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Article
Publication date: 6 July 2010

G. Mishra, S.R. Mohapatra, P.R. Behera, B. Dash, U.K. Mohanty and B.C. Ray

The main objective of this experimental investigation is to assess the effect of thermal and cryogenic treatment on hygrothermally conditioned glass fibre reinforced epoxy matrix…

Abstract

Purpose

The main objective of this experimental investigation is to assess the effect of thermal and cryogenic treatment on hygrothermally conditioned glass fibre reinforced epoxy matrix composites, and the impact on its mechanical properties with change in percentage of individual constituents of the laminates.

Design/methodology/approach

The present investigation is an attempt at evaluating the performance of the laminates subjected to different thermal and cryogenic treatments for varying time with prior hygrothermal treatment. The variability of hygrothermal exposure is in the range of 4‐64 h. Glass fibre reinforced plastics laminates with different weight fractions 0.50‐0.60 of fibre reenforcements were used. The ILSS, which is a matrix dominated was studied by three‐point bend test using INSTRON 1195 material testing machine.

Findings

The post‐hygrothermal treatments (both thermal and cryogenic exposures) resulted in an increase in the rate of desorption of moisture. It is noted that the hygrothermal treatment prior to the exposure to thermal or cryogenic conditioning is the major attribute to the variations in the ILSS values. The extent of demoisturisation of the hygrothermally conditioned composites due to a thermal or a cryogenic exposure is observed to be inversely related to its ILSS, independent of the fibre‐weight fractions. Also the ILSS is inversely related to the fibre‐weight fraction irrespective of the post‐hydrothermal treatment.

Originality/value

The reported data are based on experimental investigations.

Details

Aircraft Engineering and Aerospace Technology, vol. 82 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 2 September 2019

Kamila Piotrowska, Feng Li and Rajan Ambat

The purpose of this paper is to investigate the decomposition behavior of binary mixtures of organic activators commonly used in the no-clean wave flux systems upon their exposure…

Abstract

Purpose

The purpose of this paper is to investigate the decomposition behavior of binary mixtures of organic activators commonly used in the no-clean wave flux systems upon their exposure to thermal treatments simulating wave soldering temperatures. The binary blends of activators were studied at varying ratios between the components.

Design/methodology/approach

Differential scanning calorimetry and thermogravimetric analysis were used to study the characteristics of weak organic acid (WOA) mixtures degradation as a function of temperature. The amount of residue left on the surface after the heat treatments was estimated by gravimetric measurements as a function of binary mixture type, temperature and exposure time. Ion chromatography analysis was used for understanding the relative difference between decomposition of activators in binary blends. The aggressivity of the left residue was assessed using the acidity indication gel test, and effect on reliability was investigated by DC leakage current measurement performed under varying humidity and potential bias conditions.

Findings

The results show that the typical range of temperatures experienced by electronics during the wave soldering process is not sufficient for the removal of significant activator amounts. If the residues contain binary mixture of WOAs, the final ratio between the components, the residue level and the corrosive effects depend on the relative decomposition behavior of individual components. Among the WOA investigated under the conventional wave soldering temperature, the evaporation and removal of succinic acid is more dominant compared to adipic and glutaric acids.

Practical implications

The findings are attributed to the chemistry of WOAs typically used as flux activators for wave soldering purposes. The results show the importance of controlling the WOA content and ratio between activating components in a flux formulation in relation to its tendencies for evaporation during soldering and the impact of its residues on electronics reliability.

Originality/value

The results show that the significant levels of flux residues can only be removed at significantly higher temperatures and longer exposure times compared to the conventional temperature range used for the wave soldering process. The potential corrosion issues related to insufficient flux residues removal will be determined by the residue amount, its composition and ratio between organic components. The proper time of thermal treatment and careful choice of fluxing formulation could ensure more climatically reliable product.

