Search results

1 – 10 of 275
Article
Publication date: 9 August 2019

Jinsong Luo, Ligong Zhang, Haigui Yang, Nan Zhang, Yongfu Zhu, Xingyuan Liu and Qing Jiang

This paper aims to study the oxidation kinetics of the nanocrystalline Al ultrathin films. The influence of structure and composition evolution during thermal oxidation will be…

139

Abstract

Purpose

This paper aims to study the oxidation kinetics of the nanocrystalline Al ultrathin films. The influence of structure and composition evolution during thermal oxidation will be observed. The reason for the change in the oxidation activation energy on increasing the oxidation temperature will be discussed.

Design/methodology/approach

Al thin films are deposited on the silicon wafers as substrates by vacuumed thermal evaporation under the base pressure of 2 × 10−4 Pa, where the substrates are not heated. A crystalline quartz sensor is used to monitor the film thickness. The film thickness varies in the range from 30 to 100 nm. To keep the silicon substrate from oxidation during thermal oxidation of the Al film, a 50-nm gold film was deposited on the back side of silicon substrate. Isothermal oxidation studies of the Al film were carried out in air to assess the oxidation kinetics at 400-600°C.

Findings

The activation energy is positive and low for the low temperature oxidation, but it becomes apparently negative at higher temperatures. The oxide grains are nano-sized, and γ-Al2O3 crystals are formed at above 500°C. In light of the model by Davies, the grain boundary diffusion is believed to be the reason for the logarithmic oxidation rate rule. The negative activation energy at higher temperatures is apparent, which comes from the decline of diffusion paths due to the formation of the γ-Al2O3 crystals.

Originality/value

It is found that the oxidation kinetics of nanocrystalline Al thin films in air at 400-600°C follows the logarithmic law, and this logarithmic oxidation rate law is related to the grain boundary diffusion. The negative activation energies in the higher temperature range can be attributed to the formation of γ-Al2O3 crystal.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 5
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 25 May 2010

Vahid Afshari and Changiz Dehghanian

The purpose of this paper is to demonstrate the effect of grain‐size reduction on the stability of passive films formed on pure iron. Possible mechanisms capable of their…

Abstract

Purpose

The purpose of this paper is to demonstrate the effect of grain‐size reduction on the stability of passive films formed on pure iron. Possible mechanisms capable of their improvement are discussed.

Design/methodology/approach

Nanocrystalline iron was produced by pulse electrodeposition using a citric acid bath. The grain size of the nanocrystalline surface was analyzed by X‐ray diffractometry and atomic force microscopy. The tests were carried out in 95‐97 percent H2SO4 aqueous solution. The stability of the passive films was investigated using Tafel polarization curves and electrochemical impedance spectroscopy measurements.

Findings

The corrosion resistance of Fe in concentrated sulfuric acid solution increased as the grain size decreased from microcrystalline to nanocrystalline. The decreased passive current density of nanocrystalline Fe may be due to the more rapid formation of continuous passive films at surface crystalline defects, compared with coarse‐grained Fe structures.

Originality/value

The behavior of passive film growth and corrosion is considered in terms of excess free energy caused by the nanocrystalline surface.

Details

Anti-Corrosion Methods and Materials, vol. 57 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 7 December 2020

Michał Mazur, Roman Pastuszek, Damian Wojcieszak, Danuta Kaczmarek, Jarosław Domaradzki, Agata Obstarczyk and Aneta Lubanska

Indium tin oxide (ITO) is a material belonging to the group of transparent conductive oxides, which are widely used in many fields of technology including optoelectronics and…

Abstract

Purpose

Indium tin oxide (ITO) is a material belonging to the group of transparent conductive oxides, which are widely used in many fields of technology including optoelectronics and photovoltaics. However, the properties of ITO thin films depend on many factors. Therefore, the aim of the study was thorough investigation of the properties of sputtered ITO thin films of various thicknesses.

Design/methodology/approach

ITO coatings were deposited by magnetron sputtering in pure argon atmosphere using ceramic ITO target. Various deposition times resulted in obtaining thin films with different thickness, which had significant influence on the optoelectronic properties of deposited coatings. In this work the results of investigation of structural, surface, optical and electrical properties were presented.

