Topologically Close-Packed Frank-Kasper C15 Phase Intermetallic Ir Alloy Electrocatalysts Enables High-Performance Proton Exchange Membrane Water Electrolyzer.

Chemical synthesis of unconventional topologically close-packed intermetallic nanocrystals (NCs) remains a considerable challenge due to the limitation of large volume asymmetry between the components. Here, a series of unconventional intermetallic Frank-Kasper C15 phase Ir2M (M = rare earth metals La, Ce, Gd, Tb, Tm) NCs is successfully prepared via a molten-salt assisted reduction method as efficient electrocatalysts for hydrogen evolution reaction (HER). Compared to the disordered counterpart (A1-Ir2Ce), C15-Ir2Ce features higher Ir-Ce coordination number that leads to an electron-rich environment for Ir sites. The C15-Ir2Ce catalyst exhibits excellent and pH-universal HER activity and requires only 9, 16, and 27 mV overpotentials to attain 10 mA cm-2 in acidic, alkaline, and neutral electrolytes, respectively, representing one of the best HER electrocatalysts ever reported. In a proton exchange membrane water electrolyzer, the C15-Ir2Ce cathode achieves an industrial-scale current density of 1 A cm-2 with a remarkably low cell voltage of 1.7 V at 80 °C and can operate stably for 1000 h with a sluggish voltage decay rate of 50 µV h-1. Theoretical investigations reveal that the electron-rich Ir sites intensify the polarization of *H2O intermediate on C15-Ir2Ce, thus lowering the energy barrier of the water dissociation and facilitating the HER kinetics.

Structure and properties of mixed valent CeFe2Al8.

Temperature dependent magnetic, electrical transport and thermal properties of polycrystalline orthorhombic CeFe2Al8intermetallic compound have been studied along with its isostructural La counterpart, LaFe2Al8. For the cerium compound, low field dc magnetization exhibits an antiferromagnetic like ordering (TN) ~ 4 K. The main feature of the magnetic susceptibility plot is a broad hump spanning a large temperature range, indicating mixed valence of Ce in the compound, in good agreement with reported literature. However, contrary to the reported observations we find that the mixed valence state is very robust and was evident even up to very high magnetic fields (> 2 T). Further, in this work we report 3d core level photoemission spectra of cerium in CeFe2Al8, to understand the valence state of cerium ions in this system. Additionally, from resistivity measurements it is found that, CeFe2Al8is metallic with no indication of any anomaly, till the lowest temperature of measurement. Specific heat measurements show very low value of heat capacity and electronic contribution. The isostructural La analogue, LaFe2Al8compound shows broadness in susceptibility with maxima around 44 K which may be attributed to ordering of Fe moments. The comparison of Ce and La compounds brings out the role of Fe magnetic moments which may be responsible for competing with cerium moments and resulting in the dilution of long-range magnetic order, also contributing to magnetic frustration in CeFe2Al8. .

L10-PtCo and L12-Pt3Co Intermetallics for Oxygen Reduction Reaction: the Influence of Composition and Structure on Properties.

Pt-based intermetallics are regarded as highly efficient electrocatalysts for oxygen reduction reaction (ORR). However, Pt-based intermetallics with different Pt: M atomic ratios have different atomic arrangements and crystal structures, which will change the electronic structure and coordination environment of Pt, thus affecting the electrocatalytic activity. In this work, we prepared L12-Pt3Co and L10-PtCo intermetallic catalysts by modulating the molar ratio of Pt and Co precursors using a thermal annealing method. The mass activity (MA) of L10-PtCo is 0.52 A mg-1Pt at 0.9 V, which is 1.44 times larger than that of L12-Pt3Co (0.36 A mg-1Pt). In addition, the MA of L10-PtCo decreases by 17.31 % after 10,000 CV cycles, which is smaller than that of L12-Pt3Co (25.00 % loss in MA), showing excellent structural stability. Theoretical calculations reveal that compared to L12-Pt3Co, L10-PtCo has more electrons transferred to the Pt sites, which further optimizes the electronic structure of Pt and reduces the d-band center, leading to the increase of the electrocatalytic performance. This work provides new insights into the study of Pt-based intermetallics with different Pt: M ratios, which is helpful for the screening and preparation of high-performance Pt-based intermetallics.

Design of PtSn Nanocatalysts for Fuel Cell Applications.

