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Article
Publication date: 1 October 2001

A. Mimaroglu, M. Çaliskan and I. Calli

Advanced ceramics such as alumina are widely in use in the design of components for high engineering applications mainly because of their high wear resistance, high…

Abstract

Advanced ceramics such as alumina are widely in use in the design of components for high engineering applications mainly because of their high wear resistance, high compressive strength, low specific density and high temperature capability. Processing and manufacturing of pure alumina products is a difficult and expensive task. Therefore, additional compounds are added to alumina to achieve a more complex component design and to minimise the product processing and manufacturing costs. This paper examines the effects of speed, load values and the addition of Cr2O3, SiO2 and MnO2 compounds on the friction and wear behaviour of alumina ceramic. Wear tests for alumina and alumina samples containing w1.5% Cr2O3 w3% SiO2 and w1.5% MnO2 compounds was carried out on a pin‐on‐disc machine. Tribological tests were under 2.5, 5 and 10N loads and at 0.5, 0.75 and 1m/Sec speeds. The specific wear rates were deduced from mass loss. The wear rate for alumina without additional compounds was in the order of 10–8 to 10–7mm2/N, while the wear rate values for alumina with additional compounds were in the order of 10–6. Moreover, the wear rate showed more sensitivity to the applied load, particularly at low sliding speeds. Furthermore, it is concluded that a 20 per cent decrease in the sintering temperature resulted in 300 per cent increase in the specific wear rate of alumina ceramic material.

Details

Industrial Lubrication and Tribology, vol. 53 no. 5
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 1 February 1983

C. Val and N. Humbert

Previous studies on special dielectrics for multilayer screen printing led to defining a new concept for standard alumina substrate. The modification of the process and…

Abstract

Previous studies on special dielectrics for multilayer screen printing led to defining a new concept for standard alumina substrate. The modification of the process and structure permits an increase of the thermal conductivity. The thermal conductivity of this new material is between that of alumina and BeO. It is possible to increase the thermal conductivity of 94% standard alumina (used in chip‐carriers) up to 3·6 times. It it known that the thermal conductivity of beryllia is 7 times higher than that of alumina. The thermal model gives an increase of 4 times for other configurations non‐tested in this study. With this material, the other characteristics such as thermal expansion, adhesion of the conductors, etc., scarcely change. The ‘percolation’ effect of the physical properties can usually be found with the addition of another material inside the matrix. In this particular case, the material is not submitted to the percolation law. Different configurations of metallic insert alumina with beryllia are compared by a simulation programme. The main applications are in the field of electronic packaging such as chip‐carriers with higher thermal dissipation and substrates for power devices. Since the process used to produce this new material is based on standard operations well known by alumina manufacturers, the cost is potentially much lower than for BeO.

Details

Microelectronics International, vol. 1 no. 2
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 20 June 2008

J. Paulo Davim, Edgar Santos, Catarina Pereira and J.M.F. Ferreira

The paper aims to study the friction behaviour of alumina and zirconia against steel DIN‐Ck45K under water lubricated conditions.

Abstract

Purpose

The paper aims to study the friction behaviour of alumina and zirconia against steel DIN‐Ck45K under water lubricated conditions.

Design/methodology/approach

The tests were performed with a contact stress of 3.5 MPa and a constant sliding velocity of 0.5 m/s for 5.35 km of sliding distance, using a pin‐on‐disk tribometer.

Findings

The friction coefficient and the energy dissipated in the contact were considered in this comparative study. The zirconia ceramic present less friction coefficient and contact temperature than alumina ceramic. The zirconia present about 70 per cent of the energy dissipated against when compared with the alumina. Abrasive scars of the surface ploughing were observed on every wear track for two pairs in contact.

Research limitations/implications

This research used only one test condition.

Originality/value

The paper describes the tribological conditions used and a new methodology based on the energy dissipated in the contact is proposed.

