scholarly journals Joining with Reactive Nano-Multilayers: Influence of Thermal Properties of Components on Joint Microstructure and Mechanical Performance

2019 ◽  
Vol 9 (2) ◽  
pp. 262 ◽  
Author(s):  
Bastian Rheingans ◽  
Irina Spies ◽  
Axel Schumacher ◽  
Stephan Knappmann ◽  
Roman Furrer ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Heat Dissipation ◽  
Mechanical Performance ◽  
Local Heat ◽  
Exothermal Reaction ◽  
Excessive Heat ◽  
Component Material ◽  
The Given

Reactive nano-multilayers (RNMLs), which are able to undergo a self-heating exothermal reaction, can, e.g., be utilised as a local heat source for soldering or brazing. Upon joining with RNMLs, the heat produced by the exothermal reaction must be carefully adjusted to the joining system in order to provide sufficient heat for bond formation while avoiding damaging of the joining components by excessive heat. This heat balance strongly depends on the thermal properties of the joining components: a low thermal conductivity leads to heat concentration within the joining zone adjacent to the RNML, while a high thermal conductivity leads to fast heat dissipation into the components. The quality of the joint is thus co-determined by the thermal properties of the joining components. This work provides a systematic study on the influence of the thermal properties upon reactive joining for a set of substrate materials with thermal conductivities ranging from very low to very high. In particular, the evolution of the microstructure within the joining zone as a function of the specific time-temperature-profile for the given component material is investigated, focusing on the interaction between solder, RNML foil and surface metallisations, and the associated formation of intermetallic phases. Finally, the specific microstructure of the joints is related to their mechanical performance upon shear testing, and suggestions for optimum joint design are provided.

Effect of extrusion treatment on mechanical, thermal conductivity and corrosion resistance of magnesium alloys

2019 ◽  
Vol 9 (5) ◽  
pp. 405-412
Author(s):  
Bo Zhang ◽  
Huichao Jia ◽  
Quanyong Lian ◽  
Lianyu Jiang ◽  
Guangxin Wu
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Corrosion Resistance ◽  
Thermal Properties ◽  
Magnesium Alloys ◽  
Driving Force ◽  
Mechanical Performance ◽  
Cast Alloy ◽  
Extrusion Temperature ◽  
Zr Alloys

The effect of extrusion treatment on the mechanical, thermal and corrosion resistance of Mg–La–Zn–Zr alloys were presented. It is suggested that the amount of recrystallized grains played a major role in both mechanical properties and thermal properties. It should be noted the as-cast alloy shows the best thermal conductivity reached the value about 137.507 W/(m · K), however, the mechanical performance of magnesium alloys does not reach the expected results. The thermal properties of extruded alloys have slightly decreased and then increased with the increase of extrusion temperature. Then the tensile properties of Mg–La–Zn–Zr were significantly improved after extrusion treatment. Furthermore, with the increase of extrusion temperature, the elongation-to-fracture increased substantially. After extrusion treatment, the corrosion driving force of the alloy decreases, which reduces the corrosion tendency of the magnesium alloy. The alloy presented in this paper is expected to be applied in industry.

scholarly journals Investigation of Thermal Properties of Novel Phase Change Material Mixtures (Octadecane-Diamond) with Laser Flash Analysis

2019 ◽  
Vol 26 (4) ◽  
pp. 211-218
Author(s):  
Mateusz Sierakowski ◽  
Wojciech Godlewski ◽  
Roman Domański ◽  
Jakub Kapuściński ◽  
Tomasz Wiśniewski ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Phase Change ◽  
Power Plants ◽  
Large Scale ◽  
Phase Change Materials ◽  
Heat Dissipation ◽  
Electronics Cooling ◽  
Diamond Powder ◽  
Heat Of Fusion