The challenges in the fuel cell industry lie in the cost, performance, and durability of the electrode components, especially the platinum-based catalysts. Alloying has been identified as an effective strategy to reduce the cost of the catalyst and increase its efficiency and durability. So far, most studies focused on the design of PtM bimetallic nanocatalyst, where M is a transition metal. The resulting PtM materials show higher catalytic activity, but their stability remained challenging. In addition, most of the transition metals M are expensive or low abundant. Tin (Sn) has gained attention as alloying element due to its versatility in manufacturing both anode and cathode electrodes. If used as anode catalyst, it is able to overcome poisoning from CO and related intermediates. As cathode catalyst, it improves the kinetics of the oxygen reduction reaction (ORR). Additionally, Sn is an abundant and cheap element. The current contribution outlines the state of the art on the alloy and shape effect on PtSn activity and stability, demonstrating its high potential to develop cheaper, more efficient and durable catalysts for fuel-cell electrodes. Additionally, in situ analytical and spectroscopic studies can shed light on the elementary steps involved in the use of PtSn catalytic systems. Finally, this intriguing material can be used as a parent system for the synthesis of high-entropy-alloys and intermetallics materials.

Ti4Fe2C0.82O0.18.

The phase with composition Ti4Fe2C0.82O0.18, tetra-titanium diiron carbide oxide, was unexpectedly synthesized by high-pressure sinter-ing (HPS) of a stoichiometric mixture with nominal composition Ti2Fe. The Ti4Fe2C0.82O0.18 phase crystallizes in the Fd m space group and can be considered as the Ti2Fe structure filled with C and O atoms co-occupying the same octa-hedral void [occupancy ratio 0.82 (7):0.18 (7)]. The Ti4Fe2C0.82O0.18 phase is isotypic with Ti4Ni2C and Ti4Fe2O0.407, and is the first example where C and O atoms co-occupy the same site in filled Ti2Fe structures.

Influence of Noble Metals on Morphology and Topology of Structural Elements in Magnesium Alloy.

The main motivation for this study was to improve implant materials. The influence of silver and gold on the structure and mechanical properties of Mg-Nd-Zr alloy was studied. In the work, quantitative and qualitative evaluation of the structural components of magnesium alloy with noble metal additives was performed. The research methods used were investigation of the mechanical properties and observation of micro- and macrostructures. The results showed that modification of magnesium alloy with Ag and Au contributes to the formation of spherical intermetallics of smaller size groups, which become additional centers of crystallization and grind the cast structure. The best composition from additional alloying with silver and gold was determined. Their positive effect on the strength and ductility properties of the metal was established. Preclinical and clinical testing was performed and the prospects for noble metal modification of bioabsorbable magnesium alloy for implant production usage were shown.

Influence on the properties of TMCs of ceramic and intermetallic composite reinforcements (B4C, TixAly and TixSiy) fabricated by inductive hot pressing.

Ambitious and competitive, the aerospace industry continuously demonstrates to be one of the leading engineering sectors either at exigence and new technologies development. As lightning the weight of aircrafts is one of the main targets, the spotlight is usually on material research by which new ones may be produced to pursue this aim and still offer the necessary performances. The combination of the properties of titanium and other materials as reinforcements provides really interesting results as titanium matrix composite materials, also known as TMCs. Various samples of titanium matrix composite materials with different reinforcements have been under study to determine the influence of the reinforcements and their respective proportions on the properties of the material. These samples composed of grade 1 commercially-pure titanium as matrix and B4C, TixAly and TixSiy as reinforcements, have been manufactured through powder metallurgy in the same conditions of temperature and pressure via Inductive Hot Pressing (IHP). A total of eight composite materials have been arranged in several different groups to confront their compositions. Thus, this analysis reports results for the influence of the powder size of the matrix and the ceramic reinforcement, the effect of varying the volumetric composition of B4C, and the selection of different intermetallic reinforcements. These tests and the obtained information serve for a project in which the main goal is to determine which compositions of the studied composite materials reach a high enough specific stiffness for a suitable application in the aerospace industry.

Semimetal-triggered covalent interaction in Pt-based intermetallics for fuel-cell electrocatalysis.

