Introduction Of Zr Research Articles

Formation of structural-phase state of Ti–Al materials with Zr-additives obtained by hydride technology

The structural and phase composition of TiZr50, AlZr50, TiAl49Zr2 composite materials obtained by the hydride technology was investigated. A model three-component phase diagram was constructed for Ti–Al–Zr at a temperature of 1150°C. The structural state of TiAl49Zr2 alloys was predicted based on reference lattices (USPEX code with VASP interface), quantum-chemical calculations of the energy of TiAl49Zr2 were carried out in the CASTEP code. Solid solutions dominate in TiAl49Zr2, in the composition of which the main elements are predominant: Al10–Ti9Al23–Ti8. Zr atoms can be introduced into the interstitial sites [– 0.257 0.042 0.2545] (St–Zr–27), [0.0053–0.0120–0.0765] (St–Zr–143), [–0.3251–0.3983 0.4880] (St–Zr– 75). The introduction of Zr into the specified lattice sites does not violate the stabilizing effect in the TiAl49Zr2 systems. All reference lattices are stable. In the TiAl49Zr2 alloy, the main phases are Al10Ti9Zr, Al23Ti8Zr, the contributions of which to the theoretical intensity are 78.57 and 21.43%. In the AlZr50 sample, the phases ZrAl, Zr2Al3, ZrAl2.

Preparation of a novel high-entropy alloy AlNbTiVZr with excellent strength and ductility: The effect of Zr composition on microstructure and properties

Light-weight refractory high-entropy alloys with low density and good ductility are widely used in various engineering fields. Despite their potential, achieving an optimal strength-ductility balance in these lightweight alloys remains an emerging field of study. In this study, Al0.8Nb0.5Ti2V2Zrx (x = 0, 0.3, 0.6, and 0.9) alloys were prepared by vacuum arc melting. A comprehensive evaluation of their microstructure, density, hardness, and compressive behavior at both room and 873 K temperatures was conducted. The introduction of Zr transforms the alloy phase structure from body-centered cubic (BCC) to BCC + C14-Laves. The areal fraction of the C14-Laves phase increased from 0 % to 32.47 % with increasing Zr content from x = 0 to 0.9, respectively. Furthermore, the Zr content had an obvious effect on the mechanical properties of the alloys. The compressive strength and hardness of the alloys improved, but the ductility simultaneously decreased, with increasing Zr content. The yield strengths of the alloys with x = 0, 0.3, 0.6, and 0.9 reached 971, 1216, 1483, and 1714 MPa, respectively, at room temperature, and 946, 1287, 1319, and 1469 MPa, respectively, at 873 K. In addition, the alloys maintained their deformation resistance and good ductility at 873 K. In particular, the Al0.8Nb0.5Ti2V2Zr0.3 exhibited a good balance between strength and ductility at room and 873 K temperatures due to the strengthening effect of a granular secondary phase. Upon comparison with other reported high-entropy alloys, the Al0.8Nb0.5Ti2V2Zrx series showcased superior specific yield strength and ductility.

Unveiling the influence of zirconium on the corrosion behavior of Fe-36Ni Invar alloy

The influence of zirconium (Zr) on the corrosion resistance of Fe-36Ni Invar alloy in a 3.5 wt% NaCl solution was systematically investigated. Results indicated that adding Zr promoted the formation of Zr-bearing intermetallic compounds (Ni7Zr2 and Ni2Zr). The phases suppressed the grain growth and numerous dislocations were enriched around the Ni-Zr phases. Unfortunately, the incorporation of Zr into Fe-36Ni Invar alloy impaired corrosion resistance. The marked disparity in Volta potential between the Ni-Zr phases and the matrix signified the existence of micro-galvanic coupling, which caused the matrix to dissolve preferentially. Furthermore, the matrix around the Ni-Zr phases possessed high dislocation density, promoting the emergence of local galvanic corrosion. The introduction of Zr also decreased the protectiveness of the passive film, which was ascribed to the reduction of the thickness of the passive film and the beneficial oxide content in the passive film.