AbstractPhase change materials (PCMs) are widely used in numerous engineering fields because of their good heat storage properties and high latent heat of fusion. However, a big group of them has low thermal conductivity and diffusivity, which poses a problem when it comes to effective and relatively fast heat transfer and accumulation. Therefore, their use is limited to systems that do not need to be heated or cooled rapidly. That is why they are used as thermal energy storage systems in both large scale in power plants and smaller scale in residential facilities. Although, if PCMs are meant to play an important role in electronics cooling, heat dissipation, or temperature stabilization in places where the access to cooling water is limited, such as electric automotive industry or hybrid aviation, a number of modifications and improvements needs to be introduced. Investigation whether additional materials of better thermal properties will affect the thermal properties of PCM is therefore of a big interest. An example of such material is diamond powder, which is a popular additive used in abradants. Its thermal diffusivity and conductivity is significantly higher than for a pure PCM. The article presents the results of an analysis of the effect of diamond powder on thermal conductivity and diffusivity of phase change materials in the case of octadecane.

scholarly journals Effect of the Circular Perforations on the Heat Transfer Enhancement by the Forced Convection from the Rectangular Fins

2018 ◽  
Vol 11 (3) ◽  
pp. 62-70 ◽  
Author(s):  
Wadhah Hussein Abdulrazzaq Al-Taha
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Heat Dissipation ◽  
Transfer Enhancement ◽  
Geometrical Dimensions

This study aims to investigate the effect of the circular perforation of the rectangular fin on the enhancement of the heat transfer by forced convection. The solid rectangular fin considered as a reference for comparison purpose with the perforated fin. The parameters taken into consideration are thermal properties and geometrical dimensions of the fin and its perforations. The area and heat transfer gain of the perforations fins were considered being the main parameters in this study. The results of this study showed that the heat dissipation was improved when used the perforation fins compared with the equivalent solid fin. The enhancement quantity of the heat dissipation from the fin depends on the thermal conductivity, the perforation dimension, thickness, longitudinal and lateral spacing. Finally, the perforating of the fins enhances the rate of heat dissipation as well as decreases the weight of the fin

Thermal Properties of Porous Copper Manufactured by Lost Carbonate Sintering

2014 ◽  
Vol 783-786 ◽  
pp. 1603-1608 ◽  
Author(s):  
Z. Xiao ◽  
Y.Y. Zhao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Pore Size ◽  
Heat Dissipation ◽  
Fluid Transport ◽  
Porous Metals ◽  
Porous Copper ◽  
Layer Structures ◽  
The Heat Transfer Coefficient

Active cooling techniques are often required to achieve high rates of heat dissipation in thermal management applications. Open-cell porous metals are good candidates for use as heat exchangers. This paper studies the fluid transport and thermal properties of porous copper samples with different pore structures manufactured using the LCS method. The results showed that the permeability increases with porosity but decreases with pore size. The thermal conductivity increases with relative density according to the power law. The effects of porosity and pore size on the heat transfer performance of the porous copper samples are significant, due to their effects on the permeability and thermal conductivity. For the porous copper samples with double-layer structures, the permeability follows the rule of mixture and the heat transfer coefficient can be predicted by a recently developed segment model.

EVALUATION ON THE THERMAL AND STRUCTURAL PROPERTIES OF COPPER ALUMINUM OXIDE (Cu-Al2O3) THIN FILM ON AL SUBSTRATE: EFFECT OF ANNEALING TEMPERATURE

2018 ◽  
Vol 25 (07) ◽  
pp. 1950017
Author(s):  
WEI QIANG LIM ◽  
SUBRAMANI SHANMUGAN ◽  
MUTHARASU DEVARAJAN
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Structural Properties ◽  
Heat Dissipation ◽  
Rf Magnetron Sputtering ◽  
Xrd Analysis ◽  
Annealed Sample ◽  
Significant Difference ◽  
The Difference ◽  
Copper Aluminum

Layer stacking technique is incorporated in the deposition of copper aluminium oxide (Cu-Al2O3) thin films on Al substrate using RF magnetron sputtering. The Cu/Al2O3 stack is sputtered using Cu and Al2O3 target at ambient temperature and then annealed to yield the resultant Cu-Al2O3 films. The structural properties of the films are investigated through X-ray Diffraction (XRD) whereas the chemical structure of the films is studied using Fourier-transform infrared (FTIR). The thermal conductivity analyzer is used to evaluate the thermal properties of coated film on the Al substrate. XRD analysis revealed that the synthesized films are polycrystalline film composed mainly of CuAl2O4 phase along with Al2O3 and CuO phases. The thermal properties of Cu-Al2O3 coated Al substrates showed improvement in terms of thermal conductivity and diffusivity compared to bare Al substrate. The Cu-Al2O3 sample annealed at 400∘C exhibited a significant difference in thermal conductivity ([Formula: see text][Formula: see text]W/mK) compared to bare Al. The difference in thermal conductivity displayed by the annealed sample verified that TIMs did enhance the thermal path of entire substrate by allowing the heat to dissipate to surrounding environment more efficiently, thereby improving the heat dissipation system. From the results observed, it can be concluded that Cu-Al2O3 coated Al substrate can be made as alternative TIM in thermal management application.

