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11 – 20 of 610Birk Wollenhaupt, Quang Hoa Le and Georg Herdrich
This paper aims to provide an overview of current and historical arcjet development. The reviewed arcjets are considered with respect to both design and thruster relevant…
Abstract
Purpose
This paper aims to provide an overview of current and historical arcjet development. The reviewed arcjets are considered with respect to both design and thruster relevant parameters. Correspondingly, the paper enables the identification of adequate design criteria and of the probable thruster parameters.
Design/methodology/approach
The approach consists of a database for thruster relevant parameters in conjunction with relevant operational requirements (such as type of propellant) and specific design criteria (such as e.g. propellant injection systems).
Findings
The synopsis of both operational parameter and respectively assigned design allows for the derivation of development approaches for arcjets under given high level requirements such as power regime.
Research limitations/implications
The paper is a general review. However, its strength is in the synthesis of the arcjet classification, the functional evidence of design criteria and the application scenario.
Practical implications
Not only basic but also specific design criteria are analyzed and evaluated leading to a recommendation feature of the paper with respect to the overall design of adequate arcjets.
Social implications
Within the scope of the Clean Space initiative, new applications and scenarios from the operation of arcjets arise enabling EOL phases of spacecraft that fulfill respective levels of debris mitigation and, in addition, the requirements concerning the adequately adapted re-entry of spacecrafts that are at end of life.
Originality/value
The paper is a general review. However, its strength is in the synthesis of the arcjet classification, the functional evidence of design criteria and the application scenario.
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Anis Suhaili Bakri, Nafarizal Nayan, Chin Fhong Soon, Mohd Khairul Ahmad, Ahmad Shuhaimi Abu Bakar, Wan Haliza Abd Majid and Nur Amaliyana Raship
This paper aims to report the influence of sputtering plasma deposition time on the structural and mechanical properties of the a-axis oriented aluminium nitride (AlN) thin films.
Abstract
Purpose
This paper aims to report the influence of sputtering plasma deposition time on the structural and mechanical properties of the a-axis oriented aluminium nitride (AlN) thin films.
Design/methodology/approach
The AlN films were prepared using RF magnetron sputtering plasma on a silicon substrate without any external heating with various deposition times. The films were characterized using X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), atomic force microscope (AFM) and nanoindentation techniques.
Findings
The XRD results show that the AlN thin films are highly oriented along the (100) AlN plane at various deposition times indicating the a-axis preferred orientation. All the AlN thin films exhibit hexagonal AlN with a wurtzite structure. The hardness and Young’s modulus of AlN thin films with various deposition times were measured using a nanoindenter. The measured hardness of the AlN films on Si was in the range of 14.1 to 14.7 GPa. The surface roughness and the grain size measured using the AFM revealed that both are dependent on the deposition times.
Originality/value
The novelty of this work lies with a comparison of hardness and Young’s modulus result obtained at different sputtering deposition temperature. This study also provides the relation of AlN thin films’ crystallinity with the hardness of the deposited films.
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HfO2 has emerged as the most promising high k dielectric for an alternative gate material. As‐deposited HfO2 thin films have large number of defects resulting in increased oxide…
Abstract
Purpose
HfO2 has emerged as the most promising high k dielectric for an alternative gate material. As‐deposited HfO2 thin films have large number of defects resulting in increased oxide charge and leakage current. Film deposition condition plays an important role. This paper investigates the effect of sputtering voltage, bias sputtering and post deposition thermal annealing.
Design/methodology/approach
The microstructure of the film is examined by AFM. The I‐V and C‐V characteristics is evaluated from Al‐HfO2‐Si capacitor structures and the effect of processing conditions is studied. The experimental results are reported and discussed for improving film properties.
Findings
It is found that applying substrate bias during film deposition improves interface and reduce leakage current and oxide charges.
Originality/value
The paper studies the effect of deposition voltage and thermal annealing on thin film deposition of HfO2 by rf sputtering.
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Xiaohong Yuan, Wenzheng Xu, Fenglin Huang, Qingqing Wang, Qufu Wei and Dongsheng Chen
Structural color is more brilliant in color, more resistant to sunshine and will not fade away with time, and more environmental friendly than traditional dyes and pigments. The…
Abstract
Purpose
Structural color is more brilliant in color, more resistant to sunshine and will not fade away with time, and more environmental friendly than traditional dyes and pigments. The purpose of this paper is to prepare structural colors of fabrics coated with Ag/TiO2 composite films by magnetron sputtering, and analyze the relationship between the colors and the thicknesses of TiO2 films in Ag/TiO2 composite films.
Design/methodology/approach
Preparation of Ag/TiO2 composite films by magnetron sputtering and their deposition on textiles were investigated. The chemical compositions and surface morphology of Ag/TiO2 composite films were examined by X-ray photoelectron spectroscopy and scanning electron microscopy, and the structural color of fabric coated with Ag/TiO2 composite film was also analyzed.
