Journal articles on the topic 'Other mechanical engineering, n.e.c'
To see the other types of publications on this topic, follow the link: Other mechanical engineering, n.e.c.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Other mechanical engineering, n.e.c.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Feng, Xiu Mei, Xiao Qing Lian, Ming Xue Jiang, and Yi Ner He. "Microstructure and Mechanical Properties of In Situ Al2O3- Ti(C,N) Composites." Advanced Materials Research 239-242 (May 2011): 1243–47. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.1243.
Full textAbstract:
Al2O3-Ti(C,N)composite ceramics were prepared by in situ aluminothermic reduction and pressureless sintering. The effects of different Ti(C,N) contents and sintering temperatures on microstructure and mechanical properties (bulk density ,apparent porosity and blending strength)of samples were investigated through experiments.The results show that Al2O3-Ti(C,N) composite ceramics with 10 wt.% Ti(C,N) prepared using titanium dioxide and metal aluminum powder as raw materials and sintered at 1300 °C for 3h under a flowing nitrigen stream have good properties ,with bulk density 2.94g/cm3,apparent porosity 26.4%, and blending strength reaches to 28.04 MPa. According to the microstructure analysis,the fine in situ synthesis Ti(C,N) particles are uniformly dispersed in tabular alundum matrix. Ti(C,N) and tabular alundum phases are closely combined and can inhibit grain growth each other,which is benefical in improving the comprehensive properties of composite ceramics.
2
Qasrawi, A. F. "Performance of the Yb/n-CdSe/C Tunneling Barriers." Journal of Nanoelectronics and Optoelectronics 13, no. 10 (October 1, 2018): 1493–98. http://dx.doi.org/10.1166/jno.2018.2379.
Full textAbstract:
In this article, the design and performance of the CdSe which are deposited onto thin films of Yb metal is reported and discussed. The thin films of CdSe which are deposited by the physical vapor deposition technique are observed to exhibit slightly deformed hexagonal polycrystalline nature with excess amount of Cd as confirmed by the X-ray, energy dispersive X-ray spectroscopy and scanning electron microscopy techniques. The n-type CdSe is also found to form a Schottky barrier of tunneling type when sandwiched between Yb and carbon. The quantum mechanical tunneling mechanism in this device which was tested and modeled in the frequency domain of 10–150 MHz is found to exhibit average intersite separations of ∼5 nm. The tunneling device exhibited a widening in the depletion region associated with significantly large capacitance tunability in the studied frequency domain. On the other hand, as an optoelectronic device, the Yb/n-CdSe/C Schottky diode exhibited a responsivity of ∼0.10 A/W, photosensitivity of 6.5 × 104 and external quantum efficiency of 54% when biased with 1.0 V and exposed to laser light of wavelength of 406 nm.
3
Wang, Yao Ning, Xi Cheng Zhao, and Hong Zhou Ma. "High Temperature Deformation Mechanical Model and Processing Map of Ti-6Al-2Zr-1Mo-1V Alloy." Advanced Materials Research 199-200 (February 2011): 1988–92. http://dx.doi.org/10.4028/www.scientific.net/amr.199-200.1988.
Full textAbstract:
Based on the high temperature compression simulation experiments, the mechanical behavior of Ti-6AI-2Zr-1Mo-1V alloy were studied over the range of temperature from 850°C to 1100°C , strain rate from 0.01 to 10s-1. The results show that the flow stress reduces with temperature increasing at the constant strain rate and increases rapidly with strain rate increasing at the constant temperature. The stress index n and deformation activation energy Q is respectively 7.0874 and 610.463 kJ/mol at 850-950°C . While at 950-1100°C , n is 4.7324 and Q is 238.030 kJ/mol. From the obtained processing map, it is found that two unstable regions present at the lower temperature or higher strain rate and two optimum regions in hot deformation process. The unstable zones are 850-950°C , 0.001-0.008s-1of strain rate, and 940-1030°C , 2-10s-1of strain rate respectively. In the optimum zone with the temperature range of 1060-1100°C , strain rate of 0.05-0.65s-1, and the peak efficiency of power dissipation of about 0.42; while in the other zone with the deformation temperature 890-940°C , strain rate of 0.06-0.18s-1, and the peak efficiency of power dissipation of about 0.33.
4
Jiao, W. Y., R. Hu, S. H. Han, Y. F. Luo, H. M. Yuan, M. K. Li, and H. J. Liu. "Surprisingly good thermoelectric performance of monolayer C3N." Nanotechnology 33, no. 4 (November 2, 2021): 045401. http://dx.doi.org/10.1088/1361-6528/ac302c.
Full textAbstract:
Abstract The rapid emergence of graphene has attracted numerous efforts to explore other two-dimensional materials. Here, we combine first-principles calculations and Boltzmann theory to investigate the structural, electronic, and thermoelectric transport properties of monolayer C3N, which exhibits a honeycomb structure very similar to graphene. It is found that the system is both dynamically and thermally stable even at high temperature. Unlike graphene, the monolayer has an indirect band gap of 0.38 eV and much lower lattice thermal conductivity. Moreover, the system exhibits obviously larger electrical conductivity and Seebeck coefficients for the hole carriers. Consequently, the ZT value of p-type C3N can reach 1.4 at 1200 K when a constant relaxation time is predicted by the simple deformation potential theory. However, such a larger ZT is reduced to 0.6 if we fully consider the electron–phonon coupling. Even so, the thermoelectric performance of monolayer C3N is still significantly enhanced compared with that of graphene, and is surprisingly good for low-dimensional thermoelectric materials consisting of very light elements.
5
Xue, Lin, Qiang Miao, Wenping Liang, Hui Zhao, Weiwei Shi, Shiwei Zuo, and Hanchun Ma. "Effect of shot peening on the wear behavior of Ti(C,N) coating on TA15 alloy prepared by double glow plasma carbonitriding." Industrial Lubrication and Tribology 73, no. 3 (January 25, 2021): 443–49. http://dx.doi.org/10.1108/ilt-07-2020-0283.
Full textAbstract:
Purpose The purpose of this paper is to prepare Ti(C,N) coatings on TA15 treated and not treated by shot peening using double glow plasma alloying technique. The effect of shot peening on the wear behavior of Ti(C,N) coatings is discussed. Design/methodology/approach The Ti(C,N) coatings were prepared by double glow plasma alloying technique on two different TA15 substrate; one is shot peened and the other is not. Findings Ti(C,N) coating on SP-treated TA15 was thicker and denser, and the grain size was smaller compared with that on original TA15. Compared with the Ti(C,N) coating on original TA15, the wear resistance of that on SP-treated TA15 is improved. Ti(C,N) coating on SP-treated TA15 showed higher nanohardness and bearing capacity than that on original TA15. Originality/value For double glow plasma alloying technique, surface quality, surface activity and other factors will have influence on the thickness and density of the coating. The wear mechanisms of Ti(C,N) coating on original TA15 are serious abrasive wear and oxidation wear. However, the wear mechanism of Ti(C,N) coating on SP-treated TA15 is slightly oxidation wear. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0283/
6
Ma, Yong Jie, and Guang Liang Zhang. "Effect of the HTP to X80 Ferrite Steel Structure and Mechanical Properties." Advanced Materials Research 189-193 (February 2011): 4216–20. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.4216.
Full textAbstract:
The structure and mechanical properties of pipeline steel X80 through HTP rolled into 16mm thick slab were tested. The results show that the yield strength of tested has reached above 600Mpa, and the ratio of tensile strength to yield strength is 0.86, and duetile brittle transition temperature is lower than -60°C , and good strength and toughness are obtained. Low content of P, S, high content of Mn and fine microstructure have good effect on reducing the ductile-brittle transitiop temperature. Two different precipitations are observed in pipeline steel X80, a class of TiN precipitations is mainly and a small number of (Nb, V)(C, N) complex precipitations in the TiN around, and the other for large number of NbC precipitations and a small amount of TiC、VC and simultaneous deposition of the complex formed precipitations. Remarkable strengthening and grain refinement can ne caused by these precipitations.
7
de Koning, A. C., J. D. Harston, K. D. Nayler, and R. K. Ohm. "Feeling Free Despite LBZ." Journal of Offshore Mechanics and Arctic Engineering 112, no. 2 (May 1, 1990): 115–26. http://dx.doi.org/10.1115/1.2919845.
Full textAbstract:
It is sometimes argued that the occurrence of local brittle zones (LBZs) is a new phenomenon relevant only to modern low-carbon steels, while others claim that such LBZs are also present in the heat-affected zones of the C-Mn steels of the late sixties/seventies. In order to elucidate on this matter, both an “old” normalized (N) steel (1970s) and two modern low-carbon types of steel, normalized (N) and controlled rolled-accelerated cooled (CONRAC) have been investigated and compared with each other. In addition, consideration has been given to the correlation between the level of heat input during welding and the occurrence of local brittle zones. This has led in practice to a restriction of the heat input to 3.5 kJ/mm maximum for the modern low-carbon normalized steel investigated, which was used in recent projects. Furthermore, the engineering significance of LBZs is considered in the light of design aspects. It is concluded that there is little reason for concern with respect to a detrimental effect of LBZs in tubular connections of offshore structures, which is supported by a satisfactory performance of the latter to date.