Hydrophilicity modification of polyphenylene sulfide: A comparative study on the introduction of Zr by physical blending and copolymerization

Polyphenylene sulfide (PPS) is widely used in auto components, machinery parts, electrical accessories, and anti-corrosion coatings, but its hydrophobicity restricts its application in biomaterials, medical equipment, battery separators, and oil pollution separation membranes. To improve the hydrophilicity of PPS, zirconium oxynitrate reacted with 3,5-dichlorosalicylic acid (SA) to generate zirconium-carboxylate (ZrSA). ZrSA was then incorporated into the main chain of PPS through copolymerization to yield hydrophilic copolymers (ZrSA-PPS). Meanwhile, SA was copolymerized into the main chain of the PPS to produce SA-PPS. Next, SA-PPS and ZrO2 were physically blended to obtain hydrophilic composites (ZrO2/SA-PPS). The melting point of ZrSA-PPS ranged from 278.19 to 281.16 °C, which was slightly higher than that of ZrO2/SA-PPS (278.39–279.95 °C), but its crystallinity (34.3–41.2 %) was lower than that of ZrO2/SA-PPS (42.2–51.6 %). The maximum decomposition temperatures of ZrSA-PPS and ZrO2/SA-PPS were increased by about 10 °C, indicating that the Zr–O bonds obstruct the thermally induced movements of the molecular chain. The ZrSA-PPS possessed a tensile strength of 40.8–70.5 MPa and a flexural strength of 46.4–103.4 MPa. The tensile and flexural strengths of ZrO2/SA-PPS (14.6–65.1 Mpa and 23.1–100.3 Mpa) were significantly inferior to that of ZrSA-PPS. This revealed that the ZrSA cross-linked structure can prevent crack propagation. The water contact angle of ZrSA-PPS and ZrO2/SA-PPS were ranged from 59.0° to 76.5° and 61.6°–78.5° (Neat-PPS, ∼87.9°), respectively. The agglomeration of ZrO2 resulted in a slightly higher water contact angle for ZrO2/SA-PPS than for ZrSA-PPS. The enhanced hydrophilicity of ZrSA-PPS benefited from the formation of large chain spacing, strong polar groups, and hydrogen bonds. Our study may shed light on the hydrophilic modification of PPS, which should offer a valuable guide and option for PPS in hydrophilic applications.

Research and selection of catalysts for the process of alkylation of oil fractions with catalytic cracking gases

The article presents the results of the study and use of modified zeolite-containing catalysts (ZSM-5) and natural alumosilicates (halloisite) in the process of alkylation of distillate fraction with catalytic cracking gases. Based on thermogravimetric analysis, it was determined that modification of halloisite with the Al+CCl4 system leads to the appearance of peaks indicating exo- and endo processes under the influence of temperature. When the oil fraction was alkylated at a temperature of 50 oC on Al+CCl4+halloisite catalyst with catalytic cracking gases containing olefins of 43.47 % the viscosity index was increased from 32 to 84. Based on NMR spectra, it was determined that alkylates differ from the original oil fraction by increased values isoparaffin index, the number of protons in aromatic structures and those furthes from the aromatic nucleus. These data confirm the improvement in the viscosity temperature characteristics of the oil fraction. Alkylation of an oil fraction with a viscosity index of 49.9 on ZSM-5 and ZSM-5-ZrO2 catalysts made it possible to obtain oils with a viscosity index of 80.7 and 137, respectively. Based on X-ray diffraction studies using rentgenographic method, it was shown that Zr is contained in the structure of ZSM-5 zeolite in the form of ZrO2. The introduction of Zr into the crystaline structure of the zeolite helps to increase the activity of the modified catalyst ZSM-5-ZrO2. Research has shown that the phase composition of samples of the modified ZSM-5-ZrO2 zeolite changes depending on the calcination temperature. An increase in temperature from 200 to 550 oC leads to the transition of the amorphous phase to the crystalline phase, and at a given calcination temperature a phase belonging to ZrO2 appears. The introduction of Zr into the catalyst composition leads to a change in the ratio of the Lewis and Brensted acid sites of the ZSM-5 catalyst. Namely, there is an increased Lewis and a decreased Brensted acid sites. Based on this it can be assumed that both Brensted and Lewis acid sites take part in the alkylation process.

