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11.
Jiří Matějíček František Zahálka Jan Bensch Weiguang Chi Josef Sedláček 《Journal of Thermal Spray Technology》2008,17(2):177-180
Copper and copper-tungsten composite coatings were produced by high-velocity oxy-fuel spraying (HVOF). After initial optimization
of the spraying parameters, coatings of various compositions were made and their structure, composition, mechanical, thermal,
and electrical properties were characterized. The HVOF technique was able to produce rather dense coatings with minimal oxide
content and relatively good mechanical and thermal properties compared to, for example, plasma-sprayed coatings; however,
the achieved tungsten content was quite low. 相似文献
12.
13.
Michal KORENKO ;Zuzana VASKOVA ;Frantisek SIMKO ;MICHAL SIMURDA ;Marta AMBROVA ;石忠宁 《中国有色金属学会会刊》2014,24(12):3944-3948
以热解碳化硼管作电导池,用固定电导池常数法研究由Na F-Al F3-Si O2构成的二元系和三元系熔盐的电导率;用扭摆法测定Na3Al F6-Si O2二元系的黏度。研究发现,所研究熔盐体系的电导率和黏度均与温度呈直线关系。Na3Al F6-Si O2二元系的电导率与Si O2含量关系曲线可分为0-10%和10%-40%(摩尔分数)两段,当SiO 2含量超过10%之后,电导率随着Si O2含量的增加而快速下降,而当Si O2含量小于10%时,电导率随着Si O2含量的增加而缓慢增加。在Si O2含量大于10%的冰晶石熔盐中添加少量的SiO 2,熔盐的黏度增加,但增加的趋势基本相同,这与熔盐中形成玻璃网状结构的离子团有关。当在冰晶石熔盐中继续增大Si O2含量到50%时,黏度发生急剧变化。 相似文献
14.
František Lofaj Milan Ferdinandy Gregorz Cempura Ján Dusza 《Journal of the European Ceramic Society》2012,32(9):2043-2051
Instrumented indentation, AFM (atomic force microscopy) and tribological studies were performed on PE CVD (Plasma Enhanced Chemical Vapor Deposition) nanocomposite WC–C coatings to investigate the effects of surface roughness on the reliability of nanoindentation data and the possibilities of different AFM modes in nanomechanical testing, which can be used as a feedback to optimize deposition technology from the viewpoint of their mechanical properties. It was confirmed that surface roughness below 30 nm is necessary to keep the scatter of indentation modulus, EIT, and hardness, HIT, below 15%. PF QNM (Peak Force Quantitative NanoMechanical) mode was successfully applied for qualitative mapping of the elastic modulus of coatings with the stiffness above 300 GPa. LFM (lateral force microscopy) mode showed only weak contrast and quantitative measurements in both AFM modes require precise calibration. Coefficients of friction of the studied WC–C coatings were below 0.2 at RT, but increased to 0.7–0.8 at 450 °C due to the formation of a transfer film. Optimization of the deposition conditions based on nanoindentation resulted in the increase of EIT from ~220 GPa to 350 GPa and HIT from ~17 GPa to ~29 GPa. 相似文献
15.
Petr Ptáček Tomáš Opravil František Šoukal Jaromír Wasserbauer Jiří Másilko Jan Baráček 《Journal of the European Ceramic Society》2013,33(13-14):2793-2799
The structural order of kaolinite is an important factor that shows a substantial effect on the processes which take place during the thermal treatment of kaolin. The influence of structural order on the dehydroxylation process was investigated by simultaneous thermogravimetry and differential thermal analysis (TG-DTA). The thermal analysis was performed on the samples with gradually decreasing structural order prepared by milling procedure. The apparent activation energy of dehydroxylation process decreases with decreasing structural order according to the exponential function. The extrapolation of experimental data leads to the estimation of apparent activation energy of 76.6 kJ mol?1 and of frequency factor of 0.12 × 104 s?1 related to completely disordered form of kaolinite, while the ordered form shows the apparent activation energy of 216.17 kJ mol?1 and the frequency factor of 9.26 × 104 s?1. The relationships between features such as the infrared pattern of treated material, the degree of structural order and the apparent activation energy were established. 相似文献
16.
