Effect of Temperature on Tribological Properties of Cu/Ti3AlC2 Composites

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Zijue Zhou ◽  
Yi Feng ◽  
Hao Zhao ◽  
Gang Qian ◽  
Jingcheng Zhang ◽  
...  

Abstract In aerospace and power generation, components will serve in high-temperature environments. In this work, the influence of temperature on the tribological performances of Cu/Ti3AlC2 composites was investigated from 25 °C to 700 °C. Cu/Ti3AlC2 composites were fabricated by hot-pressing at 800 °C. The friction coefficients of the composites were in the range of 0.19–0.28. From 25 °C to 300 °C, the wear-rates increased with temperature from 9.05 × 10−5 mm3/Nm to 110 × 10−5 mm3/Nm, and the wear-rate reached the highest value at 300 °C. Interestingly, the wear-rates plummeted to 30.8 × 10−5 mm3/Nm at 500 °C, and 31.2 × 10−5 mm3/Nm at 700 °C. It was found that tribofilms consisting of Ti3AlC2 and Cu2O covered on the wear surfaces at 25 °C and 100 °C. Plastic flow and material transfer occurred at 300 °C. From 500 °C to 700 °C, oxidation layers formed on the wear surfaces of the composites. For simplicity, a schematic of the tribological mechanisms is proposed.

2012 ◽  
Vol 706-709 ◽  
pp. 768-773
Author(s):  
Masahiro Nishida ◽  
Koichi Hayashi ◽  
Junichi Nakagawa ◽  
Yoshitaka Ito

The influence of temperature on crater formation and ejecta composition in thick aluminum alloy targets were investigated for impact velocities ranging from approximately 1.5 to 3.5 km/s using a two-stage light-gas gun. The diameter and depth of the crater increased with increasing temperature. The ejecta size at low temperature was slightly smaller than that at high temperature and room temperature. Temperature did not affect the size ratio of ejecta. The scatter diameter of the ejecta at high temperature was slightly smaller than those at low and room temperatures.


1978 ◽  
Vol 29 (6) ◽  
pp. 1203 ◽  
Author(s):  
HC Harris ◽  
JR McWilliam ◽  
WK Mason

The influence of temperature on the oil content and composition of sunflower was studied on plants grown under field conditions and in a range of controlled environments. Traces of oil were detectable in cypsela (seed) almost immediately after pollination. Much of this appeared to be present in the hull (pericarp), which is well developed at this stage. Significant production of oil commenced with the development of the embryo about 150 day-degrees after pollination, and the oil content reached a maximum value just prior to physiological maturity of the seed. Linoleic acid constituted the major component of the oil at all stages of seed development, and under favourable temperature conditions increased from c. 50% soon after pollination to over 70% at physiological maturity. High temperature during the development of the seed was associated with a reduction in total oil yield. However, under field conditions this effect was variable owing to confounding with other environmental factors such as moisture stress, which also influence the yield of oil through their effects on growth and development of seed. Elevated temperatures, and in particularly high night temperatures, caused a marked reduction in the percentage of linoleic acid, apparently due to the effect of temperature on the activity of the desaturase enzymes which are responsible for the conversion of oleic to linoleic acid.These results support the hypothesis that reduced yields and altered composition of sunflower oil from crops matured under high temperature conditions in midsummer are due to the effects of heat stress on the biosynthesis of fatty acids.


2018 ◽  
Vol 163 ◽  
pp. 04004
Author(s):  
Beata Łaźniewska-Piekarczyk

The paper presents the results of the research on the impact of low and high temperature on the air content and consistency of non-airentrained and air-entrained and plasticized or superplasticized mortars according to PN-EN 480-1, which were made with CEM I cement. In case of the mortar with CEM I, various types of plasticizers and superplasticizers as well as aeration admixtures differing in chemical base were used. The analysis of the results of the research indicates that the effect of temperature influences the consistency and air-content of the mortar depending on the result of the type of plasticizing and superplasticizing admixture.


Author(s):  
T. Geipel ◽  
W. Mader ◽  
P. Pirouz

Temperature affects both elastic and inelastic scattering of electrons in a crystal. The Debye-Waller factor, B, describes the influence of temperature on the elastic scattering of electrons, whereas the imaginary part of the (complex) atomic form factor, fc = fr + ifi, describes the influence of temperature on the inelastic scattering of electrons (i.e. absorption). In HRTEM simulations, two possible ways to include absorption are: (i) an approximate method in which absorption is described by a phenomenological constant, μ, i.e. fi; - μfr, with the real part of the atomic form factor, fr, obtained from Hartree-Fock calculations, (ii) a more accurate method in which the absorptive components, fi of the atomic form factor are explicitly calculated. In this contribution, the inclusion of both the Debye-Waller factor and absorption on HRTEM images of a (Oll)-oriented GaAs crystal are presented (using the EMS software.Fig. 1 shows the the amplitudes and phases of the dominant 111 beams as a function of the specimen thickness, t, for the cases when μ = 0 (i.e. no absorption, solid line) and μ = 0.1 (with absorption, dashed line).