8
Lu, Y. H., and Y. G. Shen. "Effect of carbon content on thermal stability of Ti–Cx–Ny thin films." Journal of Materials Research 23, no. 3 (March 2008): 671–78. http://dx.doi.org/10.1557/jmr.2008.0082.
Full textAbstract:
A series of Ti–Cx–Ny thin films with solid-solution and nanocomposite structures were deposited at 500 °C by reactive, unbalanced, direct-current magnetron sputtering. These films were subsequently vacuum annealed at 600, 700, 800, 900, and 1000 °C for 1 h. The effect of C content on the thermal stability of Ti–Cx–Ny thin films was investigated by way of studying the nanostructure and mechanical behaviors of pre- and postannealed samples using x-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy, and microindentation measurements. The result indicated that C content played a great role in the nanostructure of Ti–Cx–Ny thin films. A small amount of C fully dissolved in the TiN lattice and produced SS Ti(N,C) thin films. Nanocomposite nanocrystalline (nc)-Ti(N,C)/amorphous-(C, CNx) thin films were followed to be formed with the incorporation of more C. On the other hand, the addition of C had a positive effect on the structural stability of Ti–Cx–Ny thin films. This effect was further enhanced after the formation of a nanocomposite structure. However, neither C content nor film structure had an effect on the thermal stability of mechanical behaviors. Both microhardness and residual stress were successively decreased with temperature and did not show any temperature retardation. The decrease in hardness values was found to be attributed to a decrease of residual compressive stress because of defect annihilation and an increase in nc size.
9
Hull, B. A., S. E. Mohney, and Z.-K. Liu. "Thermodynamic modeling of the Ni–Al–Ga–N system." Journal of Materials Research 19, no. 6 (June 2004): 1742–51. http://dx.doi.org/10.1557/jmr.2004.0218.
Full textAbstract:
Isothermal sections in the Ni–Al–Ga–N quaternary phase diagram were calculated to provide a greater understanding of interfacial reactions between Ni contacts and AlxGa1−xN. The calculations were performed employing a thermodynamic database of the Ni–Al–Ga–N system that was constructed by combining the six binary systems of the four component system. The model of the Ga–N binary system was created in this work. The models of the Ni–Ga and Ni–Al systems, both of which were taken from the literature, were modified to be compatible with one another. Thermodynamic data and phase boundaries for other binary systems were taken from the literature, as was information on portions of the Al–Ga–N and Ni–Al–Ga phase diagrams. The calculated sections reveal that during reaction between Ni and AlxGa1−xN, Ni is favored to react with the GaN component of the semiconductor alloy, leaving an Al-enriched AlxGa1−xN. These predictions are consistent with a recent analysis of the Ni, Al, and Ga elemental distributions across the interface between a Ni thin film and an Al0.47Ga0.53N epitaxial layer following annealing at 850 °C. Consideration of the thermodynamic driving forces suggests that this may be a general phenomenon existing in other metal–Al–Ga–N systems.
10
Essafti, A., C. Gómez-Aleixandre, J. L. G. Fierro, M. Fernández, and J. M. Albella. "Chemical vapor deposition synthesis and characterization of co-deposited silicon–nitrogen–boron materials." Journal of Materials Research 11, no. 10 (October 1996): 2565–74. http://dx.doi.org/10.1557/jmr.1996.0322.
Full textAbstract:
Si–N–B films have been deposited by LPCVD from SiH4/B2H6/NH3 gas mixtures. The influence of the temperature and the composition of the gas mixture on the deposition process and film properties has been investigated. At 1000 °C, for the highest ammonia flow rate (SiH4 :B2H6 : NH3, 10 : 25 : 500), a mixture of turbostratic boron nitride and silicon nitride was deposited. For decreasing ammonia flow rates the Si–N–B ternary system was formed (1260 cm−1 band in the infrared spectra), which co-exists with the unstable turbostratic boron nitride structure. Finally, for a low NH3 flow rate of 100 sccm, stable amorphous films are obtained. On the other hand, at 800 °C, stable films with a high content in the ternary Si–N–B compound were obtained for a wide range of ammonia concentrations (100–500 sccm). At this temperature (800 °C), the composition of the films, as measured by Auger and photoelectron spectroscopies, strongly depends on the [SiH4]/[B2H6] ratio in the gas mixture. The improvement in the mechanical and chemical properties of the samples has been associated with the increase in the content of Si–N bonds in the Si–N–B films.
11
Wisnujati, Andika, and Juni Andryansyah. "Analysis Of Mechanical Properties SMAW (Shielded Metal Arc Welding) Welding Joints Of Portable Electric Hydraulic Jack Frame." INTEK: Jurnal Penelitian 7, no. 2 (April 9, 2021): 155. http://dx.doi.org/10.31963/intek.v7i2.2134.
Full textAbstract:
Welding is a very important part of the development and growth of the industry because it has a role in engineering, reparation, and construction. Shielded Metal Arc Welding (SMAW) or the conventional arc welding process is particularly dominant in structural joints, pressure vessels and in maintenance and repair work. In welding, different metals are joined economically and at a much faster rate as compared with other fabrication processes like riveting and casting. The purpose of this research is to find out the cooling media cooler against SMAW smelter tensile strength by using the E6013 electrode. This study uses low carbon steel material that has levels Fe = 98,3%; C = 0,30%, Si = 0,23%. The material is given 75A welding current with cooling variation on the connection result using oil, water, and room temperature. The highest tensile stress value obtained in the oil cooling treatment was 844,76 N/mm2, the highest strain value was obtained on the raw materials of 16%, the highest elasticity value was obtained in the oil cooling treatment of 703.96 N/mm2. According to the research results can be concluded that the variations of cooling media greatly affect the strength of the welding connection.
12
Watanabe, Shuichi, Shojiro Miyake, and Masao Murakawa. "Tribological Behavior of Cubic Boron Nitride Film Sliding Against Diamond." Journal of Tribology 117, no. 4 (October 1, 1995): 629–33. http://dx.doi.org/10.1115/1.2831527.
Full textAbstract:
Cubic boron nitride (c-BN) film was deposited onto a silicon substrate by means of a magnetically enhanced plasma ion plating method utilizing a hot cathode plasma discharge in parallel magnetic field. In this study, the friction and wear behaviors of the c-BN film, particularly when it came into sliding contact with diamond, were investigated using a reciprocating tribometer in an applied normal load range of 0.1 ~ 4.9 N. The results showed that the friction coefficient of the c-BN film sliding against the diamond indenter tended to decrease as the load increased, and was very low, exhibiting values of 0.03 ~ 0.065 at the maximum load of 4.9 N. Furthermore, the study confirmed that the friction coefficient of annealed c-BN film was lower than that of as-deposited c-BN film throughout the whole load range. Judging from the results of comparable investigations in which c-BN film came into contact with other materials such as c-BN compact, SiC and stainless steel, the wear performance and peeling resistance of the c-BN film proved to be significantly better in the case of contact with diamond.
13
Shen, I. Y. "Vibration of Elastic Structures With Cracks." Journal of Applied Mechanics 60, no. 2 (June 1, 1993): 414–21. http://dx.doi.org/10.1115/1.2900809.
Full textAbstract:
An analytical algorithm is proposed to represent eigensolutions [λm2, ψm(r)]m=1∞ of an imperfect structure C containing cracks in terms of crack configuration σc and eigensolutions [ωn2, φn(r)]n=1∞ of a perfect structured without P the cracks. To illustrate this algorithm on mechanical systems governed by the two-dimensional Helmholtz operator, the Green’s identity and Green’sfunction of P are used to represent ψm(r) in terms of an infinite series of φn(r). Substitution of the ψn(r) representation into the Kamke quotient of C and stationarity of the quotient result in a matrix Fredholm integral equation. The eigensolutions of the Fredholm integral equation then predict λm2 and ψm(r) of C. Finally, eigensolutions of two rectangular elastic solids under antiplane strain vibration, one with a boundary crack and the other with an oblique internal crack, are calculated numerically.
14
Kunuku, Srinivasu, Mateusz Ficek, Aleksandra Wieloszynska, Magdalena Tamulewicz-Szwajkowska, Krzysztof Gajewski, Miroslaw Sawczak, Aneta Lewkowicz, Jacek Ryl, Tedor Gotszalk, and Robert Bogdanowicz. "Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films." Nanotechnology 33, no. 12 (December 28, 2021): 125603. http://dx.doi.org/10.1088/1361-6528/ac4130.
