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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.

The binary Cu–Cr and Cu–Zr and ternary Cu–Cr–Zr copper-base alloys are successfully prepared by the conventional metallurgy. Electrochemical measurements are used for examining the effect of single and binary addition of chromium and zirconium metals on the corrosion resistance of pure copper in 0.01–1 M NaCl solutions. Significant reduction in the corrosion resistance is observed when chromium and zirconium are added simultaneously to copper instead of single addition of chromium or zirconium metals. Meanwhile, the results of cyclic voltammetry show that the element Cr plays an offsetting role to the Cu 2 O film while the element Zr plays a deteriorated role. Finally, the corrosion mechanism for element Cr and Zr is suggested.

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 S–N and Coffin–Manson plot, cyclic stress–strain response, changes of microstructure, and the surface morphology of ultra-fine grain (UFG) low-purity copper processed by ECAP were tested and observed in present study. And the formation mechanism of shear bands was discussed in detail. The results show that the UFG Cu represents longer lifetime under stress-controlled fatigue, but lower fatigue resistance under strain-controlled fatigue when compared with the coarse grain counterpart. Cyclic stress–strain responses of UFG Cu under stress-controlled fatigue alter from cyclic softening to cyclic hardening as stress amplitude decreases. But the responses always show cyclic softening under strain-controlled fatigue in present testing. By electron back scattering diffraction and transmission electron microscope technique, the shear bands were discovered on the surface of all cycled samples and no grain coarsening was discovered near the shear bands, which indicated that there was no inevitable relationship between formation of SBs and cyclic softening/grain coarsening. The discovery should be related to impurities in copper. The oriented distribution of defects along the shear plane in the last ECAP processing is one of the major mechanisms of SBs formation.

Photo-electrochemical measurement was used to explore the formation potential, formation time, chloride ions concentration, applied potential and pH value of the solution on the electronic property of passive film formed on X80 pipeline steel in 1 M NaHCO 3 /0.5 M Na 2 CO 3 buffer solution. The results showed that the photocurrent is positive, indicating an n-type semiconductor character of the passive film, the photocurrent increased with increasing the formation potential, prolonging the formation time, decreasing chloride ions concentration, rising applied potential and decreasing the pH value of the solution. Capacitance measurement exhibited a positive slope of Mott-Schottky plot, and the slopes of Mott-Schottky plots increased with the increasing formation potential, showing a decrement of the donor density of the passive film.

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 effect of discharge current on the synthesis of single-walled carbon nanotubes (SWCNTs) was studied under controlled atmosphere at 500 °C by electric arc discharge. It was shown that the production rate of collected soot was increased but the purity of SWCNTs decreased with increasing discharge current. With a current of 100 A, the SWCNT was very uniform in diameter and a high purity rate of 55% was achieved, as shown by TEM and Raman spectra. Then the influence of electric force, discharge current and catalyst distribution on the formation of SWCNTs was also discussed.

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 effect of oxygen on the growth of single-walled carbon nanotubes was studied with Ni–Co alloy powder as catalyst under helium atmosphere of 500 Torr by electric arc discharge. The oxygen included in nickel or (and) cobalt oxides was added in catalyst. The content of oxygen in atmosphere was controlled by changing vacuum degree inside furnace before inputting buffer gas. The examinations of TEM and Raman scattering showed that oxygen in metal oxide as catalyst promotes the nucleation of SWCNT by taking effect on the metal catalyst particles. However, O2 in atmosphere has the role of oxidizing amorphous particles along with nanotubes. When its molar proportion is higher than 0.22 ppm (Parts per million), the carbon nanotubes produced are oxidized and their purity decreases. The diameter of single-walled carbon nanotube obtained under different condition has a narrow distribution around 1.28 nm.

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.

A new low cobalt hydrogen storage electrode alloys La1 − xCaxNi3.2Co0.3Al0.3 (0 ≤ x ≤ 0.4) was developed. The microstructure and electrochemical properties were investigated and the results showed that the prepared alloys were basically composed of LaNi5 as matrix phase and LaNi3 as second phase (x ≤ 0.1). The second phase LaNi3 is substituted by a new phase Al(NiCo)3 gradually with increasing Ca content, and cycle stability is improved correspondingly. The highest discharge capacity can reach to 295 mAh g−1 (x = 0.2) and it can remain 82.5% (x = 0.2) after 300 charge/discharge cycles.

La 1.3 − x Sm x CaMg 0.7 Ni 9 ( x = 0–0.3) hydrogen storage alloys were prepared by inductive melting and the effect of the Sm content on the structure and electrochemical properties was investigated in the paper. The Sm substitution for La in La 1.3 − x Sm x CaMg 0.7 Ni 9 ( x = 0–0.3) alloys does not change the main phase structure (the rhombohedral PuNi 3 -type structure), but leads to a shrinkage of unit cell and a decrease of hydrogen storage capacity. With the increase of the Sm content in the alloys, the maximum discharge capacity of electrode decreases from 400.2 ( x = 0) to 346.6 mAh g −1 ( x = 0.3), but the high-rate dischargeability and cycling stability is improved. After 100 cycles, the capacity retention rate increases from 75 ( x = 0) to 85% ( x = 0.3).

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.

Large amounts of amorphous carbon nanotubes (ACNTs) were prepared with Co–Ni alloy powders as catalyst in hydrogen gas atmosphere by a modified arc discharging furnace which can control temperature during the electric arcing process. The experimental results indicate that the cooperative function of temperature and catalyst plays an important role in the soot production rate and the relative ACNT purity. When temperature increases from 25 °C to 700 °C, the soot production rate increases from around 1 g/h to 8 g/h, the best relative ACNT purity at 600 °C can reach up to 99% compared to the room temperature sample. Without catalyst, only plate graphite is formed at 25 °C and very few carbon nanotubes are found when temperature increases to 600 °C. TEM, SEM, HRTEM and XRD analysis showed that the as-prepared carbon nanotubes are almost amorphous. The soot production rate is 8 g/h and diameter range of amorphous carbon nanotubes is about 7–20 nm, respectively.

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.

Polyhedral graphite (PG) particles have been synthesized by DC arc vaporization of pure graphite in He and H 2 gases with a fan blowing across the arc zone. The crystal structure and character of PG particles have been investigated by transmission electron microscopy, X-ray powder diffraction, and Raman scattering spectroscopy. The PG particles produced by arc discharge, ranging in diameter from 70 to 300 nm, have a turbostratic structure and have no hollow cavities in their centers. The yield of PG particles is about 50%. The cooling rate increase of carbon vapor caused by the forced flow plays a significant role for PG formation.

Multi-walled carbon nanotubes (MWCNTs) were synthesized by hydrogen DC arc discharge at elevated environment temperature. The sample collected from the soot on the inner wall of the arc discharge furnace was investigated using TEM, HRTEM and X-ray diffraction. The results show that environment temperature has a significant effect on the formation of MWCNTs in the soot in hydrogen atmosphere as well as the diameter of the tubes. When environment temperature in the furnace is higher than about 500 °C, MWCNTs can be formed on the furnace walls with a great quantity.

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.