Nat. Commu.: Nano-diamond, 10 times better!

Electric card refrigeration technology is based on the charge and discharge of dielectric capacitors to achieve efficient refrigeration. EC ceramics and polymers have attracted much attention due to their high energy reversibility, high recovery rate, easy actuation and compact structure. These materials are adaptable to existing large-scale production processes and demonstrate the potential of solid-state refrigeration technology. Through active electrothermal regeneration cycle verification, EC equipment can achieve a large temperature span, comparable to traditional refrigeration technology. Electrostatically driven polymer film coolers are an important breakthrough for use in confined environments. However, in order to increase the total power, EC materials need to be added, resulting in thickening of the working body and prolonged heat transfer time. Therefore, research needs to explore more efficient EC materials to improve refrigeration performance.

EC polymers play a significant role in refrigeration due to their flexibility, low density, and electrical stability, but low thermal conductivity (0.2 W·m−1·K−1) and high electric field requirements are efficiency challenges. Polymer-rich nanocomposites are expected to improve ECE and thermal conductivity while maintaining soft material properties. High dielectric constant (k) ferroelectric inorganic oxide nanoparticles are commonly used as fillers, which can amplify electric field deformation, promote interface polarization, and enhance ECE. Chen et al. improved polarization and ECE through (P(VDF–TrFE–CFE))/ZrO2 nanocomposite. The dielectric constant of ZrO2 (ε~30) is similar to the basic ternary polymer (ε~45). The interface The inner field deformation is significant.

Professor Qian Xiaoshi’s research group at Shanghai Jiao Tong University successfully achieved the electrical cooling effect and thermal conductivity by innovatively introducing low dielectric constant nanodiamond filler (ND) into the relaxor ferroelectric polymer P (VDF-TrFE-CFE). Significant improvement in performance and breakdown field strength. This result was published in "Nature Communications" under the title "Low dielectric nanomaterials help high dielectric ferroelectric polymers achieve sustainable electric cooling". The research team introduced ND into commercially available relaxor ferroelectric polymers to optimize the conductivity, electrical stability and thermal conductivity of nanocomposites. By reducing the dielectric response of the polymer dielectric, the mixture significantly enhanced polarization and ECE performance upon addition of a small amount of ND. In particular, when the ND content is 2.6%, the ECE is improved by up to 60%, which is nearly 70% higher than the performance of previously reported high-dielectric constant fillers. At the same time, due to the low ND content, the thermal conductivity of nanocomposites has also increased by 75%, providing a new way for the sustainable development of electric card refrigeration technology.

In-situ XRD experiments show that the improvement in ECE results from the reduction of the non-polar-polar phase transition energy barrier in the nanocomposite. Electrostatic force microscopy (EFM) tests revealed a significant increase in ND-polymer interface potential, which may directly enhance the polarization properties of the material. Based on the dual improvement of ECE and thermal conductivity, we developed a continuous rotating cycle EC refrigeration device model. Numerical analysis shows that nanocomposites as core refrigeration components can significantly enhance the refrigeration capacity and efficiency of EC equipment. At a temperature difference of 10K, the refrigeration device using T-ND-2.6% nanocomposite has a refrigeration coefficient (COP) as high as 5.3 (terpolymer is only 0.8), and the refrigeration power remains above 240W, which is relatively pure ternary copolymer. Physical equipment increased by 10 times.

Figure 1. Overall performance of base terpolymer and ND-doped nanocomposites.

Figure 2. SAXS and in situ WAXD tests show that low-k ND can lower the energy barrier for terpolymer phase transition.

Figure 3. Characteristics of the main causes of polarization enhancement.

Figure 4. Environmental friendliness of ND-incorporated nanocomposites.

Figure 5. Refrigeration performance of electronic refrigerator based on fluid-solid coupling

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Nat. Commu.: Nano-diamond, 10 times better!

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