Details

Industrial Lubrication and Tribology, vol. 60 no. 4
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 12 February 2018

Ebrahim Yousefi, Morteza Adineh and Mohammad Bagher Askari

The purpose of this paper is to fabricate zirconia-nano alumina porous nanocomposites with different amount of alumina (0-30 Wt.%). Specimens were prepared by solid state…

Abstract

Purpose

The purpose of this paper is to fabricate zirconia-nano alumina porous nanocomposites with different amount of alumina (0-30 Wt.%). Specimens were prepared by solid state sintering method at different temperature (1,400-1,700°C).

Design/methodology/approach

Effects of processing temperature and amount of alumina on microstructure, distribution of nanoparticles, flexural and compressive strengths, micro-hardness and densification were investigated.

Findings

Results indicated that interpenetration of particles and their contacts increased by increasing sintering temperature. As a consequence of better particles contacts and microstructure coarsening, the porosity decreased. As alumina nanoparticles content increased, the amount of porosity decreased conversely and distribution of pores become more uniform. Simultaneous enhancement of temperature and alumina nanoparticles content caused an improvement of flexural and compressive strengths because of an improvement of sintering process resulted from porosity reduction. Increase in hardness and density were observed as porosity values diminished and alumina nanoparticles were distributed well at micro zirconia grain boundaries as a result of increasing the process temperature.

Originality/value

This article contains original research.

Details

Anti-Corrosion Methods and Materials, vol. 65 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 2 January 2018

Gennady Gorokh, Yauhen Belahurau, Anna Zakhlebayeva, Igor Taratyn and Viatcheslav Khatko

This paper aims to present new technological approaches of manufacturing of micromechanical gyroscope ring-sensitive element based on the nanoporous anodic alumina instead…

Abstract

Purpose

This paper aims to present new technological approaches of manufacturing of micromechanical gyroscope ring-sensitive element based on the nanoporous anodic alumina instead of traditional silicon technology. Simulation and the operation analyses of such elements have been performed.

Design/methodology/approach

The design of gyroscope represents a sensitive element on a glass substrate; in the center of a ring, there is a permanent magnet in a steel box. The sensitive element is made of profiled nanoporous anodic alumina consisting of an octagonal frame which is connected to a ring in the center with eight N-shaped spokes. The technology of the sensitive element fabrication involves the electrochemical formation of nanoporous anodic alumina substrate given the thickness and porosity and its chemical etching on the element topology. The basic parameters and the operation principle of the nanoporous alumina-sensitive element have been defined by finite element simulation.

Findings

It is shown that the resonance frequencies of the sensitive element change as functions of the alumina porosity. The main parameters of the nanoporous alumina-sensitive element have been compared with parameters of a silicon-sensitive element. Calculations have shown that the mechanical deformations of the von Mises are approximately lower by two times in the nanoporous alumina-sensitive element.

Practical implications

High-precision angular rate measurement will be achieved by reducing mechanical and electrical noises practically to zero through careful designing of a ring magnetoelectric gyroscope

Originality/value

The ring resonator made of nanoporous anodic alumina will allow to increase the threshold of sensitivity and stability of micromechanical gyroscope characteristics owing to the high precision of geometric dimensions, the stability of the elastic properties and the quality factor.

Details

Aircraft Engineering and Aerospace Technology, vol. 90 no. 1
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 1 April 1985

J.M. Wheeler

Platinum gold conductors, used as solderable terminations, contain a glass frit which reacts with the minority constituents in debased alumina substrates forming an…

