| Maintaining normal body temperature is one of the necessary conditions for human activities.It is difficult to satisfy the comfort level of human body only by relying on clothes.However,the widespread use of the heating and ventilation equipment causes the increasingly serious problem of energy shortage,which further brings great difficulties to energy conservation and emission reduction.Understanding the thermal radiation behavior of multifunctional laminated membranes constructed on demand is of great theoretical guiding value for its application in human thermal management.Therefore,the development of new materials that possess ultra-low energy consumption,green environmental protection and high added value for human thermal management has become one of the most urgent problems in the field of energy conservation and emission reduction.This thesis aims at the on-demand construction of flexible wearable laminated materials based on biomass cellulose and the study of its infrared radiation performance.Focusing on the directional design and thermal management performance optimization of cellulose laminated membranes,the evolution law between the characteristics of laminated interface and human thermal management performance were explored,and the optimal preparation process of flexible wearable laminated membranes material was established.The main research contents are as follows:(1)Preparation of single temperature-controlled flexible cellulose laminated membranes and research on human thermal management performance(a)Inorganic-organic hybrid cellulose membrane(ICM)was prepared from the cellulose of indocalamus leaves as raw material by phase transformation method.NiAl bimetallic hydroxide nanosheets were grown on its surface(Ni-Al-LDH/ICM)by one-step hydrothermal method.Then boron nitride nanosheets(BNNS)were deposited on the surface to construct radiative laminated membranes.The prepared Ni-AlLDH/ICM coating has a high infrared emissivity(0.77),which is helpful to achieve radiation cooling effect through human radiation.Compared with ICM,the laminated membranes can reduce the body surface temperature by 2.7 ℃,effectively realizing radiation cooling,and this will provide an effective solution for cooling the body.(b)The composite membranes with multiple thermal insulation functions were prepared by the orderly assembly of CSC,Ni-Ag nanowires with core-shell structure(Ni@Ag NWs)and BNNs.Ni@Ag-NWs layer has a lower infrared emissivity(0.1)and better electrical conductivity,which not only can reduce the radiation loss of human body,but also has a better electric heating performance,so as to achieve the purpose of double insulation.The results show that the radiation insulation effect of laminated membranes can increase the body surface temperature by 5 ℃ compared with CSC membrane,the surface temperature can be increased by 33.6 ℃ in 1 min at 4.8 V voltage.This membrane material has excellent application potential in human body thermal insulation.(2)Preparation of flexible unidirectional temperature control cellulose laminated membranes and research on human thermal management performanceIn view of the shortcoming of single function of the material prepared above,the fiber laminated membranes with controllable infrared emissivity were prepared by designing the surface structure and element composition of the material to achieve the adjustment of thermal management performance.Using cotton cellulose(CF)as the substrate,multifunctional laminated membranes with ultraviolet resistance and human thermal management properties were prepared by magnetron sputtering,hydrothermal method and in-situ growth techniques.The effect of radiation heat preservation to heat dissipation can be realized by changing the infrared emissivity of the inner surface of the membranes.First,aluminum coating sputtered on CF surface(CF@ANC)which has a low infrared emissivity can inhibit the loss of human radiation to achieve thermal insulation performance.Then,using aluminum coating as the aluminum source,zincaluminum bimetallic hydroxide nanosheets(CF@Zn-Al LDH)with high infrared emissivity were further in-situ grown on CF@ANC surface by hydrothermal method,which can promote the radiation loss of human body to achieve the heat dissipation effect,so as to realize the thermal management performance from radiation insulation to radiation dissipation.The results show that the infrared emissivity of CF@ANC coating is low(0.30),and the infrared emissivity of CF@Zn-Al LDH coating is very high(0.98).It can increase the body surface temperature by 1.9 ℃ in low temperature environment,and reduce the body surface temperature by 1.6 ℃ in high temperature environment.Therefore,the transformation from radiation insulation to heat dissipation performance can be realized by changing the emissivity of the material surface,so as to realize the comfortable thermal management of human body.These two kinds of membrane materials show good unidirectional temperature control performance in human thermal management.(3)Preparation of bidirectional temperature-controlled flexible Janus cellulose laminated membranes and research on human thermal management performanceIn view of the defect of one-way temperature control of the materials prepared above,the structure and element composition of the material surface were changed,and the fiber laminated membranes with asymmetric infrared emissivity were prepared for achieving the effect of on-demand control of human thermal management.The flexible bidirectional temperature control Janus laminated membranes with asymmetric infrared emissivity were constructed based on corn bracts cellulose membrane(CBM)by hydrothermal method and magnetron sputtering technology.Zn O nanosheets were intersected vertically on the CBM surface(Zn O-NSs/CBM)as a coating with high infrared emissivity.Then,cellulose was deposited on one side to form a second layer,and copper nanoparticles were sputtered on its surface(Cu-NC/CBM)as a coating with low emissivity.The infrared emissivity(0.45)of Cu-NC/CBM layer is lower than that of CBM,which is helpful to return infrared radiation to human body.Zn O-NSs/CBM layer has high infrared emissivity(～ 0.94)and high visible reflectance(0.95),it is conducive to promoting the release of human radiation and reflecting visible light to achieve cooling effect.These results show that the Janus laminated membranes have better radiation cooling effect when the Zn O-NSs/CBM layer is outward,this can reduce the body surface temperature by 1.1 ℃.When Cu-NC/CBM layer is outward,Janus laminated membranes can achieve the effect of radiation insulation and increase the surface temperature by 5.9 ℃.In addition,Janus laminated membranes have excellent UV resistance,flexibility and mechanical properties,which can satisfy comfort of the wearers.This research can not only provide a strategy based on the utilization of agricultural waste resources,but also has potential applications in personal thermal management due to its energy saving and environmental advantages.It provides a new idea for the fabrication of wearable fabric with dual functions of radiation insulation and heat dissipation.In this study,a series of flexible wearable bio-cellulose laminates were constructed through the directional design of cellulose laminates to achieve on-demand personal thermal management performance.The study in the thesis is helpful to reveal the internal relationship between the interface of various layers of bio-cellulose laminated membranes and the radiation performance,and provides a new research approach for further research on the interface design and performance regulation of other wearable materials,as well as a new idea and design concept for realizing controllable human thermal management performance. |
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