Nanocrystalline Electrodeposits Research Articles

Electrodeposition as an Alternative Approach for Monolithic Integration of InSb on Silicon.

High-performance electronics would greatly benefit from a versatile III-V integration process on silicon. Unfortunately, integration using hetero epitaxy is hampered by polarity, lattice, and thermal expansion mismatch. This work proposes an alternative concept of III-V integration combining advantages of pulse electrodeposition, template-assisted selective epitaxy, and recrystallization from a melt. Efficient electrodeposition of nano-crystalline and stochiometric InSb in planar templates on Si (001) is achieved. The InSb deposits are analysed by high resolution scanning transmission electron microscopy (HR-STEM) and energy-dispersive X-ray spectroscopy (EDX) before and after melting and recrystallization. The results show that InSb can crystallise epitaxially on Si with the formation of stacking faults. Furthermore, X-ray photoelectron (XPS) and Auger electron (AE) spectroscopy analysis indicate that the InSb crystal size is limited by the impurity concentration resulting from the electrodeposition process.

Synergistic effect of surfactant and saccharin on dispersion and crystal refinement for electrodeposition of nanocrystalline nickel/graphene oxide composite

Homogeneous dispersion of graphene oxide (GO) in nickel sulfamate solution is a significant challenge for electrodepositing high-performance nickel/GO composite coatings. In the present work, three typical surfactants, including anionic surfactant Sodium dodecyl sulfate (SDS), cationic surfactant Cetyltrimethylammonium bromide (CTAB), and non-ionic surfactant Polyethylene glycol (PEG), and saccharin are used to disperse GO nanoparticles and refine crystallite size of nickel/GO composite coating. The synergistic effect of surfactant and saccharin is revealed from the perspectives of dispersion, crystal refinement and their impact on mechanical and tribological properties of nickel/GO composite coating. Our results indicate that PEG possesses the optimal dispersibility to GO dispersion, followed by CTAB and SDS. The addition of saccharin in electrolyte does not affect the surface charge of GO particles, but it helps to reduce the particle size of GO and thus reduce potential reaggregation. Additionally, PEG shows the most significant reduction of crystallite size from ~35 nm to ~19 nm. The synergetic effect of surfactant and saccharin is indicated by increasing the concentration of saccharin from 0 to 0.2 g/L with various surfactants, where the overall crystallite size is gradually reduced. Moreover, the hardness of PEG-GO and CTAB-GO coatings is remarkably increased by 252% and 312%, respectively, compared to pure nickel coating. The increased hardness is due to the synergistic effect of crystal refinement from both additions of GO and saccharin. The tribological test indicates that the PEG-GO coating can achieve the maximum reduction of friction coefficient with 0.15 with the addition of saccharin of 0.2 g/L.

Electrodeposition of Bulk Nanocrystalline Ni-Fe-P Alloys and Their Mechanical and Soft Magnetic Properties

Electrodeposited Ni-Fe alloys are expected to have an improved mechanical strength because of their nanocrystalline structure. However, unsatisfactory grain refinement yields a higher coercivity compared with conventional permalloys, which is undesirable in soft magnetic materials. We report electrodeposited Ni-Fe-P alloys that combine the mechanical properties of nanocrystalline materials with soft magnetism that is achievable in coarse-grained permalloys. Up to 2.0 at% P, the resultant Ni-Fe-P alloys achieved a tensile strength of 2.1 GPa, along with a plastic deformability. The electrodeposited alloys exhibited a saturation magnetic flux density of 1.1 T and a coercivity of 8.4 A/m. Our approach indicates that graine refinement by the P alloying can result in a lower coercivity, according to the law of the grain size and coercivity.

Electrodeposition of nanocrystalline nickel embedded with inert nanoparticles formed via inverse hydrolysis

Nanocrystalline electrodeposits embedded with inert hard nanoparticles are applied to coating on engineering materials for high hardness and thermal stability. They have mainly been synthesized from a solution containing a suspension of particles in electrodeposition. In this conventional synthesis, finer particles tend to agglomerate in the electrolyte and are embedded inhomogeneously in the electrodeposits. This work provides a different approach to synthesizing nanocrystalline metal electrodeposits embedded with inert metal oxide particles that are formed through inverse hydrolysis in an electrolyte before embedding in the electrodeposits. In principle, this approach would allow the embedding of particles ranging, in size, from the molecular to the micron scale through control of the pH and the duration of stand-by reaction prior to electrodeposition. Effect of this approach on the hardness and thermal stability of Ni electrodeposits was validated, and agree semi-quantitatively with theoretical values predicted by Orowan strengthening and Zener pinning, both of which assume that dispersed particles are smaller than the matrix grain size.

