Construction And Applications Of Functional Fire-Resistant Paper Based On Ultralong Hydroxyapatite Nanowires

Benefiting from optical,electronic and magnetic properties,one-dimensional inorganic nanomaterials have been widely applied in transistor,sensor,air filtration,energy storage and conversion,flexible electronics,etc.To date,most of studies focus on the elemental or binary one-dimensional inorganic nanomaterials,while studies on the ternary or multielement one-dimensional inorganic nanomaterials and their applications are seldom reported in the literature.Hydroxyapatite(Ca₁₀（PO₄）₆（OH）₂)is the main inorganic component of the hard tissue（bone and tooth）of vertebrates.Hydroxyapatite nanomaterials have high biocompatibility,excellent ion exchange and adsorption capabilities,and thermal stability.The research purpose of this dissertation is to explore the advantages of one-dimensional hydroxyapatite nanowires for the construction of new inorganic fire-resistant paper.The research contents of this dissertation include:（1）Construction,properties and applications of the superhydrophobic fire-resistant papera.Ultralong hydroxyapatite nanowires are synthesized by the calcium oleate precursor solvothermal method,then sodium oleate is used to modify the surface of ultralong hydroxyapatite nanowires.Finally,the superhydrophobic fire-resistant paper is obtained by the vacuum-assisted suction filtration of the modified ultralong hydroxyapatite nanowires.b.The cross section of the fire-resistant paper exhibits a unique layered structure.Based on the experimental results,three effects are proposed to explain the formation of the layered structure,including surface charge amplified effect,surface charge superimposed effect,and pillarlike supporting effect.c.We have tested the properties of the fire-resistant paper including liquid repellency,self-cleaning ability,thermal stability,and mechanical stability.Moreover,the potential applications of the superhydrophobic fire-resistant paper are explored in the oil/water separation,fire-shielding protection,and water-proof fire-resistant writing paper.（2）Construction and applications of the flexible electrically conductive fire-resistant paperThe ultralong hydroxyapatite nanowires serve as a stable substrate to load the conductive filler（Kejten black）,then polydimethylsiloxane（PDMS）is coated on the surface of the paper to construct a flexible electrically conductive fire-resistant paper.Because the flexible electrically conductive fire-resistant paper integrates the superhydrophobic surface,electrothermal effect,and flame retardancy,it shows excellent corrosion/moisture resistance,high thermal stability,excellent self-cleaning and deicing capabilities,and can steadily work under water and in the flame.（3）Construction and applications of the fire alarm fire-resistant wallpaperA smart fire alarm fire-resistant wallpaper has been prepared by using glass fiber-reinforced ultralong hydroxyapatite nanowire paper as the substrate and graphene oxide as the thermosensitive sensor.The as-prepared fire alarm fire-resistant wallpaper can prevent the fire from spreading and automatically send out the fire alarm to people when a fire disaster occurs.In order to further improve the working stability of the thermosensitive sensor in the flame,the graphene oxide is modified with polydopamine.The polydopamine-modified graphene oxide thermosensitive sensor has a low thermal responsive temperature（126.9°C）,rapid response time（within 2 s）,and long alarm time（>5 min）in the flame.（4）Construction and applications of the functional organic/inorganic composite paperThe organic/inorganic composite paper sheets are constructed after introducing the organic materials into the inorganic ultralong hydroxyapatite nanowires.a.Plant fiber/ultralong hydroxyapatite nanowire composite paper.The composite paper is used as a secret paper to protect the covert information.It is found that the covert information on the blank secret paper written with white vinegar is totally invisible by the naked eyes,so that the information can be encrypted.The covert information is decrypted and revealed at high resolution upon exposure to the flame.b.Metal-organic framework material/ultralong hydroxyapatite nanowire test paper.The metal-organic framework（MIL-100（Fe））nanocrystals have been grown on the surface of ultralong hydroxyapatite nanowires to obtain HAP@MIL-100（Fe）nanofibers by using the template-directed layer-by-layer deposition.HAP@MIL-100（Fe）nanofibers are further used as building blocks to construct the test paper.The application of the test paper on the qualitative detection of H₂O₂ and glucose has been investigated.The test paper shows the varying degrees of color change in response to different concentrations of H₂O₂ and glucose.More importantly,the HAP@MIL-100（Fe）test paper can be recovered easily for reuse by simply dipping in absolute ethanol for just 30 min.The recycled test paper can still achieve the qualitative detection without obvious loss of the catalytic activity.In this dissertation,ultralong hydroxyapatite nanowires are used as building blocks to construct a series of functional fire-resistant paper.The research contents mainly consist of two parts:the ultralong hydroxyapatite nanowire fire-resistant paper is used as a substrate to improve working stability of flexible electronics under high-temperature and fire environments;and the ultralong hydroxyapatite nanowires serve as a framework to combine with organic materials.The functional organic/inorganic composite paper sheets are constructed after integrating their respective features.The research results show that the ultralong hydroxyapatite nanowires have high flexibility,excellent surface modification capability,high thermal stability,and fire resistance,enabling them to be ideal building blocks for the construction of new inorganic functional paper.