Papers by Keyword: Bias Voltage

Abstract: In this work, the adhesion and corrosion resistance of TiN coating by magnetron sputtering on stainless steel substrates under different bias voltages conditions (-50 V and-100 V) was investigated. AFM was used for surface roughness and grain size analysis, XRD for phase identification, Rockwell C for adhesion and nanoindentation for hardness and elastic modulus. According to AFM the coating deposited at-100V bias had decreased surface roughness, the value decreased from 2.7 nm (for-50V sample) to 1.8 nm, this was due to an etching like process which occurs when ions with higher energies start hitting the surface. The coated samples came under HF1 adhesion parameter which is the highest class of adhesion in the model on the basis of Rockwell C adhesion test. nanoindentation hardness and elastic modulus results of-50 V and-100V were found to be 224 GPa and 182 GPa, respectively and the value of hardness, 16 GPa and 22 GPa, respectively. The corrosion behavior of TiN coatings were studied in 3.5wt. % NaCl solutions using Tafel Extrapolation, Cyclic Polarization and Open Circuit Potential. It was noted on the basis of these corrosion tests that, as bias voltage is increased, it leads to the formation of more densely packed, fine grained columnar structures with less pores, which decreases the chances of corrosion. .

Abstract: Generally, bias voltage exercises a great influence on micro-properties (morphology, preferred orientation, mechanical properties, and so on) of the coatings in the process of coating deposited. In order to more systematically explore the influence of bias voltage on microstructure, hardness and adhesion of TiN coatings, TiN coatings were deposited successfully on the surface of 316 stainless steel by high power pulsed magnetron sputtering (HPPMS). A field emission scanning electron microscopy equipped with energy dispersive spectrometer (FESEM/EDS) and an X-ray diffractometer were employed to analyze the surface morphology, chemical composition and phase structure of coatings, respectively. And a nanoindentation and scratch tester was used to investigate the hardness, elastic modulus and adhesion of TiN coatings. Results showed that bias voltage has a great influence on surface morphology of TiN coatings. Moreover, bias voltage can promote preferential orientation and the phase in TiN coating is mainly TiN with a small amount of Ti₂N. The influence of bias voltage on the hardness and modulus of TiN coating is not obvious, however, the binding force increases fast first and then decreases slow with the increase of bias voltage. TiN coating has excellent performance when bias voltage is-100V.

Abstract: CrN coatings were deposited by reactive magnetron sputtering at different substrate bias voltages. The effects of bias voltage on micro-structure and mechanical properties of CrN coatings were studied by scanning electron microscopy, X-ray diffraction, micro-hardness tester and a multi-functional tester for material surface properties, respectively. The results showed that bias voltage had a great influence on morphologies of CrN coatings and CrN coatings presented obvious preferred orientation with the increase of bias voltage. In addition, bias voltages in a certain range can also improve hardness and adhesion of CrN coatings, but higher voltages were not good. In this paper, the adhesion and hardness of CrN coatings presented the trend that a rise first followed by a decline with the ever-increasing bias voltages at the same time, but CrN coating had the superior mechanical properties when the bias voltage was-100 V.

Abstract: The spark plug ion current signal carries abundant information about the engine combustion process. Real-time acquisition of the spark plug ion current signal can effectively extract the characteristic parameters, then enhance the power, fuel economy and emissions of the engine. The paper analyzed the influence factors of ion current, designed an acquisition and analysis system of spark plug ion current signal, and mainly studied the influence of spark plug gap and bias voltage on ion current signal in a six-cylinder four-stroke gas engine. The results show that the bias voltage and the spark plug gap have a great impact on the spark plug ion current signal. The ion current signal intensity is directly proportional to the bias voltage applied cross the spark plug, and inversely proportional to the spark plug gap. Results also indicates that the ion current is directly proportional to the mobility and concentration of charged particles in burned gas plasma.

Abstract: CrN_x coatings were prepared by closed filed unbalanced magnetron sputtering (CFUMS), and the effects of N₂ flux ratio and bias voltage on CrN coatings were investigated. Results showed that the phase in coatings was the coexistence of CrN, Cr₂N and Cr, and CrN(111) always showed an intensive preferred orientation in both cases, but CrN(200) enhanced with the rise of bias voltage. The hardness of coatings decreased with an increasing N₂ flux ratio, while improved with an increasing bias voltage. The grain edges were polished off and the boundaries became blurred when higher bias voltage was applied. All in all, the surface morphologies of CrN coatings became flatter and denser with both increasing N₂ content and bias voltage, respectively.

