Ultrafast Response and Threshold Adjustable Intelligent Thermoelectric Systems for Next‑Generation Self‑Powered Remote IoT Fire Warning

Fire warning is vital to human life,economy and ecology.However,the development of effective warning systems faces great challenges of fast response,adjustable threshold and remote detecting.Here,we propose an intelligent self-powered remote IoT fire warning system,by employing single-walled carbon nanotube/titanium carbide thermoelectric composite films.The flexible films,prepared by a convenient solution mixing,display p-type characteristic with excellent high-temperature stability,flame retardancy and TE(power factor of 239.7±15.8μW m^(-1) K^(-2))performances.The comprehensive morphology and structural analyses shed light on the underlying mechanisms.And the assembled TE devices(TEDs)exhibit fast fire warning with adjustable warning threshold voltages(1–10 mV).Excitingly,an ultrafast fire warning response time of~0.1 s at 1 mV threshold voltage is achieved,rivaling many state-of-the-art systems.Furthermore,TE fire warning systems reveal outstanding stability after 50 repeated cycles and desired durability even undergoing 180 days of air exposure.Finally,a TED-based wireless intelligent fire warning system has been developed by coupling an amplifier,analogto-digital converter and Bluetooth module.By combining TE characteristics,high-temperature stability and flame retardancy with wireless IoT signal transmission,TE-based hybrid system developed here is promising for next-generation self-powered remote IoT fire warning applications.

Temperature‑Arousing Self‑Powered Fire Warning E‑Textile Based on p-n Segment Coaxial Aerogel Fibers for Active Fire Protection in Firefighting Clothing

Firefighting protective clothing is a crucial protective equipment for firefighters to minimize skin burn and ensure safety firefighting operation and rescue mission.A recent increasing concern is to develop self-powered fire warning materials that can be incorporated into the firefighting clothing to achieve active fire protection for firefighters before the protective clothing catches fire on fireground.However,it is still a challenge to facilely design and manufacture thermoelectric(TE)textile(TET)-based fire warning electronics with dynamic surface conformability and breathability.Here,we develop an alternate coaxial wet-spinning strategy to continuously produce alternating p/n-type TE aerogel fibers involving n-type Ti_(3)C_(2)T_(x)MXene and p-type MXene/SWCNT-COOH as core materials,and tough aramid nanofiber as protective shell,which simultaneously ensure the flexibility and high-efficiency TE power generation.With such alternating p/n-type TE fibers,TET-based self-powered fire warning sensors with high mechanical stability and wearability are successfully fabricated through stitching the alternating p-n segment TE fibers into aramid fabric.The results indicate that TET-based fire warning electronics containing 50 p-n pairs produce the open-circuit voltage of 7.5 mV with a power density of 119.79 nW cm-2 at a temperature difference of 300℃.The output voltage signal is then calculated as corresponding surface temperature of firefighting clothing based on a linear relationship between TE voltage and temperature.The fire alarm response time and flame-retardant properties are further displayed.Such self-powered fire warning electronics are true textiles that offer breathability and compatibility with body movement,demonstrating their potential application in firefighting clothing.

Fire Intumescent,High-Temperature Resistant,Mechanically Flexible Graphene Oxide Network for Exceptional Fire Shielding and Ultra-Fast Fire Warning

Smart fire alarm sensor(FAS)materials with mechanically robust,excellent flame retardancy as well as ultra-sensitive temperature-responsive capability are highly attractive platforms for fire safety application.However,most reported FAS materials can hardly provide sensitive,continuous and reliable alarm signal output due to their undesirable temperature-responsive,flame-resistant and mechanical performances.To overcome these hurdles,herein,we utilize the multi-amino molecule,named HCPA,that can serve as triple-roles including cross-linker,fire retardant and reducing agent for decorating graphene oxide(GO)sheets and obtaining the GO/HCPA hybrid networks.Benefiting from the formation of multi-interactions in hybrid network,the optimized GO/HCPA network exhibits significant increment in mechanical strength,e.g.,tensile strength and toughness increase of~2.3and~5.7 times,respectively,compared to the control one.More importantly,based on P and N doping and promoting thermal reduction effect on GO network,the excellent flame retardancy(withstanding~1200℃flame attack),ultra-fast fire alarm response time(~0.6 s)and ultra-long alarming period(>600 s)are obtained,representing the best comprehensive performance of GO-based FAS counterparts.Furthermore,based on GO/HCPA network,the fireproof coating is constructed and applied in polymer foam and exhibited exceptional fire shielding performance.This work provides a new idea for designing and fabricating desirable FAS materials and fireproof coatings.

