• Title, Summary, Keyword: arrhenius plot

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Determination of Reorganization Energy from the Temperature Dependence of Electron Transfer Rate Constant for Hydroquinone-tethered Self-assembled Monolayers (SAMs)

  • Park, Won-choul;Hong, Hun-Gi
    • Bulletin of the Korean Chemical Society
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    • v.27 no.3
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    • pp.381-385
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    • 2006
  • The temperature dependence on the electron transfer rate constant $(k_{app})$ for hydroquinone redox center in $H_2Q(CH_2)_n$SH-SAMs (n = 1, 4, 6, 8, 10, and 12) on gold electrode was investigated to obtain reorganization energy $(\lambda)$ using Laviron’s formalism and Arrhenius plot of ln $[k_{app}/T^{1/2}]$ vs. T^{-1} based on the Marcus densityof-states model. All the symmetry factors measured for the SAMs were relatively close to unity and rarely varied to temperature change as expected. The electron tunneling constant $(\beta)$ determined from the dependence of the $k_{app}$ on the distance between the redox center and the electrode surface gives almost the same $\beta$ values which are quite insensitive to temperature change. Good linear relationship of Arrhenius plot for all $H_2Q(CH_2)_n$SH-SAMs on gold electrode was obtained in the temperature range from 273 to 328 K. The slopes n Arrhenius plot deduced that $\lambda$ of hydroquinone moiety is ca. 1.3-1.4 eV irrespectively of alkyl chain length of the electroactive SAM.

Studies on the Drying Methods of Sea Foods 2. Fixed-Bed Drying of Cuttlefish (수산식품의 건조방법에 관한 연구 2. 갑오징어의 고정층건조)

  • HUR Jong-Wha
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.15 no.3
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    • pp.207-210
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    • 1982
  • For the removal of initial water content in cuttlefish, the effects of fixed-bed drying condition on the drying rate were investigated, with following results. 1. The drying rate of cuttlefish dried at fixed-bed condition was also faster than that at natural convection type or hot air dryer.2. By controlling air temperature and its direction to cut-and-peeled sample the drying time can be reduced to 2 hrs. 3. Shirai's equation and Arrhenius' law were applicable to fixed-bed dried cuttlefish. Drying rate constant (k) by Shirai's equation, and Arrhenius' plot were as shown in Table 3, 4 and Fig.3, respectively.

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Effect of Cure System on the Life-time of Hydrogenated NBR O-ring using Intermittent Compression Stress Relaxation(CSR) (간헐 압축응력 완화를 이용한 가교 구조가 hydrogenated NBR 오링의 수명에 미치는 영향 연구)

  • Lee, Jin-Hyok;Bae, Jong-Woo;Kim, Jung-Su;Hwang, Tae-Jun;Choi, Yu-Seok;Baek, Kwang-Sae;Jo, Nam-Ju
    • Elastomers and Composites
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    • v.46 no.2
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    • pp.144-151
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    • 2011
  • Intermittent CSR testing was used to investigate the degradation of a hydrogenated NBR(HNBR) O-rings, and also the prediction of its life-time. The cure system of HNBR O-ring was controlled as sulfur cure and peroxide cure system. An intermittent CSR jig was designed taking into consideration the O-ring's environment under use. The testing allowed observation of the effects of friction, heat loss, and stress relaxation by the Mullins effect. Degradation of O-rings by thermal aging was observed between 100 and $120^{\circ}C$. In the temperature range of $100-120^{\circ}C$, O-rings showed linear degradation behavior and satisfied the Arrhenius relationship. The activation energy of HNBR-S was about 70.6 kJ/mol. From Arrhenius plots, predicted life-times of HNBR-S O-ring were 31.1 years and 33.7 years for 50% and 40% failure conditions, respectively. In case of HNBR-P, the activation energy was about 72.1kJ/mol, and predicted life-times were 34.0 years and 36.5 years for 50% and 40% failure conditions, respectively. The peroxide cure system showed slower degradation rate and higher activation energy than the sulfur cure system.

Effects of Thermal Aging on Properties and Life-time Prediction of NBR and EPDM Vulcanizates (열 노화에 따른 NBR과 EPDM 가황물의 물성변화 및 노화수명 예측)

  • Woo, C.S.;Choi, S.S.
    • Elastomers and Composites
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    • v.40 no.2
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    • pp.119-127
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    • 2005
  • Material characteristics and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the material test and accelerated heat aging test were carried out to predict the useful life of NBR and EPDM rubber mount for a compression motor which is used in a refrigerator. In order to investigate the effects of heat-aging on the material properties, crosslink density, modulus at 100% strain, stress-strain curves were obtained from uniaxial and equi-biaxial tensile tests. The change of compression set were used for assessment of the useful life and the time to threshold value were plotted against the reciprocal of absolute temperature to give the Arrhenius plot. The useful life at variable temperatures are obtained in the Arrhenius relationship.

Life Time Prediction Using Accelerated Ageing Test for a CR/CB Rubber Composite

  • Ahn, WonSool;Lee, Hyung Seok
    • Elastomers and Composites
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    • v.52 no.4
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    • pp.237-241
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    • 2017
  • The tensile strength (TS) and elongation-at-break (EB) loss of a CR/CB rubber composite sample prepared for the automotive parts were measured after accelerated thermal ageing at temperatures of 100, 120, 140, and $150^{\circ}C$. The change in TS was observed to be linear from the master curve prepared using the time-temperature superposition-principle (TTSP). An Arrhenius type of shift factor, $a_T$ was used to predict the life time of the sample, and a plot of ln $a_T$ vs. 1/T was also shown to be linear. The activation energy ($E_a$) of the sample was calculated as 70.30 kJ/mole from the Arrhenius plot. The expected life time of the sample was predicted at the given operating conditions by applying Arrhenius analysis. Assuming the $E_a$ value was constant at lower operating condition, life time of the sample was calculated as 2.3 years when the life limit was set as time to reach the 20% decrease of the initial TS value at operating temperature of $40^{\circ}C$.

