Gold nanoparticles have been used for centuries, both for decoration and in medical applications. More recently, many of the major advances in cluster chemistry have involved well-defined clusters ...containing tens or hundreds of atoms, either with or without a ligand shell. In this paper we report the synthesis of two gold/lead clusters, Au
Pb
and Au
Pb
, both of which contain nido Au@Pb
icosahedra surrounding a core of Au atoms. Analogues of these large clusters are not found in the corresponding Ag chemistry: instead, the Ag-centered nido icosahedron, Ag@Pb
, is the only isolated product. The structural chemistry, along with the mass spectrometry which shows the existence of Au
Pb
but not Ag
Pb
, leads us to propose that the former species is the key intermediate in the growth of the larger clusters. Density functional theory indicates that secondary π-type interactions between the Au@Pb
ligands and the gold core play a significant part in stabilizing the larger clusters.
Rotary ultrasonic machining (RUM) has been successfully used to drill Ti (titanium and its alloy), CFRP, and CFRP/Ti stacks. In all studies on RUM reported in the literature, feedrate was fixed ...during each experimental test. It has been shown that low feedrate should be used for RUM of Ti, but RUM of CFRP could be done using feedrate 10 times higher. This paper, for the first time, reports a study on RUM of CFRP/Ti stacks using variable feedrate (high feedrate for CFRP and low feedrate for Ti). It also makes comparisons on RUM of CFRP/Ti stacks using fixed and variable feedrate.
The endohedral Zintl-ion cluster Fe3Sn184− contains a linear Fe3 core with short Fe–Fe bond lengths of 2.4300(9) Å. The ground state is a septet, with significant σ and π contributions to the Fe–Fe ...bonds. The Sn18 cage is made up of two partially fused Sn9 fragments, and is structurally intermediate between Ni2CdSn186−, where the fragments are clearly separated and Pd2Sn184−, where they are completely fused. It therefore represents an intermediate stage in cluster growth. Analysis of the electronic structure suggests that the presence of the linear Fe–Fe–Fe unit is an important factor in directing reactions towards fusion of the two Sn9 units rather than the alternative of oligomerization via exo bond formation.
We report here the synthesis and characterization of two endohedral Zintl-ion clusters, Fe4Sn184− and Fe4Pb184−, which contain rhombic Fe4 cores. The Fe–Fe bond lengths are all below 2.5 Å, ...distinctly shorter than in the corresponding Cu clusters, indicating the presence of Fe–Fe bonding. Subtle differences in the structure of the Fe4 core between the two clusters suggest that the change in tetrel element causes a change in electronic ground state, with a very short Fe–Fe bond length of 2.328 Å present across the diagonal of the rhombus in the lead case.
The Nb@As83– anion was first isolated from solution in 1986, and a number of isostructural M@Pn8 n− clusters (M = Nb, Cr, or Mo; Pn = As or Sb; n = 2 or 3) have since been reported. We show here how ...anions of this class can be used as synthetic precursors that, in combination with sources of low-valent late transition metals (Cu and Ag), generate ternary polyarsenide cluster anions with unprecedented structural motifs. Chain type MM′As164– (M = Nb or Ta; M′ = Cu or Ag) units are found in compounds 2–5. These clusters contain a nortricyclane-like As7 cage and a M@As8 crown, linked by a single As atom, and represent a fusion of two quite distinct branches of polyarsenide chemistry. Our analysis of the electronic structure confirms that the cluster retains many of the features of the component units. Electrospray ionization mass spectrometry reveals a series of smaller component ions containing 8–12 As atoms, the density functional theory-computed structures of which can be understood in terms of the pseudoelement concept. This work not only presents a new type of coordination mode for As clusters but also offers a point of entry for the rational design of multinary arsenic-based materials.
We report here the structure of an endohedral plumbaspherene, Cu4Pb224–, the gold analogue of which was previously postulated to be a “missing link” in the growth of larger clusters containing three ...and four icosahedral subunits. The cluster contains two Cu2Pb112– subunits linked through a Cu2Pb4 trigonal antiprism. Density functional theory reveals that the striking ability of mixed Pb/coinage metal Zintl clusters to oligomerize and, in the case of Au, to act as a site of nucleation for additional metal atoms, is a direct consequence of their nd10(n + 1)s0 configuration, which generates both a low-lying (n + 1)s-based LUMO and also a high-lying Pb-centered HOMO. Cluster growth and nucleation is then driven by this amphoteric character, allowing the clusters to form donor–acceptor interactions between adjacent icosahedral units or to additional metal atoms.
Drilling is involved in many applications of carbon fiber-reinforced plastic (CFRP) composites. Rotary ultrasonic machining (RUM) has been successfully employed to drill holes in CFRP using either ...cutting fluid or cold air as coolant. However, there are no reported studies to compare the results in RUM of CFRP using these two types of coolant. This article, for the first time, presents an experimental study to compare cutting force, torque, surface roughness, burning of machined surface, and tool wear in RUM of CFRP using these two types of coolant. This study will result in knowledge about machining conditions under which it is feasible to use cold air instead of cutting fluid and differences in machined hole quality produced using cold air vs. cutting fluid.
We report here the synthesis and characterization of two endohedral Zintl-ion clusters, Fe
Sn
and Fe
Pb
, which contain rhombic Fe
cores. The Fe-Fe bond lengths are all below 2.5 Å, distinctly ...shorter than in the corresponding Cu clusters, indicating the presence of Fe-Fe bonding. Subtle differences in the structure of the Fe
core between the two clusters suggest that the change in tetrel element causes a change in electronic ground state, with a very short Fe-Fe bond length of 2.328 Å present across the diagonal of the rhombus in the lead case.
The endohedral Zintl-ion cluster Fe
Sn
contains a linear Fe
core with short Fe-Fe bond lengths of 2.4300(9) Å. The ground state is a septet, with significant σ and π contributions to the Fe-Fe ...bonds. The Sn
cage is made up of two partially fused Sn
fragments, and is structurally intermediate between Ni
CdSn
, where the fragments are clearly separated and Pd
Sn
, where they are completely fused. It therefore represents an intermediate stage in cluster growth. Analysis of the electronic structure suggests that the presence of the linear Fe-Fe-Fe unit is an important factor in directing reactions towards fusion of the two Sn
units rather than the alternative of oligomerization
exo bond formation.
► A power consumption measurement method in rotary ultrasonic machining (RUM) is proposed. ► Effects of ultrasonic power, tool rotation speed, feedrate, and type of CFRP on power consumption are ...investigated. ► Power consumption percentages of each component are studied. ► Ultrasonic power supply in RUM system is not the largest power consumer during machining.
Carbon fiber reinforced plastic (CFRP) composites are very difficult to machine. A large number of holes need to be drilled in CFRP for many applications. Therefore, it is important to develop cost-effective drilling processes. CFRP has been drilled by rotary ultrasonic machining (RUM) successfully. The literature has reports about the effects of input variables on output variables (including cutting force, torque, surface roughness, tool wear, and workpiece delamination) in RUM of CFRP. However, there are no reports on power consumption in RUM of CFRP. This paper reports the first study on power consumption in RUM of CFRP. It reports an experimental investigation on effects of input variables (ultrasonic power, tool rotation speed, feedrate, and type of CFRP) on power consumption of each component (including ultrasonic power supply, spindle motor, coolant pump, and air compressor) and the entire RUM system.
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