Long Jiang Deng

The Microstructure, Resistivity and Infrared Emissivity of ITO Film with O/Ar Ratio Variation in Al2O3 Buffer Layer

ITO films with different oxygen-argon ratios varies from 0 % to 8 % for Al2O3 buffer layer have been fabricated by magnetron sputtering on soft PET substrate. The microstructure, resistivity, transmittance in visible light range and infrared emissivity were measured by XRD, four-point probe technology, UV-Vis spectrophotometer and Fourier Transform Infrared Spectroscopy (FTIR) as a function of different oxygen-argon ratios of Al2O3 buffer layers, respectively. It can be found that the (222) plane crystallization improves with the increase of O/Ar ratio, (622） peak under 2% O/Ar ratio and (440), (211) peaks under 8% O/Ar ratio appear, respectively. The resistivity is also influenced significantly by the O/Ar ratio, though the variation of resistivity is not sensitive to O/Ar ratio higher than 2%. The results reveal that the best ITO film performance under the oxygen-argon ratio 2% for Al2O3 buffer layer. It is also found that surface roughness and interface state play an important role in the variation of transmittance and emissivity. The emissivity of all the ITO films deposited on Al2O3 buffer layer is dominated by both sheet resistance and surface morphology.

Crystal Orientation and Hardness of Au/NiCr/Ta Films on Si-(111) Substrate Prepared by Magnetron Sputtering

Au/NiCr/Ta soft multi-layered metal films were deposited on hard Si-(111) substrate by magnetron sputtering. The crystal orientation, Hardness (H) and Elastic modulus (E) were investigated as a function of substrate temperature by XRD and nanoindentation techniques. The XRD revealed that all films on Si-(111) substrate are Au-(111) preferred orientation, indicating there are no alloying phases in the films, which is different from Au/NiCr/Ta films on Al2O3 substrate with a mixture of Au-(111) and Au-(200) orientation. Nanoindentation tests at shallow indentation depths (h≤t/4) where the hardness is reliable for metal films on hard substrate. Au film at substrate temperature 200°C has the highest hardness 4.2GPa. Meanwhile, the H/E value also indicated that the Au/NiCr/Ta films have preferable wear resistance at substrate temperature 200°C.

Microstructure and Resistivity of Low Temperature Deposition ITO Films on PET Substrate by Magnetron Sputtering

Sn doped indium oxide (ITO) films were fabricated on polyethylene terephtalate (PET) substrate by magnetron sputtering at low deposition temperature using a 10 wt % SnO2-doped In2O3 target applied in the infrared regions as low emissivity materials. The microstructure and surface morphology of ITO films was studied using X-ray diffraction (XRD) and atomic force microscopy (AFM); the resistivity was investigated by four-point probe technology. It was found that the film with amorphous microstructure has highest resistivity to 1.956×10-3 2.cm at low deposition temperature and the surface roughness and resistivity increase with the increasing Ar sputtering pressure from 0.5Pa to 1.4Pa. The most interesting is that the resistivity increases with the increasing surface roughness, it indicates that there are internal correlation between roughness and resistivity.

Synthesis and Characterization of Magnetic Al/NiO Composite Pigments with Low Infrared Emissivity

Generally, traditional low infrared coatings based on metallic pigments cannot have low lightness, low infrared emissivity and low radar reflectivity simultaneously. Herein, we used a simple and efficient method to synthesize magnetic Al/NiO composite pigments which possessed all these attributes to a degree. The results indicated that the covering area of NiO on the aluminum flake could be tuned by the addition amount of NiCO3 and the reaction temperature of hot-flowing, both of which played a key role on the VIS/IR spectral reflectance and magnetic properties. The magnetic Al/NiO composite pigments with low lightness and low infrared emissivity could be obtained at 130 °C for 24 h in hot flowing liquid. The lightness L* could be decreased to 75.94, however the infrared emissivity (8-14 μm) was also low to 0.421. Compared with the single aluminum flakes, the Al/NiO magnetic composite pigments presented stronger magnetic properties. Therefore, the Al/NiO magnetic composite pigments offered a new choice for the pigments of multispectral stealth coating.