Full textAbstract:
Abstract Boron doped diamond (BDD) has great potential in electrical, and electrochemical sensing applications. The growth parameters, substrates, and synthesis method play a vital role in the preparation of semiconducting BDD to metallic BDD. Doping of other elements along with boron (B) into diamond demonstrated improved efficacy of B doping and exceptional properties. In the present study, B and nitrogen (N) co-doped diamond has been synthesized on single crystalline diamond (SCD) IIa and SCD Ib substrates in a microwave plasma-assisted chemical vapor deposition process. The B/N co-doping into CVD diamond has been conducted at constant N flow of N/C ∼ 0.02 with three different B/C doping concentrations of B/C ∼ 2500 ppm, 5000 ppm, 7500 ppm. Atomic force microscopy topography depicted the flat and smooth surface with low surface roughness for low B doping, whereas surface features like hillock structures and un-epitaxial diamond crystals with high surface roughness were observed for high B doping concentrations. KPFM measurements revealed that the work function (4.74–4.94 eV) has not varied significantly for CVD diamond synthesized with different B/C concentrations. Raman spectroscopy measurements described the growth of high-quality diamond and photoluminescence studies revealed the formation of high-density nitrogen-vacancy centers in CVD diamond layers. X-ray photoelectron spectroscopy results confirmed the successful B doping and the increase in N doping with B doping concentration. The room temperature electrical resistance measurements of CVD diamond layers (B/C ∼ 7500 ppm) have shown the low resistance value ∼9.29 Ω for CVD diamond/SCD IIa, and the resistance value ∼16.55 Ω for CVD diamond/SCD Ib samples.
15
Yoon, Seok J., So Y. Yoo, Jong H. Moon, Hyung J. Jung, and Hyun J. Kim. "Effects of La2O3 and MnO2 on the piezoelectric properties of 0.02Pb(Y2/3W1/3)O3−0.98Pb(Zr0.52Ti0.48)03." Journal of Materials Research 11, no. 2 (February 1996): 348–52. http://dx.doi.org/10.1557/jmr.1996.0041.
Full textAbstract:
The effects of the addition of La2O3 (0.1 wt. %−1 wt. %) and MnO2 (0.1 wt. %−1 wt. %) on the piezoelectric properties of the 0.02Pb(Y2/3W1/3)O3−0.98Pb(Zr0.52Ti0.48)O3 system were investigated to develop the composition available for an actuator. In the case of the addition of La2O3 to the system, the maximum values of d33 and kp were observed in the 0.1 wt. % La2O3, and the values of Qm did not change with the amount of La2O3. The values of d33, kp, and Qm were 428 × 10−12 C/N, 57%, and 71, respectively. On the other hand, the introduction of 0.5 wt. % MnO2 as an acceptor into the system resulted in the maximum Qm value of 741, exhibiting a d33 of 298 × 10−12 C/N, and a kp of 50%. In the case of the simultaneous addition of La2O3 and MnO2, the best piezoelectric properties are obtained from the composition of 0.02Pb(Y2/3W1/3)O3−0.98Pb(Zr0.52Ti0.48)O3 + 0.1 wt. % La2O3 + 0.3 wt. % MnO2. The values of d33, kp, and Qm were 345 × 10−12 C/N, 55%, and 741, respectively.
16
Vianco, Paul, Jerome Rejent, Gary Zender, and Alice Kilgo. "Kinetics of Pb-rich Phase Particle Coarsening in Sn–Pb Solder Under Isothermal Annealing–cooling Rate Dependence." Journal of Materials Research 20, no. 6 (June 1, 2005): 1563–73. http://dx.doi.org/10.1557/jmr.2005.0198.
Full textAbstract:
The coarsening behavior of the Pb-rich phase particles in 63Sn–37Pb (wt%) solder was investigated following isothermal annealing treatments. Samples were exposed to cooling rates of 0.1, 1.0, 10, and 100 °C/min. Annealing temperatures were 25, 55, 70, 85, and 100 °C, and times were 2–100 days. The mean particle diameter decreased from 1.8 × 10−3 to 0.8 × 10−3 mm with increased cooling rate, indicating two solidification regimes: one for cooling rates ≤1 °C/min and the other for cooling rates of ≥10 °C/min. The Pb-rich phase particles coarsened more quickly in samples made at the two fastest cooling rates. There was little Pb-rich phase particle coarsening at 25 and 55 °C for all annealing times. Coarsening rate kinetics were examined specifically for the 10 and 100 °C/min data using the expression Atnexp[−ΔH/RT]. The values of n were 0.23 ± 0.11 and 0.36 ± 0.13, respectively; n was not sensitive to annealing temperature. The corresponding 1/n values indicated that the coarsening mechanism changed from a fast diffusion to a bulk diffusion controlled process with a faster cooling rate. The apparent activation energy ΔH ranged from 16 ± 8 to 41 ± 8 kJ/mol; the values increased with cooling rate from 10 to 100 °C/min. The ΔH value was sensitive to annealing temperature only for the faster cooling rate of 100 °C/min. Together, the n and ΔH values indicated that an accelerated, fast diffusion mechanism with low activation barriers characterized the Pb-rich phase coarsening in samples exposed to a slower cooling rate, greater annealing, or a combination of the two conditions. That mechanism likely originated from the in situ development of recover/recrystallization microstructures in the Sn-rich phase. At faster cooling rates, those microstructures were not as well developed, so coarsening was controlled more by the higher activation barriers of bulk diffusion processes.
17
Park, Gun-Tae, Chee-Sung Park, Jong-Jin Choi, and Hyoun-Ee Kim. "Orientation control of sol-gel-derived lead zirconate titanate film by addition of polyvinylpyrrolidone." Journal of Materials Research 20, no. 4 (April 1, 2005): 882–88. http://dx.doi.org/10.1557/jmr.2005.0109.
Full textAbstract:
Highly (100)- and (111)-oriented lead zirconate titanate (PZT) films with a thickness of 350 nm were deposited on platinized Si substrates through a single spinning of a PZT sol containing polyvinylpyrrolidone (PVP) as an additive. The crystallographic orientation of the film was strongly influenced by pyrolysis conditions after spin coating. When the spin-coated sol was pyrolyzed at temperatures above 320 °C for relatively long periods of time (>5 min), (111)-oriented film was formed after annealing at 700 °C for 10 min. On the other hand, when the same sol was pyrolyzed at 320 °C for short periods of time (<5 min), the film was strongly oriented to the (100) direction after annealing. Organic residues derived from PVP decomposition acted as nucleation sites for the (100) oriented grains during annealing after the pyrolysis. The effective d33 of the (100)-oriented PZT film (100 pC/N) was much higher than that of the (111)-oriented film (62 pC/N) with the same thickness.
18
Merritt, Glen R., Malcolm B. Williams, Paul G. Allison, James B. Jordon, Timothy W. Rushing, and Christian A. Cousin. "Closed-Loop Temperature and Force Control of Additive Friction Stir Deposition." Journal of Manufacturing and Materials Processing 6, no. 5 (August 24, 2022): 92. http://dx.doi.org/10.3390/jmmp6050092.
Full textAbstract:
Additive Friction Stir Deposition (AFSD) is a recent innovation in non-beam-based metal additive manufacturing that achieves layer-by-layer deposition while avoiding the solid-to-liquid phase transformation. AFSD presents numerous benefits over other forms of fusion-based additive manufacturing, such as high-strength mechanical bonding, joining of dissimilar alloys, and high deposition rates. To improve, automate, and ensure the quality, uniformity, and consistency of the AFSD process, it is necessary to control the temperature at the interaction zone and the force applied to the consumable feedstock during deposition. In this paper, real-time temperature and force feedback are achieved by embedding thermocouples into the nonconsumable machine tool-shoulder and estimating the applied force from the motor current of the linear actuator driving the feedstock. Subsequently, temperature and force controllers are developed for the AFSD process, ensuring that the temperature at the interaction zone and the force applied to the feedstock track desired command values. The temperature and force controllers were evaluated separately and together on setpoints and time-varying trajectories. For combined temperature and force control with setpoints selected at a temperature of 420 °C and a force of 2669 N, the average temperature and force tracking errors are 5.4 ± 6.5 °C (1.4 ± 1.6%) and 140.1 ± 213.5 N (5.2 ± 8.0%), respectively.
19
Aziz, Wisam J., Marwa Abdul Muhsien Hassan, and Mohammed Jwad Khadam. "Biosynthesis of Iron and Cobalt Nanoparticles Using Garlic (Allium cativum) Extract and their Some Applications." Key Engineering Materials 882 (April 2021): 165–70. http://dx.doi.org/10.4028/www.scientific.net/kem.882.165.
Full textAbstract:
It has been employed nano particles using garlic (Allium cativum) extract at conditions (pH=12, concentration = 0.1 M, temperature = 90 °C, time =3 hr. and Oxidizing agent (hydrozoan). X-Ray diffraction of Co NPs using Allium cativum with polycrystalline as compared to specification (JCPDS Card no. 030-0443) and the structure is cubic phase and showed nothing at any article than to extract used as search (chemical) method with the outfit that successful chemical picas distinct and no trace of moisture dust concentrations are enlargement were appropriate for the sample. XRD of Fe NPs using Allium cativum is polycrystalline depend on (JCPDS Card no. 052-0513) with peaks (111, 200, 220) and 2θ(42.7, 49.7, 73.1). FESEM pictures of cobalt and Iron nano particles. The nano particles morphology demonstrates irregular, cubic and hexagonal pattern of different sizes which are agglomerated. Other findings with larger magnifications show that all these pictures have soft surfaces. Co NPs / Fe NPs / c-Si n-type (100) structure has a better performance against Co NPs/Si n-type (100) and Fe NPs /Si n-type (100) structures, such that the output of solar cells efficiencies are 6.31, 7.03 and 7.8 % respectively. Cobalt and iron nanostructures produced naturally used to have anti bacterial behavior against pathogenic bacteria such as B-cereus and E-coli with (37, 39) mm, respectively.