2021 ◽  
pp. 107754632110026
Author(s):  
Zhou Sun ◽  
Siyu Chen ◽  
Xuan Tao ◽  
Zehua Hu

Under high-speed and heavy-load conditions, the influence of temperature on the gear system is extremely important. Basically, the current work on the effect of temperature mostly considers the flash temperature or the overall temperature field to cause expansion at the meshing point and then affects nonlinear factors such as time-varying meshing stiffness, which lead to the deterioration of the dynamic transmission. This work considers the effect of temperature on the material’s elastic modulus and Poisson’s ratio and relates the temperature to the time-varying meshing stiffness. The effects of temperature on the elastic modulus and Poisson’s ratio are expressed as functions and brought into the improved energy method stiffness calculation formula. Then, the dynamic characteristics of the gear system are analyzed. With the bifurcation diagram, phase, Poincaré, and fast Fourier transform plots of the gear system, the influence of temperature on the nonlinear dynamics of the gear system is discussed. The numerical analysis results show that as the temperature increases, the dynamic response of the system in the middle-speed region gradually changes from periodic motion to chaos.


Author(s):  
Yiqun Huang ◽  
Pawan Singh Takhar ◽  
Juming Tang ◽  
Barry G Swanson

Rheological behaviors of high acyl (HA) gellan are not well understood partially because of its relatively late commercialization compared to low acyl gellan. The objective of this study was to investigate the effect of temperature (5-30 °C), calcium (0, 1 and 10 mM) and gellan concentrations (0.0044-0.1000% w/v) on the flow behaviors of high acyl gellan aqueous solutions using rheological tests. Gellan solutions with 0 or 1 mM added Ca++ exhibited shear thinning behavior at gellan concentrations above 0.0125%. The influence of temperature on apparent viscosity (shear rate, 100 s-1) of gellan solutions can be described with an Arrhenius relationship. The apparent viscosity of gellan solution at low concentrations was more sensitive to temperature changes. The addition of Ca++ led to a decrease in flow resistance for a dilute gellan solution (<0.0125%), but an increased resistance for a relatively concentrated gellan solution (>0.0125%).


2021 ◽  
Vol 99 (1) ◽  
pp. 18-23
Author(s):  
Charlie Joe Croxford ◽  
Rajpreet Kaur ◽  
Kultar Singh ◽  
Mandeep Singh Bakshi

Stable colloidal zein nanoparticles (NPs) were synthesized by using controlled precipitation method. They were made fluorescence active by incorporating a small amount of fluorescence quinolinium surfactant. The incorporation of fluorescence surfactant provided both the colloidal stability and the fluorescence ability to determine the phase transition in zein NPs under the effect of temperature variation. Maintaining colloidal stability under the effect of temperature variation is an essential aspect of zein NPs applicability as a source of vegetarian protein supplement in different food suspensions. Different techniques such as fluorescence, DLS size, zeta potential, and FTIR measurements were applied to determine the influence of temperature on the colloidal stability of zein NPs. Zein NPs undergo phase transition well above room temperature while maintaining their size in nanometer range, and the phase transition temperature decreased with the amount of zein used in the synthesis of zein NPs. The results highlighted the potential use of zein NPs as a vegetarian supplement protein in different food products.


1970 ◽  
Vol 15 ◽  
pp. 41-46 ◽  
Author(s):  
MM Rahman ◽  
W Islam ◽  
KN Ahmed

Xylocoris flavipes (Reuter) is one of the dominant predators of many stored product insect pest including Cryptolestes pusillus. The influence of temperature on predator development, survival and some selected life history parameters was determined. Eggs laid/female (27.27±2.52) and egg hatching rate (%) (88.25±2.19) were highest at 30°C and lowest at 20°C (5.43±1.19 and 30.79±4.63%) respectively but no eggs laid at 15°C. Mortality among immature stages (%) was highest (51.71±1.48) at 35°C and lowest (24.25c±1.14) at 25°C. Developmental times decreasing with the increasing of temperature. Maximum numbers of progeny/female/day (3.55±0.76) were produced at 25°C and minimum (0.83±0.04) were at 20°C.The sex ratios (% female) of X. flavipes were 47.04, 56.68, 51.66 and 50.07 for 20, 25, 30 and 35°C respectively. Survivorship of ovipositing females was highest at 25°C but lowest at 35°C respectively. Key words: Xylocoris flavipes, Cryptolestes pusillus, life history, temperature, developmental time   doi: 10.3329/jbs.v15i0.2201 J. bio-sci. 15: 41-46, 2007


2013 ◽  
Vol 687 ◽  
pp. 130-135
Author(s):  
Si Feng Liu ◽  
Si Jun Guo ◽  
Pei Ming Wang

The hydration heat of polymer modified mortar were measured at 5°C、10°C、20°C and 40°C using Multi-channel Isothermal calorimeter. The effects of temperature on hydration heat of polymer modified mortars with 0.1% methyl hydroxylpropyl cellulose (MHPC), 3% ethylene vinyl acetate (EVA) and 0.1%MHPC+3%EVA were investigated. The curves of hydration heat show that the polymer reduces the hydration heat of mortars and it is related to the temperature. The effects will be more and more remarkable with the increasing of temperature; Temperature also affects the exothermic rate peak of polymer modified mortars. The exothermic rate peak of polymer modified mortar at low temperature is almost equal to that of the ordinary cement mortar. However, it is obviously lower than that of ordinary cement mortar at high temperature ; The time to the exothermic rate peak of polymer modified mortar is also related to the temperature.


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