Copper Counterpart Research Articles

From Aluminum Dissolution in Supercapacitors to Electroplating: A New Way for Al Thin Film Deposition?

AbstractThe present work addresses a new finding observed while performing aluminum dissolution experiments for supercapacitors (SCs) stability investigation. Supercapacitor (SC) electrodes based on carbon‐coated aluminum foils are electrochemically cycled in harsh conditions into bis‐trifluoromethylsulfonyl imide (TFSI)‐based electrolyte and using Acetonitrile (ACN) as solvent. Dissolution of aluminum is observed with subsequent plating on the carbonaceous surface of counter electrodes. Moreover, the same process can be reproduced also on standard SC activated carbon electrodes. This mechanism can open the way to an effective strategy to achieve Al film deposition by electroplating becoming competitive with the most common copper counterpart.

Converting copper sulfide to copper with surface sulfur for electrocatalytic alkyne semi-hydrogenation with water

Electrocatalytic alkyne semi-hydrogenation to alkenes with water as the hydrogen source using a low-cost noble-metal-free catalyst is highly desirable but challenging because of their over-hydrogenation to undesired alkanes. Here, we propose that an ideal catalyst should have the appropriate binding energy with active atomic hydrogen (H*) from water electrolysis and a weaker adsorption with an alkene, thus promoting alkyne semi-hydrogenation and avoiding over-hydrogenation. So, surface sulfur-doped and -adsorbed low-coordinated copper nanowire sponges are designedly synthesized via in situ electroreduction of copper sulfide and enable electrocatalytic alkyne semi-hydrogenation with over 99% selectivity using water as the hydrogen source, outperforming a copper counterpart without surface sulfur. Sulfur anion-hydrated cation (S2−-K+(H2O)n) networks between the surface adsorbed S2− and K+ in the KOH electrolyte boost the production of active H* from water electrolysis. And the trace doping of sulfur weakens the alkene adsorption, avoiding over-hydrogenation. Our catalyst also shows wide substrate scopes, up to 99% alkenes selectivity, good reducible groups compatibility, and easily synthesized deuterated alkenes, highlighting the promising potential of this method.

In-situ deposition of diamond on functionally graded copper scaffold for improved thermal conductivity and mechanical properties

A novel functionally graded structure of diamond was developed with significantly enhanced thermal conductivity and compressive strength, based on synergistic effects combining chemical vapor deposition (CVD) and selective laser melting (SLM). In-situ diamond growth was achieved without conventionally complex pretreatment steps thanks to the high surface roughness of as-printed graded copper scaffold. The continuous diamond film coated on graded copper scaffold forms a monolith with interconnected network, acting as an effective layer for heat conduction with an exceptional increase (459%) in thermal conductivity compared with copper counterpart. The functionally graded structure also demonstrates a progressive mechanical response to loading compared with the uniform structure. This work opens a new avenue for realizing three-dimensional diamond structure and proves its multifunctionalities, especially for high-power electronics applications.

Temperature-dependent crosstalk and frequency spectrum analyses in adjacent interconnects of a mixed CNT bundle

This paper presents temperature-dependent circuit modeling and performance analyses of single as well as capacitively coupled interconnects of a mixed CNT bundle (MCB) with consideration of the tunneling effect at temperatures from 300 to 500 K at the 14-nm technology node. Four possible MCB structures, viz. MCB-1, MCB-2, MCB-3, and MCB-4, are considered, and their results are compared with those for a copper-based interconnect at the same technology node. For the single line architecture, as the temperature is increased from 300 to 500 K, MCB-4 exhibits a shorter propagation delay in comparison with the other MCBs (1–3) and copper. The results of the frequency spectrum analysis reveal that MCB-4 exhibits a 17.70% wider bandwidth than its copper counterpart. Also, the bandwidth of MCB-4 decreases with increasing temperature, indicating greater signal loss at higher temperatures. For the coupled line architecture, considering different switching conditions of the aggressor and victim lines, MCB-4 exhibits a shorter average dynamic crosstalk-induced delay compared with the other MCBs (1–3) or copper. In comparison with the odd mode of switching, MCB-4 exhibits a 36.45% shorter crosstalk-induced delay with the even mode of switching when the temperature is varied from 300 to 500 K. Similarly, the functional crosstalk noise levels in terms of the overshoot, undershoot, rise glitch, and fall glitch are also found to be significantly lower for MCB-4 compared with the other MCBs (1–3) or copper. The results of the simulations further reveal that MCB-4 exhibits frequency noise components with 70.66% lower amplitude compared with copper, which means that MCB-4 filters more noise components than copper. Furthermore, the amplitude of the frequency noise components increases with rise in temperature.

