Orientation Specific Thermal Properties of Polyimide Film

2000 ◽  
Vol 123 (3) ◽  
pp. 273-277 ◽  
Author(s):  
Robert J. Samuels ◽  
Nancy E. Mathis
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Polyimide Film ◽  
New Materials ◽  
Polyimide Films ◽  
Nondestructive Technique ◽  
Theoretical Understanding ◽  
First Time ◽  
The Relationship ◽  
Transfer Mechanisms

The present study examines the relationship between thermal conductivity and planarity in polyimide films. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation of the polyimide film have been characterized by polarizing microscope techniques, while the thermal conductivity measurements were done using a new rapid nondestructive technique. This correlation represents the first time thermal conductivity has been measured by modified hot wire techniques and related to the internal structure of polyimide. This work contributes to a deeper theoretical understanding of thermal conductivity and heat transfer mechanisms as they relate to orientation. Thermal conductivity evaluation could provide a new tool in the arsenal of structural characterization techniques. This relationship between thermal conductivity and orientation is key for applications of directional heat dissipation in the passive layers of chip assemblies. Such a correlation has potential to speed the development cycles of new materials during formulation as well as assure properties during production.

Thermal Penetration Times as a Nondestructive Measure of Orientation in Polyimide Film

1999 ◽  
Vol 591 ◽  
Author(s):  
C. Chandler ◽  
N.E. Mathis ◽  
R.J. Samuels
Keyword(s):  
Temperature Stability ◽  
Polyimide Film ◽  
Advanced Materials ◽  
Hot Wire ◽  
High Temperature Stability ◽  
Polyimide Films ◽  
Theoretical Understanding ◽  
End Use ◽  
First Time ◽  
Penetration Time

ABSTRACTMaterial properties depend on their fabricated structure and orientation. It is thus important to develop rapid nondestructive techniques that will both allow determination of the orientation fabricated, and identify any changes that occur over time as a result of subsequent in service environmental conditions.The present study examines the relationship between the thermal penetration time and planarity in polyimide films. Polyimides are advanced materials that have good high temperature stability, excellent dimensional stability, and excellent mechanical, electrical, and chemical resistance properties. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation in the polyimide film was characterized by polarizing microscope techniques, while the thermal penetration time measurements utilized a new rapid nondestructive modified hot wire instrument.This correlation will be the first time thermal penetration time has been measured by modified hot wire techniques and related to the internal structure of a polyimide. The work contributes to a deeper theoretical understanding of heat transfer mechanisms as they relate to orientation. Thermal penetration time evaluation could provide a new tool in the arsenal of structural characterization techniques.This relationship between thermal penetration time and orientation is key for film manufacturers. Such a correlation has potential to speed the development cycles of new materials and assure properties during production and end-use applications.

Effect of FeCl4– intercalation on the transport properties of a graphitized polyimide film

1993 ◽  
Vol 8 (9) ◽  
pp. 2299-2304 ◽  
Author(s):  
B. Nysten ◽  
J-P. Issi ◽  
H. Shioyama ◽  
M. Crespin ◽  
R. Setton ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Thermoelectric Power ◽  
Synthesis Method ◽  
Structural Disorder ◽  
Polyimide Film ◽  
Polyimide Films ◽  
Electrochemical Intercalation ◽  
Power Measurements ◽  
High Degree

The temperature variation of the thermal conductivity, the electrical resistivity, and the thermoelectric power of a graphitized polyimide film have been measured in the temperature range 2 < T < 300 K. The effect of the electrochemical intercalation with FeCl4− ions has also been studied. The thermal conductivity measurements confirm the high degree of graphitization that may be obtained with polyimide films. They show how intercalation increases the structural disorder and how the intercalate substantially contributes to the thermal conductivity at low temperatures. The electrical-resistivity and thermoelectric-power measurements reveal that the density of free carriers is about three times lower in stage-2 FeCl4− solvated intercalation compounds obtained by an electrochemical way than in stage-2 FeCl3 compounds obtained by a classical synthesis method.

scholarly journals Unravelling the Mechanisms that Drive the Performance of Photocatalytic Hydrogen Production

