Static recovery activation energy of pure copper at room temperature

2007 ◽  
Vol 57 (8) ◽  
pp. 667-670 ◽  
Author(s):  
Chen-Ming Kuo ◽  
Chih-Sheng Lin
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Pure Copper ◽  
Static Recovery

Static Recovery Activation Energy of Pure Aluminum at Room Temperature

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Yeh An-Chou ◽  
Chuang Ho-Chieh ◽  
Kuo Chen-Ming
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Pure Aluminum ◽  
Pure Copper ◽  
Tensile Tests ◽  
Engineering Strain ◽  
Static Recovery ◽  
Thermally Activated ◽  
Recovered Strain ◽  
Dislocation Annihilation

Thermally activated energy, which varies linearly with static recovered strain, is calculated from static recovery experiments of pure aluminum initially plastically deformed by strain-rate-controlled tensile tests up to 10% engineering strain at room temperature. The activation energy at the initial static recovery is 20 kJ mol−1, which is much less than that of pure copper and attributed to the dislocation annihilation by glide or cross-slip as well as higher stacking fault energy. Once dislocation annihilation processes are exhausted, more energy is required for subgrains to form and then grow. Eventually the recovered strain is slowed down and gradually saturated.

Annealing of Deformed Materials Developed by Continuous/Discontinuous Dynamic Recrystallization

2007 ◽  
Vol 550 ◽  
pp. 327-332 ◽  
Author(s):  
Taku Sakai ◽  
Hiromi Miura
Keyword(s):  
Dynamic Recrystallization ◽  
Room Temperature ◽  
Static Recrystallization ◽  
Pure Copper ◽  
Large Strains ◽  
Static Recovery ◽  
Fine Grained ◽  
Texture Change ◽  
Characteristic Nature ◽  
Fine Grained Structure

Annealing behaviour was studied in deformed copper developed by continuous or discontinuous dynamic recrystallization (cDRX or dDRX). Pure copper was deformed to large strains by multi-directional forging at room temperature, resulting in an ultra-fine grained structure due to operation of cDRX. Subsequent annealing of such a fine-grained copper can be controlled mainly by grain growth accompanied with recovery and no texture change, that is continuous static recrystallization (cSRX). On the other hand, 4 kinds of static restoration processes operate during annealing of dDRXed copper, i.e. metadaynamic recovery and recystallization (mDRV and mDRX), and classical static recovery and recrystallization. The stable existence of mDRVed grains containing moderate dislocations leads to incomplete recrystallization even after a long period of annealing time. It is discussed how such various types of annealing processes, occurring in cDRXed or dDRXed matrices, can be connected with the characteristic nature of the deformed microstructures.

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

scholarly journals Experimental and Numerical Investigation of the ECAP Processed Copper: Microstructural Evolution, Crystallographic Texture and Hardness Homogeneity

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 607
Author(s):  
A. I. Alateyah ◽  
Mohamed M. Z. Ahmed ◽  
Yasser Zedan ◽  
H. Abd El-Hafez ◽  
Majed O. Alawad ◽  
...  
Keyword(s):  
Grain Size ◽  
Equal Channel Angular Pressing ◽  
Cross Section ◽  
Room Temperature ◽  
Pure Copper ◽  
High Density ◽  
Ecap Processing ◽  
Heterogeneous Distribution ◽  
Angular Pressing ◽  
Average Grain Size

The current study presents a detailed investigation for the equal channel angular pressing of pure copper through two regimes. The first was equal channel angular pressing (ECAP) processing at room temperature and the second was ECAP processing at 200 °C for up to 4-passes of route Bc. The grain structure and texture was investigated using electron back scattering diffraction (EBSD) across the whole sample cross-section and also the hardness and the tensile properties. The microstructure obtained after 1-pass at room temperature revealed finer equiaxed grains of about 3.89 µm down to submicrons with a high density of twin compared to the starting material. Additionally, a notable increase in the low angle grain boundaries (LAGBs) density was observed. This microstructure was found to be homogenous through the sample cross section. Further straining up to 2-passes showed a significant reduction of the average grain size to 2.97 µm with observable heterogeneous distribution of grains size. On the other hand, increasing the strain up to 4-passes enhanced the homogeneity of grain size distribution. The texture after 4-passes resembled the simple shear texture with about 7 times random. Conducting the ECAP processing at 200 °C resulted in a severely deformed microstructure with the highest fraction of submicron grains and high density of substructures was also observed. ECAP processing through 4-passes at room temperature experienced a significant increase in both hardness and tensile strength up to 180% and 124%, respectively.

Processing of Copper by Equal Channel Angular Pressing (ECAP) – Microstructure Investigations

2015 ◽  
Vol 641 ◽  
pp. 286-293
Author(s):  
Beata Leszczyńska-Madej ◽  
Maria W. Richert ◽  
Agnieszka Hotloś ◽  
Jacek Skiba
Keyword(s):  
Equal Channel Angular Pressing ◽  
Room Temperature ◽  
Subgrain Size ◽  
Pure Copper ◽  
Shear Bands ◽  
Angular Pressing ◽  
Ecap Process ◽  
Transmission Electron ◽  
Different Types ◽  
Diffraction Patterns