Design of NMR RF Probe Constructed With High-Temperature Superconducting Elliptical–Coupled Resonators

A high-temperature superconducting (HTS) radio frequency (RF) probe has been designed for nuclear magnetic resonance spectroscopy that is constructed of two newly developed HTS elliptical-coupled resonators that are placed on either side of the sample. The probe has a higher quality factor and a more uniform magnetic field along the z-axis than one with square resonators. The measured unloaded quality factor (Qu) of a pair of elliptical-coupled resonators fabricated using YBa2Cu3Oy thin films on an Al2O3 substrate was about 30 000 at 15 K, which is about 82 times higher than the simulated Qu of a copper counterpart at room temperature. Measurement of the input power dependence of Qu showed that a Qu of over 20 000 was obtained up to 16 dBm. Measurement of the RF magnetic field profile along the z-axis showed that the RF magnetic field was more than 85% uniform around the sample region.

High-conductive graphene film based antenna array for 5G mobile communications

Graphene antennas and relevant microwave devices have attracted wide attention due to their lightweight, low-cost, and flexible characteristics. However, their performances are usually not satisfactory because of low conductivity of graphene materials in the macroscopic scale. In this article, an antenna array made of flexible high-conductivity graphene materials is fabricated and reported for potential application in 5G mobile communications. The antenna array has a high gain of 6.77 dBi at 3.51 GHz with an excellent return loss, which is comparable to the identical copper counterpart. Moreover, the graphene antenna has similar radiation patterns to the copper antenna.

Properties and microstructure of copper/nickel-iron-coated graphite composites prepared by electroless plating and spark plasma sintering

In order to improve the interfacial bonding between copper and graphite, the quasi-spherical graphite powders were coated with nickel-iron alloy and copper in sequence by electroless plating. Copper/nickel-iron-coated graphite composites (graphite content: 80 vol%) were successfully prepared by spark plasma sintering (SPS). For comparison, copper/graphite composites with graphite content of 80 vol% were prepared by the same process. The microstructure, mechanical, electrical and wear properties of copper/nickel-iron-coated graphite composites were compared with those of copper/graphite composites. The results indicated that the introduction of nickel-iron coating obviously improved the wettability between copper and graphite due to the formation of carbides (Fe3C), borides (FeB, Fe3B and Ni3B) and solid solution. The metal phases in copper/nickel-iron-coated graphite composites were distributed uniformly and formed an excellent interconnected network. Compared with copper/graphite composites, the as-fabricated copper/nickel-iron-coated graphite composites showed better mechanical and wear-resisting properties, especially the bending strength increased from 42 MPa to 73 MPa, and did less damage to the pure copper counterpart ring.

Characterization of a Dinuclear Copper(II) Complex and Its Fleeting Mixed-Valent Copper(II)/Copper(III) Counterpart.

The synthesis of a dinuclear copper(II) complex, supported by a 1,3-diamino-2-propanol-based tetraamide ligand, is reported. Structural properties in the solid state and in solution, by means of XRD analysis and NMR spectroscopy, respectively, provide evidence of a highly flexible complex that can display several conformations, leading to the image of the wings of a butterfly. The complex was fully characterized and the redox properties were investigated. Room-temperature spectro-electrochemistry was used to monitor the formation of a metastable mono-oxidized product that displayed an absorption band centered at λ=463 nm. EPR investigation of the low-temperature, chemically generated, mono-oxidized product reveals the presence of an intermediate described as a mixed-valent CuII CuIII species, which is a model of the possible highly oxidizing intermediate in particulate methane monooxygenase.