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 901
Author(s):  
Sergio San Martín ◽  
Maria J. Rivero ◽  
Inmaculada Ortiz
Keyword(s):  
Charge Transfer ◽  
Hydrogen Production ◽  
Deep Understanding ◽  
Water Remediation ◽  
Future Research ◽  
Process Variables ◽  
New Materials ◽  
Industrial Level ◽  
The Relationship ◽  
Transfer Mechanisms

The increasing interest and applications of photocatalysis, namely hydrogen production, artificial photosynthesis, and water remediation and disinfection, still face several drawbacks that prevent this technology from being fully implemented at the industrial level. The need to improve the performance of photocatalytic processes and extend their potential working under visible light has boosted the synthesis of new and more efficient semiconductor materials. Thus far, semiconductor–semiconductor heterojunction is the most remarkable alternative. Not only are the characteristics of the new materials relevant to the process performance, but also a deep understanding of the charge transfer mechanisms and the relationship with the process variables and nature of the semiconductors. However, there are several different charge transfer mechanisms responsible for the activity of the composites regardless the synthesis materials. In fact, different mechanisms can be carried out for the same junction. Focusing primarily on the photocatalytic generation of hydrogen, the objective of this review is to unravel the charge transfer mechanisms after the in-depth analyses of already reported literature and establish the guidelines for future research.

scholarly journals In situ measurement of intracellular thermal conductivity using heater-thermometer hybrid diamond nanosensor

2020 ◽  
Author(s):  
Shingo Sotoma ◽  
Chongxia Zhong ◽  
James Chen Yong Kah ◽  
Hayato Yamashita ◽  
Taras Plakhotnik ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Mean Value ◽  
Biological Processes ◽  
A Cell ◽  
First Time ◽  
Dissipation Processes ◽  
Key Parameter

AbstractUnderstanding heat dissipation processes at nanoscale during cellular thermogenesis is essential to clarify the relationships between the heat and biological processes in cells and organisms. A key parameter determining the heat flux inside a cell is the local thermal conductivity, a factor poorly investigated both experimentally and theoretically. Here, using a nanoheater/nanothermometer hybrid based on a polydopamine shell encapsulating a fluorescent diamond nanocrystal, we measured the intracellular thermal conductivity of HeLa cell with a spatial resolution of about 200 nm. Its mean value of 0.11 Wm-1K-1 determined for the first time is significantly smaller than that of water. Bayesian analysis of the data strongly supports the existence of variation of the intracellular thermal conductivity of about 40%. These results present a major milestone towards understanding the intracellular heat transfer phenomena at nanoscale.

Effect of Alkali Treatment on the Mechanical Property of Polyimide Film

2017 ◽  
Vol 744 ◽  
pp. 364-369 ◽  
Author(s):  
Ming Yu Zhang ◽  
Li Zhu Liu ◽  
K.S. Hui ◽  
K.N. Hui
Keyword(s):  
Mechanical Properties ◽  
Ion Exchange ◽  
Treatment Time ◽  
Alkali Treatment ◽  
Polyimide Film ◽  
Polyimide Films ◽  
Future Studies ◽  
Polyimide Composites ◽  
First Time ◽  
Better Than

Polyimide films treated with an alkali and ion exchange undergo surface-confined hydrolysis to produce polyimide composites. On the other hand, it is unclear what impact this method has on the mechanical properties of PI films. This paper reports the effects of the mechanical properties of PI films exposed to an alkali (KOH) solution with different treatment time. The mechanical properties of the re-cycloimidization PI films were improved when the proper initial KOH treatment time was used. The reason might be that PI could effectively reduce the formation of the shear zone to cracks due to the increase in ductility after the proper KOH treatment and more ductile PI chains led to re-orientation at the drawing process. Therefore, the strength and elongation of the re-cycloimidization PI films were better than those of the pristine PI films. This study focused on the effects of the KOH treatment on the mechanical properties of the PI film for the first time and proposed a mechanism to explain the reason that the appropriate time of KOH treatment can enhance the mechanical properties. The results presented here can provide guidelines for preparing composite PI films via ion-exchange by the proper KOH treatment time in future studies.

