Phonon-drag thermopower in cu-al and cu-si alloys.
Phonon-drag thermopower change in Cu-Al and Cu-Si alloys at cryogenic temperature
ALUMINUM ALLOY↗
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Development of Next Generation Hierarchical Hybrid Cu-Si anode Batteries via Direct-Ink Writing Application: End of (6th) Month Report - November 2025
Sustainable renewable energy continues to be in dire need to effectively combat global warming. Emerging technology for electric vehicles/ devices remains in high demand that is not only lower in cost, more efficient, but safer in comparison to commercial materials on the market. Although first-generation lithium-ion batteries have exhibited extensive commercial application, conventional graphite no longer meets this increasing demand as an efficient anode material. Due to the fact that graphite has a subpar theoretical specific capacity (372 mAh g -1 ), thus significant limitations in rate capability (for potential faster charging at higher C-rates currently commercially available.). Alternatively, silicon has gained significant attention as a superior candidate to potentially surpass graphite. Due to silicon’s exceedingly high theoretical capacity (4,200 mAh g -1 ) in comparison to standard graphite, its abundance thus in turn it’s low-cost, in addition to exhibiting a significantly low working potential (< 0.4 V vs Li/Li + ). However, one of the main (and most detrimental) challenges is silicon’s tendency to expand in volume (> 300%) upon discharge as it begins the lithiation process. As a direct result, it causes not only for the particles to both crack and pulverize under mechanical stress as the volume continues to expand and contract during cycling. Upon assembling the cell, it needs to undergo ‘charging’ for initially discharging/ ‘activating’ the cell, otherwise commonly known as the ‘formation’ step. As a result a solid electrolyte interface (SEI) layer begins to form at the anode surface because some of the electrolyte begins to react during the formation process. However, this (SEI) layer is deemed as a ‘protective’ interlayer because in theory it prevents further reaction as the cell continues to cycle. However, due to the volume change it causes significant degradation at the interface. As cracking starts to occur at the anode surface, it results in a ‘new’ altered surface with each cycle that causes further reaction with the electrolyte as a byproduct quickly consuming active Li/ and more electrolyte. Thus, fracturing this ‘protective layer,’ causing significantly higher impedance as a result, and in turn a decline in capacity due to active Li-loss. In addition to the active material exfoliating off from the current collector, further contributing to the steady decline in capacity and overall performance. Current state of the art Si-anode batteries on the market range between a maximum content of 5-10 Si wt%. It has been previously reported Tesla has utilized SiO x -C anodes containing 5 wt% Si within their ‘Model 3/ Model X’ electric vehicles. However, more recent ‘Model 3’ vehicles have started to incorporate 10 Si wt%, in which they were able to increase their energy density upwards by approximately 30%. Recent effort has been focused on continuing to increase the wt% of Si being utilized, eventually to 100 wt% of Si, to maximize the energy density even further.
36 MATERIALS SCIENCE↗
Phonon-drag thermopower in cu-al and cu-si alloys
Phonon drag thermopower in copper-aluminum and copper-silicon alloys
PHONON↗
Silicon purification using a Cu-Si alloy source
Production of 99.9999% pure silicon from 98% pure metallurgical grade (MG) silicon by a vapor transport filtration process (VTP) is described. The VTF process is a cold wall version of an HCl chemical vapor transport technique using a Si:Cu3Si alloy as the silicon source. The concentration, origin, and behavior of the various impurities involved in the process were determined by chemically analyzing alloys of different purity, the slag formed during the alloying process, and the purified silicon. Atomic absorption, emission spectrometry, inductively coupled plasma, spark source mass spectrometry, and secondary ion mass spectroscopy were used for these analyses. The influence of the Cl/H ratio and the deposition temperature on the transport rate was also investigated.
Powell, R. C.↗
End of (3rd) Month Progress Report - PhD Committee
For the months of (May-August), the focus has been to: ● Comply and attend all mandatory LLNL training(s). ● Practice & gain experience, using a 3D printer for direct-ink writing application. ● Construct & Test Cu-Si anodes for battery application: - Si nanoparticles (<100 nm) is alloyed within a Cu-based current collector, via direct-ink writing. - Tuning the overall architecture of the current collector (to accommodate the volume expansion of Si more efficiently/ stabilize its kinetics - of active Si loss). - Based on the following designed configurations: tape-casted, 2D (spiral-square), and 3D (spiral-square/ zig-zag) structures; utilizing commercial-based Cu paste. - Fabricated (half-cell) coin-cells are currently cycling long-term. ● Synthesize new Cu-Si paste, to further tune the rheology properties, for further comparison with commercial Cu-based paste.