Study of Processing Conditions on the Forming of Ribbed Features Using Randomly Oriented Strands Thermoplastic Composites

2015 ◽  
Vol 60 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Dominic LeBlanc ◽  
Benoit Landry ◽  
Arthur Levy ◽  
Pascal Hubert ◽  
Steven Roy ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Filling Pressure ◽  
Thermoplastic Composites ◽  
Void Content ◽  
Component Level ◽  
Polyether Ether Ketone ◽  
Fast Processing ◽  
The Given ◽  
Complex Parts

Compression molding of randomly oriented strands (ROS) composites offers the possibility to manufacture complex parts with a fast processing cycle. In this paper, effects of pressure, strand size, temperature, and material placement in the mold cavity on the quality of a T-shape part were studied experimentally with carbon/polyether ether ketone ROS composites. Minimum filling pressure was obtained for the consolidation of a 25-mm deep cavity. Parts processed at filling pressure showed a void content no greater than 1.2%. Increasing pressure to 70 bar resulted in decreased void content as low as 0.03%. Mechanical testing of the T-shape showed similar strengths for parts processed at filling pressure and higher (70 bar). At the component level, initial strand placement greatly affected mechanical performance as the presence of a knit line was responsible for a reduction of 60% in tensile strength. The main findings show that processing a complex feature at filling pressure Pfill was sufficient to reach nominal mechanical properties. This suggested that moderate porosity was not detrimental to the mechanical performance for the given tests where fatigue performance was not evaluated.

scholarly journals Reduced Graphene Oxide Embedded with MQ Silicone Resin Nano-Aggregates for Silicone Rubber Composites with Enhanced Thermal Conductivity and Mechanical Performance

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1254 ◽  
Author(s):  
Weijie Liang ◽  
Xin Ge ◽  
Jianfang Ge ◽  
Tiehu Li ◽  
Tingkai Zhao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Silicone Rubber ◽  
Heat Dissipation ◽  
Mechanical Performance ◽  
Thermal Interface Material ◽  
Silicone Resin ◽  
Blending Method ◽  
Reduced Graphene

With developments of the electronics industry, more components are being included in electronic devices, which has led to challenges in thermal management. Using reduced graphene oxide embedded with MQ silicone resin (RGO/MQ) nano-aggregates as the composite filler and silicone rubber (SR) as the matrix, a simple approach is designed to prepare RGO/MQ/SR composites. Reduced graphene oxide (RGO) was first used as a substrate for the growth of MQ silicone resin by hybridization, forming sandwich-like micro structured RGO/MQ nano-aggregates successfully. Then, RGO/MQ was integrated into α,ω-dihydroxylpolydimethylsiloxane based on the in situ solvent-free blending method, followed by condensation and vulcanization, fabricating the final RGO/MQ/SR composites. The effective strategy could enhance the adaptability between graphene and silicone matrix under external stimuli at room temperature by embedding nanoscale MQ into the interface of graphene/silicone as the buffer layer. Obvious improvements were found in both thermal conductivity and mechanical properties due to excellent dispersion and interfacial compatibility of RGO/MQ in the host materials. These attractive results suggest that this RGO/MQ/SR composite has potential as a thermal interface material for heat dissipation applications.

scholarly journals Enhancing an Aerospace Grade Benzoxazine Resin by Means of Graphene Nanoplatelet Addition

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2544
Author(s):  
Vanessa García-Martínez ◽  
Maria R. Gude ◽  
Silvia Calvo ◽  
Alejandro Ureña
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Performance ◽  
Water Environment ◽  
Barrier Properties ◽  
Complete Characterization ◽  
Graphene Nanoplatelets ◽  
Hot Water ◽  
Maximum Water

