Synthesis and Characterization of Phase Change Material Microcapsules Using Different Emulsifiers

In this study, a series of phase change material microcapsules (MicroPCMs) were synthesized by a core-shell-like emulsion polymerization method using different emulsifiers. The interactions between core material, shell material and dispersed medium were investigated in detail. The copolymer (PS-MAA) of styrene and methylacrylic acid and paraffin were used as wall materials and core materials respectively. High temperature interfacial tensiometer was employed to measure the interactions between different materials. Fourier transformed infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Thermogravimetry (TG), Differential scanning calorimeter (DSC) and laser particle size analyzer were used to characterize the chemical structure, morphology, thermal properties, particles size and size distribution of the MicroPCMs. The results indicated that alkylphenol polyoxyethylene (OP-10) is the optimal emulsifier in this method. The MicroPCMs prepared by using OP-10 as emulsifier displayed smooth and compact surface, the productivity was as high as 93.35%. The melting enthalpy and crystallization enthalpy were -84.6J/g and 83.5J/g, respectively. The mean particle size was 16.33μm

Chebyshev pseudosite matrix product state approach for the spectral functions of electron-phonon coupling systems

The electron-phonon ($e$-ph) coupling system often has a large number of phonon degrees of freedom, whose spectral functions are numerically difficult to compute using matrix product state (MPS) formalisms. To solve this problem, we propose a new and practical method that combines the Chebyshev MPS and the pseudosite density matrix renormalization group (DMRG) algorithm. The Chebyshev vector is represented by a pseudosite MPS with global $U(1)$ fermion symmetry, which maps $2^{N_p}$ bosonic degrees of freedom onto $N_p$ pseudosites, each with two states. This approach can handle arbitrary $e$-ph coupling Hamiltonians where pseudosite DMRG performs efficiently. We use this method to study the spectral functions of the doped extended Hubbard-Holstein model in a regime of strong Coulomb repulsion, which has not been studied extensively before. Key features of the excitation spectra are captured at a modest computational cost. Our results show that weak extended $e$-ph couplings can increase the spectral weight of the holon-folding branch at low phonon frequencies, in agreement with angle-resolved photoemission observations on one-dimensional (1D) cuprates.Comment: 12 pages, 8 figures, new results adde

Investigation of the shape transferability of nanoscale multi-tip diamond tools in the diamond turning of nanostructures

In this article, the shape transferability of using nanoscale multi-tip diamond tools in the diamond turning for scale-up manufacturing of nanostructures has been demonstrated. Atomistic multi-tip diamond tool models were built with different tool geometries in terms of the difference in the tip cross-sectional shape, tip angle, and the feature of tool tip configuration, to determine their effect on the applied forces and the machined nano-groove geometries. The quality of machined nanostructures was characterized by the thickness of the deformed layers and the dimensional accuracy achieved. Simulation results show that diamond turning using nanoscale multi-tip tools offers tremendous shape transferability in machining nanostructures. Both periodic and non-periodic nano-grooves with different cross-sectional shapes can be successfully fabricated using the multi-tip tools. A hypothesis of minimum designed ratio of tool tip distance to tip base width (L/Wf) of the nanoscale multi-tip diamond tool for the high precision machining of nanostructures was proposed based on the analytical study of the quality of the nanostructures fabricated using different types of the multi-tip tools. Nanometric cutting trials using nanoscale multi-tip diamond tools (different in L/Wf) fabricated by focused ion beam (FIB) were then conducted to verify the hypothesis. The investigations done in this work imply the potential of using the nanoscale multi-tip diamond tool for the deterministic fabrication of period and non-periodic nanostructures, which opens up the feasibility of using the process as a versatile manufacturing technique in nanotechnology