Effect of Mo2C Addition on the Microstructure and Properties of TiC-High Manganese Steel-Bonded Carbide

TiC-high manganese steel-bonded carbide was prepared by powder metallurgy method with varied Mo2C content (0, 2.5%, 5%, 7.5% and 10% respectively), and the effects of Mo2C addition on the microstructure and mechanical properties of the fabricated cermets were studied. The microstructures of the fabricated cermets were observed and analyzed by scanning electron microscope (SEM), and the physical and mechanical properties of the cermets were also tested. The results show that the microstructure of the cermet without Mo2C additive was finer than that of the cermets with 2.5% and 5% Mo2C addition, though Mo2C was an effective grain growth inhibitor of TiC- and/or TiCN-based refractory materials because of low inherent solubility of TiC in Fe binder. An interesting phenomenon was also found that black core-gray rim was observed in the microstructure of the cermet without Mo2C addition. The microstructure of the fabricated cermets was fine with the increase of Mo2C content. The results also show that the relative density and hardness of the cermet increased monotonously with the increase of Mo2C content, hence, the transverse rupture strength (TRS) and impact toughness (IM) of the fabricated cermets increased first and then decreased, and the TRS and IM reached the maximum valve of 2189 MPa and 11.7 J/cm2 when Mo2C content was 7.5% and 5% respectively.

Effect of Additives on Stability of Alumina—Waste Alumina Suspension for Slip Casting: Optimization Using Box-Behnken Design

The green machining of alumina (Al2O3) green bodies generates a certain amount of waste alumina powder. Waste alumina ceramic powder should be disposed of as non-hazardous waste in a legally compliant manner. The influence of additives on the stability of 70 wt.% (≈40 vol.%) alumina—waste alumina water-based suspension was investigated in the presented research. A Box-Behnken three-factor response surface design was used for the preparation of stable highly-concentrated suspensions with the addition of three additives. The optimal amount of each additive was selected according to the obtained results of minimal apparent viscosity: 0.05 wt.% Tiron as dispersant, 0.1 wt.% poly (vinyl alcohol) as binder and 0.2 wt.% magnesium aluminate spinel as abnormal grain growth inhibitor. The analysis of variance was used to identify the contribution of each additive. The zeta potential and sedimentations tests were performed to confirm the suspension stability measurements at different pH values. Alumina particles were optimally dispersed at pH values between 8 and 11. According to the results, the investigated composition of 20 wt.% waste alumina powder (weight content, dry alumina powder), with the addition of optimal amounts of additives, shows a possible application in the production of ceramics by slip casting.

Metallic glassy Ti2Ni grain-growth inhibitor powder for enhancing the hydrogenation/dehydrogenation kinetics of MgH2

Metallic glassy alloy is considered as one of the best option used to enhance the kinetics behavior of MgH2.

Enhanced electrochemical performances of LiFePO4-C synthesized with PEG as the grain growth inhibitor for Li-ion capacitors in LiNO3 aqueous electrolyte

Purpose The purpose of this paper is to conduct the synthesization of LiFePO4-C (LFP-C) with fine particle size and enhanced electrochemical performance as the positive electrode material for Li-ion capacitors (LICs) with neutral aqueous electrolyte. Design/methodology/approach LFP-C was prepared by using polyethylene glycol (PEG) as a grain growth inhibitor, and the effects of the calcination temperature and PEG content on the structure and morphology of LFP-C were investigated. LICs using environment-friendly, safe and low-cost LiNO3 aqueous electrolyte were assembled with LFP-C as the positive electrode and active carbon as the negative electrode. The electrochemical performances of LFP-C and LICs were studied. Findings The results show that the particle size of LFP-C decreases significantly through the introduction of PEG. Cyclic voltammetry results show that the LFP-C prepared at 550°C with 1.0 g PEG exhibits the highest Cpe of 725 F/g at the scanning rate of 5 mA/s. Compared to LFP prepared without PEG, the electrochemical performance of optimized LFP-C dramatically increases due to the decrease of the particle size. Moreover, the LIC assembled with the optimized LFP-C exhibits excellent electrochemical performances. The LIC maintains about 91.3 per cent of its initial Cps after 200 cycles which shows a good cycling performance. Research limitations/implications The LFP-C is the suitable positive electrode material for LICs with neutral aqueous electrolyte. LICs can be used in the field of automobiles and can solve the problems of energy shortage and environmental pollution. Originality/value Both the LFP-C with fine particle size and its optimal LIC using environment-friendly, safe and low-cost LiNO3 aqueous electrolyte own good electrochemical performances.

Effects of Combined Addition of Cr3C2 and NbC on Microstructure and Properties of Cemented Carbides Prepared by WС-Co Composite Powder

With addition various contents of combined grain growth inhibitors Cr3C2 and NbC into the ultrafine WC-Co6% composite powder, and the effects of codoped Cr3C2 and NbC addition on microstructure and properties of the alloys have been investigated by X-ray diffraction, scanning electron microscopy. The results showed that increasing the content of inhibitors in the composite powder, the abnormal grain growth disappeared and homogeneous ultrafine grain structure formed, i.e., the grain growth inhibitor promoted sintering densification process. WC grains were refined by the comprehensive effects of the Cr3C2/NbC dissolving in the Co phase to alter the interface energy and interfere the WC solution in the binder phase, which prevents the structure of cobalt change from the face-center-cubic into dense-hexagonal crystal, and to increases the transverse rupture strength.

Preparation and mechanisms of cemented carbides with ultrahigh fracture strength

WC–Co cemented carbides were prepared by liquid-state sintering ofin situsynthesized composite powders with a constant Co content but different carbon concentrations, and with different size scales of VC particles as grain-growth inhibitor. With an optimized carbon addition and doping with microscale VC particles, an ultrahigh fracture strength with a mean value above 5000 MPa was achieved for cemented carbides. By detailed crystallographic analysis of the configuration and interactions of the WC, Co and VC phases, the effects of VC particle size on the microstructure and mechanical properties of cemented carbides are identified. The mechanisms by which the fracture strength depends on the VC particle size contain the effects on the changes in Co binder distribution, atomic matching at the phase boundary and WC grain size. The dominant factors for ultrahigh fracture strength of cemented carbides are proposed.