DC-2 GHz low loss cryogenic InAs/AlSb HEMT switch
A DC-2 GHz InAs/AlSb HEMT MMIC single pole double throw (SPDT) switch designed for cryogenic temperature has been fabricated and characterized. This switch is suitable for low RF power applications that require low insertion loss and high isolation. At 2 GHz, the SPDT switch demonstrated a typical low insertion loss of 0.7 dB at 300K and 0.3 dB at 90K. The isolation is greater than 40dB for both temperatures. These results demonstrate the outstanding potential of ABCS HEMT technology for low loss SPDT switches for cryogenic temperature.
Low loss cryogenic InAs/AlSb HEMT non-reflective SP4T switch
A non-reflective single pole four throw (SP4T) MMIC switch using ABCS InAs/AlSb HEMT process technology, designed for cryogenic temperature has been fabricated and characterized. This switch is suitable for low RF power applications that require very low insertion loss and good isolation. At 2 GHz, the SP4T switch demonstrated 0.52dB insertion loss and 33dB isolation at room temperature. At 90K, the switch has seen 0.2dB and 2dB improvement in insertion loss and isolation. These results demonstrate the outstanding potential of ABCS HEMT technology for low loss switches for cryogenic temperature.
Evaluation of CuAl2O4 as an Oxygen Carrier in Chemical-Looping Combustion
The chemical-looping combustion (CLC) process is a novel solution for efficient combustion with intrinsic separation of carbon dioxide. The process uses a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor where the fuel, or gasification products of the fuel, reacts with the solid oxygen carrier. In this work, copper(II) aluminate (CuAl2O4) was assessed as a potential oxygen carrier using methane as fuel. The carrier particles were produced by freeze–granulation and calcined at 1050 °C for a duration of 6 h. The chemical-looping characteristics were evaluated in a laboratory-scale fluidized-bed reactor in the temperature range of 900–950 °C during 45 alternating redox cycles. The oxygen carrier exhibited reproducible and stable reactivity behavior in this temperature range. Neither agglomeration nor defluidization was noticed in any of the cycles carried out at 900–925 °C. However, after reactivity tests at 950 °C, soft agglomeration and particle fragmentation were observed. Systematic phase analysis of the Cu–Al–O system during the redox cycle was carried out as a function of duration of reduction and oxygen concentration during the oxidation period. It was found that the CuAl2O4 is reduced to copper(I) aluminate (CuAlO2; delafossite), Cu2O, and elemental Cu. The CuAlO2 phase is characterized by slow kinetics for oxidation into CuO and CuAl2O4. Despite this kinetic limitation, complete conversion of methane with reproducible reactivity of the oxygen carrier is achieved. Thus, CuAl2O4 could be a potential oxygen carrier for chemical-looping combustion.