Findings
Ag/TiO2 composite films deposited on textile substrate exhibited structural colors, and the bright colors could be adjusted and controlled by the thickness of TiO2 thin films in Ag/TiO2 composite films without any dyes or pigments. By comparing the results of theoretical calculation and experimental results, it was found that the creation of structural colors by the experiment was coincident to the colors by theoretical calculation according to the film interference principle. There was a linear relationship between the thickness of TiO2 film and the wavelength of the structural color.
Originality/value
Compared to traditional coloration by dyes or pigments, the coloration of textile by structural color from Ag/TiO2 composite films prepared by magnetron sputtering was very environmental friendly and simple without water consuming, time consuming and tedious work. Structural colors have great potential applications in textiles in place of traditional dyes and pigments. Furthermore, the textiles coated with Ag/TiO2 composite films have good electrical, optical and magnetic properties, and can be used in apparel, home furnishings and industrial fabrics.
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Keywords
He Lu, Yuhou Wu, Zijin Liu, He Wang, Guangyu Yan, Xu Bai, Jiancheng Guo and Tongxiang Zheng
Preparing CrAlN coatings on the surface of silicon nitride bearings can improve their service life in oil-free lubrication. This paper aims to match the optimal process parameters…
Abstract
Purpose
Preparing CrAlN coatings on the surface of silicon nitride bearings can improve their service life in oil-free lubrication. This paper aims to match the optimal process parameters for preparing CrAlN coatings on silicon nitride surfaces, and reveal the microscopic mechanism of process parameter influence on coating wear resistance.
Design/methodology/approach
This study used molecular dynamics to analyze how process parameters affected the nucleation density, micromorphology, densification and internal stress of CrAlN coatings. An orthogonal test method was used to examine how deposition time, substrate temperature, nitrogen-argon flow rate and sputtering power impacted the wear resistance of CrAlN coatings under dry friction conditions.
Findings
Nucleation density, micromorphology, densification and internal stress have a significant influence on the surface morphology and wear resistance of CrAlN coatings. The process parameters for better wear resistance of the CrAlN coatings were at a deposition time of 120 min, a substrate temperature of 573 K, a nitrogen-argon flow rate of 1:1 and a sputtering power of 160 W.
Originality/value
Simulation analysis and experimental results of this paper can provide data to assist in setting process parameters for applying CrAlN coatings to silicon nitride bearings.
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Zulkifli Azman, Nafarizal Nayan, Megat Muhammad Ikhsan Megat Hasnan, Nurafiqah Othman, Anis Suhaili Bakri, Ahmad Shuhaimi Abu Bakar, Mohamad Hafiz Mamat and Mohd Zamri Mohd Yusop
This study aims to investigate the effect of temperature applied at the initial deposition of Aluminium Nitride (AlN) thin-film on a silicon substrate by high-power impulse…
Abstract
Purpose
This study aims to investigate the effect of temperature applied at the initial deposition of Aluminium Nitride (AlN) thin-film on a silicon substrate by high-power impulse magnetron sputtering (HiPIMS) technique.
Design/methodology/approach
HiPIMS system was used to deposit AlN thin film at a low output power of 200 W. The ramping temperature was introduced to substrate from room temperature to maximum 100°Cat the initial deposition of thin-film, and the result was compared to thin-film sputtered with no additional heat. For the heat assistance AlN deposition, the substrate was let to cool down to room temperature for the remaining deposition time. The thin-films were characterized by X-ray diffraction (XRD) and atomic force microscope (AFM) while the MIS Schottky diode characteristic investigated through current-voltage response by a two-point probe method.
Findings
The XRD pattern shows significant improvement of the strong peak of the c-axis (002) preferred orientation of the AlN thin-film. The peak was observed narrowed with temperature assisted where FWHM calculated at 0.35° compared to FWHM of AlN thin film deposited at room temperature at around 0.59°. The degree of crystallinity of bulk thin film was improved by 28% with temperature assisted. The AFM images show significant improvement as low surface roughness achieved at around 0.7 nm for temperature assisted sample compares to 3 nm with no heat applied.
Originality/value
The small amount of heat introduced to the substrate has significantly improved the growth of the c-axis AlN thin film, and this method is favorable in the deposition of the high-quality thin film at the low-temperature process.
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Lingling Meng, Qufu Wei, Yueli Li and Wenzheng Xu
In this study, the polyester fabrics were treated with low temperature plasma before Cu sputtering. The effect of oxygen gas plasma pre-treatment on the surface structures…
Abstract
Purpose
In this study, the polyester fabrics were treated with low temperature plasma before Cu sputtering. The effect of oxygen gas plasma pre-treatment on the surface structures, electrical properties, and mechanical properties of samples was investigated. The paper aims to discuss these issues.
Design/methodology/approach
A laboratory direct current (DC) magnetron sputter coating system was used to deposit the nanoscale copper (Cu) films onto the surface of polyester plain fabric at room temperature.
Findings
The crystal structure of the sputtered copper films did not show any obvious change on the O2-plasma-treated fabric, but the surface roughness and surface particle size increased significantly. Improvement in electrical properties of copper films was closely related to the deposition time. The tensile test results indicated that the mechanical properties of the plasma-treated polyester fabrics were also improved after copper coating.
Originality/value
The research reports on the functional textiles, and the experiment results and analysis are original. There is a great potential to commercialize such functional textiles.