Platinum-based intermetallic compounds (IMCs) play a vital role as electrocatalysts in a range of energy and environmental technologies, such as proton exchange membrane fuel cells. However, the synthesis of IMCs necessitates recombination of ordered Pt-M metallic bonds with high temperature driving, which is generally accompanied by side effects for catalysts' structure and performance. In this work, we highlight that semimetal atoms can trigger covalent interactions to break the synthesis-temperature limitation of platinum-based intermetallic compounds and benefit fuel-cell electrocatalysis. Attributed to partial fillings of p-block in semimetal elements, the strong covalent interaction of d-p π backbonding can benefit the recombination of ordered Pt-M metallic bonds (PtGe, PtSb and PtTe) in the synthesis process. Moreover, this covalent interaction in metallic states can further promote both electron transport and orbital fillings of active sites in fuel cells. The semimetal-Pt IMCs were obtained with a temperature 300 K lower than that needed for the synthesis of metal-Pt intermetallic compounds and reached the highest CO-tolerant oxygen reduction activity (0.794 A mg-1 at 0.9 V and 5.1% decay under CO poisoning) among reported electrocatalysts. We anticipate that semimetal-Pt IMCs will offer new insights for the rational design of advanced electrocatalysts for fuel cells.

Characterisation of Fe Distribution in the Liquid-Solid Boundary of Al-Zn-Mg-Si Alloy Using Synchrotron X-ray Fluorescence Microscopy.

Al-Zn-Mg-Si alloy coatings have been developed to inhibit the corrosion of cold-rolled steel sheets by offering galvanic and barrier protection to the substrate steel. It is known that Fe deposited from the steel strip modifies the microstructure of the alloy. We cast samples of Al-Zn-Mg-Si coating alloys containing 0.4 wt% Fe and directionally solidified them using a Bridgman furnace to quantify the effect of this Fe addition between 600 °C and 240 °C. By applying a temperature gradient, growth is encouraged, and by then quenching the sample in coolant, the microstructure may be frozen. These samples were analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine the morphological effects of the Fe distribution across the experimental temperature range. However, due to the sub 1 wt% concentration of Fe, synchrotron X-ray fluorescence microscopy (XFM) was applied to quantitatively confirm the Fe distribution. Directionally solidified samples were scanned at 7.05 keV and 18.5 keV using X-ray fluorescence at the Australian Synchrotron using the Maia array detector. It was found that a mass nucleation event of the Fe-based τ6 phase occurred at 495 °C following the nucleation of the primary α-Al phase as a result of a peritectic reaction with remaining liquid.

Analyses of hydrogen local environments in metals and intermetallic compounds using inelastic neutron scattering calculations based on first-principles hydrogen adiabatic potentials.

This study re-evaluates the theoretical approach to analyzing inelastic neutron spectra of hydrogen-containing metals and intermetallic compounds. Previously, these analyses utilized hydrogen quantum nuclear states, modeled as solutions to the Schrödinger equation. The potential surfaces in these models were approximated from the total energies derived from first-principles electronic structure calculations. The current study improves upon this method by employing more efficient and accurate treatments for sampling the potential surface. It utilizes symmetrically irreducible sampling points arranged on densely populated mesh grids for the first-principles calculations. A comparative analysis of the theoretical predictions with experimental spectra for hydrides of Ti2Sb and Ti3Sb, as well as a LaNi5hydrogen primary solid solution, demonstrates that this approach is promising for elucidating the unknown local environments of hydrogen atoms in systems where the approximate potential well describes the hydrogen quantum states.

Metamagnetic multiband Hall effect in Ising antiferromagnet ErGa2.

Frustrated rare-earth-based intermetallics provide a promising platform for emergent magnetotransport properties through exchange coupling between conduction electrons and localized rare-earth magnetic moments. Metamagnetism, the abrupt change of magnetization under an external magnetic field, is a signature of first-order magnetic phase transitions; recently, metamagnetic transitions in frustrated rare earth intermetallics have attracted interest for their accompanying nontrivial spin structures (e.g., skyrmions) and associated nonlinear and topological Hall effects (THE). Here, we present metamagnetism-induced Hall anomalies in single-crystalline ErGa2, which recalls features arising from the THE but wherein the strong Ising-type anisotropy of Er moments prohibits noncoplanar spin structures. We show that the observed anomalies are neither due to anomalous Hall effect nor THE; instead, can be accounted for via 4f-5d interactions which produce a band-dependent mobility modulation. This leads to a pronounced multiband Hall response across the magnetization process-a metamagnetic multiband Hall effect that resembles a topological-Hall-like response but without nontrivial origins. The present findings may be of general relevance in itinerant metamagnetic systems regardless of coplanar/noncoplanar nature of spins and are important for the accurate identification of Hall signals due to emergent magnetic fields.