Single-atom Zr-doped CoOOH with enhanced electrical conductivity as a signal amplifier and detection probe for the indirect non-enzymatic electrochemical determination of malathion in foods

Herein, a novel electrochemical sensor based on zirconium-doped cobalt oxyhydroxide (ZrCoOOH) was proposed for highly sensitive non-enzymatic determination of malathion (MAL). The doping of Zr can improve the electrical conductivity of CoOOH, of which the transfer resistance was reduced from 241.1 Ω to 140.2 Ω. Furthermore, the X-ray photoelectron spectroscopy confirmed that part of Co2+ was converted to Co3+ due to the introduction of Zr. The Co3+ in ZrCoOOH could react with MAL to form Co2+, which enhanced the electrooxidation current of Co2+. Therefore, the peak current of Co2+ was served as detection probe for MAL. Under optimal conditions, the developed sensor established the linear relationship for MAL in the concentration range of 0.001–10.0 μM with a low limit of detection (0.64 nM). The constructed sensor was employed to detect MAL in food samples (peach, kiwi fruit, spinach and tomato), verifying the accuracy and practicability of the sensor.

Zirconium doping facilitates a vertically aligned NiCoZr-layered hydroxide nanoneedle arrays electrode for hybrid supercapacitors exhibiting a 90,000 cycle durability

LDHs (Layered Double Hydroxides) are a kind of promising cathode material for high-performance hybrid supercapacitor. Nevertheless, it suffers quick capacitance decay after only thousands of cycles, which greatly prevents it from further application. In this contribution, zirconium (Zr) is introduced to the host layer of NiCo-LDH via a simple one-pot hydrothermal process. Owing to the strong bonding energy of ZrO (760 kJ mol−1) and special electronic structure (fully empty 4d orbits), the doped Zr could not only act as a structural stabilized element, but also change the mechanism of the energy storage process to alleviate the Jahn-Teller distortion of NiCo-LDH. Moreover, the introduction of Zr boosts an orderly growth of the LDHs, changing from disorder stack structure to vertically aligned nanoneedle arrays, which improve their structural stability. By controlling a varying level of Zr content, the electrode NiCoZr-LDH@CC with a Zr content ratio of 6.4 % delivers the best comprehensive electrochemical performance with a specific capacitance of 1758 F g−1 and good rate performance (73 % capacitance retention at 10 A g−1). The assembled asymmetric supercapacitor shows a highest energy density of 42.3 Wh kg−1 at 504 W kg−1 and an ultralong cycling lifespan beyond 90,000 cycles with a 97 % capacitance retention. The results exhibit the great potential of NiCoZr-LDH as a qualified candidate for high-performance hybrid supercapacitors.

Design, structural, and electrical conduction behavior of Zr-modified BaTiO3-BiFeO3 perovskite ceramics

This study employs the solid-state reaction method to synthesize [(Ba0.7 Bi0.3) (Ti0.7-y Zry) Fe0.3] O3 (y = 0.0, 0.2, 0.3, 0.4, 0.6) for investigating their structural and DC conduction behavior. XRD analysis suggests a perovskite phase for all the compositions having a cubic crystal structure. Initially, average crystallite size increases for y ≥ 0.3 and then decreases for y = 0.4. The temperature-dependent DC electrical conductivity demonstrated the semiconducting nature for all the compositions. The introduction of Zr modifies the material’s structure and electrical properties evident in the observed variations in crystallite size and conductivity behavior. These findings contribute to the understanding of Zr-modified [(Ba0.7 Bi0.3) (Ti0.7-y Zry) Fe0.3] O3 ceramics, shedding light on their potential applications in semiconductor devices and solid-state electronics. The investigation underscores the importance of tailoring composition parameters for fine-tuning material characteristics, opening avenues for optimized utilization in electronic and energy-related technologies