20
Chen, S. F., J. H. Oliver, and D. Fernandez-Baca. "A Fast Algorithm for Planning Collision-Free Paths With Rotations." Journal of Mechanical Design 120, no. 1 (March 1, 1998): 52–57. http://dx.doi.org/10.1115/1.2826676.
Full textAbstract:
Motion planning is a major problem in robotics. The objective is to plan a collision-free path for a robot moving through a workspace populated with obstacles. In this paper, we present a fast and practical algorithm for moving a convex polygonal robot among a set of polygonal obstacles with translations and rotations. The running time is O(c((n + k)N + n log n)), where c is a parameter controlling the precision of the results, n is the total number of obstacle vertices, k is the number of intersections of configuration space obstacles, and N is the number of obstacles, decomposed into convex objects. This work builds upon the slabbing method proposed by Ahrikencheikh et al. [2], which finds an optimal motion for a point among a set of nonoverlapping obstacles. Here, we extend the slabbing method to the motion planning of a convex polygonal robot with translations and rotations, which also allows overlapping configuration space obstacles. This algorithm has been fully implemented and the experimental results show that it is more robust and faster than other approaches.
21
He, Yashu, Zhenyang Wang, Fengyu Wen, Igor S. Sirotin, Jianxin Mu, and Vyacheslav V. Kireev. "MMA-based fast-curing repair materials suitable for low-temperature application." Journal of Polymer Engineering 42, no. 4 (March 3, 2022): 343–50. http://dx.doi.org/10.1515/polyeng-2021-0292.
Full textAbstract:
Abstract In this study, the application of methyl methacrylate (MMA) resin as the binder and standard sand as the aggregate has been employed to prepare the repair materials that can be cured in the sub-zero temperature environment. For this purpose, the redox initiation system of benzoyl peroxide (BPO) and N,N-dimethyl-p-toluidine (DMPT) has been used. Subsequently, the influence of initiator and accelerator content on the compressive strength, flexural strength, curing time and other properties of the materials has been revealed. At an ambient temperature of 0 °C, with BPO = 4.5% and DMPT = 3.5%, the developed repair materials can be cured within 31 min, and the 1 h compressive strength reaches 84.6 MPa. At an ambient temperature of −25 °C, with BPO = 4% and DMPT = 5%, the repair materials can be cured within 43 min, with the 1 h compressive strength reaching 53.4 MPa. The materials can be swiftly cured at low-temperature and exhibit excellent mechanical properties, thus, confirming their suitability for extreme environments. Fourier transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and other techniques have been employed to characterize the developed materials.
22
Robo, Céline, David Wenner, S. J. Kumari A. Ubhayasekera, Jöns Hilborn, Caroline Öhman-Mägi, and Cecilia Persson. "Functional Properties of Low-Modulus PMMA Bone Cements Containing Linoleic Acid." Journal of Functional Biomaterials 12, no. 1 (January 17, 2021): 5. http://dx.doi.org/10.3390/jfb12010005.
Full textAbstract:
Acrylic bone cements modified with linoleic acid are a promising low-modulus alternative to traditional high-modulus bone cements. However, several key properties remain unexplored, including the effect of autoclave sterilization and the potential use of low-modulus cements in other applications than vertebral augmentation. In this work, we evaluate the effect of sterilization on the structure and stability of linoleic acid, as well as in the handling properties, glass transition temperature, mechanical properties, and screw augmentation potential of low-modulus cement containing the fatty acid. Neither 1H NMR nor SFC-MS/MS analysis showed any detectable differences in autoclaved linoleic acid compared to fresh one. The peak polymerization temperature of the low-modulus cement was much lower (28–30 °C) than that of the high-modulus cement (67 °C), whereas the setting time remained comparable (20–25 min). The Tg of the low-modulus cement was lower (75–78 °C) than that of the high-stiffness cement (103 °C). It was shown that sterilization of linoleic acid by autoclaving did not significantly affect the functional properties of low-modulus PMMA bone cement, making the component suitable for sterile production. Ultimately, the low-modulus cement exhibited handling and mechanical properties that more closely match those of osteoporotic vertebral bone with a screw holding capacity of under 2000 N, making it a promising alternative for use in combination with orthopedic hardware in applications where high-stiffness augmentation materials can result in undesired effects.
23
Kwon, Jieun, Yun Hee Kim, Sung-Min Rhee, Tae In Kim, Jimin Lee, Saewha Jeon, and Joo Han Oh. "Effects of Allogenic Dermal Fibroblasts on Rotator Cuff Healing in a Rabbit Model of Chronic Tear." American Journal of Sports Medicine 46, no. 8 (May 10, 2018): 1901–8. http://dx.doi.org/10.1177/0363546518770428.
Full textAbstract:
Background: The failure of rotator cuffs to heal after repair is an unresolved surgical issue. There have been substantial efforts, including the use of biological supplements, to enhance tendon healing. Dermal fibroblasts are a good candidate for tendon tissue engineering because they are similar to the tenocytes used for collagen synthesis. In addition, they are easily accessible because autologous dermal fibroblasts can be obtained from individual skin without major skin defects and allogenic dermal fibroblasts (ADFs) have already been commercialized in the field of skin engineering. Purpose: To determine the effects of dermal fibroblasts on tendon-to-bone healing in a rabbit model of a chronic rotator cuff tear. Study Design: Controlled laboratory study. Methods: A total of 33 rabbits were randomly allocated into 3 groups (n = 11 each). Supraspinatus tendons were detached and left for 6 weeks to establish a chronic rotator tear model. Torn tendons were repaired in a transosseous manner with the injection of 5 × 106 ADFs with fibrin in group A, fibrin only in group B, and saline only in group C. At 12 weeks after repair, the mechanical test and histological evaluation were performed. Results: Seven rabbits died before the evaluation (1 in group A, 2 in group B, 4 in group C). In the final evaluation, the mean ± SD load to failure was 48.1 ± 13.3 N/kg for group A, 34.5 ± 8.9 N/kg for group B, and 31.1 ± 8.3 N/kg for group C, and group A showed significantly higher load-to-failure values than the other groups ( P = .011). The midsubstance tear rate, which presented stronger tendon-to-bone healing than insertional tear, was 50.0% in group A, 22.2% in group B, 28.6% in group C, but the differences were not statistically significant ( P = .413). In the histological evaluation, group A showed greater collagen fiber continuity and better orientation than the other groups. Conclusion: This controlled laboratory study verified, on the basis of biomechanics and histology, the potential for the use of ADFs in rotator cuff healing. The current results suggest a new biological supplement to increase the rate of rotator cuff healing. Clinical Relevance: The most important finding of this study was the potential for a new biological supplement to enhance rotator cuff healing—a continuing challenge.
24
Marchelli, Filippo, Giorgio Rovero, Massimo Curti, Elisabetta Arato, Barbara Bosio, and Cristina Moliner. "An Integrated Approach to Convert Lignocellulosic and Wool Residues into Balanced Fertilisers." Energies 14, no. 2 (January 18, 2021): 497. http://dx.doi.org/10.3390/en14020497.
Full textAbstract:
Valorising biomass waste and producing renewable energy or materials is the aim of several conversion technologies. In this work, we consider two residues from different production chains: lignocellulosic residues from agriculture and wool residues from sheep husbandry. These materials are produced in large quantities, and their disposal is often costly and challenging for farmers. For their valorisation, we focus on slow pyrolysis for the former and water hydrolysis for the latter, concisely presenting the main literature related to these two processes. Pyrolysis produces the C-rich biochar, suitable for soil amending. Hydrolysis produces a N-rich fertiliser. We demonstrate how these two processes could be fruitfully integrated, as their products can be flexibly mixed to produce fertilisers. This solution would allow the achievement of balanced and tuneable ratios between C and N and the enhancement of the mechanical properties. We propose scenarios for this combined valorisation and for its coupling with other industries. As a result, biomass waste would be returned to the field, following the principles of circular economy.
25
Yao, Li Rong, Wei Tao Zhao, Shan Qing Xu, and Qi Long Sun. "The Preparation of Aramid Paper and its Properties." Advanced Materials Research 796 (September 2013): 290–93. http://dx.doi.org/10.4028/www.scientific.net/amr.796.290.