Large magnetocaloric effect and giant magnetoresistance in rare earth based intermetallic compound ErAl3: construction of magnetic phase diagram.

This study explores the magnetic and magnetotransport behavior of polycrystalline ErAl3compound. The polycrystalline compound adopts HoAl3-type structures with the R-3m space group, No. 166-2 and hR60 configurations. Multiple magnetic orderings and two field-induced metamagnetic transitions are observed. ErAl3exhibits a significant magnetocaloric effect (MCE),-ΔSM= 15.25 J kg-1K-1and high relative cooling power of 383 J kg-1with applied magnetic field change (ΔH) of 70 kOe near the paramagnetic to ferromagnetic transition, showcasing its potential for magnetic refrigeration technology. The compound also demonstrates metallic behavior, with a notable magnetoresistance of 48.5%at 2 K due to the suppression of antiferromagnetism. The magnetic phase diagram reveals four distinct phases influenced by temperature and magnetic field, identified through the study of the MCE.

Tailoring Zirconia Supported Intermetallic Platinum Alloy via Reactive Metal-Support Interactions for High-Performing Fuel Cells.

Developing efficient and anti-corrosive oxygen reduction reaction (ORR) catalysts is of great importance for the applications of proton exchange membrane fuel cells (PEMFCs). Herein, we report a novel approach to prepare metal oxides supported intermetallic Pt alloy nanoparticles (NPs) via the reactive metal-support interaction (RMSI) as ORR catalysts, using Ni-doped cubic ZrO2 (Ni/ZrO2) supported L10-PtNi NPs as a proof of concept. Benefiting from the Ni migration during RMSI, the oxygen vacancy concentrations in the support are increased, leading to an electron enrichment of Pt. The optimal L10-PtNi-Ni/ZrO2-RMSI catalyst achieves remarkably low mass activity (MA) loss (17.8 %) after 400,000 accelerated durability test cycles in a half-cell and exceptional PEMFC performance (MA=0.76 A mgPt -1 at 0.9 V, peak power density=1.52/0.92 W cm-2 in H2-O2/-air, and 18.4 % MA decay after 30,000 cycles), representing the best reported Pt-based ORR catalysts without carbon supports. Density functional theory (DFT) calculations reveal that L10-PtNi-Ni/ZrO2-RMSI requires a lower energetic barrier for ORR than L10-PtNi-Ni/ZrO2 (direct loading), which is ascribed to a decreased Bader charge transfer between Pt and *OH, and the improved stability of L10-PtNi-Ni/ZrO2-RMSI compared to L10-PtNi-C can be contributed to the increased adhesion energy and Ni vacancy formation energy within the PtNi alloy.

Bonding of ceramics to silver-coated titanium-A combined theoretical and experimental study.

It would be very beneficial to have a method for joining of ceramics to titanium reliably. Although several techniques have been developed and tested to prevent extensive interfacial chemical reactions in titanium-ceramic systems, the main problem of the inherent brittleness of interfaces was still unsolved. To overcome this problem also in dental applications, we decided to make use of an interlayer material that needs to meet the following requirements: First, it has to be biocompatible, second, it should not melt below the bonding temperatures, and third, it should not react too strongly with titanium, so that its plasticity will be maintained. Considering possible material options only the metals: gold, platinum, palladium, and silver, fulfill the first and second requirements. To find out-without an extensive experimental testing program-which of the four metals fulfills the third requirement best, the combined thermodynamic and reaction kinetic modeling was employed to evaluate how many and how thick reaction layers are formed between the interlayer metals and titanium. With the help of theoretical modeling, it was shown that silver fulfills the last requirement best. However, before starting to test experimentally the effect of the silver layer on the mechanical integrity of dental ceramic/Ag/Ti joints it was decided to make use of mechanical analysis of the three-point bending test, the result of which indicated that the silver layer increases significantly the bond strength of the joints. This result encouraged us to develop a new technique for plating silver on titanium. Subsequently, we executed numerous three-point bending tests, which demonstrated that silver-plated titanium-ceramic joints are much stronger than conventional titanium-ceramic joints. Hence, it can be concluded that the combined thermodynamic, reaction kinetic, and mechanical modeling method can also be a very valuable tool in medical research and development work.