Electrochemical corrosion behavior of spinel-like high-entropy oxide (CrMnFeCoNi)3O4 and (CrMnFeCoZr)3O4/epoxy coatings

High entropy oxides (HEOs) are considered as an advanced materials having excellent properties like corrosion resistance, high hardness and wear resistance for a wide range of applications. In this study, coatings with two different types of high entropy oxides as epoxy fillers: (CrMnFeCoNi)3O4/EP and (CrMnFeCoZr)3O4/EP coatings were prepared and electrochemically tested for their corrosion resistance. Tests conducted in 3.5 wt% NaCl solution showed that the (CrMnFeCoNi)3O4/EP coatings exhibited better corrosion stability compared to the (CrMnFeCoNi)3O4/EP coatings. This is due to the fact that the introduction of Zr can significantly refine the grain and change the grain structure to a reticulated type, enhancing the corrosion resistance of the coating.

Influence of Zr Microalloying on the Microstructure and Room-/High-Temperature Mechanical Properties of an Al-Cu-Mn-Fe Alloy.

Here, 0.3 wt.%Zr was introduced in an Al-4 wt.%Cu-0.5 wt.%Mn-0.1 wt.%Fe alloy to investigate its influence on the microstructure and mechanical properties of the alloy. The microstructures of both as-cast and T6-treated Al-Cu-Mn-Fe (ACMF) and Al-Cu-Mn-Fe-Zr (ACMFZ) alloys were analyzed. The intermetallic compounds formed through the casting procedure include Al2Cu and Al7Cu2Fe, and the Al2Cu phase dissolves into the matrix and re-precipitates as θ' phase during the T6 process. The introduction of Zr results in the precipitation of L12-Al3Zr nanometric precipitates after T6, while the θ' precipitates in ACMFZ alloy are much finer than those in ACMF alloy. The L12-Al3Zr precipitates were found coherently located with θ', which was assumed beneficial for stabilizing the θ' precipitates during the high-temperature tensile process. The tensile properties of ACMF and ACMFZ alloys at room temperature and elevated temperatures (200, 300, and 400 °C) were tested. Especially, the yield strength of ACMFZ alloys can reach 128 MPa and 65 MPa at 300 °C and 400 °C, respectively, which are 31% and 33% higher than those of ACMF alloys. The strengthening mechanisms of grain size, L12-Al3Zr, and θ' precipitates on the tensile properties were discussed. This work may be referred to for designing Al-Cu alloys for application in high-temperature fields.

Boosting the power density of Zr and Ni co-doped BaFeO3 cathode for proton-conducing solid oxide fuel cells

A novel cathode material, denoted as BaZr0.26Fe0.64Ni0.1O3-δ (BZFN010), has been suggested for application in proton-conducting solid oxide fuel cells (H-SOFCs), aiming to enhance electrochemical performance. The introduction of Zr into the original BaFeO3-δ (BFO) results in improved chemical stability against CO2. However, despite this enhancement, the electrochemical performance remains unsatisfactory. Hence, we leveraged the outstanding stability of BZF and incorporated Ni, a well-known element renowned for its remarkable catalytic qualities, into the cell to augment its properties. This enhancement is substantiated by a combination of experimental and theoretical calculations. When employed as a cathode, the BZFN010 material exhibited markedly superior performance compared to the BaZr0.36Fe0.54O3 (BZF36) cathode. It demonstrated a 57% increase in power density, rising from 998 mW cm-2 to 1570 mW cm-2 at 700 °C. This study employs a chained-style cathode exploration strategy, commencing with the conventional BFO cathode, progressing to the enhanced stability of BZF36, and culminating in the optimized catalytic activity of BZFN010. Our work represents an intriguing strategy for the design of H-SOFC cathodes.