Abstract: In order to enhance the treatment processing for powder of nanoparticle, we developed a modified setup using an inductively coupled radio frequency plasma with a pulsed explosion technique. Applying a negative pulsed bias voltage of -1 kV to the substrate stage in 15 seconds with a repetition frequency of 1 kHz and a duty ratio of 50 % in ammonia plasma, a significant increase of N 1s peak intensity in the X-ray photoelectron spectroscopy spectra was observed. The intensity of N 1s peak treated in the pulsed-biasing system raised both about four times higher than those of the particles treated without bias. After plasma treatment, the amino group was suggested to be covalently functionalized onto the nanoparticle surface and quantitatively examined by chemical derivatization. The amino group population attached onto treated nanoparticles was determined about 8.2 x 10⁴ molecules per nanoparticle, roughly four times higher than that of particle without biasing which was about 1.9 x 10⁴ molecules per nanoparticle. The surface structure analysis by a high resolution-transmission electron microscopy showed no significant damages were found on the nanoparticles, indicating that the present technique is suitable mainly for surface modification of powder materials without bringing any damages on their structural and morphological surface.

Abstract: CrN coatings have been deposited successfully by Closed Filed Unbalanced Magnetron Sputter Ion Plating (CFUMSIP). The effect of substrate temperature (T_S) and bias voltage (V_B) together on microstructure, morphologies and mechanical properties of CrN coatings were studied. The results showed that the deposition rate of CrN coatings declines with the increase of V_B Under both room temperature (R.M.) and 300°C. The FCC-CrN disappeared gradually and orth-CrN arised with the increase of V_B, and the T_S promoted the transformation from FCC - CrN to orth - CrN. The surface morphology of CrN coatings with changed V_Bs was greatly different, and V_B could further improve the mechanical properties of coatings. In this paper, the CrN coating with the parameters (T_S =300°C, V_B =-30V) had relatively high deposition rate and mechanical properties.

Abstract: Amorphous hydrogenated carbon (α-C:H) thin films were deposited by the linear ion source (LIS)-physical vapor deposition (PVD) at the bias voltages ranging from 0V to-1500V. The characteristics such as surface topography and mechanism properties of the film were investigated under the voltage of 0V, -500V, -1000V and-1500V by using atomic force microscope (AFM), Ball Mills and Rockwell Indentation Tester. The results showed that with the increase of the bias voltage, the surface roughness of the film decreased initially and then increased. The wear resistance and compressive property were continuously improved. When the bias voltage was-1000V, the surface roughness was the lowest of 5.78nm.When the bias voltage went to-1500V, the film had the lowest wear rate of 7.8E-8 and the best compressive property. As a result, deeply understanding the effect mechanism of the bias voltage on α-C:H thin film is meaningful for the future deposition.

Abstract: LaB₆ films are deposited by magnetron sputtering deposition. ZrO₂ glass is used as substrate. Bias voltage and substrate temperature are adjusted. Morphology of films that deposited at different parameters is characterized by AFM. Results of AFM shows that grains diameter on surface of LaB₆ films is nanoscale, and roughness of the surface is less than 20nm. LaB₆ crystallites are seen to cover substrate surface entirely. Structure of films is smooth and compactness, and there is no obviously default is found. Bias-voltage influences morphologies of films more obviously than substrate. The best bias voltage is-100V. Structure of film that deposited at 450°C is more compactness than others, and roughness of the film is least.

Abstract: Al coatings were prepared on 316L stainless steel substrate by arc-added glow plasma depositing technique and then plasma oxidized. The influences of bias voltage and arc source current on both the thickness and surface roughness of Al coatings were investigated respectively. Then, the microstructure and the composition of Al and Al₂O₃ coatings were characterized. Finally, the bonding force and the corrosion resistance of as-prepared alumina coatings were discussed. The results indicated that nanostructured pure Al coatings with surface roughness (Ra) of 267.93 nm were obtained when the bias of the substrate was-300V and the arc current was 70A. The Al₂O₃ coatings oxidized from nanoAl coatings were dense and uniform, with a bonding force of 37.4 N, an excellent corrosion potential of-0.202V and corrosion current of 0.197 μm·cm^-2 in 3.5% NaCl solution.