Full textAbstract:
The meta-aramid fibrids were prepared by precipitation in this paper. The meta-aramid solution dissolved in the solvent system DMAc/LiCl was injected into the high shearing coagulant at room temperature and the mixture of water and N, N-dimethylacetamide(DMAc) was used as coagulant. The shearing rate, viscosity of the solution and the concentration of water in coagulant were the main factors on effecting the formation of fibrids. The meta-aramid fibrid has a gradual weight loss process when the temperature increases from 100°C to 400°C, lower thermal property of meta-aramid fibrid was due to the hydrogen bonding and crystalline structure were broken during dissolving process, however, a flexible and easy dispersing property of meta-aramid fibrid in fluid is due to its amorphous structure, which are very important that the meta-aramid fibrid has a better binding and adhesive property with the aramid short fiber in aramid paper, then yield a high mechanical and insulation property for aramid paper. Then, the properies of aramid paper were investigated. The results indicated that the proportion of meta-aramid fibrid in the aramid paper and the length of shorten aramid fiber are the main factors for affecting the strength and the other properties of aramid paper.
26
Yan, Y., M. A. Kirk, and J. E. Evetts. "Structure of grain boundaries: Correlation to supercurrent transport in textured Bi2Sr2Can−1CunOx bulk material." Journal of Materials Research 12, no. 11 (November 1997): 3009–28. http://dx.doi.org/10.1557/jmr.1997.0395.
Full textAbstract:
Two kinds of characteristic grain boundaries were observed in textured Bi2Sr2Can−1CunOx (n = 2 and 3) bulk material: one (P-type) is nearly parallel to the (001) plane, and the other (N-type) is approximately normal to the (001) plane. Low-angle tilt N-type boundaries are composed of arrays of dislocations. However, for a small c-axis misorientation, the regions between the dislocation cores are still well connected, providing “pathways” for supercurrents crossing the boundary plane. The P-type boundaries exhibit compositionally and structurally modulated faceting. Although we see local regions of the low Tc (2201) phase at low-angle tilt (<10°) P-type boundaries, there are also “pathways” crossing the boundary plane made up of the high Tc (2212) and (2223) phases. The characteristics of such low-angle tilt grain boundary structures can therefore be modeled to provide general insight into the correlation between high critical current densities and low-texture breadths. On the other hand, a weak link could be formed at high-angle (> 10°) boundaries where there are the low Tc (2201) or insulating phases.
27
Oliveira, Naelmo de Souza, Jolimar Antonio Schiavo, Miriam Ferreira Lima, Lais Thomaz Laranjeira, Geisielly Pereira Nunes, and Sidne Canassa da Cruz. "Isotopic variations of carbon and nitrogen and their implications on the conversion of Cerrado vegetation into pasture." Revista Brasileira de Ciências Ambientais (Online) 56, no. 2 (2021): 266–73. http://dx.doi.org/10.5327/z21769478845.
Full textAbstract:
Conversions of natural vegetation into pasture can, in a short time, change the carbon stock and the natural abundance of δ13C in the soil. The objective of this study was to evaluate changes in carbon (C) and nitrogen (N) stocks, as well as in the natural abundance of δ13C and δ15N of Argissolo Vermelho distrófico (Acrisol), in an area of natural vegetation and planted pasture in the Cerrado region of Aquidauana (MS), Brazil. In order to do this, an area of pasture (PA), cultivated for 25 years with Urochloa brizantha, and an area of natural vegetation (NV) were evaluated. Soil samples were collected at intervals of 0.05 m up to 0.60 m depth, and physical attributes, C and N stocks (CSt and NSt) and isotopic variations of δ13C and δ15N of soil were determined. In the 0–0.05 m layer, the highest C and N stocks occurred in NV, 21.99 and 1.9 Mg ha-1, respectively. In the conversion to PA, 14.62 Mg ha-1 of CSt and 1.36 Mg ha-1 of NSt were lost in the 0–0.05 m layer. The area with PA had greater isotopic enrichment of δ13C in the layers of 0–0.05 and 0.05–0.10 m, with values of -18.3 and -17.4‰, respectively, while in the other layers the isotopic values decreased with the mixture between C of C3 and C4 plants. NV showed enrichment in the isotopic signals, in the layers from 0.25–0.30 m up to 0.40–0.45 m, with values between -21.74 and -21.54‰, respectively, which is characteristic of mixed vegetation of C3 and C4 plants. The values of δ15 N showed isotopic enrichment as depth increased, indicating greater mineralization of soil organic matter in both areas. The conversion of Cerrado into pasture and its consequent fragmentation causes negative impacts on the C and N sequestration and storage capacity, both in pasture and in natural vegetation.
28
Yunisa, Fahmi, Nurfita Sari, and Nana Wafiqah Nursyahbani. "Surface Roughness of Artificial Teeth after Immersion in Coffee Solution and Denture Cleaning." Applied Mechanics and Materials 910 (October 21, 2022): 31–38. http://dx.doi.org/10.4028/p-e2o629.
Full textAbstract:
Artificial teeth are components in removable partial dentures or complete dentures. The denture will be exposed to various liquids from food and beverages in daily use. On the other hand, dentures should also be cleaned regularly with various cleaning methods, either mechanically or chemically. Exposure to various things can result in changes in the surface structure of artificial teeth. The purpose of this study was to evaluate the surface roughness of the denture elements that had been exposed to coffee and then cleaned mechanically and chemically. A total of 30 artificial teeth were immersed in the coffee solution for 2.5 days in an incubator at 37 ° C. Then, the samples were divided into three groups (n = 10) according to the cleaning treatment. Group A was cleaned mechanically using an electric toothbrush and toothpaste for 2 minutes, group B was cleaned chemically by soaking in a solution of alkaline peroxide for 3 minutes, and Group C was the control group and cleaned through immersion in distilled water for 3 minutes. All samples were measured for surface roughness before and after immersion in coffee solution and after cleaning treatment using a Profilometer (Surfcorder SE 1700). Data were analyzed using a paired-sample t-test and ANOVA. The surface roughness of artificial teeth (3.62 µm) increases to 4.092 µm after immersion in coffee solution (p<0.05). After the denture cleaning procedure was carried out, although group B show the highest values (3.32 µm), but the difference in the mean surface roughness between the cleaning treatment groups did not show a significant difference (p> 0.05). As the conclusion, the denture cleaning method in this study (mechanical and chemical) did not give negative results on the surface roughness of the artificial teeth that had been exposed to the coffee solution.
29
Kharangarh, Poonam Rani, George E. Georgiou, and Ken K. Chin. "Temperature Dependence of Electrical Characterization in n+ - CdS/ p - CdTe Thin Film Solar Cells – Study of Shallow/Deep Defects." MRS Proceedings 1493 (2013): 161–67. http://dx.doi.org/10.1557/opl.2013.29.
Full textAbstract:
ABSTRACTFor CdTe there is no real distinction between defects and impurities exists when non-shallow dopants are used. These dopants act as beneficial impurities or detrimental carrier trapping centers. Unlike Si, the common assumption that the trap energy level Et is around the middle of the band-gap Ei, is not valid for thin film CdTe. Trap energy levels in CdTe band-gap can distributed with wide range of energy levels above EF. To identify the real role of traps and dopants that limit the solar cell efficiency, a series of samples were investigated in thin film n+-CdS/p-CdTe solar cell, made with evaporated Cu as a primary back contact. It is well known that process temperatures and defect distribution are highly related. This work investigates these shallow level impurities by using temperature dependent current-voltage (I-V-T) and temperature dependent capacitance-voltage (C-V-T) measurements. I-V-T and C-V-T measurements indicate that a large concentration of defects is located in the depletion region. It further suggests that while modest amounts of Cu enhance the cell performance by improving the back contact to CdTe, the high temperature (greater than ∼100°C) process condition degrade device quality and reduce the solar cell efficiency. This is possibly because of the well-established Cu diffusion from the back contact into CdTe. Hence, measurements were performed at lower temperatures (T = 150K to 350K). The observed traps are due to the thermal ionization of impurity centers located in the depletion region of p-CdTe/n+-CdS junction. For our n+-CdS/p-CdTe thin film solar cells, hole traps were observed that are verified by both the measurement techniques. These levels are identical to the observed trap levels by other characterization techniques.
30
Mutlu, Rasiha Nefise, Ayşe Nur Acar, and Ahmet Murat Gizir. "The effect of borax addition to aluminum alloy produced by powder metallurgy on mechanical and thermophysical properties." Anti-Corrosion Methods and Materials 69, no. 1 (October 29, 2021): 63–70. http://dx.doi.org/10.1108/acmm-04-2021-2473.
Full textAbstract:
Purpose Lightweight, durable and economical materials production has gained considerable importance according to the needs of developing technology. The purpose of this paper is to develop an new aluminum alloy by powder metalurgy. Design/methodology/approach Powder metallurgy, which provides controllably on desired end product, method was applied. Aluminum alloy was created with Al, Zn, Mg, Cu powders and 1.5% Na2[B4O5(OH)4].8H2O added. It was pressed under high pressure and sintered at 600 °C under N2 gas atmosphere. Density, hardness behaviors and thermal properties were determined. Surfaces and crystal structures of samples were characterized. Findings The addition of borax made easier grains coming to together, acting as binders and the AlB2 crystal phase was formed. It was also observed that MgZn2, Al2CuMg phases were formed. In this way, the pores between the particles of the material were reduced from 35% to 5% total porosity and the hardness of the material was increased 29 N/mm2 to 45 N/mm2 (Brinell Hardness, HB). The surface properties improved and the hydrophobicity of the surface (from 63° to 102° contact angle with borax) increased. Thus, the heat transfer among atoms get easier and the borax addition decreased specific heat capacity and enthalpy of aluminum–borax samples. This situation was also simulated with the heat transfer module of COMSOL. As result, the energy required reduced. In the other word, sintering process occurred at low temperature and more efficient. Originality/value New aluminum alloy has been created from different amounts of Zn, Mg, Cu elemental powders. In addition to literature, relationship of borax and aluminum and other alloying elements on the mechanical, thermophysical and surface properties of new obtained aluminum alloy has been investigated.
