Fresh Alloy Research Articles

The Impact of Recasting on the Bond Strength of Metal Ceramic Restorations

Objective The objective of this study is to evaluate the effect of recasting of Nickel Chromium (Ni-Cr) alloy on the bond strength of metal-ceramic restoration. Materials and Methods Forty-five samples fabricated from one Ni-Cr alloy were divided into three groups. Group 1 consisted of 100% fresh alloy; Group 2 consisted of 50% fresh alloy mixed with 50% alloy taken from sprue and button remnants of group 1 and group 3 consisted of 50% new alloy mixed with 50% alloy taken from sprue and button remnants of group 2. All samples were then bonded to a ceramic material. The bond strength of the Metal-Ceramic was then assessed using a 3-point bending test. The failure mode was investigated under a stereomicroscope and confirmed under scanning electron microscopy (SEM). Results Group 1 (100% fresh alloy) showed the highest bond strength amongst the other groups, while the lowest was recorded for group 3 (50% fresh alloy with 50% cast twice alloy). According to the International Organization for Standardization (ISO), the bond strength of fresh alloy and the group casted once attained the required level. Conclusion The outcome of this study indicates that the use of 100% fresh Ni-Cr base metal alloy yields the highest bond strength of metal ceramic restoration.

Aging Effects in Zr(Fe0.5V0.5)2 Tritides

We report an experimental study on the tritiding capabilities over a long period of the intermetallic compound Zr(Fe0.5V0.5)2. The study was carried out with the prospect of using the alloy as a chemical converter to reduce HTO. Two identical getter beds, containing 1 gram of alloy in powder form each, were used in the experiments. While one of them was exploited to determine the tritium isotherms of the virgin alloy, the other bed was loaded at 75% of stoichiometry with 354 Ci of tritium and left to age for 1500 days. The bed was then unloaded and the isotherms of the aged alloy were determined twice to check the repeatability. The main results of the work are that, while enthalpy and entropy changes for tritium dissolution at infinite dilution are practically the same for the fresh alloy and the aged alloy, they vary significantly when the isotherms are determined on the aged alloy at a large enough distance of time (one week). This behavior is ascribed to the He3 present in the interstitial sites. However, the fact that the solubility of the alloy decreases with aging suggests that the He3 present either in the interstitial sites or in bubbles subtracts sites for dissolution. Also to be stressed is that in the tritide-forming region, these thermodynamic values decrease with aging in a monotonic way. This different behavior is tentatively explained by invoking the nature of the tritium bond.

Exploration of Sn70Li30 alloy as possible material for flowing liquid metal plasma facing components

• First wetting data for Sn 70 Li 30 alloy are reported on 316 SS, Mo and W substrates. • Wetting temperatures of 360 °C, 390 °C and 405 °C were measured respectively. • Alloy contamination/passivation worsened wettability with Δ T~130 °C in worst cases. • First depth profile characterization of the tin-lithium alloy by SIMS-ToF was carried out. • Mixing boundaries between alloy and substrates studied by SEM/EDS and 3D microscopy. • Lithium and tin induced corrosion found on 316 SS exposed at T < 550 °C during t ≤ 3 h. • Molybdenum and tungsten presented good compatibility after equivalent interaction. As an advanced alternative to solid materials, Liquid Metals (LM) may offer more resilient and feasible Plasma Facing Components (PFCs). Particularly, regarding the unavoidable material erosion/degradation produced by particle/heat fluxes in future fusion devices where much longer duty cycles are expected. Furthermore, configurations that propose a flowing LM surface can add the advantage of a continuously fresh and clean layer facing the plasma. Although lithium is the most widely tested option, tin-lithium (SnLi) alloys have been proposed to attempt to combine the positive characteristics of both pure elements and ameliorate the specific issues of lithium. In this work, the potential use of Sn 70 Li 30 alloy in such flowing concepts has been explored by addressing several preliminary and mandatory aspects for its utilization. Key issues such as wettability and compatibility of the alloy with relevant substrates have been studied in a multidisciplinary approach. The data obtained from deposited liquid tin-lithium droplets indicates approximate wetting temperatures of 360 °C, 390 °C and 405 °C for the fresh alloy on 316 stainless steel, molybdenum, and tungsten, respectively. However, the alloy contamination appeared to strongly affect the wetting characteristics of materials, increasing their wetting temperature by ~130 °C in the worst observed cases. Interestingly, in some instances, the instability of the liquid alloy surface was observed in the form of sudden gaseous ejection. The deposited droplets were posteriorly characterized in terms of absolute composition and depth profile by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Secondary Ion Mass Spectrometry (SIMS-ToF). Additionally, the nature and composition of the boundaries between the substrates and alloy microparticles was investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and 3D Laser microscopy. The overall results of this post-mortem characterization revealed that first signs of corrosion induced by both alloy elements (lithium-chromium association and iron-tin intermetallic mixing) were present on 316 stainless steel after short exposures (≤3 h) at temperatures lower than 550 °C. Conversely, molybdenum and tungsten showed good compatibility with the alloy in equivalent conditions. The global implications of these results are finally addressed, focusing on the future perspectives and the more viable scenarios for the eventual utilization of these alloys in flowing liquid metal configurations.

