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1 – 10 of over 2000
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

Keywords

Article
Publication date: 17 March 2022

Mudasir Peerzada, Khan Adnan, Basrah Bilal, Riyaz Janees, Bazila Qazi and Naqash Ahmed Javed

The purpose of this paper is to study the effect of nano alumina (Al2O3) on the properties of fresh concrete, hardened concrete and microstructure of concrete incorporated…

Abstract

Purpose

The purpose of this paper is to study the effect of nano alumina (Al2O3) on the properties of fresh concrete, hardened concrete and microstructure of concrete incorporated with high range water reducer (HRWR). This initiative was taken to improve characteristic properties of concrete using nano alumina because nano alumina can be easily be manufactured from a scrap of industrial aluminum products, so its incorporation in concrete will not only reduce industrial aluminum waste but will also change the morphology of concrete at the microstructural level.

Design/methodology/approach

To accomplish the objectives of the research, four different concrete mixes with the constant water–cement ratio (W/C) and superplasticizer (SP) content 0.4 and 0.6% by weight of cement, respectively, were prepared, whereas nano alumina content was altered by 0.3% and 0.4% by weight of cement. Fresh property of concrete was analyzed by using slump cone test, whereas hardened properties of concrete were analyzed through compression test and flexural strength test. The interaction of nano alumina with concrete composite was evaluated using an X-ray diffraction test.

Findings

It was observed that 0.6% superplasticizer by weight of cement increased workability by 22% but with the addition of 0.3%, nano alumina by weight of cement workability decreased by 31%. Compressive strength increased by 4.88% with the addition of 0.6% superplasticizer but with the addition of 0.3% nano alumina by weight of cement compressive strength increased by 18.60%. Also, flexural strength increased by 1.21% with the addition of 0.6% superplasticizer by weight of cement but with the addition of 0.3% nano alumina by weight of cement flexural strength increased by 8.76%. With the addition of superplasticizer, alite and belite phases remained un-hydrated but with the addition of nano alumina alite phase was hydrated while belite phase was un-hydrated. The size of belite crystals in mixes having nano alumina was less than that of mix having 0.6% superplasticizer. Also with the addition of nano alumina, a calcium aluminum silicate phase was formed which was responsible for the increment of strength in mixes having nano alumina.

Originality/value

Incorporation nano alumina (Al2O3) in concrete will not only reduce industrial aluminum waste but will also reduce CO2 emission. Nano alumina (Al2O3) also changes morphology of concrete at micro structural level.

Details

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

Keywords

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

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

Keywords

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

Keywords

Article
Publication date: 29 October 2021

Adel Attia, Lobna Khorshed, Samir Morsi and Elsayed Ashour

The purpose of this study was to investigate the polyacrylic polymer/Al2O3 as a new nanocomposite coating to protect brass and Al-bronze in 3.5% NaCl and the role of…

Abstract

Purpose

The purpose of this study was to investigate the polyacrylic polymer/Al2O3 as a new nanocomposite coating to protect brass and Al-bronze in 3.5% NaCl and the role of alumina formulation on their protection efficiency

Design/methodology/approach

The corrosion efficiency of the nanocomposite coating (NCC) was evaluated by open circuit potential and electrochemical impedance spectroscopy (EIS).

Findings

The protection efficiency was more in the case of Al-bronze even for the same formulation of alumina NCC indicated the Cu substrate contribution. The Cu oxides in alloys and Al2O3 from the NCC and Al-bronze were responsible for this protection.

Originality/value

All the techniques supported each other, the presence of alumina was responsible for the corrosion protection efficiency.

Details

Anti-Corrosion Methods and Materials, vol. 69 no. 1
Type: Research Article
ISSN: 0003-5599

Keywords

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

Keywords

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

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…

2918

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

Keywords

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…

1218

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

Keywords

1 – 10 of over 2000