31
Dobrocky, David, Josef Sedlak, Zdenek Joska, Jiri Prochazka, Zbynek Studeny, and Zdenek Pokorny. "Influence of Machining Parameters on the Surface Quality of Technical Plastics." ECS Transactions 105, no. 1 (November 30, 2021): 381–89. http://dx.doi.org/10.1149/10501.0381ecst.
Full textAbstract:
The article deals with the evaluation of the influence of conventional methods of machining on the surface quality of selected technical plastics. The thermoplastic polymer polyoximethylene (POM-C) Ertacetal C and polyamide (PA 6) Ertalon 6SA were selected for machining. Both materials are suitable for machining and are used for the production of precision mechanical components (e.g. gears, plain bearings, guides, etc.), but also in electronics and electrical engineering. In all these applications, the quality of machined surfaces is important, especially for functional surfaces that interact with other surfaces. Test specimens from these materials were turned and milled. The technological conditions of machining (revolutions per minute n, cutting speed vc , feed f, depth of cut ap ) were adapted to achieve approximately the same surface roughness values. The milled samples were machined with and without cooling medium (for drought). Turning was performed only dry. As the cutting speed vc increased, the surface roughness of the turned Ertacetal C material decreased, while milling led to a deterioration in the roughness as the cutting speed vc increased. Similar behavior was observed for Ertalon 6SA. The process fluid led to a deterioration in the roughness of the milled surfaces of both plastics. Turned surfaces showed worse roughness than milled surfaces.
32
Zhang, Qian, Xu Li, Jianyun Zhao, Zhifei Sun, Yong Lu, Ting Liu, and Jicai Zhang. "Effect of High-Temperature Nitridation and Buffer Layer on Semi-Polar (10–13) AlN Grown on Sapphire by HVPE." Micromachines 12, no. 10 (September 25, 2021): 1153. http://dx.doi.org/10.3390/mi12101153.
Full textAbstract:
We have investigated the effect of high-temperature nitridation and buffer layer on the semi-polar aluminum nitride (AlN) films grown on sapphire by hydride vapor phase epitaxy (HVPE). It is found the high-temperature nitridation and buffer layer at 1300 °C are favorable for the formation of single (10–13) AlN film. Furthermore, the compressive stress of the (10–13) single-oriented AlN film is smaller than polycrystalline samples which have the low-temperature nitridation layer and buffer layer. On the one hand, the improvement of (10–13) AlN crystalline quality is possibly due to the high-temperature nitridation that promotes the coalescence of crystal grains. On the other hand, as the temperature of nitridation and buffer layer increases, the contents of N-Al-O and Al-O bonds in the AlN film are significantly reduced, resulting in an increase in the proportion of Al-N bonds.
33
Bellas Chatzigeorgis, Georgios, Justin B. Haskins, and James B. Scoggins. "Transport properties for neutral C, H, N, O, and Si-containing species and mixtures from the Gordon and McBride thermodynamic database." Physics of Fluids 34, no. 8 (August 2022): 087106. http://dx.doi.org/10.1063/5.0098060.
Full textAbstract:
Accurate transport properties of non-ionized gas mixtures of C, H, O, N, and Si-containing species at temperatures up to 4000 K are essential in many scientific fields. Mixture transport properties are computed through the solution of linear transport systems, requiring collision integrals as functions of temperature for each binary collision pair in the mixture. Due to the dimensionality of the problem, no such database exists for all the 180 hydrocarbons and silicon species detailed in the nine-coefficient polynomial thermodynamic database of Gordon and McBride, widely used in many applications. This constraint was overcome by using a phenomenological inter-molecular potential energy surface suitable for transport properties, which describes the pair interaction approximated with two fundamental species physical properties, namely the dipole electric polarizability and the number of effective electrons participating in the interaction. These two parameters were calculated with ab initio quantum chemistry calculations, since they were not always available in literature. The studied methodology was verified and validated against other approaches at a species and collision integral level. Transport properties for a variety of equilibrium mixtures, including planetary atmospheres and chemical compositions of thermal protection materials relevant to aerospace applications, were calculated, assessing the predictive capabilities of this new database.
34
Shieh, J., H. L. Wang, M. S. Tsai, and M. H. Hon. "Functionally gradient PECVD Ti(C,N) coatings." MRS Proceedings 555 (1998). http://dx.doi.org/10.1557/proc-555-407.
Full textAbstract:
AbstractTi(C,N) hard coating is well known as a suitable material for protecting substrate, and functionally gradient design is a method to improve the performance of it. In this study, functionally gradient Ti(C,N) coatings were performed by the technique of capacitive RF PECVD based on the investigation of Ti(C,N) monolayers with different C and N ratios. The results show that the composition and growth rate of Ti(C,N) monolayers are influenced by the nitrogen/methane ratio as other deposition parameters are fixed. A model is also proposed from the results obtained and is employed to calculate the reaction gas ratio and duration time needed for deposition in the gradient coating. The elements of Ti and N in the gradient coatings were analyzed by Auger electron spectroscopy (AES) and revealed that the composition changed linearly as designed. The residual stress of the gradient coatings was also measured to show that the gradient design provides the possibility for adjusting the stress distribution of PECVD hard coatings.
35
Matijasevic, Milena, and Abderrahim Al Mazouzi. "Microstructure and Mechanical Properties of n-Irradiated Fe-Cr Model Alloys." MRS Proceedings 981 (2006). http://dx.doi.org/10.1557/proc-981-0981-jj07-06.
Full textAbstract:
AbstractHigh chromium ( 9-12 wt %) ferritic/martensitic steels are candidate structural materials for future fusion reactors and other advanced systems such as accelerator driven systems ADS). Their use for these applications requires a careful assessment of their mechanical stability under high energy neutron irradiation and in aggressive environments. In particular, the Cr concentration has been shown to be a key parameter to be optimized in order to guarantee the best corrosion and swelling resistance, together with the least embrittlement.In this work, the characterization of the neutron irradiated Fe-Cr model alloys with different Cr % with respect to microstructure and mechanical tests will be presented. The behavior of Fe-Cr alloys have been studied using tensile tests at different temperature range ( from -160°C to 300°C). Irradiation-induced microstructure changes have been studied by TEM for two different irradiation doses at 300°. The density and the size distribution of the defects induced have been determined. The tensile test results indicate that Cr content affects the hardening behavior of Fe-Cr binary alloys. Hardening mechanisms are discussed in terms of Orowan type of approach by correlating TEM data to the measured irradiation hardening.
36
Roughani, Bahram, Uma Ramabadran, Diana Phillips, W. C. Mitchel, and C. L. Neslen. "Chemical-Mechanical Polishing and Rapid Thermal Annealing of SiC: Raman Spectroscopy and ESCA (XPS) Studies." MRS Proceedings 640 (2000). http://dx.doi.org/10.1557/proc-640-h5.40.
Full textAbstract:
ABSTRACTThe effects of Chem-Mechanical Polishing (CMP) and Rapid Thermal Annealing (RTA) on n-type 4H:SiC samples doped with nitrogen were investigated using Raman scattering and X-ray Phtoelectron Spectroscopy (XPS a.k.a. ESCA) measurements. A comparison of the Raman spectra from Mechanically Polished (MP) SiC annealed at 600°C and 800°C displays a frequency shift in the coupled plasmon LO-phonon mode. Since the coupled mode frequency is a direct measure of the free carrier concentration, this observation may suggest the removal of polishing induced carrier traps with increasing annealing temperature. The CMP samples did not show this frequency shift, thereby indicating that such polishing traps were not created in that process. The Si-peak observed in the XPS spectra of the unannealed CMP sample indicates primarily a Si-C bonding, while that for the MP sample is more complex, indicating other bonds beside Si-C. Drastic changes in O, C, Si surface content were observed for annealing between 1000°C and 1100°C. The peaks in the XPS spectra associated with the chemical environment for C, O, and N are complex and may be explained as silicon oxycarbide type structures near the surface or possibly around the interface of the SiC substrate with a thin surface oxide layer.
37
Chen, Yan, D. J. Johnson, R. H. Prince, Liping Guo, and E. G. Wang. "Synthesis of Crystalline C3N4 films and the new C-N Phases." MRS Proceedings 441 (1996). http://dx.doi.org/10.1557/proc-441-717.
