Thermal Control Materials Research Articles

Preparation and investigation of microencapsulated thermal control material used for the cementing of gas hydrate formations

Deep-water cementing operations may encounter gas hydrate formations, and the cement slurry hydration exotherm can easily cause their decomposition and pose a threat to cementing operations. Therefore, the cement slurry with low hydration heat is needed for cementing in deep water gas hydrate zones. In this paper, a microencapsulated temperature control material (MEPCM) was synthesized. When MEPCM was incorporated into the oil well cement slurry, its temperature control effect on cement slurry was evaluated. Firstly, the chemical structure, microstructure, and phase transformation characteristics of MEPCM were researched by FTIR, SEM-EDS, DSC, etc. The results show that the thermal evolution of the cement slurry can be controlled by MEPCM. Secondly, MEPCM was introduced into oil well cement, and the temperature change of the cement slurry hydration process was detected by a self-made semi-insulating device to study the temperature control ability of MEPCM in cement slurry. The results show that the thermal development of the cement slurry is regulated by the MEPCM. At the same time, the effect and mechanism of MEPCM on the early mechanical performance of cement slurry were studied, and found that the right amount of MEPCM can promote the cement stone’s early strength development. As a result, a low hydration heat cement slurry system suitable for cementing deep-water gas hydrate formations was successfully prepared.

Flexible, infrared adjustable, thermal radiation control device based on electro-emissive PANI/Ce4+ thin films inspired by chameleon

Electrochromic materials (ECMs) with reversible change ability are widely concerned as environmental stealth materials that can actively adjust their color and infrared (IR) emissivity. Chameleon is the master of camouflage in the environment, inspired by the discoloration mechanism of chameleon's pigment capsule, we fabricated biomimetic film with superb IR thermal radiation regulation ability, in which polyaniline (PANI) and cerium ion (Ce4+) were used to simulate the skin receptor and pigment capsule in chameleon's skin respectively. In the wavelength scope of 8 ∼ 14 μm, the IR emissivity’s change (△ε) of the film from emeraldine-salt state (ESs) to leucoemeraldine-base state (LBs) is as high as 0.58. Beyond that, we use an integrated rolling thermal packaging process to assemble the films into electro-emissive devices (EEDs) with excellent cycle endurance, flexibility and IR thermal radiation management capabilities. This work provides a new strategy for the preparation of reliable IR thermal radiation control materials and devices.

Spectral decoupling of cooperative emissivity in silica-polymer metamaterials for radiative cooling

Silica-polymer metamaterials are one promising candidate of radiative-cooling materials suitable for scalable manufacture. However, the strong coupling between the silica and polymer components and their respective contribution to total emission remain unexplored. In this work, we developed a 3D full-wave model for such a randomized composite system to retrieve the spectral emissivity of individual components and uncover the interacted physical mechanisms. The results demonstrate and decouple the cooperative emission in the scatter-medium system and quantitatively evaluate the geometry-dependent light-matter interactions, which sheds more light on silica-polymer metamaterials and provides helpful guidance for designing similar thermal-control materials.

Regulation of phase transition temperature and preparation for doping-VO2 smart thermal control films

Vanadium dioxide (VO2) is considered one of the most promising smart thermal control materials due to its insulator-metal temperature (IMT) reversible phase transition, accompanied by large changes in its optical properties. However, as the crystal defects on IMT change and the optical property of VO2 is still unclear, the preparation of doped VO2 films by magnetron sputtering is still a great challenge. In this work, the IMT of 41 kinds of doping-VO2 systems were studied by high throughput calculation based on density functional theory (DFT). It was found that the IMT increased with the decrease of the β angle in M phase and expansion of cell volume difference of M-phase and R-phase for IIA elements, VIIA elements, transition elements, and rare earth element doped VO2, and increased with the increase of the β angle in M phase and a decrease of cell volume difference of M-phase and R-phase for IA, IVA, VA, and VIA element doped VO2. According to the rule, the IMT, electronic structures, and optical properties of W doped VO2 were studied based on DFT. The results show that IMT and bandgap decrease with the increase of W6+ ion concentration, which is due to the increased cell volume difference of M-phase and R-phase in W doped VO2; each doped atom can reduce the IMT of 20.2 °C, and the IMT of V0.98W0.02O2 is close to room temperature (Tc ≈ 27 °C). The rate of infrared emissivity (∆ɛ) of V0.98W0.02O2 is about 0.2 at 8–14 μm (0.088–0.155 eV) and the average solar absorption (αs) of M phase and R phase is about 0.53 and 0.59 at 0.3–1.5 μm (0.496–4.13 eV), respectively. Finally, radio frequency magnetron sputtering was used to achieve precise doping, which solved the problem of oxygen partial pressure in reactive magnetron sputtering, and V1-xWxO2 films with IMT close to room temperature and narrow hysteresis width were prepared. This is due to the fact that higher W doping content will greatly increase the density of defect-induced nucleation sites and promote nucleation. At the same time, the experimental results of IMT were consistent with the calculated results, which proved the reliability of the calculation. This will provide a theoretical basis for the development of new thermal control materials and a new method for the preparation of doping-VO2 films in the future.