(Invited) Beyond-CMOS Device and Interconnect Technology Benchmarking Based on a Fast Cross-Layer Optimization Methodology

Moore’s Law scaling has last for almost half century, leading to a tremendous performance/area improvement and cost reduction. Unfortunately, in the past decade, severe challenges have been faced by the CMOS technology as the technology node enters sub-100nm region. To sustain the growing transistor performance and density, many novel device technologies are proposed in the past decade to augment or even replace the conventional Si CMOS technology with Cu interconnect. For the device innovation, ever since the discovery of graphene with excellent physical and electrical properties, much interest has been drawn in the electron-device community and graphene-based FETs have been introduced. Based on the property of the angular dependent transmission probability of electrons observed in GPNJs, an enhanced device structure is presented. More elaborate physical models are also developed to better evaluate the upper limit of delay and power consumptions of GPNJ circuits, including ON resistance, leakage current, contact resistance, and footprint area. For the low-power applications, TFETs show promise in overcoming the power wall faced by thermionic FETs by allowing significant reduction in the supply voltage. The analytical device-level models for TFETs are developed to efficiently evaluate the overall system-level metrics. It is demonstrated that the IV characteristics of a TFET behaves like a Si CMOS switch, but it provides much lower leakage current and ultra-low supply voltage at the cost of low ON current. For the interconnect technology, as the conventional Cu interconnect scales, the resistance per unit length increases dramatically because of 1) the smaller cross-sectional area and 2) the severe size effects at sub-20nm nodes. To alleviate the interconnect challenge, a novel local interconnect structure and hybrid Al-Cu interconnect architecture are proposed and benchmarked against their copper counterpart in terms of energy and energy-delay product. Alternatively, carbon-based interconnects, such as graphene sheets and carbon nanotubes, are also potential candidates because of their outstanding electrical properties. However, graphene is a two-dimensional structure, and increasing the interconnect pitch does not lower the resistance as fast as it does in copper interconnects. Hence, comparing graphene and copper interconnects strongly depends on the interconnect pitch. As a result, system-level analyses are essential to better understand and evaluate the overall benefits of graphene interconnects. Different from existing system-level performance simulators that are based on cycle-accurate simulations, the present methodology employs three hierarchies of compact analytical models on material, device and interconnect, and system levels, respectively. Significant acceleration is achieved in the simulation speed, making multi-parameter optimization feasible. This run-time efficiency is crucial because many novel device concepts have fundamentally different operational principles, and their on/off currents and input capacitances vary drastically in accordance with their design parameters. This methodology allows technologies to evaluate various trade-offs among key design parameters and to maximize the overall chip throughputs or energy efficiencies of processors in a highly efficient way. For the validation of the proposed methodology, simulation results are compared and well matched with eight commercially available Intel multi-core processors across three technology generations from 65nm to 32nm technology nodes. For the GPNJ-based processors, the proposed design methodology is applied to efficiently perform device-, circuit-, and system-level co-optimization. For given power density and die size area budgets, various device-level parameters, including supply voltage, control voltage, gap distance, and oxide thickness, are optimized for a GPNJ core, where 2.1X throughput improvement is observed for a sharp-corner GPNJ core. This advantage is predominantly because of the smaller output resistance, which reduces both device and interconnect delay and saves the power for repeaters. For the TFET based processors, the results indicate that TFETs have excellent performance at the low power density range due to the low supply voltage. The limitations imposed by the interconnects and the large leakage current at high supply voltage restrict the driving current, leading to a lower performance of the TFETs at a high power density. For the emerging interconnect technology, the proposed Al-Cu hybrid interconnect technology is evaluated by replacing short narrow local signal interconnects by Al interconnects. Six interconnect architecture options are analyzed and their optimal aspect ratio and chip frequency are predicted for five technology generations. The optimization and benchmarking results indicate that the potential improvement in chip clock frequency can be between 50 to 100% for the 7nm technology node. A comprehensive optimization/benchmarking is also performed for the multi-layer graphene interconnects. The results show that a single core using graphene interconnects have a higher throughput within the same power density and die size area because of the power saving offered by the low capacitance graphene interconnects.

Temperature-Dependent Comparison Between Delay of CNT and Copper Interconnects

The performance of gigascale integration chips improves by cryogenic technologies such as subambient cooling. In these conditions, interconnects may perform at temperatures as low as 50 K. However, the local temperature of interconnects could easily be as high as 600 K at high-temperature chips. In this brief, we investigated the impact of temperature on delay of local, intermediate, and global interconnects of International Technology Roadmap for Semiconductors Node 2024. This is done for different values of interconnect width and length, nanotube diameter, and percentage of metallic carbon nanotubes (CNTs) in a grown bundle. Results are compared with those of copper counterpart. We showed that for local layers, a bundle of single-walled CNTs (BSWNTs) interconnects could outperform copper interconnects up to 17%, 35%, and 44%, respectively, at 50, 300, and 600 K, whereas for intermediate and global layers, there is a negligible difference between delay of copper and BSWNT interconnects at all temperatures.

