Pretreatment of agricultural residues by supercritical CO_2 at 50–80 °C to enhance enzymatic hydrolysis

Various agricultural crop residues including corn stover,corn cob,and sorghum stalk with a moisture content of 75 wt%were subjected to a long pretreatment(12–60 h)with supercritical CO_2(scCO_2),at low temperature(50–80°C)and a pressure of 17.5–25.0 MPa.The sugar yields from the enzymatic hydrolysis(EH)of the pretreated samples were as much as three-to fourfold greater than those afforded by the raw materials.However,when pretreatment was conducted within a short time(e.g.0.5 h),as previously reported in the literature,only a slight increase in the EH sugar yields was observed.The proposed sc CO_2pretreatment mechanism demonstrated the role of moisture in the system.Wetting,softening,and swelling were observed to mainly affect the lignocellulose when a suitable amount of water was added.Finally,the samples were analysed by X-ray diffraction and scanning electron microscopy,before and after pretreatment,to investigate the changes in the microscopic structure of the biomass.

Hierarchical Polyimide Nonwoven Fabric with Ultralow-Reflectivity Electromagnetic Interference Shielding and High-Temperature Resistant Infrared Stealth Performance

Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,a hierarchical polyimide(PI)nonwoven fabric is fabricated by alkali treatment,in-situ growth of magnetic particles and"self-activated"electroless Ag plating process.Especially,the hierarchical impedance matching can be constructed by systematically assembling Fe_(3)O_(4)/Ag-loaded PI nonwoven fabric(PFA)and pure Ag-coated PI nonwoven fabric(PA),endowing it with an ultralowreflectivity EMI shielding performance.In addition,thermal insulation of fluffy three-dimensional(3D)space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance.More importantly,the strong bonding interaction between Fe_(3)O_(4),Ag,and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance.Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy,and inhibit external infrared detection.

Ultrathin polyimide-based composites with efficient low-reflectivity electromagnetic shielding and infrared stealth performance

Researching and manufacturing materials that possess both electromagnetic interference(EMI)shielding and infrared stealth capabilities is of great significance.Herein,an ultrathin polyimide-based nonwoven fabric with low-reflection EMI shielding/infrared stealth performance is successfully fabricated by in-situ loading of Fe_(3)O_(4)/Ag nanoparticles on the surface of polyimide(PI)fiber(PFA),and followed by bonding with a commercial Cu/Ni mesh.The synergistic assembly of PFA and Cu/Ni promotes the rational construction of hierarchical impedance matching,inducing electromagnetic waves(EMW)to enter the composite and be dissipated as much as possible.Meanwhile,the existence of Cu/Ni mesh on back of PFA facilitates the formation of electromagnetic resonance and destructive interference of EMW reflected from composite,leading to a lowerreflectivity(0.26)EMI shielding performance of 58 dB within 24–40 GHz at a thinner thickness(430μm).More importantly,the fluffy PFA nonwoven fabric and metal Cu/Ni mesh endow composite with good thermal insulation and low infrared emissivity,resulting in excellent infrared stealth performance in various environments.As a result,such excellent compatibility makes it possible to become a promising defense material to be applied in military tent for preventing electromagnetic and infrared radiation.

3D Printed Polyimide/Silica Composite Aerogels for Customizable Thermal Insulation from-50℃ to 1300℃

Aerogels are widely used as thermal insulation materials because of their high porosity and low bulk density.However,the insulation performance of aerogels is limited to a narrow temperature range.Besides,the preparation of aerogel materials with precisely controlled and complex architectures is still challenging.Here,we report 3D printed polyimide/silica aerogel particle(PI/SAP)composite aerogels for thermal insulation in a wide range of temperature with customized applications.The printability and shape fidelity of 3D printed composite aerogels is improved by adding hydrophilic SAP as a rheology modifier.The resulting PI/SAP composite aerogel exhibits excellent flame-retardant properties and thermal insulation from-50℃ to 1300℃.Moreover,the PI/SAP composite aerogel with customized shape can be applied for battery insulation at subzero temperatures,promising to be used as customizable and stable insulating materials in a variety of complex and extreme applications.