Details

Soldering & Surface Mount Technology, vol. 32 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 April 1989

Emilio Becheri

Thermal Tour As had been identified in the Second Report on Italian Tourism (1), the market for “thermal tourism” has developed its trends with further characterizations and…

Abstract

Thermal Tour As had been identified in the Second Report on Italian Tourism (1), the market for “thermal tourism” has developed its trends with further characterizations and differentiations:

Details

The Tourist Review, vol. 44 no. 4
Type: Research Article
ISSN: 0251-3102

Article
Publication date: 29 June 2012

Caroline Pereira Moura Aranha and Neuza Jorge

This research aims to evaluate the antioxidant potential of oregano extract (OE), as well as its isolated and synergistic effect when applied to soybean oil (SO) under thermal…

Abstract

Purpose

This research aims to evaluate the antioxidant potential of oregano extract (OE), as well as its isolated and synergistic effect when applied to soybean oil (SO) under thermal oxidation.

Design/methodology/approach

In order to determine the antioxidant activity of oregano extract and its synergistic effect with tert‐butylhydroquinone (TBHQ), thermal oxidation was performed using the following treatments: SO, SO with 50 mg/kg of TBHQ, SO with 3,000 mg/kg of OE, and SO with 3,000 mg/kg of oregano extract and 50 mg/kg of TBHQ (mixture). The treatments underwent heating at 180°C for 20 hours, and analyses of oxidative stability, total polar compounds, tocopherols and fatty acids composition were performed. The results obtained were subjected to analysis of variance and Tukey test for averages at 5 percent, using the program ESTAT version 2.0.

Findings

Considering the results of antioxidant activity and total phenolic compounds, it was possible to verify that the ethanolic extract of oregano has presented antioxidant potential. Furthermore, considering the results obtained in the analyses of oxidative stability, polar compounds, tocopherols and fatty acids profile, it was possible to observe that the extract has prevented lipid oxidation when added to SO.

Originality/value

The study offers information on the use of natural antioxidants as an alternative to the use of synthetic antioxidants, which can be considered toxic.

Article
Publication date: 4 January 2016

M.Y. Zhang, L.Z. Liu, L. Weng, W.W. Cui and K.S. Hui

– The aim of this study was to fabricate polyimide (PI)/Al2O3 composite films via surface modification and ion exchange techniques, and examine their properties.

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Abstract

Purpose

The aim of this study was to fabricate polyimide (PI)/Al2O3 composite films via surface modification and ion exchange techniques, and examine their properties.

Design/methodology/approach

The method involves hydrolyzing the PI film double surface layers in an aqueous potassium hydroxide (KOH) solution and incorporating aluminium ions (Al3+) into the hydrolyzed layers of the PI film via subsequent ion exchange, followed by a treatment of the Al3+-loaded PI films with an aqueous ammonia solution, which leads to the formation of Al(OH)3 in the surface-modified layers. After a final thermal annealing treatment in ambient air, the Al(OH)3 decomposes to Al2O3, and forms composite layers on both surfaces of the re-imidized PI film.

Findings

The PI/Al2O3 composite film obtained with a 6 hours of KOH treatment exhibited excellent thermal stability, good mechanical properties and better electric breakdown strength and corona-resistance properties than the pristine PI film.

Practical implications

The method for obtaining the composite films in this paper is worth consideration, but additional research will be needed. Furthermore, this method is of general importance for the fabrication of composite PI films with tailored properties.

Originality/value

This study showed that surface modification and ion-exchange techniques are powerful methodologies for the fabrication of PI/Al2O3 composite films.

Details

Pigment & Resin Technology, vol. 45 no. 1
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 31 May 2011

S. Sethi and B.C. Ray

The purpose of this paper is to analyze microstructural integrity at the interface and consequent implicating effect on mechanical behavior of fiber‐reinforced polymer composites.

Abstract

Purpose

The purpose of this paper is to analyze microstructural integrity at the interface and consequent implicating effect on mechanical behavior of fiber‐reinforced polymer composites.

Design/methodology/approach

In the light of Fourier transform infrared spectroscope (FTIR imaging) and temperature‐modulated differential scanning calorimeter, a sorption mechanism was established. Thermal spike and thermal shock treatment was carried out at 150 and 80°C, respectively. This suggested that fiber/matrix adhesion rests on the structure and properties of both the fiber and matrix in the region near the interface during the hygrothermal treatment.