Development of Technological Parameters for Processing the Off-Grade Wastes of a VZhM4-VI Nickel Superalloy to Decrease the Carbon Content in Them

Experimental works are preformed to process the substandard wastes of a cast VZhM4-VI nickel superalloy, the carbon content of which exceeds the requirements of standards and does not allow their further use as a charge material. Some technological solutions have been tested, including high-temperature treatment of a melt (HTTM) at various temperatures and holding times, the use of an oxidizing agent in the form of nickel oxide, and their complex application. The efficiency of each of the proposed solutions in terms of the decarburization of the melt is considered, their kinetic dependences are established, and the advantages and disadvantages of each solution are noted. The results obtained demonstrate that the most effective technological solution is the combined use of HTTM and the oxidizing agent, which makes it possible to use a limited amount of the wastes after recycling in melting a VZhM4-VI alloy and provide significant savings in the scarce and expensive fresh alloy components such as ruthenium, rhenium, and tantalum.

ASSESSMENT OF PORCELAIN FUSED TO METAL BOND STRENGTH AFTER LASER SURFACE TREATMENT OF RECYCLED COBALT-CHROMIUM ALLOY

Recycling of casted alloys in dentistry is sometimes done to reduce price and minimizing environmental hazards. The current study assessed the use of laser surface treatment to enhance the shear bond strength between porcelain and Cobalt-Chromium alloy hindered by adding ratios of recasted alloy. Ninety disc-shaped samples were fabricated and assembled into six groups. Group A fabricated from fresh alloy without laser treatment (negative control), group B fresh alloy with surface treatment by laser (positive control), group C-75% fresh alloy mixed with 25% of once recasted alloy followed by laser treatment, group D-50% fresh alloy mixed with 50% of once recasted alloy followed by laser treatment, group E-75% fresh alloy mixed with 25% of twice recasted alloy and laser treated and group F-50% fresh alloy mixed with 50% of twice recasted alloy and laser treated. The results revealed non-significant values were calculated between group A (negative control group) and groups B, C, D, E and F with significance values (0.059, 0.612, 1.000, 0.922 and 0.845). Similarly, the difference between groups C, D, E and F showed non-significant values (0.479, 0.117 and 0.074). A significant difference at 0.05 level was seen between group B (positive control group) and group D, E and F with significance values (0.037, 0.003 and 0.002) respectively. Accordingly, laser surface treatment might be used as an effective surface treatment after adding recycled alloys to casting process in order to enhance bond strength with ceramic materials.

The effects of recasting on the cytotoxicity of dental base metal casting alloys.