Pool boiling heat transfer enhancement by porous interconnected microchannel nets at different liquid subcooling

Porous interconnected microchannel nets are fabricated in this study using copper powder sintering and wire electric discharge machining. Pool boiling experiments are conducted with this enhanced structure using deionized water as a working fluid at atmospheric pressure with variation in the liquid subcooling. The results of this study indicate that the enhanced structure yields a higher heat transfer coefficient (HTC) than its solid copper counterpart at any liquid subcooling and suppresses the temperature excursion by lowering the wall superheat at the onset of nucleate boiling (ONB). Lowering the liquid subcooling temperature increases the HTC, which is more prevalent at the low heat fluxes. High-speed visualization at 2000 frames/s demonstrates that the bubble departure diameter of the enhanced structure is smaller than that of the solid structure and increases with increasing heat flux for qa ≤ 475 kW/m2 but decreases for qa > 475 kW/m2. Bubble growth at low heat fluxes (qa ≤ 475 kW/m2) is governed by both the inertia-driven and the heat-transfer-driven regimes; whereas, it is governed only by inertia-driven effects for qa > 475 kW/m2. Increasing the liquid subcooling temperature reduces the bubble departure diameter but has little influence on bubble growth.

Embroidered Multiband Body-Worn Antenna for GSM/PCS/WLAN Communications

A novel textile-based body-worn antenna covering the Global System for Mobile Communications/personal communications services/wireless local-area network frequency bands is presented. This antenna was made of densely embroidered metal-coated polymer fibers (e-fibers). These e-fibers are 15 $\mu$ m thick and consist of high strength, flexible polymer cores with conductive silver coatings, providing mechanical flexibility and low loss at radio frequencies. When measured in free space, the textile antenna showed comparable performance to its copper counterpart, having ${\sim}2$ dBi realized gain at all three bands. This textile antenna was simulated and measured on a full body phantom to determine the body's influence on antenna performance, including frequency detuning and pattern shadowing. The measured radiation pattern of the body-worn antenna matched well with simulation at various on-body locations for the three bands. Field measurements were also carried out by mounting the antenna onto the shoulder of a jacket, and using it to replace the one of a cell phone. We found that the communication quality using the body-worn textile antenna was equivalent to the best location of the original cell-phone antenna. Therefore, this textile-based antenna provided for a more reliable body-worn communication when mounted on the body's shoulder.

Selective oxidation of 5-hydroxymethyl-2-furfural into 2,5-diformylfuran over VO2+ and Cu2+ ions immobilized on sulfonated carbon catalysts

Immobilization of vanadyl (VO2+) and cupric (Cu2+) ions on sulfonated carbon and their catalytic activity toward the aerobic oxidation of 5-hydroxymethyl-2-furfural (HMF) are described. The carbon material (C) was derived from commercial ion exchange resin (Amberlyst-15) by performing carbonization process. Subsequently, sulfonated carbon (CS) was prepared by treating C with 98% sulfuric acid. Finally, VO2+ and/or Cu2+ ions were immobilized on CS by ion exchange technique. The synthesized catalysts were characterized by X-ray diffraction (XRD), elemental analysis, Raman spectroscopy, and transmission electron microscopy (TEM). Interestingly, in the catalytic oxidation of HMF using these catalysts, 2,5-diformylfuran (DFF), a high-value chemical is found to be the major product. The VO2+ ion-immobilized catalyst (V-CS) exhibits highly stable catalytic activity without the leaching of vanadyl ion during recycling tests, with low selectivity to DFF. The copper counterpart (Cu-CS), however, shows the opposite behavior, i.e., high selectivity to DFF and decreasing catalytic performance due to the leaching of copper component during recycling runs. The presence of copper in low concentrations in the vanadyl-exchanged catalyst (V-Cu-CS) leads to high selectivity to DFF and good re-usability. A catalyst with the composition 0.93%V–0.26%Cu-CS exhibits the best performance.

