Vertically Aligned Silicon Carbide Nanowires/Boron Nitride Cellulose Aerogel Networks Enhanced Thermal Conductivity and Electromagnetic Absorbing of Epoxy Composites

With the innovation of microelectronics technology, the heat dissipation problem inside the device will face a severe test. In this work, cellulose aerogel(CA) with highly enhanced thermal conductivity(TC) in vertical planes was successfully obtained by constructing a vertically aligned silicon carbide nanowires(SiC NWs)/boron nitride(BN) network via the ice template-assisted strategy. The unique network structure of SiC NWs connected to BN ensures that the TC of the composite in the vertical direction reaches 2.21 W m^(-1) K^(-1) at a low hybrid filler loading of 16.69 wt%, which was increased by 890% compared to pure epoxy(EP). In addition, relying on unique porous network structure of CA, EP-based composite also showed higher TC than other comparative samples in the horizontal direction. Meanwhile, the composite exhibits good electrically insulating with a volume electrical resistivity about 2.35 × 10^(11) Ω cm and displays excellent electromagnetic wave absorption performance with a minimum reflection loss of-21.5 dB and a wide effective absorption bandwidth(<-10 dB) from 8.8 to 11.6 GHz. Therefore, this work provides a new strategy for manufacturing polymer-based composites with excellent multifunctional performances in microelectronic packaging applications.

Macroporous Hydrogels Prepared by Ice Templating: Developments and Challenges

Macroporous hydrogels are water-swollen polymer networks with porous structures beyond the mesh size.They provide high specific surface areas and hieratical mass transfer channels which are desired for emerging applications including cell culturing,bio-separation,and drug delivery.A variety of approaches have been developed to fabricate macroporous hydrogels,including gas foaming,porogen templating,phase separation,3D printing,etc.Alternatively,ice templating utilizes the crystallization of water as the porogenation mechanism which doesn't need the leaching of porogens.

Highly efficient semiconductor modules making controllable parallel microchannels for non-compressible hemorrhages

Nature makes the most beautiful solution to involuted problems.Among them,the parallel tubular structures are capable of transporting fluid quickly in plant trunks and leaf stems,which demonstrate an ingenious evolutionary design.This study develops a mini-thermoelectric semiconductor P-N module to create gradient and parallel channeled hydrogels.The modules decrease quickly the temperature of polymer solution from 20◦C to20◦C within 5 min.In addition to the exceptional liquid absorption rate,the foams exhibited shape memory mechanics.Our mini device universally makes the inspired structure in such as chitosan,gelatin,alginate and polyvinyl alcohol.Non-compressible hemorrhages are the primary cause of death in emergency.The rapid liquid absorption leads to fast activation of coagulation,which provides an efficient strategy for hemostasis management.We demonstrated this by using our semiconductor modules on collagen-kaolin parallel channel foams with their high porosity(96.43%)and rapid expansion rate(2934%).They absorb liquid with 37.25 times of the own weight,show 46.5-fold liquid absorption speed and 24-fold of blood compared with random porous foams.These superior properties lead to strong hemostatic performance in vitro and in vivo.

乳液冰冻光交联法连续化制备多孔聚合物材料

冰模板法用水作为成孔剂,已成为一种无污染且有前景的多孔材料制备方法.由水溶液制备的多孔聚合物通常耐水性较差,通过冰冻悬浮液可以制备疏水性多孔材料,但需要额外添加有机溶剂,易造成环境污染.基于此,本文提出了一种乳液冰冻光交联的方法.首先合成无乳化剂的光敏乳液,然后将乳液冰冻并通过光交联的方式固定由冰晶产生的孔结构,再将冰模板融化即可得到多孔聚合物材料.该制孔过程无需冰冻干燥,且光交联效率极高(几分钟内即可完成),有利于连续化生产多孔聚合物.此外,本方法具有较强的普适性和广阔的应用前景,通过不同乳液配方,可获得包括可拉伸的多孔材料、玻璃化转变温度可调的形状记忆多孔材料,以及具有隔热性能的多孔陶瓷等.

Tofukasu-derived biochar with interconnected and hierarchical pores for high efficient removal of Cr (Ⅵ)

Herein,we report the synthesis of interconnected hierarchical pore biochar(HTB)via an ice-templating strategy using bio-waste(tofukasu).The abundance of N-and O-containing functional groups in tofukasu makes it easy to form hydrogen bonds with water molecules and water clusters,resulting in nano-micro structures like ice clusters and snow crystals during freezing process.More importantly,tofukasu will be squeezed by micron-scale snow crystals to form coiled sheet-like structures,and its surface and interior will be affected by needle-like ice nanocrystals from several nanometers to tens of nanometers to form transverse groove needles and mesopores.The ice crystals are then removed by sublimation with tofukasu,leaving the interconnected pore structure intact.Therefore,the ice template synthesis strategy endowed the interconnected hierarchical pore structure of HTB with a large specific surface area(SBET,733 m^(2)⋅g^(−1))and hierarchical porosity(30.30%for mesopores/total pore volume ratio),which is significantly higher than the normal dry treated tofukasu biochar(TB),which had a SBET of 436 m^(2)⋅g^(−1) and contained 1.53%mesopores.In addition,the sheet-like structure with interconnected pores of HTB favors high exposure of active sites(N-and O-containing functional groups),and a fast electron transport rate.As a result,HTB had an excellent adsorption capacity of 159.65 mg⋅g^(−1),which is 4.7 times that of typical block biochar of TB(33.89 mg⋅g^(−1))according to Langmuir model.Electrochemical characterization,FTIR and XPS analysis showed that the mechanism of Cr(Ⅵ)removal by HTB included electrostatic attraction,pore filling,reduction and surface complexation.