With hexylene glycol present, the initiation of reaction products was localized on the slag surface, which considerably hampered the subsequent consumption of dissolved species and slag dissolution, ultimately delaying the bulk waterglass-activated slag hydration by several days. The observed correspondence between the calorimetric peak, the rapid evolution of microstructure, physical-mechanical parameter shifts, and the initiation of a blue/green color change, were all captured by time-lapse video. A significant relationship was found between workability loss and the first half of the second calorimetric peak, and an equivalent relationship between the most rapid increase in strength and autogenous shrinkage and the third calorimetric peak. The second and third calorimetric peaks were marked by a substantial upswing in ultrasonic pulse velocity. Despite the morphology of the initial reaction products changing, a prolonged induction period, and a slightly diminished hydration level from the presence of hexylene glycol, the fundamental mechanism of alkaline activation remained the same long-term. A supposition was advanced that a primary concern in the use of organic admixtures in alkali-activated systems is the destabilizing effect these admixtures have on the soluble silicates introduced within the activating agent.
Extensive research into nickel-aluminum alloy characteristics included corrosion testing on sintered materials produced by the advanced HPHT/SPS (high pressure, high temperature/spark plasma sintering) technique in a 0.1 molar sulfuric acid solution. This globally unique device, a hybrid, utilized for this specific task (one of only two), has a Bridgman chamber. This chamber enables high-frequency pulsed current heating and sintering of powders under high pressure, spanning from 4 to 8 GPa and reaching temperatures of up to 2400 degrees Celsius. The application of this device to material creation leads to the production of new phases not achievable through classical methods. read more This study presents the initial test results obtained for nickel-aluminum alloys, an unprecedented material combination created by this novel technique. Alloys, characterized by a 25 atomic percent inclusion of a specific element, serve diverse functions. Thirty-seven percent is the proportion of Al present, and it is 37 years old. Al constitutes 50% of the composition. All the items were produced. The alloys' formation depended on the conjunctive effect of a 7 GPa pressure and a 1200°C temperature, factors induced by the pulsed current. read more The sintering process concluded after 60 seconds had elapsed. Newly produced sinters were subject to electrochemical investigations, including open-circuit potential (OCP) measurements, polarization studies, and electrochemical impedance spectroscopy (EIS). These findings were then benchmarked against nickel and aluminum reference materials. The corrosion tests quantified good corrosion resistance in the produced sinters, revealing corrosion rates of 0.0091, 0.0073, and 0.0127 millimeters per year, respectively. It is without doubt that the strong resistance offered by materials produced by powder metallurgy is a product of astute selection of manufacturing process parameters, which are critical for achieving high material consolidation. Density measurements by the hydrostatic method, along with investigations of microstructure using both optical and scanning electron microscopy, further validated the prior findings. Although exhibiting a differentiated and multi-phase structure, the sinters were compact, homogeneous, and void of pores, while the densities of individual alloys approximated theoretical values. The Vickers hardness values, measured in HV10 units, for the alloys were 334, 399, and 486, correspondingly.
This investigation highlights the development of magnesium alloy/hydroxyapatite-based biodegradable metal matrix composites (BMMCs) using the method of rapid microwave sintering. Four distinct mixtures were produced using magnesium alloy (AZ31) and hydroxyapatite powder, with varying concentrations: 0%, 10%, 15%, and 20% by weight of hydroxyapatite. The physical, microstructural, mechanical, and biodegradation properties of the developed BMMCs were determined through a characterization process. X-ray diffraction data indicates that magnesium and hydroxyapatite are the primary phases, while magnesium oxide constitutes a secondary phase. SEM and XRD results jointly reveal the presence of magnesium, hydroxyapatite, and magnesium oxide phases. Density of BMMCs was decreased, and their microhardness increased, due to the addition of HA powder particles. The upward trend in compressive strength and Young's modulus was observed with increasing HA content, culminating at a 15 wt.% concentration. The immersion test, spanning 24 hours, indicated that AZ31-15HA showcased the greatest corrosion resistance and the lowest relative weight loss, marked by a decrease in weight gain after the 72- and 168-hour periods, attributable to the formation of Mg(OH)2 and Ca(OH)2 layers. The AZ31-15HA sintered sample underwent an immersion test; subsequently, XRD analysis was employed to determine the presence of new phases Mg(OH)2 and Ca(OH)2, potentially explaining the improved corrosion resistance. Further analysis, employing SEM elemental mapping, confirmed the presence of Mg(OH)2 and Ca(OH)2 on the sample surface, which effectively blocked further corrosion. The sample surface displayed a uniform distribution of the elements. The microwave-sintered BMMCs, resembling human cortical bone in their properties, facilitated bone growth by depositing apatite layers on the surface of the samples. Besides this, the porous structure type of the apatite layer, as observed in the BMMCs, augments osteoblast formation. read more Hence, the development of BMMCs suggests their suitability as an artificial, biodegradable composite for orthopedic applications.