热电材料与热电池在火灾预警中的应用

火灾预警对于人身安全和资产保护至关重要.热电材料和热电池能够利用火灾前期的热量,将其有效转变为电能,从而实现火灾发生之前的有效预警,是近年来新出现的潜在前沿热点之一.本文首先从电子热电(空穴/电子热扩散)、离子热扩散(Soret效应)和热电池(电极表面氧化还原反应)三个方面介绍了热-电能量转换的机理,然后简要概述了一维纤维及其热电器件、二维膜及其热电器件和三维块体及其热电器件的主要研究进展,之后重点论述了近年来热电材料和热电池在火宅预警应用的具体典型实例,最后对该领域的研究进展进行总结,并提出了一些对未来研究的观点和建议.

Temperature-induced resistance transition behaviors of melamine sponge composites wrapped with different graphene oxide derivatives

Temperature-re s ponsive resistance transition behaviors of the melamine sponges wrapped with different graphene oxide derivatives(i.e.nanoribbon,wide-ribbon and sheet)were investigated.Melamine sponge composites coated by three types of GO derivatives were prepared by a simple dip-coating approach.All these composites show good mechanical flexibility and reliability(almost unchanged compressive stress at 70%strain after 100 cycles),high hydrophobicity(water contact angle>120°),excellent flame resistance(self-extinguishing)and structural stability even after burning,which was used to construct the resistance-based fire alarm/warning sensor.Notably,the different resistance response behaviors of such sensors are strongly dependent on the GO size and network formed on the MF skeleton surface.Typically,at a fixed high temperature of~350℃,the three fire alarm sensors show different response time(to trigger the alarm light)of 6.3,8.4 and 11.1 s for nanoribbon,wide-ribbon and sheet at the same concentration,respectively.The structural observation and chemical analysis demonstrated that the discrepancy of temperature-responsive resistance transition behaviors of various GO derivatives was strongly determined by their different thermal reduction degrees during the high-tempe rature or flame treating process.This work offers a design and development for construction of smart fire alarm device for potential fire prevention and safety applications.

“Several birds with one stone”strategy of pH/thermoresponsive flame-retardant/photothermal bactericidal oil-absorbing material for recovering complex spilled oil

Although many material designs or strategic methods have been proposed for treating oil spills and oily wastewater,the complex oily state,dealing with the harsh operating conditions of oil–water separation(such as the recovery of viscous spilled crude oil,bacteria-containing oily wastewater,and removal of spilled oil under fire),and the autorecycling of oil and absorption materials remain a great challenge.This work proposed an ingenious design strategy of“several birds with one stone”to prepare p H/thermoresponsive flame-retardant/photothermal bactericidal P-Fe_(3)O_(4)-polydopamine(PDA)@melamine–formaldehyde(MF)foams.This design makes the foams remarkably effective in the recovery of spilled viscous crude oil as well as in the separation of bacteria-containing oily emulsions,particularly for instant fire extinguishing by magnetically controlled oil absorption as well as for fire alarms.The photothermal effect and p H response induce a change in the surface wettability of the foams,facilitating excellent autoadsorption/desorption of the spilled oil.The photothermal bactericidal activity and fouling resistance of the foam are beneficial to the separation of bacteria-containing oily wastewater.Outstanding flame-retardant properties and maneuverable magnetic control enable the foam to rapidly recover the spilled oil in a large range of fires,extinguish fires instantly,and facilitate early fire warning.The proposed strategy is expected to inspire further research on treating oil spills under complex conditions.