Comparison of airf low environmental effects on thermal fabrics

2016 ◽  
Vol 88 (2) ◽  
pp. 203-212 ◽  
Author(s):  
Jiahui Tong ◽  
Yuanfang Zhao ◽  
Chenxiao Yang ◽  
Li Li
Keyword(s):  
Thermal Conductivity ◽  
Wind Speed ◽  
Textile Industry ◽  
Heat Dissipation ◽  
Thermal Studies ◽  
Control Process ◽  
Thermal Control ◽  
Heating Process ◽  
The Relationship

Smart thermal textiles are becoming increasingly popular and temperature precision is one of the important targets in their industrialization and commercialization. Some thermal products do not rely on temperature sensors but rather the input electric current pulse to achieve thermal control. In this situation, the surrounding environment, especially ventilation, can greatly affect the thermal control process. Therefore, in this paper, a case study of an apparel system will be provided to study the effect of airflow on the heating process of thermal fabric. The relationship between temperature precision and ventilation is determined when the air flows at any angle to the surface of the thermal fabric. The results show that the thermal conductivity is proportional to the wind speed when the wind speed is high; in contrast, when the wind speed is near to zero, the thermal conductivity of the thermal fabric will not proportionally tend to zero as the result of self-generated heat transfer. This research also shows that the air inflow angle and the wind direction has little effect on the heat dissipation of thermal fabric. This research may generate the data archive and become a valuable reference for future soft thermal studies. It is expected that the developed system will span multidisciplinary gaps and contribute to a new form in a precise and controllable way within the textile industry.

Analysis of Bond and Anchorage Performances of Helical and Twisted Reinforcement Material

2013 ◽  
Vol 539 ◽  
pp. 158-165
Author(s):  
Jun Lin Zhang ◽  
Chun Li Wang
Keyword(s):  
Material Properties ◽  
Theoretical Basis ◽  
Mechanical Analysis ◽  
New Materials ◽  
Theoretical Understanding ◽  
Bond Slip ◽  
Mechanism Model ◽  
Reinforcement Material ◽  
Derivation Formula ◽  
The Relationship

The performance of helical-effect of the helical and twisted material is elaborated in this paper. Through analyzing the parameter of the helical and twisted material, a mechanism model based on the bond of anchorage is built. Furthermore the fundamental derivation formula is done and the sensitivity is analyzed. Based on systematic study of bond anchorage performance of helical and twisted reinforcement material, the mechanical of the helical-effect was theoretically analyzed and quantitatively studied. The relationship between pullout and bond slip was studied by mechanical analysis and mathematical modeling stage by stage, the formula was established and derived. As a result, theoretical understanding of the helical-effect was deepened, providing the theoretical basis for optimization of material properties, geometry parameters and developing new materials.

Affirmative Action and Leadership Attitudes in Brazilian Women Managers

2011 ◽  
Vol 10 (3) ◽  
pp. 139-143 ◽  
Author(s):  
Gazi Islam ◽  
Sarah E. S. Zilenovsky
Keyword(s):  
Affirmative Action ◽  
Latin American ◽  
Women Managers ◽  
Psychological Effects ◽  
Preferential Selection ◽  
Justice Perceptions ◽  
First Time ◽  
The Relationship

This note examines the relationship between affirmative action (AA) program perceptions and women’s self-ascribed capacity and desire to become leaders. We propose that women who believe that their organization implements a program of preferential selection toward women will experience negative psychological effects leading to lowered self-expectations for leadership, but that this effect will be moderated by their justice perceptions of AA programs. We test this proposition empirically for the first time with a Latin American female sample. Among Brazilian women managers, desire but not self-ascribed capacity to lead was reduced when they believed an AA policy was in place. Both desire’s and capacity’s relationships with belief in an AA policy were moderated by justice perceptions.