Aim and Objectives:In dentistry, base metal casting alloys are extensively used for the fabrication of inlays, onlays, crowns, bridges, partial dentures, etc. During the casting of these alloys, excess amount of material used than needed will be collected as sprue buttons at the end, which is either added to the fresh alloy during casting and reused or disposed of.Materials and Methods:The aim of the present in vitro experimental study was to investigate the effect of the complete recasting of four commercially available cobalt-chromium (Co-Cr) and nickel-chromium (Ni-Cr) base metal casting alloys on their cytotoxicity. During the study, four groups of alloys were subjected to complete recasting up to twenty times without the addition of new alloy. The cytotoxicity assessment of the selected alloys after recasting (Co-Cr and Ni-Cr alloys) was carried out using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.Results:The results indicated that Co-Cr alloys exhibit superior cell viability compared to Ni-Cr alloys, and cytotoxic potential of the alloys increased with repeated casting and led to increased cell death. The recasting of alloys in the present study did not show high cytotoxicity even after the 20th recasting.Conclusion:From the results of the present study, it can be concluded that the alloys generated as a waste in the dental laboratory can be safely reused up to five times or at least once before they can be disposed, which reduces the cost of the treatment and also helps in conserving the natural resources.

Copper for the Pharaoh: Identifying multiple metal sources for Ramesses' workshops from bronze and crucible remains

The origin of copper used in Late Bronze Age (LBA) Egypt is very poorly understood despite its cultural and economic importance attested in archaeological and historical sources. Extensive literature discusses major LBA copper sources such as Cyprus (oxhide ingots), Oman (bun ingots) and Egyptian-controlled sites in the Sinai. This paper presents new chemical and lead isotope data for Egyptian copper alloys excavated in several bronze production workshops from the New Kingdom capital Pi-Ramesse, expanding on earlier data from Amarna. Supporting data is obtained from the analysis of crucible remains from the same context, for which the potential contribution of lead isotope analysis is critically evaluated.Diachronic changes in the provisioning of these Egyptian workshops are discussed, incorporating an extensive overview of currently known Egyptian mining and metallurgy. The results have major implications for our understanding of LBA copper circulation in the wider region, for the first time analysing a major Egyptian ‘consumer’ assemblage.The analytical results reveal a complex picture of variable copper supply to the Ramesside workshops, which involved both the recycling of existing bronzes and the use of freshly smelted copper from various origins to produce fresh alloys. Importantly, this includes crucial new evidence for the melting of (Cypriot) oxhide ingot fragments in crucibles for alloying.The royal, internationally connected nature of these workshops makes Pi-Ramesse an exceptional case study of LBA metal trade, and hypotheses raised in this paper highlight the need for more extensive analysis of ancient Egyptian copper artefacts to grasp metal circulation throughout Egypt's long history. More refined frameworks, incorporating the variety of private as well as royal contexts, will improve understanding of Egypt's ancient economic organisation. This paper offers new perspectives onto LBA metal supply and consumption networks, with broader archaeological interpretative models of economic and political interactions across the wider ancient Near East.

Poisoning effect of oxygen on hydrogenation performance of a Zr-V-Ni Laves phase alloy

Zr-based Laves phase alloys have been considered as suitable getter materials for hydrogen isotopes recovery, storage and delivery and received considerable attention during past decades. This work focuses on hydrogenation performance of a pseudo-binary Zr-V-Ni Laves phase alloy with the composition of Zr(V0.95Ni0.05)2 after pre-exposure in different contents of O2. It is found that introduced pure oxygen can be rapidly absorbed by the fully activated Zr(V0.95Ni0.05)2 alloy within 40 s. All of the experimental samples pre-exposed in oxygen consist dominant C15 type ZrV2 Laves phase and minor Zr3V3O oxides. With the further increase the oxygen pressure to 4.0 kPa in specimen chamber, Bragg peaks of Zr2V, V-rich BCC solid solution phase and ZrO2 phase, including baddeleyite (α-ZrO2) with monoclinic structure and a small amount of tazheranite (γ-ZrO2) with cubic structure are observed in addition to the dominant ZrV2 and minor Zr3V3O phases. Meanwhile, it can be seen that the lattice parameter of cubic C15 type ZrV2 calculated from Rietveld refinement increases from 7.402 to 7.432 Å with the increase of O2 content and the corresponding unit cell volume increases 0.86 vol.% as the O2 pressure from 1.0 to 4.0 kPa, which indicates more oxygen atoms have been dissolved into the lattice of ZrV2. All of the oxygen poisoned Zr(V0.95Ni0.05)2 alloys can absorb hydrogen and the capacity decreases from 3.39 to 2.22 H A−1 with the increase of oxygen pressure from 1.0 to 4.0 kPa, comparing with the maximum hydrogen storage capacity (4.34 H A−1) of the fully activated fresh alloy. The existence of oxygen is found to decrease both capacity and kinetics of Zr(V0.95Ni0.05)2 by forming passivation layer oxides which block the dissociation of H2 molecule on the surface.