Abstract

Platinum gold conductors, used as solderable terminations, contain a glass frit which reacts with the minority constituents in debased alumina substrates forming an adhesive bond. Some conductor inks also contain copper and cadmium, in addition to the glass frit, which react directly with the alumina to form a chemical bond. Dielectric inks contain a crystalline filler, such as alumina or zirconia, in a glass matrix. The effect on the physical and electrical properties of platinum golds on various dielectrics was examined in comparison with the behaviour on alumina. Composition and surface structure of the dielectric affects the adhesion strength, solderability and solder leach resistance of the conductor inks. Interaction between the glasses in the dielectrics and conductors was determined by analysis in the SEM. Interdiffusion between the conductor and solder metals occurs and brittle intermetallic compounds are formed. The effects of the intermetallic formation on the adhesion strength and modes of failure, especially after thermal ageing at 150°C, have been examined. Thick film resistors printed and fired onto dielectrics rather than onto alumina substrates generally have different electrical properties. Chosen resistor systems, terminated with a gold conductor, were evaluated on different dielectrics. The values of electrical parameters such as resistance, TCR and noise index were compared with those on alumina. Interactions between the glasses in the resistors and dielectrics were examined as for the conductors. Thermal ageing on various resistor/dielectric combinations was carried out in order to determine the long‐term stability. The activation energies and time dependences of the ageing mechanisms for each combination were found. Corresponding ageing equations were calculated in order to predict the likely behaviour during life.

Details

Microelectronics International, vol. 2 no. 4
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 1 June 1995

Kamatchi Subramanian, Neal Vail, Joel Barlow and Harris Marcus

The selective laser sintering (SLS) process is used to prepare test bars from Al2O3/polymer binder powders. Finds that binder‐coated A12O3 particles formed bars that were…

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Abstract

The selective laser sintering (SLS) process is used to prepare test bars from Al2O3/polymer binder powders. Finds that binder‐coated A12O3 particles formed bars that were approximately twice as strong as could be formed from mixtures of alumina and polymer binder at the same binder level and processing conditions. In mixed systems, bar strengths increased nearly in proportion to increases in polymer binder content over the 20‐40 per cent volume binder range. Parts made in any particular laser scanning mode showed optimum values for strength and density as the laser energy density was systematically increased from 2‐8cal/cm2. Suggests that optima result from the counteracting influences of energy density on binder fusion and thermal degradation. The optimum energy density is mode or geometry sensitive and shifts to lower values as the laser scanning vector is reduced. Concludes that this behaviour is probably the result of the lower heat losses. Equivalently better utilization of laser energy is associated with the shorter scan vectors. Some of the SLS fabricated bars were infiltrated with colloidal alumina, fired to remove the binder, and sintered at 1,600°C to achieve alumina bars with 50 per cent relative densities, interconnected porosity, and strengths between 2 and 8MPa.

Details

Rapid Prototyping Journal, vol. 1 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 27 July 2012

J. Deckers, K. Shahzad, J. Vleugels and J.P. Kruth

The purpose of this paper is to assess a new powder metallurgy process to make alumina parts through indirect selective laser sintering (SLS). Density measurements, some…

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1122

Abstract

Purpose

The purpose of this paper is to assess a new powder metallurgy process to make alumina parts through indirect selective laser sintering (SLS). Density measurements, some geometrical assessments and scanning electron microscopy (SEM) microstructural analyses are performed after each stage of the process, allowing an objective overview to be provided of the challenges and possibilities for the processing of high density technical ceramic parts through SLS of ball milled alumina/polyamide powder agglomerates.

Design/methodology/approach

The powder production by ball milling, SLS, cold isostatic pressing (CIP) or quasi isostatic pressing (QIP), debinding and sintering (FS) stages of the powder metallurgy process were sequentially investigated.

Findings

Alumina parts with a density up to 94.1 per cent could be produced by a powder metallurgy process containing an SLS step. Microstructural investigation of the sintered samples reveals an alumina matrix with a grain size of ∼5 μm and two different kinds of pore morphologies, i.e. long elongated pores, which stem from the intergranular spacings during SLS, and intermediate pores, which likely originate from larger polyamide agglomerates in the ball milled powder. Also, QIPing at elevated temperatures is found to be a promising alternative for CIPing at room temperature to increase the final part density.

Research limitations/implications

Cracks, long elongated pores and intermediate pores remained in the sintered parts. Homogenizing the microstructure of the parts through optimizing the composite starting powder, the deposition during SLS, the SLS parameters and QIPing parameters is essential to overcome these limitations.