Selective hydrogenation of furfural to tetrahydrofurfuryl alcohol in isopropanol over hydrotalcite-derived nickel-based catalyst

A series of hydrotalcite-derived nickel-based catalysts were synthesized by coprecipitation, drying, calcination and reduction, and used for the selective hydrogenation of furfural to tetrahydrofurfuryl alcohol. Ni1Zr1Al2-R, with specific surface area (SBET) of 145.6 m2, narrow pore size distribution of 7.1 nm, and small Ni0 particle size of 7.31 nm, showed 100 % furfural conversion and 94.5 % tetrahydrofurfuryl alcohol selectivity under mild conditions (140 °C, 2 h). It was found that furfural was first hydrogenated to furfuryl alcohol, which was further hydrogenated to tetrahydrofurfuryl alcohol. XRD and TEM showed that Ni0 (111) plane played an important role on the catalytic hydrogenation process. Al increased the specific surface area (SBET) and total acid sites of the catalyst, providing more possibilities for the catalyst to contact the substrate. The introduction of Zr improved the ratio of medium acid sites and decreased the size of metal nickel particles, improving the resistance to carbon deposition and allowing the structure and catalytic performance to remain stable after five recycles.

Enhanced thermal-mechanical properties of rolled tungsten bulk material reinforced by in situ nanosized Y–Zr–O particles

Tungsten is the most promising plasma facing material for fusion reactors. Rolled W–Y2(Zr)O3 bulk material has been successfully produced in this study for future fusion engineering applications. The introduction of Zr is conducive to the refinement of the second phase particles. Nano-sized Y–Zr–O particles are observed in the powder and bulk samples. Related results show that the Y–Zr–O particle dispersion distribution improves the heat load resistance of W–Y2(Zr)O3 composite material. For four-point bend experiments in the same sampling direction, the DBTT of W–Y2(Zr)O3 composite materials is lower compared to the pure tungsten. For the same material, the DBTT of the material was selected for testing along the RD direction is lower compared to the material was selected for testing along the TD direction. Findings of this study provide suggestions for the subsequent industrial preparation of nanoscale particle-doped tungsten materials.

Highly efficient and stable Ni-based catalyst for selective conversion of biomass-derived aldehydes and ketones to primary amines

Here We report a yolk-shell structured Zr-assisted Ni-based catalyst, which could catalyze the reductive amination of a variety of biomass-derived aldehydes and ketones with high activity and robust stability. The novel LDH-derived Zr assisted-NiAl catalyst exhibits superior stability (>200 h) than traditional supported Ni/Al2O3 catalyst (<75 h) due to strong interaction between Ni0 yolk and NiAl2O4 shell. Outstanding yield of fufurylamine at 99 % is achieved under mild conditions at low temperature of 70 °C with 1 MPa H2. Other aldehydes and ketones are also transformed into primary amines with high yield above 90 % generally under mild conditions. Our study reveals that strong acidity favors the activation of imines, while strengthened hydrogen activation capability of catalyst promotes the dissociation of intermediate secondary amine to primary amine. The appropriate hydrogen activation capability regulated by Zr introduction into LDH-derived NiAl catalyst avoids over-hydrogenation of furyl-, hydroxyl- and imide-groups, which accounts for the high selectivity of mono-primary amine. Importantly, the dependence of mono-primary amine production on appropriate hydrogen activation capability of catalyst proved by this work provides ideas for tailored catalysts in the production of renewable primary amines from biomass.