A facile electrochemical approach for development of highly corrosion protective coatings using graphene nanosheets

Here, we demonstrated a facile electrochemical approach for deposition of graphene nanosheets on copper substrate. The corrosion activity of graphene coating over bare copper counterpart was investigated with potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The surface of bare copper substrates got destroyed and showed fractures in saline environment attributed to the poor corrosion resistance. Interestingly, the graphene coating remained intact under same stringent conditions and showed robust resistance to corrosion with an inhibition efficiency above 94.3%. The emerging potential of graphene sheets as a metal protecting layer can be believed to be due to the unique physical and chemical properties.

Structural and spectroscopic studies of some adducts of silver(I) salts with ethylenethiourea

Syntheses, single crystal X-ray structural and spectroscopic characterizations are described for a variety of adducts of silver salts with ethylenethiourea (etu). Ag2SO4/etu (1:6) is isomorphous with its previously studied copper(I) counterpart, the [Ag(S-etu)3]+ species disposed with their silver atoms on crystallographic 3-axes, one of the two independent cations being slightly perturbed by a distant O-sulfate approach along that axis. In AgCl/etu (1:3), the silver atom is in a four-coordinate ClAgS3 environment, while AgNO3/etu (1:3) takes the form [(etu)2Ag(µ-S-etu)2Ag(etu)2](NO3)2. AgBr/etu (1:2) is binuclear [(etu)2Ag(µ-Br)2Ag(etu)2)], unlike its previously studied copper counterpart, which is [(etu)BrCu(µ-S-etu)2CuBr(etu)]. AgCl/etu (4:6) is an interesting ionic polymer [ClAg4(etu)6](∞|∞)Cl3, containing a novel one-dimensional polymeric cation. Bands in the far IR spectra of these compounds are assigned to v(AgS) and v(AgX) (X = halogen) modes, and a correlation between v(AgS) and the Ag–S bond length d(AgS) is established for silver complexes involving the etu ligand.Key words: silver, sulfur ligands, X-ray crystal structure, coordination chemistry, complexes.

Structural Characterization of Some Coinage Metal(I) Thiosulfate Complexes, $\rm M^{1}_{a}M\rm ^{2}_{b}(X_{c}) (S_{2}O_{3})_{d}(\cdot eS)$ (M1 = Group 1 Cation, X = Univalent Anion, M2 = CuI, AgI, S = Solvent)