Practical implications

Homogenizing the starting powder mixture and the microstructure of the SLS material is the key issue for producing ceramic parts through indirect SLS.

Originality/value

Indirect SLS of ceramics has hardly been reported and the combined use of SLS and QIPing is innovative in the field of indirect SLS of ceramics.

Details

Rapid Prototyping Journal, vol. 18 no. 5
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 2 August 2021

Anas Islam, Shashi Prakash Dwivedi and Vijay Kumar Dwivedi

This paper aims to extract the Cr from chrome containing leather waste (CCLW) in order to develop composite at optimum casting parameters using RSM technique. Chrome…

Abstract

Purpose

This paper aims to extract the Cr from chrome containing leather waste (CCLW) in order to develop composite at optimum casting parameters using RSM technique. Chrome containing leather wastes (CCLW) is one of the significant cause of pollution that is exhaled by the leather industries. One of the technique to address the problem of pollution that is created by CCLW is to recycle it and produce some fruitful results from it. This will not only minimize the levels of harmful emissions to some extent but also give some befitting results.

Design/methodology/approach

The current work is all about exploring the ways by which CCLW could be used as a reinforcing material with aluminum. In this work, alumina has been used as a secondary reinforcement particle together with CCLW as with the help of stir casting process. The parameters of stir casting have been optimized by using “Response Surface Methodology.”

Findings

To maximize the hardness and tensile strength the values of optimal input casting parameters as found by the experimental results (response surface methodology) are as follows: the pre-heating temperature of collagen and alumina must be 166 °C and 300 °C, respectively, while the wt.% of collagen and alumina present in the matrix must be 2.45% and 5% sequentially 180 s of stirring time.

Originality/value

The hardness of the finally tested composite is 67.12 BHN (approx) which has been enhanced by 52.54% as compared to the base material. Tensile strength of composite also enhanced about 18% with respect to base material developed at the optimum combination of casting parameters.

Details

World Journal of Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 22 May 2020

Crislaine da Cruz, Ivan Mathias, Mariza Veiga Senk, Gelson Biscaia de Souza and Francisco Carlos Serbena

Lithium disilicate glass-ceramics (LS2 GC) are widely used as dental prosthetics and dental restorations. Based LS2 GC have hardness and translucency similar to that of…

Abstract

Purpose

Lithium disilicate glass-ceramics (LS2 GC) are widely used as dental prosthetics and dental restorations. Based LS2 GC have hardness and translucency similar to that of natural teeth. This study aims to investigate the tribological features of LS2 GC with crystalline volume fraction of 64% and different crystal sizes from 8 µm to 34 µm for different counterparts.

Design/methodology/approach

The tribological behavior was investigated using a pin-on-disc tribometer with alumina and tungsten carbide (WC) spheres, applied load of 5 N and sliding speed of 5 cm/s at normal conditions. The coefficient of friction was measured continuously up to 10,000 sliding cycles. The specific wear rate was calculated from tribological and profile measurements. The wear mechanism was investigated by surface morphology analysis.

Findings

The coefficient of friction during running-in varied from 0.8 to 1.0 for the alumina counterpart, because of severe wear. Afterwards, it reduced and reached a stationary regime, characterized by a mild wear regime and the formation of a tribolayer formed by the debris. For the WC counterpart, the coefficient of friction curves increased initially with sliding cycles up to a stationary regime. The samples tested against WC presented the lowest specific wear rate (k), and no variation of wear rate with crystal size was observed. For samples tested against the alumina, crystallization and crystal size increased the wear resistance.

Originality/value

This study evaluated the effect of different counterfaces on the tribological properties of the LS2 GC, an important glass-ceramic base for many dental prosthetics and dental restorations, discussing results in light of the contact mechanics. Different specific wear rates, wear regimes and dependence on the glass-ceramic microstructure were observed depending on the counterpart.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0352/

Details

Industrial Lubrication and Tribology, vol. 72 no. 9
Type: Research Article
ISSN: 0036-8792

Keywords

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