Findings

The carbon surface was found to selectively absorb the tertiary amine catalyst and to modify the chemical state of the cured resin apparently through the effects of absorbed water. The higher values of glass transition temperature (Tg) resulted in longer immersion time and higher exposure temperature. Together, these techniques provide a comprehensive picture of chemical and physical changes at the interphase region. Thermal spike of hybrid composite at 150°C temperature might possibly improve the adhesion level at the interface. Whereas, in case of thermal shock treatment at 80°C the fall in inter‐laminar shear strength value at higher number of cycles. This degradation of the interface region has been monitored by scanning electron microscope analysis.

Originality/value

The reported data are based on experimental investigation.

Details

International Journal of Structural Integrity, vol. 2 no. 2
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 1 May 1996

Altaf H. Basta, Naim A. Fadl and Usama I. Gabra

Studies the treatment of wood‐processing waste using different impregnants as a tool for improving its water‐resistance properties, in order to achieve a reduction in the damage…

Abstract

Studies the treatment of wood‐processing waste using different impregnants as a tool for improving its water‐resistance properties, in order to achieve a reduction in the damage to building elements prepared from the treated wood waste when exposed to weather of relatively high moisture content. Applies different variables such as type of impregnant (synthetic resins or oils), concentration of impregnant, time of impregnation and thermal treatment. Obtains results which show that, generally, using a different concentration of synthetic resins (UF and novolac), or dry oils (motor oil and linseed oil) improved the water‐resistance property of wood waste, and that thermal treatment increases the improvement percentage as a result of impregnation. Also indicates that the optimum improvement in water resistance is attained when using 50 per cent linseed oil as the impregnant for an impregnation time of ten minutes, followed by hardening for three hours at 120°C.

Details

Pigment & Resin Technology, vol. 25 no. 5
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 2 March 2023

Bahareh Nikmehr, Bidur Kafle and Riyadh Al-Ameri

This study aimed to review various existing methods for improving the quality of recycled concrete aggregates (RCAs) as a possible substitution for natural aggregates (NAs) in…

Abstract

Purpose

This study aimed to review various existing methods for improving the quality of recycled concrete aggregates (RCAs) as a possible substitution for natural aggregates (NAs) in concrete. It is vital as the old paste attached to the RCA weakens its structure. It is due to the porous structure of the RCA with cracks, weakening the interfacial transition zone (ITZ) between the RCA and binding material, negatively impacting the concrete's properties. To this end, various methods for reinforcement of the RCA, cleaning the RCA's old paste and enhancing the quality of the RCA-based concrete without RCA modification are studied in terms of environmental effects, cost and technical matters. Furthermore, this research sought to identify gaps in knowledge and future research directions.

Design/methodology/approach

The review of the relevant journal papers revealed that various methods exist for improving the properties of RCAs and RCA-based concrete. A decision matrix was developed and implemented for ranking these techniques based on environmental, economic and technical criteria.

Findings

The identified methods for reinforcement of the RCA include accelerated carbonation, bio deposition, soaking in polymer emulsions, soaking in waterproofing admixture, soaking in sodium silicate, soaking in nanoparticles and coating with geopolymer slurry. Moreover, cleaning the RCA's old paste is possible using acid, water, heating, thermal and mechanical treatment, thermo-mechanical and electro-dynamic treatment. Added to these treatment techniques, using RCA in saturated surface dry (SSD) mixing approaches and adding fibres or pozzolana enhance the quality of the RCA-based concrete without RCA modification. The study ranked these techniques based on environmental, economic and technical criteria. Ultimately, adding fibres, pozzolana and coating RCA with geopolymer slurry were introduced as the best techniques based on the nominated criteria.

Practical implications

The study supported the need for better knowledge regarding the existing treatment techniques for RCA improvement. The outcomes of this research offer an understanding of each RCA enrichment technique's importance in environmental, economic and technical criteria.

Originality/value

The practicality of the RCA treatment techniques is based on economic, environmental and technical specifications for rating the existing treatment techniques.

Details

Smart and Sustainable Built Environment, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2046-6099

Keywords

Article
Publication date: 11 May 2015

Dadasaheb D Wadikar, C.R. Vasudish and K.S. Premavalli

The purposes of this paper are to extend the shelf life of juice/fluids and reduce the thermal damage of their functional components. Thermal processing is a universal method used…

Abstract

Purpose

The purposes of this paper are to extend the shelf life of juice/fluids and reduce the thermal damage of their functional components. Thermal processing is a universal method used to extend the shelf lives of juice/fluids. However, combination processing thought to be beneficial in extending the shelf life with least possible thermal damage. The shelf life of the two thermally processed appetizer beverages, i.e. ginger beverage and karpurvalli beverage was established up to six months.