Design of high-temperature superconductors at moderate pressures by alloying AlH3 or GaH3

Since the discovery of hydride superconductors, a significant challenge has been to reduce the pressure required for their stabilization. In this context, we propose that alloying could be an effective strategy to achieve this. We focus on a series of alloyed hydrides with the AMH6 composition, which can be made via alloying A15 AH3 (A = Al or Ga) with M (M = a group ⅢB or IVB metal), and study their behavior under pressure. Seven of them are predicted to maintain the A15-type structure, similar to AH3 under pressure, providing a platform for studying the effects of alloying on the stability and superconductivity of AH3. Among these, the A15-type phases of AlZrH6 and AlHfH6 are found to be thermodynamically stable in the pressure ranges of 40–150 and 30–181 GPa, respectively. Furthermore, they remain dynamically stable at even lower pressures, as low as 13 GPa for AlZrH6 and 6 GPa for AlHfH6. These pressures are significantly lower than that required for stabilizing A15 AlH3. Additionally, the introduction of Zr or Hf increases the electronic density of states at the Fermi level compared with AlH3. This enhancement leads to higher critical temperatures (Tc) of 75 and 76 K for AlZrH6 and AlHfH6 at 20 and 10 GPa, respectively. In the case of GaMH6 alloys, where M represents Sc, Ti, Zr, or Hf, these metals reinforce the stability of the A15-type structure and reduce the lowest thermodynamically stable pressure for GaH3 from 160 GPa to 116, 95, 80, and 85 GPa, respectively. Particularly noteworthy are the A15-type GaMH6 alloys, which remain dynamically stable at low pressures of 97, 28, 5, and 6 GPa, simultaneously exhibiting high Tc of 88, 39, 70, and 49 K at 100, 35, 10, and 10 GPa, respectively. Overall, these findings enrich the family of A15-type superconductors and provide insights for the future exploration of high-temperature hydride superconductors that can be stabilized at lower pressures.

ZrO2 modification of homogeneous nitrogen-doped oxide MgTa2O6−xNx for promoted photocatalytic water splitting

Homogeneous nitrogen-doped oxides are of wide visible light utilization for promising photocatalytic water splitting to produce hydrogen, but currently the poor charge separation severely limits their photocatalytic performances. In this work, a homogeneous nitrogen-doped tunneled oxide of MgTa2O6−xNx with an absorption edge of 570 nm was selected as a prototype to investigate the influence of ZrO2 modification on the charge separation as well as photocatalytic performance. It is interesting to observe that the formation of the reduced tantalum species, regarded as recombination centers, in the MgTa2O6−xNx sample could be effectively inhibited via the surface passivation with ZrO2 nanoparticles, based on which the photocatalytic water reduction and oxidation half-reaction activities could be remarkably promoted. Together with modification of the deposited Pt cocatalyst, the optimized H2 evolution rate over Pt-ZrO2/MgTa2O6−xNx (Zr/Ta = 0.10) photocatalyst was almost 4.5 times as high as that of the pristine Pt-MgTa2O6−xNx sample free of ZrO2 modification, whose apparent quantum yield at 420 nm (± 15 nm) achieved herein was superior to those of other reported homogeneous nitrogen-doped photocatalysts. The improved charge separation probably attributes to the introduction of Zr–O–Ta bond after ZrO2 modification, which is helpful to stabilize the tantalum species at more cationic state and inhibit the formation of the reduced tantalum species. This work extends the application territory of ZrO2 modification to the homogeneous nitrogen-doped oxide photocatalysts, and demonstrates its feasibility and effectiveness for remarkably enhanced photocatalytic water splitting performance.

Role of oxygen transfer and surface reaction in catalytic performance of VOx-Ce1–xZrxO2 for propane dehydrogenation

The bulk oxygen transfer and surface reaction as important parts of the chemical looping-related process are crucial for the rational design of new redox catalysts. This paper describes an experimental study on the effect of bulk oxygen transfer and surface reaction in Ce1–xxO2 supported VOx redox catalysts for the chemical looping oxidative propane dehydrogenation reaction. It was found that the introduction of Zr dictates the reaction performance of the redox catalyst by modulating the bulk oxygen transfer and surface reaction. The kinetic study reveals that the instantaneous reduction rate of the redox catalysts is determined by the H-abstraction step in the surface reaction. The introduction of Zr can reduce the activation energy of the H-abstraction step, which leads to the enhancement of the instantaneous reduction rate. Meanwhile, the oxygen supply capacity of the cerium oxide is increased by Zr, allowing the surface reaction to proceed over longer durations. Furthermore, the reaction model derived from the kinetics study is validated using a number of (quasi) in situ techniques. This study provides fundamental insights into the role of bulk oxygen transfer and surface reaction in chemical looping or related process.