Study on the Electromagnetic Radiation Effect of a Thermal Control Layer

To study the electromagnetic radiation effect of a thermal control layer (TCL) on the surface of general spacecraft in a space environment, a model of thermal control material irradiated with microwaves was established, a particle-in-cell (PIC)-Monte Carlo collisions (MCC) simulation was used, and the processes of field emission, multipacting, outgassing, and impact ionization on the surface of thermal control materials were simulated. By comparing the primary electrons, secondary electrons, and impact ionization electrons produced under different field intensities and frequencies of electromagnetic waves, different compositions of outgassing, and different thermal control materials, the influencing factors and critical thresholds of avalanche ionization were obtained. The simulation results show that whether avalanche ionization occurs in outgassing on the surface of the TCL is affected by the electromagnetic wave amplitude, electromagnetic wave frequency, outgassing composition, and the material of the TCL. This provides a theoretical reference for the safe operation of spacecraft.

Preparation, characterization, investigation of phase change micro-encapsulated thermal control material used for energy storage and temperature regulation in deep-water oil and gas development

Based on the requirements of low hydration heat and maximum temperature of cement slurry used in deep-water natural gas hydrate formation, a novel cement slurry containing phase change micro-encapsulated thermal control material was prepared and investigated. Firstly, a novel phase change micro-encapsulated thermal control material (Micro-P1) was synthesized and studied. It was found that the Micro-P1 have spherical structure and the particle diameter is 2.664 μm, the phase change properties, thermal conductivity, mechanical properties and hydrophilicity of Micro-P1 were significantly improved by nano-SiO2. Secondly, the Micro-P1 was introduced into cement slurry, and the controlling effects of Micro-P1 on the heat development of cement slurry was investigated. Moreover, the innovation of this study is that based on the established heat transfer decomposition model of hydrate, the influences of different cement slurry on the stability of hydrate were quantitatively calculated. The results show that the maximum temperature was reduced by 9.3 °C, the hydration heat of 24 and 48 h was reduced by 26.9 and 12.78%. Especially, the quantitative calculation shows that when the decomposition interface moves distance is 0.30 m, the required time was increased by 30.6%, in other words, the stability of hydrate was obviously improved.

Influence of the space radiation environment model uncertainty on the solar absorption evaluation of ITO/Kapton/Al film

The uncertainty of the space radiation environment model has an impact on the evaluation of the solar absorption rate of spacecraft thermal control materials in the space radiation environment. This paper uses the space integrated radiation ground simulation test device to experimentally study the solar absorption rate change law of the ITO/Kapton/Al thermal control film under the electron and proton irradiation environment, and then the uncertainty of the space radiation environment model is compared to the ITO/Kapton /Al thermal control film to analyze the influence of solar absorptivity. The research shows that with the increase of the radiation fluence, the influence of different uncertainties on the solar absorption of the thermal control film first increases and then decreases, and the final effect is basically negligible; the uncertainty on the solar absorption of the thermal control film material When the uncertainty factor increases, when the uncertainty factor is less than 1, the relative deviation caused by the uncertainty of the space radiation environment model to the solar absorption rate evaluation of the thermal control film is positive, when the uncertainty factor When it is greater than 1, it is negative.

Electro-emissive device based on novel PANI/Au composite films with neoteric mosaic structure for infrared stealth and thermal radiation control

Infrared (IR) stealthy material is mainly to reduce or change the IR radiation characteristics of the target, reduce the probability of the target being detected, however, its application is limited by the ability to control the emitted thermal radiation from the material surface. This study demonstrates a novel PANI/Au composite film designed with neoteric mosaic structure prepared by the galvanostatic method which has an enormous IR radiation regulation range and good thermal radiation control ability. The results show that PANI/Au composite film exhibits supereminent IR emissivity modulation capability. At 13 μm, the variation of infrared emissivity (△ε) of leucoemeraldine base (LB) state and emeraldine salt (ES) state can up to 0.552. In the wavelength range of 8–14 μm and 2.5–25 μm, the emissivity of the composite film changes by 0.491 and 0.403, respectively. Electro-emissive devices (EEDs) based on PANI/Au composite films show excellent infrared stealth and thermal radiation control effects. The maximum adjustable temperature between the device and the environment can up to 4.8 °C. The research results provide a basis for the selection of thermal radiation control materials combining infrared stealth and radiation information management.