Design/methodology/approach

Both appetizer beverages were processed using irradiation in combination with heat treatment. A short thermal treatment at 95°C for 5 minutes was given to the bottled beverages, and these were then irradiated with different dosages of 1, 2 and 3 kGy. The samples were stored at room temperature (18-33°C), as well as at 37°C and periodically analysed for changes in pH, acidity, TSS, browning index, antioxidant activity and gingerol/carvacrol contents and for their microbiological quality.

Findings

The results revealed that in both products, the antioxidant activity and the gingerol/carvacrol content reduced, making these microbiologically safe up to eight months. However, combination of irradiation was not found suitable for the appetizer beverages due to more than 50 per cent losses in the functional components.

Research limitations/implications

The combination of thermal and irradiation processing was effective to ensure microbial safety and extend the shelf life of beverages. However, it may not be suitable for preserving all functional properties.

Originality/value

The outcome is result of original work done, and information provided can be a preamble to the researchers targeting improved stability of functional beverages.

Details

Nutrition & Food Science, vol. 45 no. 3
Type: Research Article
ISSN: 0034-6659

Keywords

Article
Publication date: 3 February 2023

Arad Azizi, Fatemeh Hejripour, Jacob A. Goodman, Piyush A. Kulkarni, Xiaobo Chen, Guangwen Zhou and Scott N. Schiffres

AlSi10Mg alloy is commonly used in laser powder bed fusion due to its printability, relatively high thermal conductivity, low density and good mechanical properties. However, the…

Abstract

Purpose

AlSi10Mg alloy is commonly used in laser powder bed fusion due to its printability, relatively high thermal conductivity, low density and good mechanical properties. However, the thermal conductivity of as-built materials as a function of processing (energy density, laser power, laser scanning speed, support structure) and build orientation, are not well explored in the literature. This study aims to elucidate the relationship between processing, microstructure, and thermal conductivity.

Design/methodology/approach

The thermal conductivity of laser powder bed fusion (L-PBF) AlSi10Mg samples are investigated by the flash diffusivity and frequency domain thermoreflectance (FDTR) techniques. Thermal conductivities are linked to the microstructure of L-PBF AlSi10Mg, which changes with processing conditions. The through-plane exceeded the in-plane thermal conductivity for all energy densities. A co-located thermal conductivity map by frequency domain thermoreflectance (FDTR) and crystallographic grain orientation map by electron backscattered diffraction (EBSD) was used to investigate the effect of microstructure on thermal conductivity.

Findings

The highest through-plane thermal conductivity (136 ± 2 W/m-K) was achieved at 59 J/mm3 and exceeded the values reported previously. The in-plane thermal conductivity peaked at 117 ± 2 W/m-K at 50 J/mm3. The trend of thermal conductivity reducing with energy density at similar porosity was primarily due to the reduced grain size producing more Al-Si interfaces that pose thermal resistance. At these interfaces, thermal energy must convert from electrons in the aluminum to phonons in the silicon. The co-located thermal conductivity and crystallographic grain orientation maps confirmed that larger colonies of columnar grains have higher thermal conductivity compared to smaller columnar grains.

Practical implications

The thermal properties of AlSi10Mg are crucial to heat transfer applications including additively manufactured heatsinks, cold plates, vapor chambers, heat pipes, enclosures and heat exchangers. Additionally, thermal-based nondestructive testing methods require these properties for applications such as defect detection and simulation of L-PBF processes. Industrial standards for L-PBF processes and components can use the data for thermal applications.

Originality/value

To the best of the authors’ knowledge, this paper is the first to make coupled thermal conductivity maps that were matched to microstructure for L-PBF AlSi10Mg aluminum alloy. This was achieved by a unique in-house thermal conductivity mapping setup and relating the data to local SEM EBSD maps. This provides the first conclusive proof that larger grain sizes can achieve higher thermal conductivity for this processing method and material system. This study also shows that control of the solidification can result in higher thermal conductivity. It was also the first to find that the build substrate (with or without support) has a large effect on thermal conductivity.

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