Full textAbstract:
AbstractCrystalline C-N films composed of α- and β-C3N4, as well as other C-N phases, have been synthesized via bias-assisted hot-filament chemical vapor deposition using a gas mixture of nitrogen and methane. Scanning electron microscopy(SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the films. Lattice constants of the α- and β-C3N4 phases obtained coincide very well with the theoretical values. In addition to these phases, two new C-N phases in the films have been identified by TEM and XRD; one having a tetragonal structure with a = 5.65 Å, c = 2.75Å, and the second having a monoclinic structure with a = 5.065 Å, b= 11.5 Å, c = 2.801 Å and β = 96°. Their stoichiometric values and atomic arrangements have not yet been identified. Furthermore, variation in growth parameters, for example methane concentration, bias voltage, etc., can yield preferred growth of different C-N phases.
38
YAKUT, Rifat, and Ömer ÇİFTÇİ. "The Effects of Reinforcement with TaC on the Microstructure and Wear Properties of Lamellar Graphite Cast Irons." European Journal of Technic, June 30, 2022. http://dx.doi.org/10.36222/ejt.1088994.
Full textAbstract:
Lamellar graphite cast irons are prevalently used in several industrial applications, especially the automotive industry, due to their high compressive strength, high thermal conductivity, high castability, vibration damping ability, good mechanical strength, friction and wear resistance, better machinability than other cast irons, and good mold filling. In this study, changes in the wear volumes, wear rates, wear track profiles, and friction coefficients of lamellar graphite cast irons in which Tantalum Carbide (TaC) was added at different reinforcement ratios (A (0.025 wt.%), B (0.155 wt.%), C (0.285 wt.%), and K (unreinforced, 0 wt.%)) were investigated. Additionally, by examining the wear surfaces of the samples using a scanning electron microscope (SEM), their wear mechanisms were determined. As a result of the analyses, it was determined that different reinforcement ratios did not have a noticeable effect on wear track profiles under a load of 1 N. On the other hand, different reinforcement ratios showed an effect on wear track profiles under loads of 3 N and 5 N. The most perceptible wear track profile was formed in Sample C under 5 N. It was observed that increased load values resulted in increased wear volumes, but the increases in the wear rates of the samples were not significant, and the numerical values were close to each other. The highest wear volumes were determined in the reinforced C sample and the unreinforced K sample under 5 N load. As the magnitude of the load that was applied increased, the friction coefficients of Samples B and C decreased, but the friction coefficients of Samples K and A increased.
39
Ma, Yaoyao, Qiang Miao, Wenping Liang, Haiyang Yu, Mengjuan Yin, Kai Zang, Xueqing Pang, and Xianfeng Wang. "Microstructure, mechanical and tribological properties of Ta(C, N) coatings deposited on TA15 substrates with different nitrogen partial pressure." Industrial Lubrication and Tribology, November 29, 2022. http://dx.doi.org/10.1108/ilt-08-2022-0245.
Full textAbstract:
Purpose The purpose of this paper is to obtain the optimal N2/Ar ratio parameters for preparing Ta (C, N) coating. Three coatings with different N2/Ar ratios were prepared on the TA15 substrate, and their effects on the wear properties of the coatings were discussed. Design/methodology/approach Ta(C, N) coatings with three different N2/Ar ratios were prepared on TA15 substrates using the double cathode glow metallurgical plasma alloying technique (DGMPA) using a step-by-step diffusion method. Findings With the increase of N2/Ar flow ratio, the hardness and elastic modulus of the coating first increase and then decrease. Compared with the S1 sample (N2/Ar gas ratio 25: 75) and the S3 sample (N2/Ar gas ratio 75: 25), the S2 sample (N2/Ar gas ratio 50: 50) has better mechanical properties, with hardness increased by 48.45% and 6.8%, respectively, and elastic strain ratio increased by 22.8% and 28.5%, respectively. Moreover, the wear degree of the S2 sample is less than other samples. The wear rate of the S2 sample was 32.4% lower than the S3 sample at 300°C and 14.3% lower than the S3 sample at 500°C. Therefore, the S2 sample has the best mechanical properties and the best high temperature wear resistance. Originality/value Ta(C, N) coatings were prepared by DGMPA technology, and the wear mechanism of Ta(C, N) coatings with different N2/Ar ratios was investigated to reduce the wear rate.
40
Loubser, J. H. N., and J. A. Van Wyk. "A Dynamic Jahn-Teller Effect in the ESR Spectrum of the N1 Centre in Diamond." MRS Proceedings 46 (1985). http://dx.doi.org/10.1557/proc-46-587.
Full textAbstract:
AbstractThe N1 centre in Type Ia diamonds is a di-nitrogen centre with S = ½. One nitrogen's interaction with the unpaired electron at room temperature gives a large splitting, All = 46.4 G, A ⊥ = 32.2 G with <111> symmetry while the hyperfine splitting due to the other one has <110> symmetry with parameters All = 2.95 ±.03 G, A⊥ = 2.81 ±.03 G. As the temperature is increased averaging effects start; first some hyperfine lines broaden at about 150°C and disappear at 200°C. At still higher temperatures new lines appear and at about 850°C the averaging process is completed. The interpretation of the dynamics leads to a model of a non-planar N-C-C-N configuration with the electron jumping between the two N-C bonds. The measured activation energy is 0.4 eV which is about midway between the measured values for a similar effect in the isolated nitrogen centre, P1, (E = 0.7eV) and the N-C-N, W7, centre (E = 0.24 eV).
41
Sho, J. S., R. A. Weber, L. G. Provost, D. Goldstein, and A. D. Kurtz. "High Temperature Ohmie Contacts for N-Tvpe Β-Sic Sensors." MRS Proceedings 242 (1992). http://dx.doi.org/10.1557/proc-242-573.
Full textAbstract:
ABSTRACTIn order to fabricate high temperature sensors and other devices, it is necessary to develop ohmic contact metallizations that can withstand elevated temperatures. A variety of ohmic contact metallizations were investigated with contact resistivity measured as a function of anneal time in air. The metallizations were based on Ti and W ohmic contacts, which have contact resistivities as low as 10-4 Ω-cm2. Several of the contact metallizations were stable after 10 hrs. at 650°C, while one system, based on a Ti ohmic contact, was able to withstand > 20 hrs. at 650°C with only a 30–40% increase in contact resistivity.
42
Chor, E. F., and X. J. Kang. "Effects of Plasma Surface treatment on Ohmic Contact to n-GaN." MRS Proceedings 680 (2001). http://dx.doi.org/10.1557/proc-680-e6.4.
Full textAbstract:
ABSTRACTWe have investigated the effects of plasma surface treatment on ohmic contacts to n-type GaN. Prior to metal evaporation, n-GaN surface was etched either chemically using aqua-regia (control sample) or by means of inductively coupled Cl2/BCl3, N2 or Ar plasmas. The metal system adopted in our investigation was Ti/Al/Pd/Au. The as-deposited Ti/Al/Pd/Au contact on aqua-regia treated n-GaN exhibits an ohmic behavior with a specific contact resistance (ρc) of 2×10−4ωcm2. After annealing at 500°C for 5min, ρc is reduced by approximately 2 orders of magnitude to 5×10−6ωcm2. For Cl2/BCl3 and N2 plasma treated n-GaN surface, the as-deposited Ti/Al/Pd/Au contacts also yield ohmic behavior and ρc's are about 2×10−4 and 5×10−4 ωcm2 respectively. After annealing at 500°C for 5min, ρc's are reduced by about 3 orders of magnitude to around 5×10−7 and 8×10−7 ωcm2 respectively. On the other hand, the as-deposited Ti/Al/Pd/Au contact on Ar plasma treated n-GaN exhibits a non-ohmic behavior. After annealing at 500°C for 5min, ρc is about 5×10−7 ωcm2 and the lowest ρc of 7×10−8 ωcm2 is obtained after annealing at 700°C for 5min. The contacts on other surface treated n-GaN are found to degrade at 700°C annealing. By comparing the values of ρc for various surface treatments, particularly those after annealing, it is observed that plasma etching can be used beneficially in the formation of ohmic contacts – plasma surface treatment using Cl2/BCl3, N2 or Ar has resulted in an order of magnitude reduction in ρc compared to chemical surface treatment by aqua-regia.
43
Köck, F. A. M., J. M. Garguilo, B. Brown, and R. J. Nemanich. "Thermionic FEEM, PEEM and I/V Measurements of N-Doped CVD Diamond Surfaces." MRS Proceedings 621 (2000). http://dx.doi.org/10.1557/proc-621-r6.5.1.
Full textAbstract:
ABSTRACTImaging of field emission and photoemission from diamond surfaces is accomplished with a high resolution photo-electron emission microscope (PEEM). Measurements obtained as a function of sample temperature up to 1000°C display thermionic field emission images (TFEEM). The system can also record the emission current versus applied voltage. N-doped diamond films have been produced by MPCVD with a N/C gas phase ratio of 48. The surfaces display uniform emission in PEEM at all temperatures. No FEEM images are detectable below 500°C. At ∼680°C the T-FEEM and PEEM images are nearly identical in intensity and uniformity. This is to be contrasted with other carbon based cold cathodes in which the emission is observed from only a low density of highly emitting sites. The I/V measurements obtained from the N-doped films in the T-FEEM configuration show a component that depends linearly on voltage at low fields. At higher fields, an approximately exponential dependence is observed. At low temperatures employed (<700°C), the results indicate a thermionic component to the emitted current.
