemble into either a water-resistant coating through Ca^(2+)-mediated coordination or redox-responsive hydrogels with tunable physical properties.The TSRL-based hydrogels showed stronger 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical scavenging rates than glutathione(GSH)and ascorbic acid(Aa)and protected cells against external oxidative stress significantly more effectively.When topically applied to mice skin,TSRL alleviated epidermal hyperplasia and suppressed the degradation of collagen and elastic fibers caused by ultraviolet radiation B(UVB)irradiation,confirming that it enhanced antioxidant activity in vivo.This is the first study to successfully characterize natural antioxidant biomaterials created from marine invertebrate adhesives,and the findings indicate the excellent prospects of these biomaterials for great applications in tissue regeneration and cosmeceuticals.

In-situ growth of polypyrrole on aramid nanofibers for electromagnetic interference shielding films with high stability

Flexible electromagnetic interference(EMI)shielding films with high stability have shown promising prospect in harsh working conditions such as military,communication,and special protection fields.Herein,flexible aramid nanofibers@polypyrrole(ANF@PPy)films with high stability were easily achieved by the in-situ growth of PPy on the surface of ANF and the subsequent pressured-filtration film-forming process.When the amount of pyrrole(Py)monomer is 40μL,the ANF@PPy(AP40)film exhibited excellent EMI shielding performance with shielding effectiveness(SE)of 41.69 dB,tensile strength of 96.01 MPa,and fracture strain of 21.95%at the thickness of 75.76μm.Particularly,the anticipated EMI shielding performance can be maintained even after being heated at 200℃in air,soaked in 3.5%NaCl solution,repeated folding for one million times,or burned directly,indicating superior environmental durability in harsh conditions.Therefore,it is believed that the ANF@PPy films with high stability offer a facile solution for practical protection for high-performance EMI shielding applications.

Acid-catalyzed crosslinking of cellulose nanofibers with glutaraldehyde to improve the water resistance of nanopaper

In this study,cellulose nanofibers(CNFs)were crossed-linked with glutaraldehyde(GA)under acid condition for tailoring the mechanical properties and water-resistance of nanopaper or films.The impact of carboxyl content of CNFs,GA concentration,temperature,pH,and reaction time on the crosslinking was investigated,and the process conditions for the crosslinking were optimized.FT-IR analyses showed that CNFs/GA cross-linked nanopaper was successfully fabricated by acetalization between the-OH groups of CNFs and the-CHO groups of GA,resulting in the formation of a dense,three-dimensional network.The elastic modulus of CNFs/GA cross-linked film was 7.66GPa,62.98%higher than that of CNFs film.The water-resistance of the cross-linked CNFs/GA films was improved.The crossed-linked CNFs/GA films was still intact after 24 h after being immersed in water,while the CNFs films almost dissolved completely after 20 min of soaking in water.This method provides a facile route to enhance the elastic modulus and water-resistance of CNFs for potential applications including bullet-proof glass interlayer,flexible electronic device,and new packing materials.