Property changes in materials due to atomic oxygen in the low Earth orbit

We expect satellites at altitude below 300 km, very low Earth orbit (VLEO), making observations of the Earth at optical wavelength with increasingly higher resolution. The density of atomic oxygen (AO) at VLEO is significantly higher than that at LEO; severe degradation of spacecraft materials (polymers) due to the high-flux AO is a serious concern. To clarify VLEO environmental effects on spacecraft materials, we designed the Material Degradation Monitor (MDM) and MDM2 missions. The MDM is a material exposure experiment onboard the Super Low-Altitude Test Satellite (SLATS). It aims to understand reactions and degradation of polymeric materials depending on AO fluence in VLEO. In the MDM, samples of spacecraft material were exposed at altitude of 160–560 km; their degradation behaviors were observed optically by a CCD camera for 1.8 years. The MDM2 is a material exposure experiment onboard the International Space Station (ISS) and aims to correctly understand surface reactions and degradation of the same samples used in the MDM at a given AO fluence. In the MDM2, the samples were exposed at altitude of 400 km for 1 year and then returned to Earth for analysis. Based on the results from both missions, we will help in the molecular design of more-durable materials, and establish design standards for future VLEO satellites. This study aims to quantitatively understand the surface reactions and degradation of the 11 types of thermal control materials exposed on the ISS in the MDM2. Five types of multilayer insulation (MLI) films (three types of Si-containing AO protective materials (a silsesquioxane-(SQ-) containing coated polyimide film, two types of polysiloxane-block polyimide (BSF-30) films), an ITO-coated polyimide film, and a Beta Cloth), and flexible optical solar reflectors (flexible OSRs) were found to have a high durability against erosion by AO. This was determined by measuring their loss of mass and thermo-optical properties. The Ag/Inconel layer’s discoloration and peeling were observed for three types of FEP/Ag films as determined by the Ag layer’s oxidation by AO. Also, X-ray photoelectron spectroscopy (XPS) showed that reactions of the Si-containing materials, the SQ-coated polyimide film and the BSF-30 film, form a layer of silica that protects against AO. Even though the concentration of Si in the SQ-coating is the same or greater than in the BSF-30 film, the amount of the SQ-coating that reacted was larger than that of the BSF-30 film under the same AO fluence. Moreover, the effective ability of the UV-shielding coating, composed of ITO and CeO2 coated onto one of the BSF-30 films, was demonstrated by UV–Vis spectrometry. Its sufficient AO protection was confirmed by mass measurements, XPS analyses, and FE-SEM observations.

Preparation and evaluation of micro-encapsulated thermal control materials for oil well cement slurry

Abstract In the process cementing of deep water, cement particles react with water to produce a lot of hydration heat, which can lead to decomposition of natural gas hydrate. We synthesized a kind of micro-capsule thermal control material with paraffin wax as the base material and calcium carbonate as the skeleton support material. At first, the chemical structure and chemical element composition of thermal control material were obtained by FTIR and EDS, respectively. Secondly, the phase change properties of MPCM-1 were measured by using DSC. As a result, it was shown that phase change temperature and phase change enthalpy of thermal control material is 31.11 °C and 88.59 J/g, respectively. Simultaneously, the thermal stability of IPCM-1 was obtained by using a synchronous thermal analyzer. Then, the micro-encapsulated thermal control material is introduced into the cement slurry system, and the hydration heat and maximum hydration temperature rise of the cement slurry were investigated by a self-made hydration heat test device. As a result, compared with cement slurry CB, the hydration heat released to the environment by cement slurry CS12.0% decreased by 44.16% (at 48 h), and the maximum hydration temperature of cement slurry CS12.0% is reduced by 25.4 °C. Besides, compared with cement slurry CB, the compressive strength of cement slurry CS12.0% increased by 5.9% (24 h) and 9.8% (48 h). The thermal control material was added into the cement slurry, and a low hydration heat cement slurry system was successfully prepared.

