Vacuum brazing of GH99 superalloy using graphene reinforced BNi-2 composite filler

A novel graphene reinforced BNi-2 composite filler was developed for brazing GH99 superalloy. The interracial microstructure of brazed joints was analyzed by field emission scanning electron microscope and a transmission electron microscope. The effects of graphene addition on the microstructure evolu-tion and mechanical properties of brazed joints were investigated, and the strengthening mechanism of graphene was analyzed. The results revealed that due to the addition of graphene, M23（C,B）6 compounds were synthesized in the y solid solution and brittle boride precipitates near the brazing seam decreased. Graphene was effective in retarding solute atoms diffusion thus impeding the precipitation of borides. Furthermore, the low coefficient of thermal expansion （CTE） of graphene was conducive to relieve stress concentration of the brazed joints during the cooling process. The shear strengths of brazed joints were significantly improved by exerting the strengthening effect of graphene. The maximum shear strengths of the brazed joints were 410.4 MPa and 329.7 MPa at room temperature and 800 ℃, respectively.

Joints of continuous carbon fiber reinforced lithium aluminosilicate glass ceramics matrix composites to Ti60 alloy brazed using Ti-Zr-Ni-Cu active alloy

Continuous carbon fiber reinforced lithium aluminosilicate glass ceramics matrix composites(C_f/LAS composites) are joined to Ti60 alloy vacuum brazed using Ti-Zr-Ni-Cu brazing alloy. The effects of the brazing temperature on the interfacial microstructure and mechanical properties of brazed joints are investigated in details. The interfacial microstructure varies apparently with an increase of the brazing temperature. The thicknesses of the banded Ti solid solution(Ti(s, s)) and the reactive layer between Cf/LAS composites and the interlayer grow gradually. The mechanical properties of brazed joints increase firstly and then decrease with an increasing temperature. In addition, a joint that is brazed at 980 °C for 10 min shows the highest shear strength of$38.13 MPa. At the same time, the fracture paths of brazed joints also change as the temperature increases. When the brazing temperature is 950 °C, the fracture position is in the TiC + ZrC +Ti_2O + ZrSi_2+ Ti_5Si_3 layer on the composite side. When the brazing temperature is 980 °C, the fracture position is on the side of the braze seam(Ti, Zr)2(Ni, Cu), Ti_2O + ZrSi_2+ Ti_5Si_3 layer,and carbon fiber in the composite material. When the brazing temperature is 990 °C, the fracture position is in the Ti_2O + ZrSi_2+ Ti_5Si_3 layer on the composite side and the carbon fiber in the composite material.

Adsorption behaviour of molecular sieve and activated carbon for CO_(2) adsorption at cold temperatures

At present,insufficient works have provided insights into the application of adsorption to remove CO_(2) in flue gas below room temperatures under ambient pressure.In this work,the effects of temperature,CO_(2) partial pressure and moisture on dynamic adsorption characteristics for CO_(2) are conducted for various adsorbents.Based on our findings,lower the adsorbing temperature can drastically enhance the adsorption of carbon dioxide over molecular sieves and activated carbon.Among various adsorbents,13X molecular sieve shows highest adsorption capacity.With a concentration of 10%CO_(2) in flue gas,the specific adsorption capacity of CO_(2) over 13X molecular sieve is 0.11,2.54 and 5.38 mmol/g at 80℃,0℃ and -80℃,respectively.In addition,the partial pressure of CO_(2) also has a significant impact on the adsorption capacity.With the increment of the concentration of CO_(2) from 1%to 10% under 0℃,the specific capacity of 13X molecular sieve increases from 1.212 mmol/g to 2.538 mmol/g.Water vapor in flue gas can not only reduce the specific adsorption capacity of CO_(2) due to competing adsorption,but also increase the heat penalty of molecular sieve regeneration due to the water adsorption.An overall analysis is conducted on the energy penalty of capture 1 ton CO_(2) at various adsorption temperatures between -80℃ and 80℃,considering both the heat penalty of molecular sieve regeneration as well as the energy penalty for cooling the adsorber.It is found that the lowest energy penalty is about 2.01 GJ/ton CO_(2) when the adsorption is conducted at 0℃.