Crystal, electronic structure and hydrogenation properties of the Mg5.57Ni16Ge7.43 cluster phase with a new type of polyhedron.

The ternary germanide Mg5.57Ni16Ge7.43 (cubic, space group Fm-3m, cF116) belongs to the structural family based on the Th6Mn23-type. The Ge1 and Ge2 atoms fully occupy the 4a (m-3m symmetry) and 24d (m.mm) sites, respectively. The Ni1 and Ni2 atoms both fully occupy two 32f sites (.3m symmetry). The Mg/Ge statistical mixture occupies the 24e site with 4m.m symmetry. The structure of the title compound contains a three-core-shell cluster. At (0,0,0), there is a Ge1 atom which is surrounded by eight Ni atoms at the vertices of a cube and consequently six Mg atoms at the vertices of an octahedron. These surrounded eight Ni and six Mg atoms form a [Ge1Ni8(Mg/Ge)6] rhombic dodecahedron with a coordination number of 14. The [GeNi8(Mg/Ge)6] rhombic dodecahedron is encapsulated within the [Ni24] rhombicuboctahedron, which is again encapsulated within an [Ni32(Mg/Ge)24] pentacontatetrahedron; thus, the three-core-shell cluster [GeNi8(Mg/Ge)6@Ni24@Ni32(Mg/Ge)24] results. The pentacontatetrahedron is a new representative of Pavlyuk's polyhedra group based on pentagonal, tetragonal and trigonal faces. The dominance of the metallic type of bonding between atoms in the Mg5.57Ni16Ge7.43 structure is confirmed by the results of the electronic structure calculations. The hydrogen sorption capacity of this intermetallic at 570 K reaches 0.70 wt% H2.

Oxygen-Vacancy-Induced Formation of Pt-Based Intermetallics on MXene with Strong Metal-Support Interactions for Efficient Oxygen Reduction Reaction.

The Pt-based alloys can moderate the binding energies of oxygenated species on the catalytic surface, endowing the superior catalytic performance towards oxygen reduction reaction (ORR). Nevertheless, it is still challenging to explore general methods to synthesize structurally ordered intermetallics with uniform distributions. Herein, the strong metal-support interaction is employed to facilitate the interdiffusion of Pt/M atoms by establishing a tunnel of oxygen vacancy on ultrathin Ti3C2Tx (MXene) sheets, synthesizing the ordered PtFe, PtCo, PtZn, PdFe, PdZn intermetallics loaded onto Ti3C2Tx. Furthermore, the in-situ generation of Ti-O from Ti3C2Tx could be bonded with Pt and forming Pt-O-Ti, resulting in charge redistribution through Pt-O-Ti structure. Theoretical calculations demonstrate that the valuable charge redistribution can be observed at the interface and extended even to at the distance of two nanometers from the interface, which can modulate the Pt-Pt distance, optimize Pt-O binding energy and enhance intrinsic activity towards ORR. The strong coupling interaction between PtFe and Ti3C2Tx containing the titanium oxide layer endows the high stability of the composites. This work not only presents a general synthesis strategy for intermetallics but also provides a new insight that metal-support interaction is essential for the structural evolution of intermetallics on materials with oxygen vacancies.

Stabilizing Diluted Active Sites of Ultrasmall High-Entropy Intermetallics for Efficient Formic Acid Electrooxidation.

The poisoning of undesired intermediates or impurities greatly hinders the catalytic performances of noble metal-based catalysts. Herein, high-entropy intermetallics i-(PtPdIrRu)2FeCu (HEI) are constructed to inhibit the strongly adsorbed carbon monoxide intermediates (CO*) during the formic acid oxidation reaction. As probed by multiple-scaled structural characterizations, HEI nanoparticles are featured with partially negative Pt oxidation states, diluted Pt/Pd/Ir/Ru atomic sites and ultrasmall average size less than 2 nm. Benefiting from the optimized structures, HEI nanoparticles deliver more than 10 times promotion in intrinsic activity than that of pure Pt, and well-enhanced mass activity/durability than that of ternary i-Pt2FeCu intermetallics counterpart. In situ infrared spectroscopy manifests that both bridge and top CO* are favored on pure Pt but limited on HEI. Further theoretical elaboration indicates that HEI displayed a much weaker binding of CO* on Pt sites and sluggish diffusion of CO* among different sites, in contrast to pure Pt that CO* bound more strongly and was easy to diffuse on larger Pt atomic ensembles. This work verifies that HEIs are promising catalysts via integrating the merits of intermetallics and high-entropy alloys.