Findings

Increase of the coating thickness caused change of the microstructure from amorphous to nanocrystalline and occurrence of grains with a size of 40 to 60 nm on their surface. Moreover, the fundamental absorption edge was red-shifted, whereas the average transmission in the visible wavelength range remained similar. Increase of the thickness caused considerable decrease of the sheet resistance and resistivity. It was found that even thin films with a thickness of 10 nm had antistatic properties.

Originality/value

The novelty and originality of presented work consists in, among other, determination of antistatic properties of ITO thin films with various sheet resistances that are in the range typical for dielectric and semiconducting material. To date, there are no reports on such investigations in the literature. Reported findings might be very helpful in the case of, for example, construction of transparent antireflective and antistatic multilayers.

Article
Publication date: 26 April 2013

Maryam Amirhoseiny, Zainuriah Hassan and Sha Shiong Ng

The purpose of this paper was to investigate the growth dependence of InN on Si substrate with different orientation through RF reactive magnetron sputtering in ambient…

Abstract

Purpose

The purpose of this paper was to investigate the growth dependence of InN on Si substrate with different orientation through RF reactive magnetron sputtering in ambient temperature.

Design/methodology/approach

The authors fabricated indium nitride (InN) thin films by radio frequency (RF) sputtering. The InN thin films were deposited on Si (100), Si (110) and Si (111) substrates at room temperature. The crystalline structure and surface morphology of the InN films were characterized by X‐ray diffraction (XRD), scanning electron microscope (SEM), energy‐dispersive X‐ray spectroscopy (EDX) and atomic force microscopy (AFM).

Findings

X‐ray diffraction results revealed that the wurtzite InN with preferential (101) orientation are deposited. Through the Scherrer structural analysis revealed nanocrystalline structure for InN films grown on Si (110), Si (100) and Si (111) orientation with crystallite size of 42.3, 33.8 and 24.1, respectively. The optical properties of InN layers were examined by Fourier transform infrared (FTIR) and micro‐Raman reflectance spectroscopy at room temperature. The observation of the E1(TO), A1(LO), and E2(high) phonon modes of the InN from the IR and Raman results confirmed that the deposited InN thin film has hexagonal structure.

Originality/value

Si (110) surface is not isotropic and it may offer a unique orientation plane for the nitride films which could reduce the defect density and the resulting tensile stress responsible for film cracking. Therefore, it is absolutely worth exploring the growth of InN on Si (110) by using relatively simple and cheap reactive sputtering technique.

Article
Publication date: 14 September 2010

L.A. Patil, A.R. Bari, Shinde and Vinita Deo

The purpose of this paper is to show how to obtain better response, selectivity and fast response and recovery from nanocrystalline ZnO‐based gas sensors as compared to…

Abstract

Purpose

The purpose of this paper is to show how to obtain better response, selectivity and fast response and recovery from nanocrystalline ZnO‐based gas sensors as compared to conventional materials.

Design/methodology/approach

Nanocrystalline ZnO powders were prepared from the ultrasonic spray pyrolysis method. Aqueous solution of zinc acetate was atomized using ultrasonic atomizer. The aerosol generated was fed to the reaction furnace for pyrolysis. Nanocrystalline ZnO crystallites were collected using simple but novel trapping system. Thick film resistors of this powder were fabricated using screen printing technique.

Findings

As‐prepared powder was studied using X‐ray diffraction, transmission electron microscopy and scanning electron microscopy to know structure, size of nanocrystallites and microtopography, respectively. Absorption spectroscopy is used to determine the band gap energy. The gas‐sensing performance of this film was tested.

Originality/value

The sensor was found to be the most sensitive to NH3. It gives better response, selectivity and fast response and recovery as compared to conventional materials‐based thick films.

Details

Sensor Review, vol. 30 no. 4
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 8 January 2018

Yun He, Fanghong Sun and Xuelin Lei

This study aims to obtain diamond-coated mechanical seals with improved sealing performance and considerable cost. To achieve this purpose, the study focuses on depositing…

Abstract

Purpose

This study aims to obtain diamond-coated mechanical seals with improved sealing performance and considerable cost. To achieve this purpose, the study focuses on depositing uniform, wear-resistant and easily polished diamond coatings on massive mechanical seals in a large-scale vacuum chamber.

