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The tribological behavior of 1.41 wt% C ultrahigh-carbon steel (UHCS-1.41C) was investigated in comparison with a GCr15 bearing steel with a pin-on-disk and a two-disk tribometer at varying applied loads in ambient conditions. The wear surfaces of the specimens were examined with an optical microscope, EDX, and SEM. The retained austenite was measured by XRD. The results show that the friction coefficient of UHCS-1.41C is higher than that of GCr15 at a low load (6 N); however, it becomes lower than that of GCr15 at higher loads (10 N, 20 N). The wear rate of UHCS-1.41C is always lower than that of GCr15 according to the results of the two-disk test. UHCS-1.41C exhibits a stronger work hardening ability, which results in a higher resistance to wear than that of GCr15 during the two-disk test.

The structure and electrochemical properties of a cobalt-free hydrogen storage electrode alloys LaNi 4.2− x Al 0.35 Mn 0.45 Si x (0 ≤ x ≤ 0.35) have been investigated with small amount of Si in replacement of Ni. With the increase of Si content, the maximum discharge capacity and the high rate discharge (HRD) ability gradually decrease, however the cycle stability is improved correspondingly. The lowest capacity decay rate can remain 19.4% ( x = 0.35) after 300 charge/discharge cycles. The lower corrosion current densities of the alloys with the addition of Si can explain the good cycle life for them. It is found that all of the alloys are single CaCu 5 phase structure through XRD analysis. But some white dot-like LaNi 3 phase separated out in the matrix only for the alloy x = 0.35 through further EDX analysis.

A new Cu coating technique is adopted for a Co-free alloy La(NiMnAlFe)5 to improve its electrochemical properties. Compared with unmodified alloy, the Cu-coated alloys show improved electrochemical performances. The activation number decreased from 19 to 3 cycles and discharge capacity increased from 282 to 307 mAh/g. The optimal high rate discharge ability (HRD) is 25.4% (1200 mA/g) for the sample with 5 wt.% Cu. EIS reveals that decreased charge-transfer resistances and cyclic voltammograms show the higher anodic current peaks, which indicate the high electronic conductivity and electrochemical activity of alloys after Cu coating. The hydrogen diffusion coefficient increases accordingly and the cycle life is also improved.

The La 1.3 CaMg 0.7 Ni 9 alloy was modified with various metal oxides ( Fe 2 O 3 , TiO 2 , Cr 2 O 3 , ZnO), and the effects of metal oxides addition on the electrochemical properties of the La 1.3 CaMg 0.7 Ni 9 hydrogen storage alloy were investigated. The catalytic effects of metal oxides are found. Not only the discharge capacity but also the high-rate dischargeability (HRD) is improved by addition of 5 wt% TiO 2 , Cr 2 O 3 , and ZnO, while the cyclic stability does not change except for addition of Fe 2 O 3 . The low-temperature property is enhanced more obviously by addition of TiO 2 , Cr 2 O 3 , and ZnO. The electrochemical kinetics is also measured by the linear polarization and electrochemical impedance spectroscopy (EIS). In addition, the hydrogen absorption kinetic behavior is measured by gas–solid reaction.

The influences of temperature, chloride ions and chromium element on the electronic property of passive film formed on carbon steel in NaHCO 3 /Na 2 CO 3 buffer solution are investigated by capacitance measurement and electrochemical impedance spectroscopy (EIS). The results show that the passive film appears n -type semiconductive character; with increasing the solution temperature, the addition of chromium into carbon steel and increasing the concentration of chloride ions, the slopes of Mott–Schottky plots decrease, which indicates the increment of the defect density in the passive film. EIS results show that the transfer impedance R 1 and the diffusion impedance W decrease with increasing the solution temperature, with the addition of chromium into carbon steel and with increasing the chloride ions concentration. It can be concluded that the corrosion protection effect of passive film on the substrate decreases with increasing the solution temperature, adding chromium into carbon steel and increasing chloride ions concentration.