Comparison of the metal-ceramic bond after recasting and after laser sintering

Statement of problemFailure of the bond between metal and ceramic is common with metal ceramic prostheses. PurposeThe purpose of this in vitro study was to investigate how recasting affects the metal-ceramic bond strength for 1 base metal and 1 noble alloy compared with laser-sintered Co-Cr alloy by using a procedure based on ANSI/ADA Specification No. 38. Material and methodsOne laser-sintered (Co-Cr) and 2 metal (Co-Cr, Pd-Ag) alloys were used. Metal strips (25×3×0.5 mm) were obtained with 2 different methods: torch melting and laser sintering. Twelve alloy specimens were processed for each group. Vita VM13 porcelain layers (8×3×1.1 mm) were fabricated at the centers of the metal frameworks. Specimens containing 100% fresh alloy were used in the first casting group (control). Metal ceramic specimens were prepared for each alloy, and no new metal was added to the second and third castings. The findings were statistically analyzed and compared with a 2-way analysis of variance (ANOVA). ResultsThe second casting of the noble alloy-ceramic specimen had the highest mean metal-ceramic bond strength in flexure. No significant differences were found between the laser-sintered Co-Cr and the Pd-Ag metal ceramic specimens after the first and third castings. ConclusionAll groups had adequate porcelain bond strength, except C2 (second casting of Co-Cr alloy) and C3 (third casting of Co-Cr alloy). Co-Cr alloy fabricated with new laser-sintering techniques is a promising alternative for metal ceramic restorations. Further research is needed before its use can be advocated in the dental laboratory.

Evaluation of the Bond Strength of Ceramic to Nickel- Chromium Alloy with various proportions of Recast Alloy - An Invitro Study.

Aim: The purpose of this study was to evaluate the bond strength and point of failure between ceramic and Nickel-Chromium alloys with various proportions of fresh and recast alloy. Materials and method: Fresh and once recast nickel-chromium alloy were used in various proportions and divided into 5 groups, group A, B, C, D, E with 100%, 75%, 50%, 25% and 0% of fresh alloy respectively with 10 specimens in each group. All the metal specimens were veneered with VMK 95 ceramic and were then subjected to three point bend test and SEM analysis. Results: The values were statistically analyzed using One-way ANOVA and Bonferroni test. One-way ANOVA analysis showed a statistically significant difference (p < 0.001) in metal ceramic bond strength which decreased as the percentage of once recast Nickel-Chromium alloy increased. There was no statistically significant differences between Groups A, B and C but Group D and E showed statistically significant differences when compared with group A. SEM analysis showed, majority of the failure occurred at the metal- ceramic interface. Conclusion: When more than 50% fresh alloy was used in the casting procedure, the bond strength was found to be superior to that when less than 50% of fresh alloy was used. Upto 50% of once recast alloy does not have significant effect on the metal-ceramic bond strength.

Inclusion measurements in Al–6Si alloys using liquid metal cleanliness analyser technique

The present study was undertaken to investigate the capability of the liquid metal cleanliness analyser (LiMCA) technique for measuring different types of inclusions in commercial pure aluminium and Al–6Si casting alloys. The main purpose of the study was to evaluate the technique in the case of casting alloys, where the inclusion levels are considerably higher than those found in wrought aluminium alloys for which the LiMCA has generally been used to date. The inclusion types studied included Al2O3, Al4C3, MgO, CaO, TiB2 and TiAl3, representing inclusions typically found in aluminium casting alloys. The inclusion additions were made using powder, master alloy, pure metal and metal matrix composite sources. In the case of powder inclusions, the inclusions were injected into the alloy melt using a powder injection technique to prepare inclusion containing ingots, which were subsequently used for inclusion addition to fresh alloy melts to conduct the LiMCA tests. Microstructural examination of solidified samples obtained from the LiMCA probe tube used for the measurements and from samplings of the melt was also carried out using optical microscopy and electron probe microanalysis.