Design/methodology/approach

The computational fluid dynamics simulation test and its corresponding deposition experiment are carried out to improve the uniformity of diamond films on massive mechanical seals. The polishing properties and sealing performance of mechanical seals coated with three different diamond films (microcrystalline diamond [MCD], nanocrystalline diamond [NCD] and microcrystalline/nanocrystalline diamond [MNCD]) and uncoated mechanical seals are comparatively studied using the polishing tests and dynamic seal tests to obtain the optimized diamond coating type on the mechanical seals.

Findings

The substrate rotation and four gas outlets distribution are helpful for depositing uniform diamond coatings on massive mechanical seals. The MNCD-coated mechanical seal shows the advantages of high polishing efficiency in the initial polishing process and excellent wear resistance and self-lubrication property in the follow-up polishing period because of its unique composite diamond film structures. The MNCD-coated mechanical seal shows the longest working life under dry friction condition, about 14, 1.27 and 1.9 times of that for the uncoated, MCD and NCD coated mechanical seals, respectively.

Originality/value

The effect of substrate rotation and gas outlets distribution on temperature and gas flow field during diamond deposition procedure is simulated. The MNCD-coated mechanical seal exhibits a superior sealing performance compared with the MCD-coated, NCD-coated and uncoated mechanical seals, which is helpful for decreasing the operating system shut-down frequency and saving operating energy consumption.

Details

Industrial Lubrication and Tribology, vol. 70 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 23 July 2020

Wei Luo, Lei Hu, Yimin Xv, Jian Zhou, Wentao Xv and Mi Yan

This paper aims to focus on an assessment of the electrochemical corrosion performance of bulk NC copper in a variety of corrosion environments.

Abstract

Purpose

This paper aims to focus on an assessment of the electrochemical corrosion performance of bulk NC copper in a variety of corrosion environments.

Design/methodology/approach

The electrochemical corrosion behavior of bulk nanocrystalline (NC) copper prepared by inert gas condensation and in situ warm compress technique was studied by using potentiodynamic polarization and electrochemical impedance spectroscopy tests in de-aerated 0.1 M NaOH solution.

Findings

NC copper exhibited a typical active-passive-transpassive behavior with the formation of duplex passive films, which was qualitatively similar to coarse-grain (CG) copper. Although a compact passive film formed on NC copper surface, the corrosion resistance of NC copper was lower in comparison with CG copper. The increase in corrosion rate for NC copper was mainly attributed to the high activity of surface atoms and intergranular atoms. These atoms led to an enhancement of passive ability and an increase of dissolution rate of passive film in oxygen-deficiency solution. For NC copper, the corrosion resistance decreased as grain size increased in NC range.

Originality/value

The difference in corrosion resistance between bulk NC copper and its CG counterpart is dependent upon the corrosion solution. In a previous work, the potentiodynamic polarization tests revealed that NC copper bulks (grain size 48, 68, 92 nm) had identical corrosion resistance to CG copper bulk in naturally aerated 0.1 M NaOH solution. The results might be related to the dissolved oxygen in the medium.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 5
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 7 August 2018

Kaleem Ahmad Najar, N.A. Sheikh, Mohammad Mursaleen Butt and M.A. Shah

The purpose of this study is to investigate the mechanical and tribological properties of the synthetic diamond coatings deposited on WC-Co cutting tools for their prospective…

Abstract

Purpose

The purpose of this study is to investigate the mechanical and tribological properties of the synthetic diamond coatings deposited on WC-Co cutting tools for their prospective applications in mechanical industry. In this work, the concept of nanocrystalline diamond, microcrystalline diamond and multilayer-diamond coating systems were proposed and deposited on WC-Co substrates with the top-layer nanocrystallinity, optimum thickness and interfacial adhesion strength for load-bearing tribological and machining applications. Also, the overall mechanical and tribological properties of all synthetic diamond coatings were compared for the purpose of selecting a suitable type of protective layer used on the surfaces of WC-Co cutting tools or mechanical dies.