The microstructure and electrochemical properties of La 1.3 CaMg 0.7 Ni 9 - x ( Al 0.5 W 0.5 ) x ( x = 0 , 0.3 , 0.6 , 0.9 ) hydrogen storage alloys have been studied systematically. XRD and SEM analyses show that the alloys are mainly composed of the ( La , Mg ) Ni 3 phase and the LaNi 5 phase, but the Al and W substitution for Ni results the disappearance of the ( La , Mg ) 2 Ni 7 phase and the segregation of W pure metal phase. The cell volumes of the ( La , Mg ) Ni 3 phase and the LaNi 5 phase increase by adding the content of Al. With increasing x , the maximum discharge capacity of the alloy electrodes decreases from 380 ( x = 0.0 ) to 317.6 mA h/g ( x = 0.9 ) . However, cyclic stability is noticeable improved from 72.2% ( x = 0.0 ) to 85.2% ( x = 0.9 ) up to 100 cycles. The HRD and exchange current density I 0 of the alloy electrodes decrease first and then increase.

The structure and electrochemical properties of a cobalt-free hydrogen storage electrode alloy LaNi4.05−xAl0.45Mn0.5Fex (0 ≤ x ≤ 0.5) have been investigated with different additions of Fe in replacement of Ni. With the increase of Fe content the maximum discharge capacity gradually decreases from 334.8 mAh g−1 to 292.8 mAh g−1, however the cycle stability is improved correspondingly. The capacity decay can remain 28.6% (x = 0.5) after 300 charge/discharge cycles. The high rate discharge (HRD) ability of the alloys (x ≤ 0.5) is improved with the increase of Fe content. It is found that all of the alloys are single CaCu5 phase structure disclosed by XRD pattern. However, small amount of the La2O3 phase, observed from SEM photographs, exists on the matrix of all the alloys and when x = 0.5, some web-like LaNi2.28 phase is segregated out along the crystal boundary.

The microstructural and electrochemical properties of La 2.3− x Ca x Mg 0.7 Ni 9 hydrogen storage alloys have been studied systematically. The microstructure examined by XRD, SEM and EDX shows that the alloys consist of multi-phases, which are (La, Mg) 2 Ni 7 phase, LaMgNi 4 phase, (La, Mg)Ni 3 phase and LaNi 5 phase. It is can be found that Ca does not appear to segregate. This phenomenon is different from Mg. With increasing Ca content, the main phase varies from (La, Mg) 2 Ni 7 phase ( x = 0) to (La, Mg)Ni 3 phase ( x = 0.3), LaNi 5 phase ( x = 0.6, 0.8) and (La, Mg)Ni 3 phase ( x = 1.0, 1.3). The maximum discharge capacities of the alloy electrodes increase from 244.6 mAh/g ( x = 0) to 380 mAh/g ( x = 1.0), and then decrease to 353.6 mAh/g ( x = 1.3). The discharge capacities of the alloys are related to phase content. Cell volumes of LaNi 5 phase, (La, Mg) 2 Ni 7 phase and (La, Mg)Ni 3 phase all decrease and the high rate dischargeability (HRD) is improved by adding Ca. The alloy electrodes also show relative good cycling stability up to 100 cycles.

The structure and electrochemical properties of low cobalt AB 5 -type hydrogen storage electrode alloys with a small amount of Li in the A site have been investigated. With the increase of Li contents, the discharge capacity increases firstly from 240 mAh / g ( x = 0 ) to 328 mAh / g ( x = 0.1 ) and then decreases to 320 mAh / g ( x = 0.2 ) . The cycle stability is improved slightly and the electrochemical capacity can remain 71.4% ( x = 0.2 ) after 230 charge/discharge cycles. The alloy ( x ⩽ 0.1 ) showed the best rate discharge ability under the discharge current density of 1200 mA / g . It is found that as-prepared alloys are basically composed of LaNi 5 as the matrix phase and LaNi 3 as the second phase ( x ⩽ 0.1 ) . But the abundance of LaNi 3 phase dramatically decreases with increasing x . When x = 0.2 , a new phase having a chemical composition of Al ( NiCo ) 3 was observed.