Ceramometal Bond Strength Analysis using New and Recast Nonprecious Alloys with Three Different Ceramics

ABSTRACT Objectives This study is undertaken to evaluate the dependence of bond strength of 100% fresh nonprecious alloy and the combination of 50% recast (used) alloy and 50% fresh alloy with three different veneering ceramic material. Materials and methods To evaluate the shear bond strength between new and recast alloy nonprecious Ni-Cr alloy (System KN®, Adentatec, Germany) was used with three different commercially available ceramics. A total of 60 samples were prepared and divided in two groups depending on the new or recast alloy. The 30 specimens of new alloy (group A) and 30 specimens of recast alloy (group B) were fabricated. Each group was again divided into three subgroups of 10 specimens for ceramic veneering Vita VMK-95 [V], IPS Classic [I] and Noritake [N] as veneering ceramic materials. Thus, six subgroups were formed as groups AV, AI, AN, BV, BI and BN. Groups AV and BV were veneered with Vita Ceramics, Groups AI and BI were veneered with IPS Classic (Ivoclar) and Groups AN and BN were veneered with Noritake. Then, shear bond strength between new and recast alloy was analyzed for each type of ceramics using MTS machine. Results The bond strength between new [group A] and recast alloy [group B] using three different veneering ceramics were evaluated. It was found that the new or the fresh alloy had highest shear bond strength than the recast alloy. Statistically, it was found that there was significant difference in bond strength between the new and recast alloys, when same type of ceramics was compared. When comparing ceramics, the Noritake group had highest bond strength, while other groups, that is, Vita and Ivoclar had comparatively low bond strength. Conclusion From this study, conclusion can be drawn that the use of 50% recast alloy shows reduction in bond strength values. Therefore, the use of recast alloy should not exceed more than 50%, as it would compromise the properties of alloy and the efficacy of bond strength between ceramic and alloy. How to cite this article Gosavi S, Wadkar A, Gosavi SY. Ceramometal Bond Strength Analysis using New and Recast Nonprecious Alloys with Three Different Ceramics. Int J Prosthodont Restor Dent 2013;3(1):14-20.

Evaluation of Tensile Strength and Microhardness of Two Nickel- Chromium Based Casting Alloys with the Addition of Different Ratios Recasted Alloy Using Oxyacetylene Flame Casting Techniques

The objective of this study is to evaluate the tensile strength and microhardness of Ni-Cr alloy by adding two different ratios of recasted alloy (25%,50%)and one controlled group (100%fresh alloy),some technicians in our country modifies the casting of Ni-Cr alloy by adding recasted alloy because of high cost of Ni-Cr and low economical state.&#x0D; We use two different trade mark of Ni-Cr alloy (wiron99 and maxwhiteness).According to ANSI/ADA Specification No. 14 (ISO 6871); 30 specimens were made for tensile testing for each alloy type. Another 30 specimens were made for micro-hardness testing which they were square in shape (6mm for each arm and 1mm thickness). ,after statistical analysis it was found that there were no significant differences between each sub-group for the same alloy type for tensile and micro-hardness testing specimens. Although there were a great significant differences between each alloy type.

Recycled Applications of a Single Crystal Superalloy

The effects of application of recycled scraps on the composition, microstructure and mechanical properties of SRR99 alloy were studied. The compositions of recycle master alloy are similar to that of the fresh alloy. However, nitrogen content, the size and amount of microporosity increase significantly with the recycle material proportion. Granular, lamellar and strip-like MC particles mainly represent in the interdendritic regions of the revert alloy. With the addition of the recycled material proportion, the amount of the granular ones rapidly drop and the lamellar ones gently enhance. The stress rupture life decline with the addition of the recycled material proportion. The oxide and sulphide inclusions in revert superalloy can be effectively captured and removed by a foam ceramic filter so that the tensile and stress rupture property has been significantly improved.

