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Abstract: The effects of total CH4/Ar gas pressure on the growth of carbon nanomaterials on Si (100) substrate covered with CoO nanoparticles, using plasma-enhanced chemical vapor deposition (PECVD), were investigated. The structures of obtained products were correlated with the total gas pressure and changed from pure carbon nanotubes (CNTs) through hybrid CNTs/graphene sheets (GSs), to pure GSs as the total gas pressure changed from 20 to 4Torr. The total gas pressure influenced the density of hydrogen radicals and Ar ions in chamber, which in turn determined the degree of how CoO nanoparticles were deoxidized and ion bombardment energy that governed the final carbon nanomaterials. Moreover, the obtained hybrid CNTs/GSs exhibited a lower turn-on field (1.4V/μm) emission, compared to either 2.7V/μm for pure CNTs or 2.2V/μm for pure GSs, at current density of 10μA/cm2. [Copyright &y& Elsevier]

Brazing SiO 2 -BN ceramic to Ti6Al4V is often associated with the problem of brittle continuous phases and high residual stress at the reaction layer of SiO 2 -BN, inducing low joining strength. To overcome these problems, SiO 2 -BN ceramic modified with in situ synthesized carbon nanotubes (CNTs) were joined to Ti6Al4V by TiZrNiCu alloy. Results show that CNTs can improve the wettability of TiZrNiCu on SiO 2 -BN rapidly, and break the continuous reaction layer of SiO 2 -BN into fine sizes. Residual stress can also be reduced by low CTE of CNTs and fine size phases among reaction layer. The shear strength of SiO 2 -BN/Ti6Al4V joints with CNTs modified is 35.3 MPa at 970 °C for 10 min, which is 3 times higher than that of the joints without CNTs modified. [ABSTRACT FROM AUTHOR]

Abstract: Ag–Cu/Cu/Ag–Cu–Ti composite interlayer was successfully designed to braze Invar alloy and SiO2–BN ceramic. The effect of Cu-foil thickness on the microstructure and mechanical properties of the brazed joints was investigated. The results showed that, compared with single Ag–Cu–Ti brazing foil, the formation of brittle Fe2Ti and Ni3Ti compounds detrimental to the joint strength was greatly inhibited by using composite interlayer. The active Ti atoms in the liquid filler reacted with SiO2–BN ceramic to form a TiN–TiB2 fine-grain layer. The desired interfacial microstructure composed of layered Ag- and Cu-based solid solutions was obtained, which was beneficial for the joint strength. The shear strength of brazed joints was 207% higher than the joints brazed with single Ag–Cu–Ti foil when a 100μm thick Cu interlayer was used. The inhibition of brittle compounds formation was attributed to the control of reaction sequences during brazing and to the addition of Cu barrier layer. [Copyright &y& Elsevier]

Abstract: The vacuum brazing of alumina ceramic to Ti6Al4V alloy was performed using Ag–Cu eutectic filler metal. The microstructure at the ceramic-metal interfaces and the mechanical properties of the brazed joint were examined. The microstructure of the joint brazed at 825°C for 10min consisted of α–β Ti, Ti2Cu, TiCu, Ti3Cu4, Ag-based solid solution and Ti4(Cu,Al)2O phases starting from Ti6Al4V to alumina substrate. The brazing parameters had a strong influence on the microstructure and shear strength of the joint. The brittle fracture mainly propagated in the alumina substrate. The highest shear strength was obtained when the joint was brazed at 825°C for 10min. When a Cu foil was sandwiched between two Ag–Cu brazing foils, the microstructure of the joint changed greatly and the shear strength increased correspondingly. [Copyright &y& Elsevier]