Design/methodology/approach

Smooth and adhesive single layered and multilayered synthetic deposited on chemically etched cemented tungsten carbide (WC-Co) substrates using predetermined process parameters in hot filament chemical vapor deposition (HFCVD) method. A comparison has been documented between diamond coatings having different nature and architecture for the purpose of studying their mechanical and tribological characteristics. The friction characteristics were studied experimentally using ball-on-disc type linear reciprocating micro-tribometer under the influence of varying load conditions and within dry sliding conditions. Nanoindentation tests were conducted on each diamond coating using Berkovich nanoindenter for the measurement of their hardness and elastic modulus values. Also, the wear characteristics of all sliding bodies were studied under varying load conditions using cumulative weight loss and density method.

Findings

Depositing any type of diamond coating on the cemented carbide tool insert increases its all mechanical and tribological characteristics. When using boron-doping onto the top-layer surface of diamond coatings decrease slightly their mechanical properties but increases the tribological characteristics. Present analysis reveals that friction coefficient of all diamond-coated WC-Co substrates decreases with the increase of normal load. Therefore, maintaining an appropriate level of normal load, sliding time, sliding distance, atmospheric conditions and type of diamond coating, the friction coefficient may be kept to some lower value to improve mechanical processes.

Originality/value

As the single layered synthetic diamond coatings have not given the full requirements of mechanical and tribological properties when deposited on cutting tools. Therefore, the multilayered diamond coatings were proposed and developed to enhance the interfacial integrity of the nanocrystalline and microcrystalline layers (by eliminating the sharp interface) as well as increasing the hardness of tungsten carbide substrate. However, when using boron doping onto the top-layer surface of diamond, coatings decreases slightly their mechanical characteristics but also decreases the value of friction coefficient.

Details

Industrial Lubrication and Tribology, vol. 70 no. 7
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 14 January 2014

Robert Bogue

– This paper aims to provide a detailed review of gas sensor research which exploits the properties of nanomaterials and nanostructures.

1969

Abstract

Purpose

This paper aims to provide a detailed review of gas sensor research which exploits the properties of nanomaterials and nanostructures.

Design/methodology/approach

Following an introduction, this paper discusses developments in gas sensors based on carbon nanotubes, titanium dioxide nanotubes, graphene, nanocrystalline diamond and a range of metal oxide nanomaterials. It concludes with a discussion of this research and its commercial potential and a list of references to the research considered in the main text.

Findings

Gas sensors based on a multitude of nanomaterials are the subject of a global research effort which has generated an extensive literature. Prototype devices have been developed which respond to numerous important gases at concentrations which correspond well with industrial requirements. Other critical performance characteristics have been studied extensively and the results suggest commercial prospects for these technologies.

Originality/value

This paper provides details of the highly topical field of nanomaterial-based gas sensor research.

Details

Sensor Review, vol. 34 no. 1
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 2 January 2018

Kavindra Kandpal and Navneet Gupta

The purpose of this paper is to present a comprehensive review on development and future trends in zinc oxide thin film transistors (ZnO TFTs). This paper presents the development…

1062

Abstract

Purpose

The purpose of this paper is to present a comprehensive review on development and future trends in zinc oxide thin film transistors (ZnO TFTs). This paper presents the development of TFT technology starting from amorphous silicon, poly-Si to ZnO TFTs. This paper also discusses about transport and device modeling of ZnO TFT and provides a comparative analysis with other TFTs on the basis of performance parameters.

Design/methodology/approach

It highlights the need of high–k dielectrics for low leakage and low threshold voltage in ZnO TFTs. This paper also explains the effect of grain boundaries, trap densities and threshold voltage shift on the performance of ZnO TFT. Moreover, it also addresses the challenges like requirement of stable p-type ZnO semiconductor for various electronic applications and high value of ZnO mobility to meet growing demand of high-definition light emitting diode TV (HD-LED TV).

Findings

This review will motivate the readers to further investigate the conduction mechanism, best alternate for gate-dielectric and the deposition technique optimization for the enhancement of the performance of ZnO TFTs.

Originality/value

This is a literature review. The technological evolution of TFT in general and ZnO TFT in particular is presented in this paper.

Details

Microelectronics International, vol. 35 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

1 – 10 of 275