Two different contents of graphene nanoplatelets (GNPs: 0.5 and 2 wt.%) were introduced into benzoxazine resin. The main objective of this work is to obtain a polymeric nanocomposite with multifunctional properties as high electrical and thermal conductivity, maintaining or improving its mechanical performance. The quality of the dispersion, performed with a three-roll calender, was studied. Afterward, a complete characterization of the nanocomposites was carried out in order to analyse the benefits of neat resin. The main features of the nanocomposites such as the mechanical and thermo-mechanical properties, their electrical and thermal conductivity and the behaviour under hygrothermal aging, were evaluated. Results allowed us to confirm that benzoxazine/GNP composites exhibited an increase in the tensile strength of polymeric matrix which was accompanied by a rise in elongation at break. The electrical and thermal conductivities exhibited a remarkable increment with the addition of 2 wt.% of GNPs (six orders of magnitude and 49% respectively). Finally, the barrier properties of benzoxazine resin were also favoured with the presence of GNPs because the maximum water absorbed in a hot-water environment decreased from 2.52% to 2.14% when 0.5 wt.% of graphene nanoplatelets was added.

Professional dilemmas for caregivers in Turkish home care settings in Germany

2014 ◽  
Vol 1 (1) ◽  
pp. 47-56 ◽  
Author(s):  
Jan Basche
Keyword(s):  
Healthcare Services ◽  
Insurance Companies ◽  
Or Education ◽  
Migrant Communities ◽  
Caregiver Relationship ◽  
International Nursing ◽  
Nursing Literature ◽  
Intercultural Care ◽  
The Given

While calling for culturally sensitive healthcare services in migrant communities, the international nursing literature on intercultural care predominantly describes nursing staff as lacking cultural competences and immigrant customers as lacking cleverness to navigate the labyrinths of national healthcare systems. Congruences in language, culture and religion in the customer-caregiver relationship can decisively improve the quality of care. However, they do not automatically guarantee smooth working processes in monocultural in-home settings. On the contrary, new problems occur here for Turkish caregivers which are unknown to the legions of native professionals who feel challenged by migrants and which go beyond differences such as age, sex, income or education. While no cultural or religious brokering is necessary between customers and personnel in the given context in Germany, new challenges arise when caregivers are expected to legally broker between customers and insurance companies or doctors. Conflicting expectations of customers and management as well as their own colliding social and professional roles put the caregivers in a quandary and must be competently managed.

MODIFIKASI MODEL PEMBELAJARAN TEAM ASSISTED INDIVIDUALIZATION DENGAN STRATEGI PEMBELAJARAN TUGAS DAN PAKSA

2019 ◽  
Vol 2 ◽  
Author(s):  
Lea Christy Restu Kinasih ◽  
Dewi Fatimah ◽  
Veranica Julianti
Keyword(s):  
Cooperative Learning ◽  
Learning Strategies ◽  
Learning Process ◽  
Learning Model ◽  
Learning Models ◽  
Classroom Learning ◽  
Quality Of Learning ◽  
The Given

The selection and determination of appropriate learning strategies can improve the results to be obtained from the application of classroom learning models. This writing aims to discipline students to develop individual abilities of students to be more active in the learning process and improve the quality of learning. The learning process in Indonesia in general only uses conventional learning models that make students passive and undeveloped. In order for the quality of learning to increase, the Team Assisted Individualization learning model is combined with the task learning and forced strategies. The Team Assisted Individualization cooperative learning model is one of the cooperative learning models that combines learning individually and in groups. Meanwhile, task and forced learning strategies are strategies that focus on giving assignments that require students to complete them on time so that the learning process can run effectively. Students are required to do assignments according to the given deadline. This makes students become familiar with the tasks given by the teacher. Combining or modifying the learning model of the assisted individualization team with forced and forced learning strategies is expected to be able to make students more active, disciplined, independent, creative in learning and responsible for the tasks assigned. Therefore this method of incorporation is very necessary in the learning process and can be applied to improve the quality of learning in schools.

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