Thermal control technology for the space station adjoint modular satellite based on new thermal control materials

A modular satellite could perform various functions with various modules and the function of the satellite could be expanded easily. Therefore, the modularization design is an important development direction of space station adjoint satellites and others. However, every module of a modular satellite is structurally independent and the heat dissipation is unevenly distributed, while the interface between modules should support repeatable connection-separating. The traditional thermal control design could not satisfy the thermal control demand. In this paper, the thermal control technology for the space station adjoint modular satellite based on the thermal interface of carbon nanotube array on copper substrate, graphene coating and smart thermal control coating is proposed. By using the new technology, the thermal connection of the assembly and reconstruction system is built and the synergistic heat dissipation of the whole satellite is achieved. As to validate the proposed technology, the finite element model of the space station adjoint modular satellite is established and the whole flight process is simulated. The result indicates that the thermal control technology proposed in this paper can satisfy the thermal control demand of the modular satellite.

Laminated Fibrous Membrane Inspired by Polar Bear Pelt for Outdoor Personal Radiation Management.

Outdoor cold stress often causes an undesired threat to public health, but devising an efficient strategy to achieve localized outdoor warming of the human body is still a great challenge. Polar bear pelt can absorb sunlight and reflect thermal radiation generated inside the body, which helps in adapting to the cold environment. Inspired by the radiation control strategy of the polar bear pelt, this study reports a porous Ag/cellulose/carbon nanotube (CNT)-laminated nanofiber membrane, in which one side of the cellulose basement membrane is coated with CNTs using a foam finishing process and the Ag layer is deposited on the other side by magnetron sputtering. Based on the high solar radiation absorptivity from CNT coating and the high infrared radiation reflectivity from Ag coating, the biomimetic membrane provides radiation warming by maximizing the heat input from the sun and minimizing the human radiation heat output. Because of excellent electrical conductivity, the Ag layer can work as a wearable heater to induce fast thermal response and uniform electroheating for extra warmth under a low supplied voltage. Moreover, the biomimetic membrane possesses porosity, hydrophilicity, breathability, flexibility, and mechanical stability, suggesting its huge potential for outdoor personal thermal management. Because of their versatility, the applications of the biomimetic membranes may be extended to wearable electronics, smart garments, and thermal control materials.

Space Environment Exposure Test for Highly Functional Thermal Control Materials

Space Environment Exposure Test for Highly Functional Thermal Control Materials

Preparation of low hydration heat cement slurry with micro-encapsulated thermal control material

During the cementing process of natural gas hydrate (NGH) layer, the hydration heat of cement slurry can easily cause decomposition of NGH which leads to cementing risk. A thermal control material of phase change micro-capsule (PCM-1) with paraffin as the core material and urea-formaldehyde resin as the wall material was successfully synthesized, and then a low hydration heat cement slurry was prepared by using PCM-1. The basic performances of PCM-1 were characterized by using DSC, FTIR, SEM and TG, and the results show that the performances meet designed requirements. Then, the PCM-1 was introduced into cement slurry system, and the hydration heat (Q) and hydration temperature rise (Tr) were measured by using the self-developed semi-adiabatic test equipment. As a result, it was confirmed that the Q and the Tr decrease with the increase of PCM-1 content. The Tr of cement slurry CP15% was 25.4 °C, lower than that of cement slurry CB. Meanwhile, compared with cement slurry CB, at 24 and 48 h hydration heat of cement slurry CP15% were decreased by 7.68 × 104 and 7.28 × 104 J, respectively. Therefore, the decomposition of NGH was avoided attribute to the smaller Q of cement slurry, and the cementing operation risk in deep water was reduced.

Thermal regulation of satellites using adaptive polymeric materials

This paper focuses on the thermal performances of an adaptive radiator made of 16 electroemissive devices (EEDs) acting as electro-active materials for thermal control of satellites. EEDs are similar to an electrochemical cell where one electrode serves as active layer in the infrared and is made of a conducting polymer, the poly(3,4-ethylenedioxythiophene) (PEDOT), interpenetrated into a polyethylene oxide/nitrile butadiene rubber (PEO/NBR) solid gel electrolyte as supporting matrix. First, EEDs were placed in moderate vacuum (10-3 bars) to estimate their optical cyclability c.a. 4000 cycles in neutral and oxidized state. Then, an electro-emissive radiator (EER) assembled with 16 EEDs (total area of 80cm2) was tested under space vacuum conditions. “Hot” and “cold” operating cases of the satellite were simulated and ability of the radiator to control radiative exchanges between the satellite and its environment was estimated by comparison with the currently used optical solar reflector (OSR) radiators. In low emissivity state, the EER can slow down the rejection of heat in a cold environment which is an interesting feature in terms of energy saving. Also when the EER is not directly exposed to the sun, it is able to reject the heat in the same way as the OSR radiator in a hot phase. By comparing the electrical consumption with a system operating with OSR, an energy saving in the order of 25% was demonstrated. Finally the EER exhibits bistability during many hours, i.e. memory effect once electrically switched into a given emissivity state, allowing to further reduce the electrical consumption.

