Effect of honeycomb structure parameters on the mechanical properties of ZTAp/HCCI composites

Zirconia toughened alumina particles (ZTAp)/high chromium cast iron (HCCI) matrix honeycomb composites were successfully prepared by a non-pressure infiltration casting process. This paper systematically investigates the effect of pore size (6 mm, 8 mm, 10 mm, 12 mm) on the compression resistance of honeycomb structure under the same wall thickness condition. Through the simulation software Ansys Workbench and compression performance test, it was found that the compression performance tends to increase gradually with the increase of the honeycomb pore size, and the optimal compression resistance is reached when the pore size is 12 mm. This optimum performance is attributed to the fact that the reinforcement mechanism of the composite depends not only on the load sharing of the reinforcing particles, but also on the strength of the matrix

Effect of Ce on the Microstructure and Corrosion Resistance of Al-5Mg-3Zn-1Cu Alloy

The effects of different Ce content on the microstructure and corrosion resistance of Al-5Mg-3Zn-1Cu alloy in metal mold gravity casting were studied in this paper. The microstructure of the alloy was characterized by scanning electron microscope (SEM) and X-Ray diffractometer (XRD). The corrosivity of all alloys in 3.5 wt.%NaCl solution was studied by electrochemical and immersion corrosion techniques. The results show that the microstructure of the alloy is mainly composed of α-Al, T phase, and Al2Cu phase. Ce can refine the organization of the alloy, but when the addition of Ce is higher than 0.25 wt.%, a massive Ce-rich phase appears in the alloy. The results of a potential polarization test show that the corrosion potential of the alloy increases obviously from −1.253 V to −1.193 V with the increase in Ce content in the alloy

An ADRC Method for Noncascaded Integral Systems Based on Algebraic Substitution Method and Its Structure

The Active Disturbance Rejection Control (ADRC) prefers the cascaded integral system for a convenient design or better control effect and takes it as a typical form. However, the state variables of practical system do not necessarily have a cascaded integral relationship. Therefore, this paper proposes an algebraic substitution method and its structure, which can convert a noncascaded integral system of PID control into a cascaded integral form. The adjusting parameters of the ADRC controller are also demonstrated. Meanwhile, a numerical example and the oscillation control of a flexible arm are demonstrated to show the conversion, controller design, and control effect. The converted system is proved to be more suitable for a direct ADRC control. In addition, for the numerical example, its control effect for the converted system is compared with a PID controller under different disturbances. The result shows that the converted system can achieve a better control effect under the ADRC than that of a PID. The theory is a guide before practice. This converting method not only solves the ADRC control problem of some noncascaded integral systems in theory and simulation but also expands the application scope of the ADRC method

Effect of centrifugal casting temperature on the microstructure and properties of ZTAP/HCCI matrix composites

In the centrifugal casting process, the casting temperature parameters affected the microstructure characteristics, and the performance of the materials was greatly significant. ZTA (ZrO _2 reinforced Al _2 O _3 ) particles reinforced HCCI (High chromium cast iron) matrix composites with honeycomb structure were obtained by centrifugal casting. With the increased casting temperature (1450 °C, 1500 °C, 1550 °C, and 1600 °C), the austenite equivalent diameter size was 43.5  μ m, 34.8  μ m, 33.1  μ m, 22.3  μ m respective in the compound area and 58.3  μ m, 63.1  μ m, 65.2  μ m, 71.5  μ m respective in substrate area. The average size of eutectic carbides in the compound area decreased from 5.7  μ m to 2.5  μ m with the casting temperature increased. Meanwhile, the lattice constants of austenite and carbide increased with the increased temperature. The hardness of the composites increased by 4 ∼ 6HRC with a change in casting temperature. The results of three-body abrasive wear under high-stress static load conditions showed that the wear volume loss of the composites reduced with the temperature increased and the wear resistance was 1.4 times at 1600 °C than that at 1450 °C

Interface microstructure and abrasive wear properties of WC-iron matrix composites with Ni, Mo, Fe added to the preforms

WC particles with high hardness and high wear resistance were commonly used to manufacture various wear-resistant parts. In this paper, different alloying elements Ni, Mo and Fe were added to WC particles to produce the preforms, and then the cast method was used to prepare the WC-iron matrix composite. The interface microstructure of the composites was observed, and the abrasive wear properties were tested. The results showed that the interface transition layer of metallurgical bonding was produced in the composites under different alloy elements. The microstructure of the composites was mainly contained WC, Fe3W3C, Fe6W6C, M7C3 and α-Fe, and the carbides of the interface transition layer were Fe3W3C and M7C3. The width of interface transition layer was significantly different, and the width was the largest with Ni added. The work of adsorption between WC (0001) and Fe3W3C (100) was obtained by first principles calculation as 0.0086 (J/m2) and the interfacial energy as 6.8202 (J/m2). Compared with Fe and Mo, the composite with Ni addition has the smallest wear weight loss and the best wear resistance, which was mainly related to the hardness of different zones of the composite and the interface transition layer formed after adding alloy elements

Sodium Fluoride under Dose Range of 2.4-24 μm, a Promising Osteoimmunomodulatory Agent for Vascularized Bone Formation

Fluoride has essential effects on bone physiological activity and is widely used in bone biomaterials modification. However, this beneficial effect is highly related to the dose range and improper dosing can lead to pathological conditions such as fluorosis of bone. Therefore, this study first investigated the dose dependent effect of fluoride on bone regeneration. In the range of 0.24–240 μM, in vivo vascularized bone formation can be achieved via fine-tuning the fluoride concentration, and the peak osteogenic effect was found at 2.4–24 μM. The underlying mechanism is related to the modulation of the osteoimmune environment. Fluoride elicited significant osteoimmunomodulatory effect in modulation of the inflammatory cytokines and expression of osteogenic factors (BMP2, OSM, spermine/spermidine) and angiogenic factor (VEGF, IGF-1) during the early response. Fluorine with the doses of 2.4 and 24 μM could increase polyamines and IGF-1 production in macrophages, thus promoting osteogenesis of BMSCs and angiogenesis of HUVECs. These doses could also inhibit the inflammatory response of macrophages. In vitro osteogenesis and angiogenesis were both improved by the fluorine (2.4 and 24 μM)/macrophage conditioned medium, which is consistent with the in vivo results. These results collectively imply that fluoride is an effective osteoimmunomodulatory agent that can regulate both osteogenesis and angiogenesis. “Osteoimmune-smart” bone biomaterials can be developed via incorporating fluorine, and the release concentration should be controlled within the range of 2.4–24 μM for improved bone formation