Metal Ceramic Bond After Multiple Castings of Base Metal Alloy

Remelting previously cast metal can produce a critical change in metal-oxide composition at the dental alloy surface. The purpose of this study was to evaluate the effect of multiple castings on bonding of a single selected base metal and a dental ceramic, and to compare results from shear bond and 3-point-bending tests. Three groups of dental alloy (Remanium CSe) were prepared by mixing 50% fresh alloy to alloy remnants from previous castings. The specimens in the first casting group used 100% fresh alloy and served as control (C0). The second group consisted of equal amounts of fresh alloy and alloy remnants cast only once (C1). The third and fourth groups contained 50% fresh alloy and alloy cast twice (C2) and 3 times (C3), respectively. The bond load (N) between alloy and dental porcelain (VMK 95 Metal Ceramic) was evaluated, using shear bond and 3-point bending tests. The fracture surfaces of the specimens subjected to testing were analyzed using a stereomicroscope and scanning electron microscope. One-way ANOVA followed by the Tukey multiple comparison test was used for analysis of bond data (alpha=.01). The mean shear bond load (SD) of C0 (738.0 (77.1) N) was significantly higher than that of C1 (577.8(139.4) N), C2 (494.8 (77.6) N), and C3 (480.5 (60.9) N). Mean peak load for the 3-point-bending test of specimens cast from C0 (39.8 (1.79) N) was significantly higher than for other groups (P<.01). No significant difference was found between C1 (24.4 (5.60) N), C2 (23.2 (4.03) N), and C3 (22.8 (1.79) N) in terms of the shear bond test and the 3-point bending test. In general, there was agreement between the 2 bond strength tests to indicate that including re cast base alloy with fresh alloy for metal decreases metal-to-ceramic bond strengths. (J Prosthet Dent 2009;102:165-171)

A New Model to Predict the Oxidation Kinetics of Zirconium Alloys in a Pressurized Water Reactor

Abstract The previous CEA corrosion code COCHISE provided satisfactory simulations of in-reactor corrosion of the fuel cladding when used in its validity range. In contrast, it could lead to hazardous predictions if applied out of this range due to the strongly linked parameters mainly based on the analysis of French pressurized water reactor (PWR) data. To predict the oxidation kinetics for new operating conditions or new materials, the CEA and EDF decided to develop a new model, named CORCY, which is based on a more phenomenological approach and uses separate parameters deduced from analytical experiments. The aim of this paper is to present the new model for Zircaloy-4 in PWR. The phenomenological approach is described. It is based on out- and in-pile data. Typically, since (1) the oxidation kinetics of zirconium alloys in autoclave are periodic, and (2) the oxide films formed in autoclave, in out-of-pile loop, and in-reactor all exhibit periodic lateral cracks with a period similar to the oxide thickness to transition, the oxidation kinetics in CORCY are characterized by a cyclic repetition of semi-parabolic law. Each model parameter is detailed. They are deduced separately from (a) oxidation tests performed in autoclave on fresh alloys to determine their kinetics; (b) oxidation tests performed in the out-of-pile corrosion loops Corail and Reggae to quantify the effects of thermo-hydraulic conditions; (c) data provided by Testing Material Reactors (OSIRIS and Halden reactor) during isothermal oxidation to determine the effects of irradiation; and (d) oxidation tests performed on pre-hydrided alloys to take into account the accelerated corrosion phase occurring, in reactor, for Zircaloy-4 at high burn-up. After describing both the phenomenological approach and the different model parameters, a comparison of measured and calculated corrosion data from French PWRs at a burn-up up to 65 GWd/tU is provided.

