Effect of sintering temperature on microstructures and mechanical properties of ZK60 magnesium alloys

In this study, ZK60 Mg alloys were prepared via hot-press sintering under a constant pressure of 30 MPa as well as Ar atmosphere. The sintering temperature was determined to be in the range of 450–600 °C with an interval of 50 °C. The effect of sintering temperature on the microstructures and mechanical properties of the alloys was investigated. All the four sintered alloys mainly exhibited an α-Mg-phase structure and equiaxed grain microstructure. However, a specific amount of melt, enriched in Zn element, formed when the sintering temperature reached 500 °C. Thus, only the alloy sintered at 450 °C maintained the nominal composition of the alloy powder, and exhibited the favorable yield strength and hardness, which was 135.1 MPa and 57 HV, respectively. The alloys sintered at 550 °C and 600 °C exhibited a reduced yield strength and hardness due to the loss of Zn element.

Rapid, Simple and Inexpensive Fabrication of Paper-Based Analytical Devices by Parafilm® Hot Pressing

Paper-based analytical devices have been substantially developed in recent decades. Many fabrication techniques for paper-based analytical devices have been demonstrated and reported. Herein, we report a relatively rapid, simple, and inexpensive method for fabricating paper-based analytical devices using parafilm hot pressing. We studied and optimized the effect of the key fabrication parameters, namely pressure, temperature, and pressing time. We discerned the optimal conditions, including a pressure of 3.8 MPa, temperature of 80 °C, and 3 min of pressing time, with the smallest hydrophobic barrier size (821 µm) being governed by laminate mask and parafilm dispersal from pressure and heat. Physical and biochemical properties were evaluated to substantiate the paper functionality for analytical devices. The wicking speed in the fabricated paper strips was slightly lower than that of non-processed paper, resulting from a reduced paper pore size after hot pressing. A colorimetric immunological assay was performed to demonstrate the protein binding capacity of the paper-based device after exposure to pressure and heat from the fabrication. Moreover, mixing in a two-dimensional paper-based device and flowing in a three-dimensional counterpart were thoroughly investigated, demonstrating that the paper devices from this fabrication process are potentially applicable as analytical devices for biomolecule detection. Fast, easy, and inexpensive parafilm hot press fabrication presents an opportunity for researchers to develop paper-based analytical devices in resource-limited environments.

A Liberal Takes on the Progressives

A review of "Cancel This Book: The Progressive Case Against Cancel Culture," Dan Kovalik, Hot Press, 2021, pp. 199, $24.99 hardcover.

Enhanced ZT of Ca3Co4O9 by nano-sized precursor

Ca3Co4O9 sample synthesized from nanometer of CaCO3 and Co2O3 sized precursor has been prepared by solid-state reaction and fast sintering by hot press method. The fast-sintering time can maintain the particle size of the nanometer. Their thermoelectric properties at high temperatures have been studied at 300 - 1000 K. When the usage of a nano-sized precursor leads to decrease electrical resistivity, increase power factor, and would lead to huge growth, respectively. The main effect is observed on thermal conductivity that is lower than sample synthesized with micrometer precursors powder from 0.67 W/mK which became 0.36 W/mK at 973 K. The best ZT value of Ca3Co4O9 reaches 0.51 at 973 K.