AbstractBuilding on previous single crystal X‐ray structure determinations for the group 1 salts of complex thiosulfate/univalent coinage metal anions previously defined for (NH4)9AgCl2(S2O3)4, NaAgS2O3·H2O and Na4[Cu(NH3)4][Cu(S2O3)2]·NH3, a wide variety of similar salts, of the form $\rm M^{1}_{a}M\rm ^{2}_{b}(X_{c}) (S_{2}O_{3})_{d}$, M1 = group 1 metal cation, M2 = univalent coinage metal cation (Cu, Ag), (X = univalent anion), most previously known, but some not, have been isolated and subjected to similar determinations. These have defined further members of the isotypic, tetragonal $I{\bar 4} {\rm 2}d \textrm{ }{\rm M^{1}_{9}M^{2}X_{2}(S_{2}O_{3})_{4}({\equiv}M^{1}_{9}X_{2}[M^{2}}(S{\rm SO_{3})_{4}]{\equiv}2M^{1}X}.\textrm{ } {\rm M^{1}_{7}[M^{2}}(S{\rm SO_{3})_{4}]}$ series, for M1 = NH4, M2 = Cu, Ag, X = NO3, Cl, Br, I, together with the K/Cu/NO3 complex, all containing the complex anion [M2(SSO3)4]7− with M2 in an environment of $\rm {\bar 4}$ symmetry, Cu, Ag‐S typically ca. 2.37, 2.58Å, with quasi‐tetrahedral S‐M‐S angular environments. Further salts of the form $\rm M^{1}_{2n-1}M^{2}(S_{2}O_{3})_{n}(\cdot xH_{2}O)$, n = 1‐3, have also been defined: For n = 3, M2 = Cu, M1/x = K/2.25 or 1 5/6, NH4/6, (and also for the (NH4)4Na/4H2O·MeOH adduct) the arrays take the form ${\rm M^{1}_{5}[Cu}(S{\rm SO_{3})_{3}]{\cdot}xS}$ with distorted trigonal planar CuS3 coordination environments, Cu‐S distances being typically 2.21Å, S‐Cu‐S ranging between 105.31(4)–129.77(4)°; the silver counterparts take the form ${\rm M^{1}_{10}[(O_{3}S}S){\rm_{2}Ag(\mu-}S{\rm SO_{3}})_{2}{\rm Ag}(S{\rm SO_{3}})_{2}]$ for M1 = K, NH4. For n = 2, adducts have only been defined for M2 = Ag, the anions of the M1 = Na, K adducts being dimeric and polymeric respectively: Na6[(O3SS)2Ag(μ‐SSO3)2Ag(SSO3)]·3H2O, K3[Ag(μ‐SSO3)2](∞|∞)·H2O; a polymeric copper(I) counterpart of the latter is found in Na5Cu(NO3)2(S2O3)2 ≡ 2NaNO3·Na3[Cu(μ‐SSO3)2](∞|∞). For n = 1, NaAgS2O3, the an‐ and mono‐ hydrates, exhibit a two‐dimensional polymeric complex anion in both forms but with different contributing motifs. (NH4)13Ag3(S2O3)8·2H2O takes the form (NH4)13[{(O3SS)3Ag(μ‐SSO3)}2Ag], a linearly coordinated central silver atom linking a pair of peripheral [Ag(SSO3)4]7− entities. In Na6[(O3SS)Ag(μ‐SSO3)2Ag(SSO3)]·3H2O, the binuclear anions present as Ag2S4 sheets, the associated oxygen atoms being disposed to one side, thus sandwiching layers of sodium ions; the remarkable complex Na5[Ag3(S2O3)4](∞|∞)·H2O is a variant, in which one sodium atom is transformed into silver, linking the binuclear species into a one‐dimensional polymer. In (NH4)8[Cu2(S2O3)5]·2H2O a binuclear anion of the form [(O3SS)2Cu(μ‐S.SO3)Cu(SSO3)2]8− is found; the complex (NH4)11Cu(S2O3)6 is 2(NH4)2(S2O3)·(NH4)7[Cu(SSO3)4]. A novel new hydrate of sodium thiosulfate is described, 4Na4S2O3·5H2O, largely describable as sheets of the salt, shrouded in water molecules to either side, together with a redetermination of the structure of 3K2S2O3·H2O.

Trinuclear Schiff base complexes with uranium(V) and copper(II) or zinc(II) ions

Treatment of the uranium(IV) complexes [{ML 1(py)} 2U IV] (M = Cu, Zn; L 1 = N, N′-bis(3-hydroxysalicylidene)-1,3-propanediamine) with silver nitrate in pyridine led to the formation of the corresponding cationic uranium(V) species which were found to be thermally unstable and were converted back into the parent U IV complexes; no electron transfer was observed in solution between the U IV and U V compounds. In the crystals of [{ML 1(py)} 2U IV][{ML 1(py)} 2U V][NO 3], the neutral U IV and cationic U V species are clearly identified by the distinct U–O distances. Similar reaction of [{ZnL 2(py)} 2U IV] [L 2 = N, N′-bis(3-hydroxysalicylidene)-1,4-butanediamine] with AgNO 3 gave crystals of [{ZnL 2(py)}U V{ZnL 2(py) 2}][NO 3] but the copper counterpart was not isolated. Crystals of [{ZnL 1(py)} 2U V][OTf] · THF (OTf = OSO 2CF 3) were obtained fortuitously from the reaction of [Zn(H 2L 1)] and U(OTf) 3.

Syntheses, structures and vibrational spectroscopy of some unusual silver(I) (pseudo-) halide/unidentate nitrogen base polymers