99 GENERAL AND MISCELLANEOUS↗
BaCu 4/3 Si 2/3 P 2 and BaCu 2–( x + y ) Zn x Si y P 2 : Expanding the Semiconducting Landscape in the ThCr 2 Si 2 -Type Family
ThCr 2 Si 2 -type layered materials are a large family of compounds with applications ranging from thermoelectricity to magnetism, with the vast majority of the members exhibiting metallic behavior. Here, in this study, we synthesized a new group of materials with Cu-Si and Cu-Zn-Si square nets with the general formula BaCu 1.33 Si 0.67 P 2 and BaCu 2–(x+y) Zn x Si y P 2 (0 ≤ x ≤ 0.9; 0.3 ≤ y ≤ 0.7). Several synthesized compounds are charge-balanced semiconductors, which are rare in the ThCr 2 Si 2 family. All the reported compounds crystallize in the ThCr 2 Si 2 -type tetragonal I4/mmm space group, with Cu/Zn/Si jointly occupying the same 4d crystallographic site. In the Zn-free composition, BaCu 1.33 Si 0.67 P 2 , Ba, and P each occupy a single crystallographic site. The introduction of Zn results in the expansion of the unit cell and splitting the Ba atomic sites along the [001] direction. Such structural displacement of the Ba atoms was confirmed by the heat capacity measurements. Band structure and density-of-states calculations on ordered hypothetical structural models reveal either a small bandgap (∼0.2 eV) or semimetallic band structures. The compounds reported here exhibit high Seebeck coefficients and ultralow thermal conductivity, making them promising candidates for the development of thermoelectric materials.
crystal structure↗
TEM Analysis of Diffusion-Bonded Silicon Carbide Ceramics Joined Using Metallic Interlayers
SiC fiber-bonded ceramics (SA-Tyrannohex: SA-THX) diffusion-bonded with TiCu metallic interlayers were investigated. Thin samples of the ceramics were prepared with a focused ion beam (FIB) and the interfacial microstructure of the prepared samples was studied by transmission electron microscopy (TEM) and scanning TEM (STEM). In addition to conventional microstructure observation, for detailed analysis of reaction compounds in diffusion-bonded area, we performed STEM-EDS measurements and selected area electron diffraction (SAD) experiments. The TEM and STEM experiments revealed the diffusion-bonded area was composed of only one reaction layer, which was characterized by TiC precipitates in Cu-Si compound matrix. This reaction layer was in good contact with the SA-THX substrates, and it is concluded that the joint structure led to the excellent bonding strength.
Ceramics↗
Materials Data on Cu15Si4 by Materials Project
Cu15Si4 crystallizes in the cubic I-43d space group. The structure is three-dimensional. there are two inequivalent Cu+1.07+ sites. In the first Cu+1.07+ site, Cu+1.07+ is bonded in a 12-coordinate geometry to eight equivalent Cu+1.07+ and four equivalent Si4- atoms. There are four shorter (2.49 Å) and four longer (2.59 Å) Cu–Cu bond lengths. All Cu–Si bond lengths are 2.62 Å. In the second Cu+1.07+ site, Cu+1.07+ is bonded in a 9-coordinate geometry to six Cu+1.07+ and three equivalent Si4- atoms. There are two shorter (2.49 Å) and two longer (2.57 Å) Cu–Cu bond lengths. There are a spread of Cu–Si bond distances ranging from 2.43–2.58 Å. Si4- is bonded to twelve Cu+1.07+ atoms to form a mixture of face and edge-sharing SiCu12 cuboctahedra.
36 MATERIALS SCIENCE↗
Materials Data on Cu3Si by Materials Project
Cu3Si is Uranium Silicide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Cu+1.33+ is bonded in a distorted see-saw-like geometry to four equivalent Si4- atoms. There are two shorter (2.55 Å) and two longer (2.58 Å) Cu–Si bond lengths. Si4- is bonded to twelve equivalent Cu+1.33+ atoms to form a mixture of face and corner-sharing SiCu12 cuboctahedra.
36 MATERIALS SCIENCE↗
Materials Data on Cu7Si2 by Materials Project
Cu7Si2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are four inequivalent Cu+1.14+ sites. In the first Cu+1.14+ site, Cu+1.14+ is bonded in a 4-coordinate geometry to four equivalent Si4- atoms. There are three shorter (2.37 Å) and one longer (2.63 Å) Cu–Si bond lengths. In the second Cu+1.14+ site, Cu+1.14+ is bonded to three equivalent Cu+1.14+ and one Si4- atom to form corner-sharing CuCu3Si trigonal pyramids. All Cu–Cu bond lengths are 2.36 Å. The Cu–Si bond length is 2.37 Å. In the third Cu+1.14+ site, Cu+1.14+ is bonded in a 4-coordinate geometry to two Cu+1.14+ and three equivalent Si4- atoms. There are one shorter (2.51 Å) and one longer (2.57 Å) Cu–Cu bond lengths. All Cu–Si bond lengths are 2.58 Å. In the fourth Cu+1.14+ site, Cu+1.14+ is bonded in a 8-coordinate geometry to two equivalent Cu+1.14+ and six equivalent Si4- atoms. All Cu–Si bond lengths are 2.77 Å. Si4- is bonded in a 11-coordinate geometry to eleven Cu+1.14+ atoms.
36 MATERIALS SCIENCE↗