The present study attempts to apply Equal-Channel Angular Pressing (ECAP) to 99.99% pure copper. ECAP process was realized at room temperature for 4, 8 and 16 passes through route BC using a die having angle of 90°. The microstructure of the samples was investigated by means both light and transmission electron microscopy. Additionally the microhardness was measured and statistical analysis of the grains and subgrains was performed. Based on Kikuchi diffraction patterns misorientation was determined. There were some different types of bands in the microstructure after deformation. The shear bands, bands and in the submicron range the microshear bands and microbands are a characteristic feature of the microstructure of copper. Also characteristic was increasing of the number of bands with increasing of deformation and mutually crossing of the bands. The intersection of a bands and microbands leads to the formation of new grains with the large misorientation angle. The measured grain/subgrain size show, that the grain size is maintained at a similar level after each stage of deformation and is equal to d = 0.25 – 0.32 μm.

scholarly journals Synthesis and electrical characterization of Ca2Nd4Ti6O20 ceramics

2016 ◽  
Vol 34 (1) ◽  
pp. 164-168
Author(s):  
Raz Muhammad ◽  
Muhammad Uzair ◽  
M. Javid Iqbal ◽  
M. Jawad Khan ◽  
Yaseen Iqbal ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Room Temperature ◽  
Sol Gel ◽  
Electrical Characterization ◽  
Sintered Sample ◽  
First Time ◽  
Alkoxide Precursors ◽  
Room Temperature Dielectric Constant

AbstractCa2Nd4Ti6O20, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel) route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21) symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (Pr) and the coercive field (Ec) were about 400 μC/cm2 and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF) and activation energy (1.39 eV) of the grain boundary was greater than the capacitance (5.7 pF) and activation energy (1.13 eV) of the grain.

About the Electrical Activation of 1×1020 cm-3 Ion Implanted Al in 4H-SiC at Annealing Temperatures in the Range 1500 - 1950°C

2018 ◽  
Vol 924 ◽  
pp. 333-338 ◽  
Author(s):  
Roberta Nipoti ◽  
Alberto Carnera ◽  
Giovanni Alfieri ◽  
Lukas Kranz
Keyword(s):  
Activation Energy ◽  
Sheet Resistance ◽  
Annealing Time ◽  
Thermal Activation ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Thermal Activation Energy ◽  
Electrical Activation ◽  
Temperature Range ◽  
Annealing Temperatures

The electrical activation of 1×1020cm-3implanted Al in 4H-SiC has been studied in the temperature range 1500 - 1950 °C by the analysis of the sheet resistance of the Al implanted layers, as measured at room temperature. The minimum annealing time for reaching stationary electrical at fixed annealing temperature has been found. The samples with stationary electrical activation have been used to estimate the thermal activation energy for the electrical activation of the implanted Al.

scholarly journals Microstructure and Nano-hardness of Pure Copper and ODS Copper Alloy under Au Ions Irradiation at Room Temperature

2016 ◽  
Vol 29 (11) ◽  
pp. 1047-1052
Author(s):  
Jing Zhang ◽  
Yong-Qin Chang ◽  
Zhi-Meng Guo ◽  
Ping-Ping Liu ◽  
Yi Long ◽  
...  
Keyword(s):  
Copper Alloy ◽  
Room Temperature ◽  
Pure Copper

scholarly journals PENDUGAAN UMUR SIMPAN SIRUP BUAH TIN “KHAROMAH” DENGAN METODE ACCELERATED SHELF LIFE TESTING (ASLT)

Pro Food ◽  
2018 ◽  
Vol 4 (1) ◽  
pp. 277-282
Author(s):  
Ali Mursyid Wahyu Mulyono ◽  
Afriyanti . ◽  
Joko Setyo Basuki ◽  
Sri Sukaryani
Keyword(s):  
Activation Energy ◽  
Shelf Life ◽  
Room Temperature ◽  
Reducing Sugar ◽  
Life Testing

Pokoh Kidul is the center of figs plant in Wonogiri area. Figs was processed into syrup with “Kharomah” as brand by Posdaya Lancar Barokah. But, the shelf life of this syrup was not yet known. Therefore, the purpose of this study was to determine the shelf life of this syrup by the Accelerated Shelf Life Testing (ASLT) method. Product was saved at temperature of 50C, 300C and 500C for 28 days. Every 7 days, a sample was taken and then the color, pH and reducing sugar was analysed. The lowest activation energy was obtained from the analysis of reducing sugar changes, it is 287,55 mol/cal. The shelf life of figs syrup at room temperature was 19 days, and 22 days at low temperature.Keywords: ASLT, figs, shelf life, syrupABSTRAKDesa Pokoh Kidul merupakan sentra tanaman buah tin di daerah Wonogiri. Buah tin yang dihasilkan selama ini diolah menjadi sirup buah tin dengan merk “Kharomah” oleh Posdaya Lancar Barokah. Akan tetapi, belum diketahui umur simpan dari sirup ini. Oleh karena itu, tujuan dari penelitian ini untuk mengetahui umur simpan sirup buah tin dengan metode Accelerated Shelf Life Testing (ASLT). Metode penelitian yang digunakan yaitu dengan penyimpanan produk sirup pada tiga suhu yang berbeda yaitu 50, 300 dan 500C selama 28 hari. Setiap 7 hari sekali diambil sampel dan dilakukan analisis warna, pH dan kadar gula reduksi. Energi aktivasi terendah didapatkan dari hasil analisis perubahan kadar gula reduksi yaitu 287,55 mol/kal. Umur simpan sirup buah tin di suhu ruang selama 19 hari, sedangkan di suhu rendah selama 22 hari.

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