44
Knotek, O., and F. Löffler. "Tribological Properties of Superhard PVD Coatings." MRS Proceedings 239 (1991). http://dx.doi.org/10.1557/proc-239-263.
Full textAbstract:
AbstractIn order to advance the development of extremely hard coatings, new homogeneous and metastable films were prepared by magnetron sputter ion plating (MSIP) and arc ion plating (AIP) in the DC. or RF. mode.In the present study coatings in the systems Ti-B-C-N, Si-C-N and amorphous carbon coatings (ADLC) were investigated and compared with other hard coatings. Multicomponent layers of different compositions and structures were deposited by varying the reactive gases methane (CH4) and nitrogen (N2) and the dominant process parameters (e. g. C/V-characteristic of the cathode, substrate bias).X-ray diffraction studies of the Ti-B-C-N coatings revealed either an amorphous structure or crystallization in a hexagonal lattice. The ADLC and Si-C-N coatings were always amorphous. Electron microprobe analysis and auger electron spectroscopy were used to determine the coating compositions.The tribological properties were determined by a ball on disc tribometer (e.g. friction coefficent), a pin on disc tribometer and a special abrasive wear test.
45
Murthy, Niranjan, S. Deepak, P. C. Arunakumara, and Arun Y. Patil. "Experimental Study of Multiple Jet Impingement Cooling on a Flat Plate." International Journal of Vehicle Structures and Systems 14, no. 2 (March 8, 2022). http://dx.doi.org/10.4273/ijvss.14.2.11.
Full textAbstract:
Heat transfer to a straight multiple impinging air/ water jet is studied experimentally. A 22 cm thin copper plate, 1 mm thick was electrically heated and cooled from one side. The temperature was measured on the other side. A geometrical prearrangement of 77 arrays in-line with a pitch of 3 mm was tested. The heat flux is varied from 20 to 250 W/cm2 with 0.25 and 0.5 mm diameter jets. The temperature differences between jet exits to test surface is within 700°C for air jets and 300°C for water jets. Though the jet impingement using multiple jets is a complicated heat transfer phenomenon, the results were interrelated using a relation in the mathematical form of the Nusselt number which is a function of two exponents, n and m. The exponent (n) shows the effect of Reynolds number for both air and water jets. The exponent (m) specifies the consequences of heat flux on the working fluid and diameter of jet.
46
Nipoti, R., M. Puzzanghera, and F. Moscatelli. "P+ implanted 6H-SiC n+-i-p diodes: evidence for a post-implantation-annealing dependent defect activation." MRS Proceedings 1693 (2014). http://dx.doi.org/10.1557/opl.2014.600.
Full textAbstract:
ABSTRACTTwo n+-i-p 6H-SiC diode families with P+ ion implanted emitter have been processed with all identical steps except the post implantation annealing: 1300°C/20min without C-cap has been compared with 1950°C/10min with C-cap. The analysis of the temperature dependence of the reverse current at low voltage (-100V) in the temperature range 27-290°C shows the dominance of a periphery current which is due to generation centers with number and activation energy dependent on the post implantation annealing process. The analysis of the temperature dependence of the forward current shows two ideality factor n region, one with n = 1.9/2 at low voltage and the other one with 1 < n < 2 without passing through 1 for increasing voltages. For both the diode families the current with n = 1.9/2 is a periphery current due to recombination centers with a thermal activation energy near the 6H-SiC mid gap. In the forward current region of 1 < n < 2, the two diode families show different ideality factor values which could be attributed to a different post implantation annealing defect activation.
47
Arnold, G. W., G. Battaglin, A. Boscolo-Boscoletto, P. Mazzoldi, and C. Meneghini. "The Role of Glass Structure in the Formation of Implanted Gold Nanoclusters for Enhanced Nonlinear Optical Properties." MRS Proceedings 396 (1995). http://dx.doi.org/10.1557/proc-396-397.
Full textAbstract:
AbstractVarious silicate glasses (fused silica, soda-lime, Na- and K-borosilicates, lithia-alumina silicate, and Pyrex®) were implanted with 8 x 1015 285 keV Au/cm2. Colloid growth was monitored as a function of annealing and N implantation (2 x 1017 35 keV N/cm2). Annealing to 1040 °C for fused silica and to 600 °C for the other glasses resulted in Au aggregation and optical absorption. Radiation damage removal is associated with the fused silica annealing; the aggregation of Au at lower temperatures for the other glasses is expected because of the lower glass transition temperature. Phase-seption in the alkali-borosilicates may be important because of grain-boundary diffusion. N implantation did not significantly affect nanocluster growth.
48
Deepa, T., E. Bhakya Lakshmi, M. Kayalvizhi, and A. Arun. "Biodegradable poly(urethane-urea-amide): Synthesis, characterization and mechanical studies." Journal of Thermoplastic Composite Materials, October 5, 2020, 089270572096353. http://dx.doi.org/10.1177/0892705720963537.
Full textAbstract:
Biodegradable polyurethane with excellent mechanical property finds a lot of applications in the biomedical field. In this study, multi block copolymer poly(urethane-urea-amide) (PUUA) is prepared using polyethylene oxide, 1,6-hexamethylene diisocyanate and diamide (N1, N4-bis(6-aminohexyl)benzene-1,4-dicarboxamide (6T6) or N 1, N 6-bis(6-aminohexyl)hexanediamide (6A6)) by a method of solution/melt polymerization techniques. The polymer formation is confirmed by the 1H NMR spectroscopic method. Other techniques such as viscosity measurements, FT-IR, DSC, TGA, and biodegradability are used to characterize the synthesized copolymers. The hard segment crystallinity is an analyzed by FT-IR spectroscopy, it revealed that the 6T6 based polymer showed 70% of crystallinity. The synthesized copolymer shows three transitions in the DSC curve. The melting enthalpy of the hard segment depends on the amide unit employed in the polymerization process. These materials are fast crystallizing due to low under cooling value. This material has a very high thermal stability and stable up to 400°C. Tensile test confirms the strain induced crystallization of hard segment occurred in the PUUA. The biodegradability of the polymer depends on the pH and chain extenders. This type of materials can be a good candidate for tissue engineering application.
49
Hayman, Danika, Christie Bergerson, Samantha Miller, Michael Moreno, and James E. Moore. "The Effect of Static and Dynamic Loading on Degradation of PLLA Stent Fibers." Journal of Biomechanical Engineering 136, no. 8 (June 3, 2014). http://dx.doi.org/10.1115/1.4027614.
Full textAbstract:
Understanding how polymers such as PLLA degrade in vivo will enhance biodegradable stent design. This study examined the effect of static and dynamic loads on PLLA stent fibers in vitro. The stent fibers (generously provided by TissueGen, Inc.) were loaded axially with 0 N, 0.5 N, 1 N, or 0.125–0.25 N (dynamic group, 1 Hz) and degraded in PBS at 45 °C for an equivalent degradation time of 15 months. Degradation was quantified through changes in tensile mechanical properties. The mechanical behavior was characterized using the Knowles strain energy function and a degradation model. A nonsignificant increase in fiber stiffness was observed between 0 and 6 months followed by fiber softening thereafter. A marker of fiber softening, β, increased between 9 and 15 months in all groups. At 15 months, the β values in the dynamic group were significantly higher compared to the other groups. In addition, the model indicated that the degradation rate constant was smaller in the 1-N (0.257) and dynamic (0.283) groups compared to the 0.5-N (0.516) and 0-N (0.406) groups. While the shear modulus fluctuated throughout degradation, no significant differences were observed. Our results indicate that an increase in static load increased the degradation of mechanical properties and that the application of dynamic load further accelerated this degradation.
50
Du, Li, and James Edgar. "Thermodynamic Analysis and Purification for Source Materials in Sublimation Crystal Growth of Aluminum Nitride." MRS Proceedings 1202 (2009). http://dx.doi.org/10.1557/proc-1202-i05-08.
Full textAbstract:
AbstractSource material purification according to a thermodynamic analysis is reported for the sublimation crystal growth of aluminum nitride in an inert reactor. OAlOH is strongly favored over all other possible oxygen containing compounds in both the Al-O-H-N and Al-O-H-C-N systems, while Al2O, proved to be the most favorable oxygen containing gas species for Al-O-N system in previous study, become secondary favorable gas species. A low temperature (<1200 °C) treatment is effective in eliminating oxygen and hydrogen from the source powder. Carbon monoxide is another important oxygen containing gas species in the Al-O-H-C-N system, and is favored over Al2O at certain temperature and pressure. Carbothermal reduction with intentionally added carbon (graphite) can further reduce the oxygen concentration. Experiments show that high-temperature sintering minimizes the oxygen concentration and reduces the specific surface area of the source. With only 5.5% of mass loss, the purification produced a source with low O, H, and C concentrations of 0.018 wt%, 6ppm, and 0.006wt%.