Influence of Space Radiation Model Uncertainties on the Solar Absorptance Evaluation of OSR Second Reflector

Space radiation model uncertainties may have important influence on the evaluation of thermo physical properties of anti-electrostatics thermal control materials. The sources of space radiation model uncertainties are analyzed and the uncertainty factor is defined firstly, then the simulation test was performed on the surface resistivity of OSR in electron or proton radiation environments. After that, the influence of space radiation model uncertainties on the solar absorption of OSR was analyzed. As the increase of irradiation fluence, the influence of space radiation model uncertainties on the solar absorption increases firstly and then decrease utile it can be ignored. The influence of space radiation model uncertainties on surface resistivity of OSR increases with the uncertainty factor. When the uncertainty factor lower than 1, the error from space radiation model uncertainty to surface resistivity of OSR is positive, while the uncertainty factor larger than 1, the error is negative.

An Apparatus for Spectral Emissivity Measurements of Thermal Control Materials at Low Temperatures.

Thermal control materials are employed to adjust the temperature of a spacecraft operating in deep space. The spectral emissivity is a crucial factor in evaluating the thermal radiative properties of such materials. An apparatus, composed of a Fourier transform infrared spectrometer (FTIR), a sample cooling chamber and a mechanical modulation system was demonstrated to measure low temperature infrared spectral emissivity under vacuum. The mechanical modulation system, which includes a chopper and a lock-in amplifier, is employed to reduce the interference of background radiation during measurements. The limitation of the Fourier transform frequency on the chopper frequency can be eliminated by setting the FTIR on step-scan mode. The apparatus is separated into two parts and evacuated by different pumps. In this study, a high quality emission spectrum of a sample is measured by the apparatus. The spectral emissivity of thermal control materials are obtained in the wavelength range of 8 to 14 μm at 173 and 213 K. The combined standard uncertainty of the apparatus is 3.30% at 213 K.

Space Exposure Experiment of Thermal Control Materials for Radiator

Space Exposure Experiment of Thermal Control Materials for Radiator

Flexible phase change materials for thermal storage and temperature control

Flexible phase-change materials (PCMs) have great potential applicability in thermal energy storage and temperature control. A binary composite mixture comprising polyethylene glycols of solid and liquid phases (PEG2000 and PEG400, respectively) was synthesized as a PCM base material. The PEG400 liquid phase was uniformly dispersed in the PEG2000 phase-change crystal on a molecular scale, thus creating many micro- and nanocrystals of PEG2000 via polycrystalline growth from a single crystal. To retain solidity and flexibility in the composite’s melted state, hydrogel technology and low-temperature drying were applied. We prepared flexible polymer gel shaped PCMs by adding sodium stearate (NaR) to the binary fused mixture. Needle-shaped NaR crystal grains of several hundred nanometers formed three-dimensional network structures, binding the binary flexible PCM within the network structure to form a polymer gel. These geometric structures not only achieve the solid–liquid PCM structure but also maintain flexibility in both the melted and solidified states (20–80 °C). The latent heats of melting and solidification for the polymer gel were 109.7 and 107.2 J/g, accounting for 87.5% and 85.8% of the PP20 binary eutectic, respectively. The demonstrated use of polymer gels provides a new route for investigating PCMs for heat storage.

Thermal-Control-Material-Impact Effect by Micron Space Debris

The thermal-control material of spacecraft is easily impacted by micrometeoroid and space debris in orbit. Optical solar reflector is a kind of silvered glass second-surface mirrors, which are applied as spacecraft outer-surface material to reflect sunlight. A system for launching flyer using a -switched Nd:YAG laser with a flattop-appearance beam has been developed for simulating space-debris-impact effects on optical solar reflector. The velocities of the flyer were obtained by laser no-contact velocity-measurement apparatus based on the principle of laser light curtain, which could measure impact velocity unto with a high accuracy of 95%. By launching three kinds of flyer diameter and five kinds of flyer thickness, 56 impact tests have been conducted in flyer velocity ranging from 3.15 to . The results had shown that the splashed-zone diameter of the impacted sample increased obviously, as impact velocity was improved at the same flyer diameter and flyer thickness. The surface thermal-radiation-property degradation was obviously as the change of flyer velocity, flyer thickness, and flyer diameter.