Effective Application of Magnetic Material Based on Metamaterial Absorber

We simulate, fabricate and measure a microwave absorber by introducing metamaterial design method to magnetic material. The proposed absorber is composed of periodic copper wire array, magnetic material coated on copper wires, a foam substrate and a bottom metal plane. The results show a nearly perfect absorption peak around 8.7GHz (simulated) and 7.6GHz (measured). Even though the electric and magnetic field distribution indicate that the absorption is a typical metamaterial absorption, the power loss is neither Ohmic nor dielectric loss but magnetic loss, which is different from typical metamaterial absorber. The skillful introduction of the magnetic loss improves the absorption performance, including the absorption bandwidth and intensity. The designed absorber shows an effective application of the magnetic material, which is only 1/60000 volume proportion of the total absorber. Dependences of the absorption on frequency and the coating volume of the magnetic material manifest that the coated magnetic material can adjust the absorption peak position and intensity. The absorber can be an attractive candidate of electromagnetic wave absorber.

A Ferromagnetic Resonance Numerical Computation Method of Ferromagnetic Nano-Sphere

We have studied the approach for dynamic micromagnetic equilibrium conditions (Brown’s equations) in terms of nucleation theory provide micromagnetic solutions for linearized forms of the equilibrium equations. We focus on the case of ferromagnetic resonance here described for a ferromagnetic sphere with uniform magnetization and with no losses. With the linear approximation we have derived uniform and symmetric resonance mode to the micromagnetic equations describing the dynamic properties of the near single-domain states by ignoring the magnetostatic potential gradient in symmetric case. Moreover, using numerical integration solution to calculate exchange and magnetic energy, both resonance modes are proved to be effective approximate solution of Brown’s equations in the nanometer range.

High Frequency Magnetic Properties of A Composite Material Prepared from Z-Type Hexaferrite and Bi2O3

The composite materials are composed by Z-type hexaferrite and Bi2O3 by solid-state reaction method. Crystalline phase, microstructure and magnetic properties were measured by XRD, SEM, and VNA. The results showed that the sintering temperature and the content of Bi2O3 can effectively affected both uniformity and densification. Whats more, Z-type hexaferrite mixed with proper content of Bi2O3 and sintered at a low temperature presented a high Q-factor in a high frequency.

Composite of Flake-Shape Sendust Particles and its Application on Patch Antenna

Flake-shape Sendust particles with high microwave magnetic permeability and permittivity were prepared with the method of wet ball milling, and then mixed with the polymer to get a sheet-type composite as an effective EMW absorber. It was found that the composite has a very high shape factor owing to the flaky Sendust particles, which can break through the traditional Snoeks limit, and achieve a high effective magnetic permeability. HFSS simulation results show the sheet-type composite can be used on the patch antenna for improving the front-to-back ratio of the hand-held patch antenna and reducing the EMW pollution around antenna operators.

Influence of Al2O3 Buffer Layers on the Properties of Indium–Tin Oxide Films on PET Substrate by RF-Magnetron Sputtering

Indium Tin Oxide (ITO) films on PET substrate sandwiching Al2O3 buffer layers with different thickness have been prepared by magnetron sputtering at low deposition temperature. The crystal structures, electrical and optical properties of ITO films have been investigated by XRD, four-point probe technology and UV-Vis spectrophotometer as a function of different Al2O3 buffer layers thickness, respectively. XRD reveals that there is an amorphous structure in ITO films with no buffer layer. However, ITO films became crystalline after sandwiching the buffer layer. It can be found that there are two major peaks, (222) and (400) of ITO film. A smallest resistivity of 3.53×10-4 Ω.cm was obtained for ITO film with Al2O3 buffer layers thickness 75nm. The average transmittance of ITO/Al2O3/PET films in the visible range of 400-760nm wavelength was around 80%. It can be conclude that the (222) orientation of ITO film is more in favor of low resistivity.

Α-Fe /Nd2Fe14B Nanocomposites for Electromagnetic-Wave-Absorber in GHz Microwave Frequencies

Nd5Fe92B3 alloy was induction-melted. The α-Fe compounded low content of Nd2Fe14B nanocomposites were prepared using a melt-spinning method, subsequent annealing treatment, and ball milling. The complex permittivity, permeability of composites was measured in the 0.5-18 GHz frequency range. The permeability spectra exhibits relaxation type characteristic. The α-Fe/Nd2Fe14B composites shows an excellent microwave absorption property (reflection loss: RL<-20dB) in 9-17GHz with thin matching thickness 1.6-2.5 mm, due to the cooperate effect of magnetic loss and dielectric loss. α-Fe/Nd2Fe14B nanocomposites are thought to be a good microwave absorbers in GHz microwave range.