Evaluation of variations in composition, corrosion behavior and surface hardness on reusing a Co-Cr-Mo denture alloy

We evaluated the variations in the surface composition, corrosion resistance and surface hardness of cobalt-chromium-molybdenum (Co-Cr-Mo) removable partial denture alloy on repeated usage until six generations by adding 50% of weight of fresh alloy pellets to the left-over button and sprue in the previous generation. Corrosion testing was performed with WenkingLB81M potentiostat to evaluate the anodic polarization behavior of the specimens from artificial saliva at room temperature. The breakdown potential for each generation was determined. Scanning electron microscope (SEM) evaluation of the corroded and uncorroded specimens was performed. Vickers hardness number (VHN) was evaluated using Zwick3212 micro hardness indenter with values ranging from 317 to 329 VHN. Surface composition of the corroded and uncorroded specimens was analyzed using X-ray energy dispersive analysis. The Mann Whitney U-test was used to analyze the numerical findings. The breakdown potential values for all six generations were recorded in between + 480 mV and + 500 mV. The hardness and composition showed variations among generations but were statistically insignificant. On the corroded surface, an increase in the Cr and Mo content and decrease in the Co content was observed. SEM photographs show a definite alteration in the surface topography at the corroded site. Within limitations, it was concluded that this alloy could be reused by adding 50% (by weight) of new alloy pellets without significant variation in the abovementioned properties.

Cycling stability of La-Mg-Ni-Co type hydride electrode with Al

The mechanism of the improvement of the cycling stability of the La-Mg-Ni-Co based hydrogen storage alloy electrode was systematically investigated. The results show that the cell volume expansion upon hydrogenation is obviously decreased after the partial substitution of Al for Ni. Therefore a decrease in the pulverization of the alloy particles is obtained, which leads to the decrease of the contact area of the fresh alloy surface with alkaline electrolyte and the increase of the charge/discharge efficiency. Moreover, the occurrence of Al in the alloy can create a dense Al oxide film on the surface of the alloy during charge/discharge cycling. This dense oxide film can prevent further oxidation of the active components in the alloy, which is believed to be the most important factor responsible for the improvement of the cycling stability of the La-Mg-Ni-Mn-Co-Al type alloy electrodes.

Cycling stability of La-Mg-Ni-Co type hydride electrode with Al

Abstract The mechanism of the improvement of the cycling stability of the La-Mg-Ni-Co based hydrogen storage alloy electrode was systematically investigated. The results show that the cell volume expansion upon hydrogenation is obviously decreased after the partial substitution of Al for Ni. Therefore a decrease in the pulverization of the alloy particles is obtained, which leads to the decrease of the contact area of the fresh alloy surface with alkaline electrolyte and the increase of the charge/discharge efficiency. Moreover, the occurrence of Al in the alloy can create a dense Al oxide film on the surface of the alloy during charge/discharge cycling. This dense oxide film can prevent further oxidation of the active components in the alloy, which is believed to be the most important factor responsible for the improvement of the cycling stability of the La-Mg-Ni-Mn-Co-Al type alloy electrodes.

Cycling durability and degradation behavior of La–Mg–Ni–Co-type metal hydride electrodes

The cycling durability and degradation behavior of the La–Mg–Ni-based hydrogen storage alloys La 0.7Mg 0.3Ni 3.4− x Co x Mn 0.1 ( x = 0, 0.75, 1.3) during charge/discharge cycling has been systematically studied by XRD, SEM, EIS, XPS and AES measurements. The reasons for the improvement of the cycling stability of the alloy electrodes with increasing Co content have also been analyzed and discussed. The results show that the pulverization of the alloy particles and the oxidation/corrosion of the active components of the alloys during charge/discharge cycling in the alkaline electrolyte are the two main factors responsible for the fast capacity degradation of the La–Mg–Ni-based alloy electrodes, and the capacity degradation mechanism can be decomposed into three consequent stages, i.e., the pulverization and Mg oxidation stage, the Mg and La oxidation stage and the oxidation and passivation stage. With the increase in Co content, the cell volume expansion ratio Δ V/ V of the two main phases during hydrogenation/dehydrogenation was obviously decreased, which results in a reduction of the pulverization of the alloy particles and, consequently, in an increase in the charge and discharge efficiency and a decrease in the rate of contact of the fresh alloy surface with alkaline electrolyte and a subsequent lower rate of oxidation/corrosion. It is believed to be the most important reason responsible for the improvement of the cycling stability of the alloy electrodes with increasing Co content.