Annamaria Duszová Radoslav Halgaš Marek Bľanda Pavol Hvizdoš František Lofaj Ján Dusza Jerzy Morgiel 《Journal of the European Ceramic Society》2013,33(12):2227-2232
WC–Co cemented carbide has been investigated using instrumented indentation with maximum applied loads from 0.1 to 10 mN. The hardness and indentation modulus of individual phases and the influence of crystallographic orientation of WC on the hardness and indentation modulus have been studied. The hardness of the Co binder was approximately 10 GPa and that of WC grains up to 50 GPa with relatively large scatter under the indentation load of 1 mN. Investigation of the role of crystallographic orientation of WC grains on hardness at 10 mN load revealed average values of HITbasal = 40.4 GPa (EITbasal = 674 GPa) and HITprismatic = 32.8 GPa (EItprismatic = 542 GPa), respectively. The scatter in the measured values at low indentation loads is caused by the effects of surface and sub-surface characteristics (residual stress, damaged region) and at higher loads by “mix-phase” volume below the indenter. 相似文献
17.
Failure analysis of mechanical elements in steelworks equipment by methods of experimental mechanics
František Trebuňa František Šimčák Jozef Bocko Peter Trebuňa 《Engineering Failure Analysis》2010,17(4):787-801
New technological equipment is mostly designed with the goal of increasing the productivity of manufacturing. This aim often results in an increased loading of structural support members. In the paper attention is given to the reasons for crack initiation in the supporting part of the converter torsion system that ensures transfer of the tilting moments from the converter vessel to the converter pedestal. The numerical and experimental analysis of the reasons for crack initiation in the pedestals of the converter torsion systems was carried out over the period of 2 years. In the paper forces and stresses in the structure are analysed both under normal and extraordinary operational conditions of the converter (big steel residues on the converter wall, demolition of the converter lining). Alongside the reasons for crack initiation the ways for solving the problem of further safe operation of the converter are suggested. 相似文献
18.
Various syntactical phenomena play an important role when developing grammars for natural languages. Among them are the dependencies (subordination) or valences, which are closely related to the complexity of the word-order of the language considered, and the number and types of categories that are used during the process of syntactic disambiguation. Here we present the freely rewriting restarting automaton (FRR-automaton), which is a variant of the restarting automaton that is tuned towards modeling such phenomena. We study proper languages of deterministic FRR-automata that are (strongly) lexicalized, where we focus on two types of constraints: the number of rewrites per cycle, which models the degree of valences within sentences, and the number of occurrences of auxiliary symbols (categories) in the sentences (words) of the corresponding characteristic language, which models the use of categories during the process of syntactic disambiguation. Based on these constraints we obtain four variants of two-dimensional hierarchies of language classes. 相似文献
19.
The goal of this paper is to provide an architectural analysis of the existing distributed objectoriented platforms. Based on a relatively small number of design patterns, our analysis aims at a unified view of the platforms. We achieve this by articulating a series of key issues to be addressed in analyzing a particular platform. This approach is applied systematically to the CORBA, Java RMI and COM/DCOM platforms. 相似文献
20.
High pressure effects (300, 600, and 800 MPa) on polyethylene crosslinking initiated by benzoyl peroxide have been studied at 120°C. An increase in pressure leads to a decrease in yield of the insoluble gel; the yields at 300, 600, and 800 MPa were respectively 96, 86, and 79%. With increasing pressure the rate of polyethylene crosslinking decreases and the rate of benzoyl peroxide decomposition at 300, 600, 800 MPa can be anticipated from the time of crosslinking. The activation volume was determined for benzoyl peroxide decomposition on polyethylene at 120°C. 相似文献