Microwave Sintering of Multilayer Integrated Passive Devices

Microwave sintering of multilayer capacitor/varistor-based integrated passive devices (IPDs) has been investigated for the first time. The sintered samples were characterized for density, microstructure, composition, and electrical performance. It was found that IPDs with varistor/capacitor formulations could be microwave sintered to fully dense device components within 3 h of total cycle time, which is o1/10th of the time required by conventional methods. Microwave sintering resulted in products with a finer grain structure and without delamination or significant interdiffusion between the ceramic/electrode and varistor/ capacitor interfaces. The microwave method also completely eliminated the need for a separate binder burnt-out step. The electrical properties of the microwave-sintered samples were found to better or match those obtained by conventional, industrial processing. In general, the simplicity, rapidity, and superior product performance make the microwave technique an attractive sintering methodology for the processing of IPDs

Microwave-enhanced densification of sol–gel alumina films

Alumina films prepared by the sol-gel method were sintered at 1160 °C and 1200 °C using a 2.45 GHz microwave / conventional hybrid furnace in order to study the influence of microwave power on the sintering process and resultant samples. Experiments were designed to ensure that each series of samples underwent an identical thermal history in terms of temperature / time profiles. Sintering was carried out using three different heating approaches: pure conventional heating and hybrid heating with 600 W and 1000 W of microwave radiation, respectively. The results obtained showed that, compared with pure conventional heating, the presence of the microwave field led to higher sintered densities and crystallinity in the samples, indicating that the microwave field enhanced the sintering of the sol-gel alumina films and supporting the existence of the microwave effect

Unlocking the Separation Capacities of a 3D-Iron-Based Metal Organic Framework Built from Scarce Fe₄O₂ Core for Upgrading Natural Gas

Methane is an important alternative fuel, and upgrading it to improve fuel efficiency is an imperative target. Solid sorbents capable of selectively removing the major impurities CO2 and N2 from the natural gas contribute immensely to this process. We report a porous 3D iron-MOF built by linking scarce Fe4O18N2 clusters through readily available terephthalate and diaminotrizaole ligands. The 1-D channels with a high density of polarizing amine groups, aromatic rings, and carboxylate oxygen adsorb CO2 and the even less polarizable CH4. The MOF uptakes 4.7 mmol/g of CO2 at 273 K, 1 bar, with an optimal heat of adsorption of ≈24.5 kJ/mol and CO2/N2 IAST selectivity of ≈26. At higher pressures, the MOF exhibits a Langmuir type isotherm for methane and nitrogen with a CH4/N2 IAST selectivity of ≈4. The MOF’s excellent cyclic stability is affirmed by the TGA- and iso-cycling. Modeling studies propound the amine’s interactions with the CO2, but more dominant is the CO2···CO2 cooperative interactions. At 20 bar, CH4 interacts with many framework sites through weak dispersive interactions. In contrast, N2 interacts specifically with the triazole moiety; thus, the MOF favors the former. The CO2, CH4, and N2 diffusion coefficients, calculated using MD simulations, are quite favorable (Dc for CO2 = 1.11 × 10–6; CH4 = 9.04 × 10–6; N2 = 1.875 × 10–5 cm2/s). The dynamic breakthrough studies confirm the potential of the Fe-MOF to separate the gas mixtures. With these advantageous sorbent characteristics of this Fe-MOF, we propose using it in a two-stage PSA for the natural gas purification process, Stage I: removal of CO2 and Stage II: removal of N2. The outcomes point to the potential of a readily accessible iron-based amine MOF as sorbent for natural gas upgrading. A process optimization using a 4-step PSA validates the ability of our MOF to yield >96% purity of CH4 as required for pipeline transportation