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51.
二硼化钛(TiB2)因其优良的综合性能引起了广泛的关注.但是由于难以获得完全致密的二硼化钛陶瓷,其广泛应用受到限制.金属基体增强是改善和提高二硼化钛性能的有效途径.本文从金属体系的选择以及制备方法与致密化技术的改进简述了二硼化钛基金属陶瓷的研究进展,并提出了在二硼化钛基金属陶瓷制备过程中需要注意的一些问题. 相似文献
52.
用Ti+Cr活性钎料高温钎焊高强石墨 总被引:3,自引:0,他引:3
用Ti Cr活性钎料对高强石墨进行了高温钎焊试验。研究了焊接温度、保温时间、降温速率对试样连接强度的影响。确定最佳工艺为:焊接温度1420℃,保温时间2min,随炉冷却。所得连接件的最高弯曲强度为石墨母材的57%。微观结构研究表明,在石墨/焊料界面处形成了2个反应层:一个为富Cr的反应层,一个为富Ti的反应层。XRD分析表明:富Cr的反应层由Cr2Ti和Cr33C6组成;富Ti的反应层由TiC,Ti和Cr7C3组成;焊料内部主要含有TiC,Cr2Ti和Cr33C6。 相似文献
53.
《Ceramics International》2022,48(6):8025-8030
In order to meet the high demand for joining ceramic/superalloy composite structure in extreme environments, a novel high-temperature resistant adhesion technique was developed for joining ZrO2 and Inconel 625 by applying an aluminum phosphate emulsion/zirconium sol based adhesive. With increasing temperature, a series of reactions occurred in adhesive, and its high-temperature bonding was attributed to the formation of a composite structure containing various ceramics and intermetallics. The adhesive after RT curing could find direct applications in extreme environments, and provide bonding strength no less than 2.5 MPa in the temperature range of RT-1100 °C. The bonding strength was higher than 4 MPa in the temperature range of 800–1000 °C, which was further attributed to the formation of an effective CTE-gradient relationship among ZrO2, adhesive and Inconel 625, as well as the interfacial reactions between the two substrates. The work broadened the application of adhesion technique and brought new ideas for joining dissimilar engineering materials. 相似文献
54.
《Journal of the European Ceramic Society》2022,42(13):5195-5207
Molybdenum and a molybdenum alloy were fusion welded to ZrB2-based ceramics to determine if the electrical and thermal properties of the metals and ceramics affected their weldability. Commercial ceramic powders were hot pressed, machined into coupons, and preheated to 1600 °C before joining the ceramics to commercial metals using plasma arc welding. Weldability varied as indicated by the range of porosity observed within the fusion zones. Measured thermal and electrical properties appeared to have little to no effect on the weldability of metal-ceramic welds despite the large range of values measured across each property. Differences in melting temperatures between metal and ceramic coupons did affect weldability by changing the weld penetration depth into ceramic coupons. Future studies on metal-ceramic welds are suggested to investigate the effect that work function, melt viscosity, wetting, or other properties have on weldability. 相似文献
55.
Hajnalka Laura Plinks Lrinc Pongor Mt Balajti dm Nagy Kinga Nagy Angla Bksi Giampaolo Bianchini Beta G. Vrtessy Balzs Gyrffy 《International journal of molecular sciences》2022,23(2)
The clonal composition of a malignant tumor strongly depends on cellular dynamics influenced by the asynchronized loss of DNA repair mechanisms. Here, our aim was to identify founder mutations leading to subsequent boosts in mutation load. The overall mutation burden in 591 colorectal cancer tumors was analyzed, including the mutation status of DNA-repair genes. The number of mutations was first determined across all patients and the proportion of genes having mutation in each percentile was ranked. Early mutations in DNA repair genes preceding a mutational expansion were designated as founder mutations. Survival analysis for gene expression was performed using microarray data with available relapse-free survival. Of the 180 genes involved in DNA repair, the top five founder mutations were in PRKDC (n = 31), ATM (n = 26), POLE (n = 18), SRCAP (n = 18), and BRCA2 (n = 15). PRKDC expression was 6.4-fold higher in tumors compared to normal samples, and higher expression led to longer relapse-free survival in 1211 patients (HR = 0.72, p = 4.4 × 10−3). In an experimental setting, the mutational load resulting from UV radiation combined with inhibition of PRKDC was analyzed. Upon treatments, the mutational load exposed a significant two-fold increase. Our results suggest PRKDC as a new key gene driving tumor heterogeneity. 相似文献
56.