Metallurgical characteristics of AA6061 aluminium and AZ31B magnesium dissimilar joints by fusion welding technique.

Aluminium (Al) and magnesium (Mg) alloys are extensively used in the automobile sector because of their high strength-to-weight ratio, excellent castability low density and simplicity of recycling. Al-Mg structures used in the automotive sector can potentially reduce their weight. Although there is a significant opportunity for substantial cost reduction, the use of magnesium in aluminium structures remains restricted. This study aims to weld 3 mm-thick rolled sheets of AA6061 Al and AZ31B Mg alloy using the cold metal transfer (CMT) arc welding process. Three different filler wires (ER1100, ER4043, and ER5356) were used in the experiment. In this article, the mechanical and microstructure characteristics of Al/Mg dissimilar joints manufactured by CMT are evaluated and discussed in detail. Optical microscope (OM), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), and x-ray diffraction (XRD) were used to analyze the CMT-welded Al/Mg dissimilar joints. Of the three filler wires used, ER4043 (Al-5%Si) filler wire yielded defect-free sound joints due to the presence of Si, which improves the flow ability of molten filler during welding. The presence of Mg-rich intermetallics-Al12Mg17) and Al-rich intermetallics-Al3Mg2 were observed. The fractured area of the CMT-welded Al/Mg dissimilar joints revealed the presence of the Mg-rich intermetallics (Al12Mg17), which is responsible for the decrease in tensile strength. The reduction of intermetallics, particularly of Mg-rich intermetallics (Al12Mg17) is important for improving joint strength. RESEARCH HIGHLIGHTS: Cold metal transfer (CMT) arc welding was used to control the Al-Mg-rich intermetallics in the Al/Mg dissimilar joints. The microstructure, morphology and phase composition of the welded joints were studied by OM, SEM, TEM, EDS and XRD. The weld metal and AL substrate bonded with a strong interface, while weld metal and Mg substrate were joined at the epitaxial solidification area where the intermetallic compounds of Mg2Al3, Mg17Al12 and Mg2Si are generated. The weld metal on the Mg side experienced brittle fracture, with a continuous distribution of Mg2Al3, Mg17Al12 and Mg2Si.

Phase Equilibria Related to NiGa5 in the Binary Ni-Ga System.

The assembly of Ga alloys with Ni or Ni alloy has been widely developed for various low-temperature applications in recent years. In the constituent Ni-Ga binary system, however, the phase equilibrium with the phase "NiGa5" and its stability has scarcely been investigated. The present study used the diffusion couple technique combined with SEM-EPMA and XRD analysis to examine the phase stability and the homogeneity range of the phase. The results show that "NiGa5" is a stable phase in the binary system with little homogeneity range and suggest that the peritectic reaction L+Ni3Ga7→NiGa5 lies between 112.0 and 115.5 °C. This work provides new information for the modification of the Ga-rich low-T region of the Ni-Ga phase diagram.

From caged compounds with isolated U atoms to frustrated magnets with 2- or 3-atom clusters: a review of Al-rich uranium aluminides with transition metals.

Crystal structures and physical properties of four families of Al-rich ternary uranium compounds with transition metals (TE) are reviewed, namely UTE2Al20, UTE2Al10, U6TE4Al43, and U3TE4Al12. The compounds can be described as consisting of 1 (isolated), 2 (dumbbells) or 3 (triangles) uranium atom clusters, surrounded (1-2-20, 1-2-10 and 6-4-43) or not (3-4-12) by large cages, which strongly influence their magnetic and related properties. Indeed, the ground states of the described systems evolve from Curie-like paramagnetism in the case of the phases with well-isolated, single U-atoms, to complex magnetic order or possible frustrated magnetism in the case of the systems with uranium triangles forming a breathing kagome lattice. We argue that the four families of uranium aluminides described in this review provide a unique opportunity to study magnetic interactions between U magnetic moments while gradually increasing the number of their nearest magnetic neighbors, and may also be helpful in understanding the fundamental origin of magnetic freezing phenomena.