Enhanced non-radical degradation of organic pollutants by peroxymonosulfate activation with Zr-Mn composite oxide

Non-radical activation of peroxymonosulfate (PMS) with MnOX can degrade organic pollutants more selectively. However, improving the performance of MnOX is still a challenge. In this work, a series of Zr-Mn composite oxides were synthesized by a hydrothermal method and characterized by various techniques. Their performance for PMS activation was studied using phenol and ofloxacin as the target pollutants. The characterization results show that the introduction of Zr into MnOX increased the oxygen mobility, while the surface area and surface oxygen content of the composite oxides decreased with increasing the content of Mn. The combination of Zr-Mn led to a synergistic effect for PMS activation and the sample (ZM2) with the Zr:Mn ratio of 1:1 exhibited the highest activity. This can be attributed to its high oxygen mobility, suggesting that the manipulation of oxygen mobility should be an effective strategy for improving the performance of PMS catalyst. Singlet oxygen was found to be the reactive species for pollutants degradation, and this process was barely affected by coexisting substances due to the non-radical mechanism. Moreover, ZM2 exhibited good stability and reusability, suggesting its potential application in wastewater treatment.

Tailoring hydrogenation and anti-oxidation properties of titanium - iron - chromium alloys by regulating zirconium content at room temperature

The effects of Fe substitution by Zr on the microstructure, hydrogen storage properties and oxidation resistance of the TiFe0.85-xCr0.15Zrx (x = 0, 0.05, 0.10, 0.15) alloys are studied in this work. It is shown that all the alloys are consisted of TiFe phase, MgZn2-type phase and minor Ti phase. The introduction of Zr causes no change for the TiFe main phase. All the alloys absorb hydrogen directly under mild conditions without any activation process. As Zr content increases, the maximum hydrogen storage capacity of the first hydrogenation increases while the reversible hydrogen storage capacity decreases. The marked change of the first hydrogenation properties may be due to the formation of the bright phase (MgZn2-type phase). The decrease of the reversible hydrogen storage capacity is due to the formation of the stable hydrides Cr2ZrH3 and TiH2, which start to decompose at around 700 °C. During the air exposure test, the alloys with higher Zr content show good oxidation resistance. For the PCT measurement, the alloys with higher Zr show lower hydrogen absorption and desorption platform pressure, which means more stable hydrides are formed during the first hydrogenation. Moreover, the rate limiting step model of the first and fifth hydrogenation processes of all the alloys has also been investigated in detail.

Development of non evaporable getter pumps for large hydrogen throughput and capacity in high vacuum regimes

In vacuum technology, capture pumps based on Non Evaporable Getters are commonly applied to ultra-high vacuum systems. Recent improvements in the absorption of hydrogenic species, with the introduction of Zr–V–Ti–Al alloys (ZAO®), make them an appealing and viable solution for the application in fusion research, and in particular for the vacuum system of neutral beam injectors (hydrogen pumping speed of thousands of m3/s, pressure of tens of mPa). This paper describes the characterization of the new NEG material in pumps of increasing dimensions, including the development, construction and test of a large mockup pump of modular design, to demonstrate the scalability of the technology. Effective pumping speeds of the order of 14 m3/s or higher at a concentration of 130 Pa m3/kg were achieved by the mockup pump, for an installed getter mass of about 16 kg, and a stability within 10% up to 1300 Pa m3/kg The measured effective pumping speed per unit area of sintered disks is of the order of 3.5 m/s, corresponding to 4.9 m/s at the disk surfaces as derived from numerical simulations. General guidelines for the design of large NEG pumps for hydrogen are discussed, including thermal aspects and duty cycle of the pump.