Ceramic cold gas microthruster with integrated flow sensor

For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as common for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. This paper describes the  design, manufacturing and characterization of a ceramic, heated cold-gas microthruster with integrated flow sensor, using HTCC processing and silicon tools. The calorimetric flow sensor is integrated in the structure, and heaters are embedded in the stagnation chamber of the nozzle. The heater was shown to improve the efficiency of the thruster, as confirmed by measurements of the flow rate. Flow rate changes were seen as changes in resistance of the fabricated flow sensor. The choice of yttria stabilized zirconia as material for the components make them robust and capable of withstanding  very high temperatures. Samples have been shown  capable of achieving temperatures locally exceeding 1000ºC

Ceramic cold gas microthruster with integrated flow sensor

For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as common for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. This paper describes the  design, manufacturing and characterization of a ceramic, heated cold-gas microthruster with integrated flow sensor, using HTCC processing and silicon tools. The calorimetric flow sensor is integrated in the structure, and heaters are embedded in the stagnation chamber of the nozzle. The heater was shown to improve the efficiency of the thruster, as confirmed by measurements of the flow rate. Flow rate changes were seen as changes in resistance of the fabricated flow sensor. The choice of yttria stabilized zirconia as material for the components make them robust and capable of withstanding  very high temperatures. Samples have been shown  capable of achieving temperatures locally exceeding 1000ºC

Ceramic microcomponents for high-temperature fluidics

For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as abundant for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. A major reason is the lack of means for high-resolution structuring. This paper describes the application of silicon-based manufacturing processes in the fabrication of ceramic yet truly micromechanical structures and devices for very high-temperature applications, and demonstrates the technique’s implementation in, and significance for, high-temperature microfluidics. Embossing of structures down to 2 µm wide is demonstrated, as well as deep embossing (50 µm), punching through 15 µm tape, and lamination of structured layers. The resulting samples survive temperatures of 1400ºC

Ceramic microcomponents for high-temperature fluidics

For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as abundant for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. A major reason is the lack of means for high-resolution structuring. This paper describes the application of silicon-based manufacturing processes in the fabrication of ceramic yet truly micromechanical structures and devices for very high-temperature applications, and demonstrates the technique’s implementation in, and significance for, high-temperature microfluidics. Embossing of structures down to 2 µm wide is demonstrated, as well as deep embossing (50 µm), punching through 15 µm tape, and lamination of structured layers. The resulting samples survive temperatures of 1400ºC

Ceramic microcomponents for high-temperature fluidics

For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as abundant for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. A major reason is the lack of means for high-resolution structuring. This paper describes the application of silicon-based manufacturing processes in the fabrication of ceramic yet truly micromechanical structures and devices for very high-temperature applications, and demonstrates the technique’s implementation in, and significance for, high-temperature microfluidics. Embossing of structures down to 2 µm wide is demonstrated, as well as deep embossing (50 µm), punching through 15 µm tape, and lamination of structured layers. The resulting samples survive temperatures of 1400ºC

Ceramic cold gas microthruster with integrated flow sensor

For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as common for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. This paper describes the  design, manufacturing and characterization of a ceramic, heated cold-gas microthruster with integrated flow sensor, using HTCC processing and silicon tools. The calorimetric flow sensor is integrated in the structure, and heaters are embedded in the stagnation chamber of the nozzle. The heater was shown to improve the efficiency of the thruster, as confirmed by measurements of the flow rate. Flow rate changes were seen as changes in resistance of the fabricated flow sensor. The choice of yttria stabilized zirconia as material for the components make them robust and capable of withstanding  very high temperatures. Samples have been shown  capable of achieving temperatures locally exceeding 1000ºC

Electronic structure and excited state properties of iron carbene photosensitizers - A combined X-ray absorption and quantum chemical investigation

The electronic structure and excited state properties of a series of iron carbene photosensitizers are elucidated through a combination of X-ray absorption measurements and density functional theory calculations. The X-ray absorption spectra are discussed with regard to the unusual bonding environment in these carbene complexes, highlighting the difference between ferrous and ferric carbene complexes. The valence electronic structure of the core excited FeIII-3d5 complex is predicted by calculating the properties of a CoIII-3d6 carbene complex using the Z+1 approximation. Insight is gained into the potential of sigma-donating ligands as strategy to tune properties for light harvesting applications

A low-spin Fe(iii) complex with 100-ps ligand-to-metal charge transfer photoluminescence

Transition-metal complexes are used as photosensitizers1, in light-emitting diodes, for biosensing and in photocatalysis2. A key feature in these applications is excitation from the ground state to a charge-transfer state3,4; the long charge-transfer-state lifetimes typical for complexes of ruthenium5 and other precious metals are often essential to ensure high performance. There is much interest in replacing these scarce elements with Earth-abundant metals, with iron6 and copper7 being particularly attractive owing to their low cost and non-toxicity. But despite the exploration of innovative molecular designs6,8,9,10, it remains a formidable scientific challenge11 to access Earth-abundant transition-metal complexes with long-lived charge-transfer excited states. No known iron complexes are considered12 photoluminescent at room temperature, and their rapid excited-state deactivation precludes their use as photosensitizers13,14,15. Here we present the iron complex [Fe(btz)3]3+ (where btz is 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene)), and show that the superior σ-donor and π-acceptor electron properties of the ligand stabilize the excited state sufficiently to realize a long charge-transfer lifetime of 100 picoseconds (ps) and room-temperature photoluminescence. This species is a low-spin Fe(iii) d5 complex, and emission occurs from a long-lived doublet ligand-to-metal charge-transfer (2LMCT) state that is rarely seen for transition-metal complexes4,16,17. The absence of intersystem crossing, which often gives rise to large excited-state energy losses in transition-metal complexes, enables the observation of spin-allowed emission directly to the ground state and could be exploited as an increased driving force in photochemical reactions on surfaces. These findings suggest that appropriate design strategies can deliver new iron-based materials for use as light emitters and photosensitizers