A study on ignition delays of sprays using a shock tube (충격파관을 이용한 분무연료의 착화지연에 관한 연구)

  • 정진도;류정인;수곡행부
    • Journal of the korean Society of Automotive Engineers
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    • v.11 no.6
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    • pp.48-56
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    • 1989
  • A shock tube technique was developed in which a freely falling droplets column produced by an ultrasonic atomizer was ignited behind reflected shock. In the present study, the effects of turbulent mixing on the ignition delay of a cetane was decided, also, ignition process was investigated. For the purpose of disturbance of droplets column and mixing, authors installed turbulent lattice in shock tube. Usually, the ignition delay is so called Arrhenius plot which found break point in the Arrhenius plot on the high temperature side. The rate of misfiring increased rapidly below 1080K, but ignition took place from 838k and luminous flame was seen to spread over the whole section by turbulent lattice. Length, from end plate to turbulent lattice, was varied with 60,40,20mm. Also, ignition process was detected by Photo transistor. As a result, it was found that physical factors changed ignition delay greatly and turbulent mixing had a considerable effects in the ignition process.

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Dielectric and Electrical Properties of Ce,Mn:SBN

  • Kang, Bong-Hoon;Paek, Young-Sop;Rhee, Bum-Ku;Lim, Ki-Soo;Joo, Gi-Tae
    • Journal of the Korean Ceramic Society
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    • v.40 no.7
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    • pp.615-619
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    • 2003
  • Temperature and frequency dependence of dielectric and electrical properties was investigated in cerium and manganese doped Sr$\_$0.6/Ba$\_$0.4/Nb$_2$O$\_$6/(60SBN) ceramic system. Structural deformation of 60SBN by dopants did not appeared. 1350$^{\circ}C$-10 h sintered specimen had higher densification than 1250$^{\circ}C$-10 h sintered one, to which dielectric properties are related. That the feature of dielectric maxima peaks was typical Diffusive Phase Transition (DPT), it was explained by "random-field Ising model". Even though 60SBN has large dielectric loss at high frequency above 100 ㎑, it is desirable for optical applications because of low dielectric loss at low frequency. From Arrhenius plot of temperature, the activation energy was calculated to 0.45-0.49 eV.

Temperature Dependence of the Electrical Activation Energy and Defect Density in Undoped Amorphous Germanium (a-Ge : H) (비정질 게르마늄(a-Ge : H)의 전기전도 활성화에너지 및 결함밀도의 온도의존성)

  • Jo, U-Seong;Yu, Jong-Hun
    • Korean Journal of Materials Research
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    • v.5 no.6
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    • pp.639-643
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    • 1995
  • The temperature dependence of the dark conductivity was studied on undoped hydrogenated amorphous germanium (a-Ge : H) over the range from 297 to 423 K. The pre-exponential factor $\sigma$$\_$0/ and activation energy E$\_$C/-E$\_$F/ are determined by an Arrhenius plot. The Arrhenius plot of the electrical conductivity shows a kink around the kink temperature and then is composed of two exponential functions. The obtained statistical shift ${\gamma}$$\_$F/ was about 8.65${\times}$10$\^$-3/eV/K and the pre-exponential factor $\sigma$$\_$0/ was about 2$\Omega$$\^$-1/cm$\^$-1/. A temperature dependent defect density is numerically calculated from the conductivity data. A change of the defect density is observed in the factor of about two in the range of the experimental temperature.

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Study on the Degradaion Behavior of Acrylonitrile Rubber(NBR) O-ring by Intermittent CSR and Time-Temperature Superposition Principle (간헐 압축응력완화 시험법과 시간-온도 중첩 이론을 이용한 NBR 오링의 노화 거동 분석 연구)

  • Lee, Jin Hyok;Bae, Jong Woo;Choi, Myung Chan;Yun, Yu Mi;Kim, Wonho;Park, Sung Han;Jo, Nam-Ju
    • Journal of the Korean Society of Propulsion Engineers
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    • v.23 no.1
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    • pp.46-51
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    • 2019
  • Intermittent CSR testing was used to investigate the degradation of a NBR O-ring, and also the prediction of its life-time. An intermittent CSR jig was designed taking into consideration the O-ring's environment under use. Degradation of O-rings by thermal aging was observed between $40^{\circ}C$ and $120^{\circ}C$. O-rings showed non-linear degradation behavior under $80^{\circ}C$. At 20% of failure condition, predicted life-times were 32.5 years by Arrhenius plot and 22.6 years by WLF plot.

A Study on the Lifetime Prediction of Rubber Mount for Refrigerator Component (냉장고 압축기용 고무마운트 수명예측에 관한 연구)

  • Woo Chang-Su;Park Hyun-Sung
    • Journal of Applied Reliability
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    • v.6 no.2
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    • pp.135-150
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    • 2006
  • Rubber material properties and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. This paper discusses the failure mechanism and material tests were carried out to predict the useful lifetime of NBR and EPDM for compression motor, which is used in refrigerator component. The heat-aging process leads not only to mechanical properties change but also to chemical structure change so called degradation. In order to investigate the aging effects on the material properties, the accelerated test were carried out. The stress-strain curves were plotted from the results of the tensile test for virgin and heat-aged rubber specimens. The rubber specimens were heat-aged in an oven at the temperature ranging from $70^{\circ}C\;to\;100^{\circ}C$ for a period ranging from 1 to 180 days. Compression set results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the compression set test, several useful lifetime prediction equations for rubber material were proposed.

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