Rajiv Asthana Natalia Sobczak Mrityunjay Singh 《International Journal of Applied Ceramic Technology》2022,19(2):1029-1049
Joining and integration technologies are integral to manufacturing of components based on ultrahigh-temperature ceramics (UHTCs) such as transition metal diborides. Brazing is a particularly attractive joining technique because of its simplicity and versatility, but its use to join the UHTCs demands knowledge of the complex interplay among high-temperature wettability, interfacial reactions, and chemical and thermoelastic compatibilities. This paper summarizes the research and development activities carried out over the last two decades to characterize the wettability and interfacial phenomena in brazing of refractory diboride ceramics. The contact angle data of various metal alloys on diboride-based ceramics have been collected and critically evaluated in conjunction with an analysis of the chemistry and structure of the interface to understand the underlying mechanisms and phenomena that govern interface formation. It explores how solid–liquid interactions impact and are impacted by physical, chemical, and mechanical properties of joined materials. It also describes how this knowledge has been successfully utilized to create liquid-phase bonded diboride-based joints. The paper concludes with a summary of the current state of the art and highlights integration challenges and future research and technology development needs in the area. 相似文献
57.
Green State Joining of Silicon Carbide Using Polycarbosilane 总被引:1,自引:0,他引:1
Green state joining of SiC was investigated using a paste consisting of polycarbosilane polymer and SiC powder. The joining process and densification were described. Initial experiments resulted in the formation of symmetrical black bands and cracks on both sides of the joint. However, with modifications in processing conditions, the cracks were eliminated and the resulting joints were indistinguishable from the matrix. The flexural strength of joined samples was measured to be 234 MPa, which was comparable to that of the control sample with similar density. As the applied pressure during joining was increased from 34 to 138 MPa, the strength of the joined samples increased from 180 to 250 MPa. 相似文献
58.
A. Yu. Polyakov S. M. Furmanov T. I. Bendik A. M. Kurlenkov 《Welding International》2017,31(11):868-873
A highly efficient energy-saving method of resistance projection welding of 3–4 components in a single cycle is described. The method is based on the automatically regulated gradual introduction of electric energy into the zone between the electrodes. 相似文献
59.
M. A. Korchagin V. Yu. Filimonov E. V. Smirnov N. Z. Lyakhov 《International Journal of Self-Propagating High-Temperature Synthesis》2009,18(2):133-136
Explored was thermal explosion in mechanoactivated 3Ni + Al mixtures. Mechanoactivation was found to result in an abnormal
decrease in the effective activation energy E and ignition temperature Tign for thermal explosion. Analysis of reaction thermogram allowed us to find out the kinetic function. Mechanoactivation conditions
for synthesis of Ni3Al in thermal explosion mode have been optimized. SHS reaction in 3Ni + Al mixtures mechanoactivated for 180 s was found to
obey the first-order kinetics.
相似文献
60.
T. V. Barinova I. P. Borovinskaya 《International Journal of Self-Propagating High-Temperature Synthesis》2009,18(1):30-33
Combustion of silicon powders containing organic dopants in nitrogen gas under pressure was found to yield a mixture of α-Si3N4, β-Si3N4, SiC, and Si2N2O. Relative amount of these compounds in combustion product was found to depend on the pressure of nitrogen gas, type and
concentration of dopants, combustion geometry, and cooling rate. The formation of α-Si3N4 was found to occur in the presence of oxygen-containing dopants. The type of dopant was also found to affect the morphology
of product particles.
相似文献