Ml0.8Mg0.2Ni3.2Co0.6−xAlx (x=0–0.6) hydrogen storage alloys were prepared by induction melting and the effect of Al substitution for Co on the structure and hydrogen storage characteristics was investigated. These alloys are confirmed to be composed of LaNi5 as matrix and (LaMg)Ni3 as the secondary phase. The Al substitution leads to an expansion of the unit cell volume of matrix and an enhancement of the stability of the alloy hydrides. The thermodynamic properties such as ΔH and ΔS and the diffusion coefficient of hydrogen in these alloys were also evaluated.

Ml1−xMgxNi2.4Co0.6 (x = 0–0.6) hydrogen storage alloys were prepared by inductive melting and the effect of Mg on the crystal structure and hydrogen storage characteristics was investigated. These alloys are confirmed to be LaNi3 phase with the PuNi3 type structure. The Mg substitution for Ml in the alloys leads to a shrinkage of the unit cell volume and a reduction of the stability of alloy hydrides. With increasing the Mg substitution for Ml, the atom ratio of hydrogen to alloy (H/M) decreases, but the weight ratio of H/M and the discharge capacity of electrodes increase in a certain range of Mg content (x ≤ 0.4). The Ml0.6Mg0.4Ni2.4Co0.6 alloy has the highest weight ratio of H/M (1.75 wt.%) at 1 MPa H2 and 298 K and the largest discharge capacity of electrodes (326 mAh g−1). In addition, the increase of Mg substitution for Ml results in better high-rate dischargeability and cycling stability of electrodes.

Two non-stoichiometric low-Co AB 5 alloys, Ml 0.95 Mg 0.05 Ni 3.8 Co 0.3 Mn 0.3 Al 0.4 (AB 4.8 ) and Ml 0.95 Mg 0.05 Ni 3.6 Co 0.3 Mn 0.3 Al 0.4 (AB 4.6 ), were designed to reduce the cost of AB 5 alloys. The maximum discharge capacities of the two low-Co alloys can reach 307 mAh/g for AB 4.8 alloy and 298 mAh/g for AB 4.6 alloy, respectively. After 300 cycles, the capacity decay is 23% for AB 4.8 alloy and 19.1% for AB 4.6 alloy. XRD patterns and the microstructure, examined by optic microscope and SEM, show that both of the two low-Co alloys are composed of three phases, LaNi 5 matrix phase, AlMnNi 2 secondary phase and LaNi tertiary phase. For the two low-Co alloys, the microhardness (HV) of the secondary phase are only half of that of the matrix phase, which could resist the crack propagating and make the alloys not amenable to pulverization. The small amount of Mg promotes to form the soft secondary phase, which is believed to be the reason for improving the cycling stability.

An ultrahigh-carbon steel containing 1.6 wt.% carbon (UHCS-1.6C) was processed to obtain ultrafine spheroidized ferrite, pearlite and tempered martensite, respectively. The tensile properties of these structures were evaluated at room temperature. The ultimate tensile strengths of UHCS-1.6C ranged from 930 to 1570 MPa, elongations to failure from 4.4 to 19%, and yield ratios from 0.65 to 0.92. The fracture mechanisms of these structures were clarified based on an examination to the fracture surfaces. The present results indicate that ultrahigh-carbon steels can be easily processed to achieve unique microstructures and properties.

In order to improve the electrochemical properties of Co-free Ml 0.8 Mg 0.2 Ni 3.4 Al 0.4 alloy, the alloy powder was ballmilled with Ni and Mo powders, respectively. The surface morphology and composition of the treated powder were examined by metallograph and X-ray photoelectron spectrum. The electrochemical capacity, rate dischargeability, and cycle life were investigated. It was found that the surface of the alloy powder was coated with a Ni or Mo film and the surface modification enhanced the electrochemical capacity, high-rate dischargeability, and cycle life. The Ni-coated alloy electrode had the highest electrochemical capacity of 325 mAh/g and high-rate dischargeability of 59.4%, while the Mo-coated alloy electrode exhibited the best cycle life. An electrochemical capacity of 320 mAh/g was achieved, and 85% of the initial capacity remained after 300 cycles for the Mo-coated alloy, which shows a great potential for applications for Ni-MH batteries.