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D. Desideri, M. Bagatin, M. Spolaore, V. Antoni, R. Cavazzana, E. Martines, G. Serianni and M. Zuin
The aim of this paper is to obtain an extensive experimental characterization of a DC magnetron sputtering device used for plasma processing of materials.
Abstract
Purpose
The aim of this paper is to obtain an extensive experimental characterization of a DC magnetron sputtering device used for plasma processing of materials.
Design/methodology/approach
Models and measurements are combined for an interdisciplinary characterization of a DC magnetron sputtering device. Langmuir probes are used for the plasma characterization; the magnetic field is measured by using Hall probes and the data are used to validate a magnetostatic three‐dimensional numerical analysis of the device; precision mechanical measurements are done for the target erosion profile and the results are related to a simple estimation formula; a simple model is proposed for the target heating.
Findings
Data on magnetic and electric fields, electron temperature and density, plasma potential and target erosion are provided. An estimation of the target heating is proposed. Finally, an application concerning thin film deposition is reported.
Research limitations/implications
Measurement of the target surface temperature for the validation of the proposed target heating estimation has not been done.
Originality/value
In the field of the electromagnetic processing of materials, the reported extensive device characterization is a valuable set of information for an optimized utilization of DC magnetron sputtering devices.
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Siti Kudnie Sahari, Muhammad Kashif, Norsuzailina Mohamed Sutan, Zaidi Embong, Nik Amni Fathi Nik Zaini Fathi, Azrul Azlan Hamzah, Rohana Sapawi, Burhanuddin Yeop Majlis and Ibrahim Ahmad
The quality of GeOx–Ge interface and the equivalent oxide thickness (EOT) are the main issues in fabricating high-k/Ge gate stack due to the low-k of GeOx interfacial layer (IL)…
Abstract
Purpose
The quality of GeOx–Ge interface and the equivalent oxide thickness (EOT) are the main issues in fabricating high-k/Ge gate stack due to the low-k of GeOx interfacial layer (IL). Therefore, a precise study of the formation of GeOx IL and its contribution to EOT is of utmost importance. In this study, the GeOx ILs were formed through post-oxidation annealing of sputtered Al2O3 on the Ge substrate. The purpose of this paper is to report on growth kinetics and composition of IL between Al2O3 and Ge for HCl- and HF-last Ge surface.
Design/methodology/approach
After wet chemical cleaning with HCl or HF, Al2O3 was grown onto the Ge surface by RF sputtering. Thickness and composition of IL formed after post-anneal deposition at 400°C in dry oxygen ambience were evaluated as a function of deposition time by FESEM and characterized by X-ray photoelectron spectroscopy, respectively.
Findings
It was observed that the composition and thickness of IL were dependent on the starting surface and an aluminum germinate-like composition was formed during RF sputtering for both HF- and HCl-last starting surface.
Originality/value
The novelty of this work is to investigate the starting surface of Ge to IL growth between Al2O3/Ge that will lead to the improvement in Ge metal insulator field effect transistors (MISFETs) application.
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Modupeola Dada, Patricia Popoola and Ntombi Mathe
This study aims to review the recent advancements in high entropy alloys (HEAs) called high entropy materials, including high entropy superalloys which are current potential…
Abstract
Purpose
This study aims to review the recent advancements in high entropy alloys (HEAs) called high entropy materials, including high entropy superalloys which are current potential alternatives to nickel superalloys for gas turbine applications. Understandings of the laser surface modification techniques of the HEA are discussed whilst future recommendations and remedies to manufacturing challenges via laser are outlined.
Design/methodology/approach
Materials used for high-pressure gas turbine engine applications must be able to withstand severe environmentally induced degradation, mechanical, thermal loads and general extreme conditions caused by hot corrosive gases, high-temperature oxidation and stress. Over the years, Nickel-based superalloys with elevated temperature rupture and creep resistance, excellent lifetime expectancy and solution strengthening L12 and γ´ precipitate used for turbine engine applications. However, the superalloy’s density, low creep strength, poor thermal conductivity, difficulty in machining and low fatigue resistance demands the innovation of new advanced materials.
Findings
HEAs is one of the most frequently investigated advanced materials, attributed to their configurational complexity and properties reported to exceed conventional materials. Thus, owing to their characteristic feature of the high entropy effect, several other materials have emerged to become potential solutions for several functional and structural applications in the aerospace industry. In a previous study, research contributions show that defects are associated with conventional manufacturing processes of HEAs; therefore, this study investigates new advances in the laser-based manufacturing and surface modification techniques of HEA.
Research limitations/implications
The AlxCoCrCuFeNi HEA system, particularly the Al0.5CoCrCuFeNi HEA has been extensively studied, attributed to its mechanical and physical properties exceeding that of pure metals for aerospace turbine engine applications and the advances in the fabrication and surface modification processes of the alloy was outlined to show the latest developments focusing only on laser-based manufacturing processing due to its many advantages.
Originality/value
It is evident that high entropy materials are a potential innovative alternative to conventional superalloys for turbine engine applications via laser additive manufacturing.
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