The meagre (structurally defined) array of 1:2 silver(I) (pseudo-)halide:unidentate nitrogen base adducts is augmented by the single-crystal X-ray structural characterization of the 1:2 silver(I) thiocyanate:piperidine (‘pip’) adduct. It is of the one-dimensional ‘castellated polymer’ type previously recorded for the chloride: ⋯Ag(pip) 2(μ- SCN)Ag(pip) 2⋯ a single bridging atom ( S) linking successive silver atoms. By contrast, in its copper(I) counterpart, also a one-dimensional polymer, the thiocyanate bridges as end-bound SN-ambidentate: ⋯Cu SC NCu SC N⋯ A study of the 1:1 silver(I) bromide:quinoline (‘quin’) adduct is recorded, as the 0.25 quin solvate, isomorphous with its previous reported ‘saddle polymer’ chloride counterpart. Recrystallization of 1:1 silver(I) iodide:tris(2,4,6-trimethoxyphenyl)phosphine (‘tmpp’) mixtures from py and quinoline (‘quin’)/acetonitrile solutions has yielded crystalline materials which have also been characterized by X-ray studies. In both cases the products are salts, the cation in each being the linearly coordinated silver(I) species [Ag(tmpp) 2] +, while the anions are, respectively, the discrete [Ag 5I 7(py) 2] 2− species, based on the already known but unsolvated [Cu 5I 7] 2− discrete, and the [ Ag 5 I 7 ] ( ∞ | ∞ ) 2 - polymeric, arrays, and polymeric [ Ag 5 I 6 ( quin ) ] ( ∞ | ∞ ) - . The detailed stereochemistry of the [Ag(tmpp) 2] + cation is a remarkably constant feature of all structures, as is its tendency to close-pack in sheets normal to their P–Ag–P axes. The far-IR spectra of the above species and of several related complexes have been recorded and assigned. The vibrational modes of the single stranded polymeric AgX chains in [XAg(pip) 2] (∞|∞) (X = Cl, SCN) are discussed, and the assignments ν(AgX) = 155, 190 cm −1 (X = Cl) and 208 cm −1 (X = SCN) are made. The ν(AgX) and ν(AgN) modes in the cubane tetramers [XAg(pip)] 4 (X = Br, I) are assigned and discussed in relation to the assignments for the polymeric AgX:pip (1:2) complexes, and those for the polymeric [XAg(quin)] (∞|∞) (X = Cl, Br) compounds. The far-IR spectra of [Ag(tmpp) 2] 2[Ag 5I 7(py) 2] and its corresponding 2-methylpyridine complex show a single strong band at about 420 cm −1 which is assigned to the coordinated tmpp ligand in [Ag(tmpp) 2] +, and a partially resolved triplet at about 90, 110 and 140 cm −1 which is assigned to the ν(AgI) modes of the [Ag 5I 7L 2] 2− anion. An analysis of this pattern is given using a model which has been used previously to account for unexpectedly simple ν(CuI) spectra for oligomeric iodocuprate(I) species.

Compact superconducting dual-log spiral resonator with high Q-factor and low power dependence

A new dual-log spiral geometry is proposed for microstrip resonators, offering substantial advantages in performance and size reduction at subgigahertz frequencies when realized in superconducting materials. The spiral is logarithmic in line spacing and width such that the width of the spiral line increases smoothly with the increase of the current density, reaching its maximum where the current density is maximum (in its center for /spl lambda//2 resonators). Preliminary results of such a logarithmic ten-turn (2 /spl times/ 5 turns) spiral, realized with double-sided YBCO thin film, showed a Q.-factor seven times higher than that of a single ten-turn uniform spiral made of YBCO thin film and 64 times higher than a copper counterpart. The insertion loss of the YBCO dual log-spiral has a high degree of independence of the input power in comparison with a uniform Archimedian spiral, increasing by only 2.5% for a 30-dBm increase of the input power, compared with nearly 31% for the uniform spiral. A simple approximate method, developed for prediction of the resonant frequency of the new resonators, shows a good agreement with the test results.

FABRICATION AND CHARACTERIZATION OF Cu-SiCp COMPOSITES FOR ELECTRICAL DISCHARGE MACHINING APPLICATIONS

Cu-SiCp composites made by the powder metallurgy method were investigated. To avoid the adverse effect of Cu-SiCp reaction, sintering was controlled at a reaction temperature less than 1032 K. Electroless plating was employed to deposit a copper film on SiCp powder before mixing with Cu powder in order to improve the bonding status between Cu and SiC particles during sintering. It was found that a continuous copper film could be deposited on SiCp by electroless copper plating, and a uniform distribution of SiCp in Cu matrix could be achieved after the sintering and extrusion process. The mechanical properties of Cu-SiCp composites with SiCp contents from 0.6 to 10 wt% were improved evidently, whereas electrical properties remained almost unchanged as compared with that of the pure copper counterpart. In the electrical discharge machining (EDM) test, the as-formed composite electrodes exhibited a character of lower electrode wear ratio, justifying its usage. The optimum conditions for EDM were Cu–2 wt% SiCp composite electrode operating with a pulse time of 150 μsec.