The current study focused on the potential of elevating the calcium carbonate (CaCO3) level in paper sheets, with the intent of achieving property optimization. We propose a new category of polymeric additives designed for papermaking, and demonstrate a procedure for their incorporation into paper sheets supplemented with precipitated calcium carbonate. The flocculating agent, comprised of cationic polyacrylamide like polydiallyldimethylammonium chloride (polyDADMAC) or cationic polyacrylamide (cPAM), was applied to calcium carbonate precipitate (PCC) and cellulose fibers. In the laboratory, the double-exchange reaction of calcium chloride (CaCl2) with a sodium carbonate (Na2CO3) suspension led to the acquisition of PCC. Following the testing phase, the PCC dosage was determined to be 35%. The materials produced from the studied additive systems were subjected to characterization and analysis of their optical and mechanical properties, a crucial step in system improvement. The PCC positively impacted all the paper samples, but the use of cPAM and polyDADMAC polymers resulted in a significant enhancement of paper properties over those generated without any additives. Samples produced alongside cationic polyacrylamide showcase significantly better characteristics compared to those generated with polyDADMAC.
Molten slags, encompassing a range of Al2O3 contents, were employed to produce solidified CaO-Al2O3-BaO-CaF2-Li2O-based mold flux films, achieved through immersion of an enhanced water-cooled copper probe. This probe facilitates the procurement of films displaying representative structures. Different approaches to slag temperature and probe immersion time were tested for understanding the crystallization process. X-ray diffraction analysis determined the crystals in the solidified films, and optical and scanning electron microscopy characterized their shapes. Differential scanning calorimetry was used to determine and interpret the kinetic conditions, specifically the activation energy of devitrified crystallization within glassy slags. The growing speed and thickness of solidified films were enhanced by the addition of more Al2O3, lengthening the time required to achieve a stable film thickness. Along with the initial solidification process, fine spinel (MgAl2O4) precipitated within the films upon the addition of an extra 10 wt% Al2O3. LiAlO2 and spinel (MgAl2O4) served as nucleation sites for the deposition of BaAl2O4. A decrease in the apparent activation energy of initial devitrified crystallization was observed, starting at 31416 kJ/mol in the original slag, decreasing to 29732 kJ/mol when 5 wt% Al2O3 was introduced, and further declining to 26946 kJ/mol with 10 wt% Al2O3 added. An increase in the crystallization ratio of the films was witnessed after the addition of extra Al2O3.
Elements categorized as either expensive, rare, or toxic are typically found in high-performance thermoelectric materials. The abundant and cost-effective thermoelectric compound TiNiSn can be modified through doping with copper, an n-type donor, leading to potential performance improvements. The fabrication of Ti(Ni1-xCux)Sn involved an arc melting stage, followed by thermal treatment and a final hot pressing stage. XRD and SEM examinations of the resulting material were coupled with a study of its transport properties in order to determine its phase composition. Samples with undoped copper and 0.05/0.1% copper doping exhibited solely the matrix half-Heusler phase. Conversely, 1% copper doping triggered the appearance of Ti6Sn5 and Ti5Sn3 precipitates. Copper's transport properties exhibit its role as an n-type donor, thereby contributing to a reduction in the lattice thermal conductivity of the material. The 0.1% copper sample achieved the best figure of merit (ZT) of 0.75, showcasing an average of 0.5 within the 325-750 Kelvin temperature range. This remarkable performance surpasses that of the undoped TiNiSn sample by 125%.
Marking a significant milestone 30 years past, Electrical Impedance Tomography (EIT) emerged as a detection imaging technology. The conventional EIT measurement system utilizes a long wire connecting the electrode and excitation measurement terminal, which renders the measurement susceptible to external interference and unstable. Employing flexible electronics technology, the current paper demonstrates a flexible electrode device, which can be softly attached to the skin surface for real-time physiological monitoring. An excitation measuring circuit and electrode are integral components of the flexible equipment, eliminating the detrimental effects of extended wiring and improving the potency of the measurement signals.