An Experimental Investigation on Thermal Conductivity and Viscosity of Graphene doped CNTs /TiO2 Nanofluid

2020 ◽  
Vol 17 (3) ◽  
Author(s):  
A.M. Zetty Akhtar ◽  
M.M. Rahman ◽  
K. Kadirgama ◽  
M.A. Maleque
Keyword(s):  
Thermal Conductivity ◽  
Zeta Potential ◽  
Base Fluid ◽  
Minimum Quantity Lubrication ◽  
Cutting Fluid ◽  
Cutting Zone ◽  
Observation Method ◽  
The Stability ◽  
The Relationship ◽  
Zeta Potential Analysis

This paper presents the findings of the stability, thermal conductivity and viscosity of CNTs (doped with 10 wt% graphene)- TiO2 hybrid nanofluids under various concentrations. While the usage of cutting fluid in machining operation is necessary for removing the heat generated at the cutting zone, the excessive use of it could lead to environmental and health issue to the operators. Therefore, the minimum quantity lubrication (MQL) to replace the conventional flooding was introduced. The MQL method minimises the usage of cutting fluid as a step to achieve a cleaner environment and sustainable machining. However, the low thermal conductivity of the base fluid in the MQL system caused the insufficient removal of heat generated in the cutting zone. Addition of nanoparticles to the base fluid was then introduced to enhance the performance of cutting fluids. The ethylene glycol used as the base fluid, titanium dioxide (TiO2) and carbon nanotubes (CNTs) nanoparticle mixed to produce nanofluids with concentrations of 0.02 to 0.1 wt.% with an interval of 0.02 wt%. The mixing ratio of TiO2: CNTs was 90:10 and ratio of SDBS (surfactant): CNTs was 10:1. The stability of nanofluid checked using observation method and zeta potential analysis. The thermal conductivity and viscosity of suspension were measured at a temperature range between 30˚C to 70˚C (with increment of 10˚C) to determine the relationship between concentration and temperature on nanofluid’s thermal physical properties. Based on the results obtained, zeta potential value for nanofluid range from -50 to -70 mV indicates a good stability of the suspension. Thermal conductivity of nanofluid increases as an increase of temperature and enhancement ratio is within the range of 1.51 to 4.53 compared to the base fluid. Meanwhile, the viscosity of nanofluid shows decrements with an increase of the temperature remarks significant advantage in pumping power. The developed nanofluid in this study found to be stable with enhanced thermal conductivity and decrease in viscosity, which at once make it possible to be use as nanolubricant in machining operation.

“Little Trio” for clarinet, bassoon and piano

2018 ◽  
pp. 75-79
Author(s):  
N. Yakovchuk
Keyword(s):  
Chamber Music ◽  
Instrumental Music ◽  
Instrumental Ensemble ◽  
Interesting Phenomenon ◽  
Theoretical Understanding ◽  
Classical Traditions ◽  
And Performance ◽  
Instrumental Ensembles ◽  
Written Compositions ◽  
First Time

The chamber-instrumental ensemble music in the Ukrainian musical culture of the last third of the 20th and the beginning of the 21st centuries occupies one of the leading places and is characterized by powerful processes in its development. Such circumstances caused the Ukrainian musicologist interests to the problems of chamber-instrumental music creativity and performance. There are appeared researches in the field of theory, history and performance problems covering the most important questions like chamber music definitions, specific genre issues, the growing function of piano in the Ukrainian chamber music, the increasing questions of technique and timbre importance of modern instrumental ensembles. In the significant multifaceted creative work of contemporary Ukrainian composer, Oleksandr Yakovchuk, the genre of chamber instrumental ensemble music represents a complex and interesting phenomenon. Original and skillfully written compositions reflect artistic world of the composer of postmodern time and gained recognition in music life of Ukraine and beyond. These works are highly appreciated in performing practice of our days. The purpose of the article is to analyze the work — “Little Trio” for clarinet, bassoon and piano (1980), which has the signs of neoclassical tendency in the composer’s style. The methodological basis of this research is a comprehensive approach in theoretical understanding of the subject of research (the methods of textology, source study as well as the method of interviewing the author were used). The scientific novelty of this article is in the priority of its main provisions, since the “Little Trio” entered the scientific circulation for the first time. The three-movement “Little Trio” (1980) is notable for the light feeling of timbre colours and the shape clarity. The Ist movement — Allegretto giocoso — is written in a sonata form following all classical traditions. Quite interesting are the two monologues of clarinet and bassoon from the IInd movement, they represent very modern line in Ukrainian chamber music — the possibility of sincere confession which comes through the solo cadence. In the IIIrd movement, the composer took advantage from the folk Ukrainian dance “hopak” using the rhythm of it and creating dance character of the Final.

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