Electrodeposition of nanocrystalline zinc‑tin alloy from aqueous electrolyte containing gluconate in the presence of polyethylene glycol and hexadecyltrimethylammonium bromide

Electrodeposition of nanocrystalline Zn-Sn alloy was investigated in aqueous acidic electrolyte containing gluconate in the absence and presence of additives. Distribution diagrams of Zn (II) and Sn (II) species in acidic gluconate electrolyte showed that ZnSO4 and Sn(GH4)+ were the main species over the pH range of 2 to 5. The surface morphology of the Zn-Sn alloy deposited under various plating conditions showed that the production of nanocrystalline structure was not possible in the absence of additives. Additions of hexadecyltrimethylammonium bromide (CTAB) and polyethylene glycol (PEG) with various molecular weight (M¯n = 400 and 2050 g mole−1) were found to assist the formation of nanocrystalline structure. In the presence of CTAB and equal concentrations of PEG, the surface morphology of deposits exhibited a finer and more uniform structure with PEG 2050 than PEG 400. Nanocrystalline Zn-Sn alloy coating was produced from the bath containing 1 mM of CTAB and 1 g/L of PEG 2050. All zinc‑tin alloy deposits exhibited a low tin content (<35 wt%) as identified by EDS. X-ray diffraction patterns of deposits showed peaks of hexagonal zinc and tetragonal tin and confirmed the production of a co-deposited alloy coating, akin to a mechanical type zinc‑tin plating.

One-Step Electrodeposition of Nanocrystalline TiO2 Films with Enhanced Photoelectrochemical Performance and Charge Storage

With the rapid development of renewable energy technologies there is an urgent need to find synthesis routes that address the needs of materials in a reproducible and affordable way. In this study, we present a one-step electrochemical method for the deposition of nanocrystalline titanium dioxide films on different carbon substrates. By optimizing the synthetic conditions, electrodeposition of nanocrystalline and porous titanium dioxide layers was achieved in only a few minutes. To deconvolute the complex effect of the solution pH and temperature, as well as the deposition potential, a set of systematic experiments was carried out on glassy carbon electrodes. The robustness and general applicability of this synthetic approach is demonstrated by extending it to graphene film electrodes. The phase composition of TiO2 was controlled by varying the solution composition. The photoelectrochemical performance of the electrodeposited titanium dioxide films was better than, or at least comparable to the benchmark...

Corrosion behaviour of electrodeposited nanocrystalline nickel-iron (NiFe) alloys in dilute H2SO4

Electrodeposited nanocrystalline and conventional polycrystalline NiFe alloys of similar iron content were investigated to understand the effect of grain size on the corrosion behaviour of these materials. Potentiodynamic polarization testing in 1N H2SO4 revealed similar active-passive-transpassive behaviour with negligible differences in the Tafel and transpassive regions regardless of grain size. It is shown that differences in the region of active dissolution are the result of strong contributions of sulfur impurities in the nanocrystalline electrodeposits rather than being due to grain size alone.

Electrodeposition of nanocrystalline Zn/Ni multilayer coatings from single bath: Influences of deposition current densities and number of layers on characteristics of deposits

Zn/Ni nanocrystalline multilayer coatings were electrodeposited using single bath method and switching current densities. Effect of deposition current densities (i1 and i2) and number of layers (n) on composition, surface morphology and roughness, microhardness, phase structure and corrosion resistance of Zn/Ni multilayers were studied and compared with that of single layer. Analyzing and optimizing the influences of mentioned parameters on corrosion resistance of multilayers carried out through Response Surface Methodology. The model based on RSM results demonstrated that improvement in corrosion resistance due to increase in “difference of deposition current densities” was more effective in higher number of layers. Also, as the mentioned difference surpassed from a defintie value, the reduction trend of corrosion current density approximately stopped. The overall Ni content of the multilayer with least corrosion current was less than that of specimens with higher Ni content. Increase in number of layers could enhance the microhardness more than 50%. Also, layering leaded to finer surface morphology as well as lower roughness. The interfaces in deposited multilayers comprised of same crystall structure (Ni2Zn11) but different composition and crystallite size.

(Invited) Stable Nanocrystalline Electrodeposits: Case Studies Spanning from Theory to Products

Although many metals and alloys can be electrodeposited with nanoscale internal structure, few of these are stable enough for engineering use. Many more have processing and property disadvantages that prohibit commercialization. This talk will describe a general recipe developed at MIT and subsequently at Xtalic Corporation (Marlborough, MA) for the design of stable and deployable nanocrystalline electrodeposits. Such deposits have the strength, hardness and wear benefits well known to nanostructured metals, but with a stabilized structure that resists coarsening even under significant heating conditions. Three case studies will be discussed, for alloy coatings based on Ni, Ag, and Al. With emphasis on the basic theory of alloy design, through reduction to practice, and to commercialization at the level of billions of coated components, the talk will highlight the role of thermodynamic thinking in streamlining the search for product-viable electrodeposits.

Electroplating Titanium on Conductive and Non-Conductive Substrates

Crista Chemical Company LLC’s (3C) goal was to develop a novel, low-cost, industrial method of plating titanium on metallic and nonmetallic materials. Crista Chemical Company achieved this goal by developing an innovative technology of titanium electroplating and receiving a patent for the achievement U.S. Patent No. 9,023,187, and soon to be published ASTM B999-15. The innovation was ground breaking as before the discovery, titanium electroplating was considered impossible. Crista Chemical Company’s revolutionary innovation electrodeposits coatings of Titanium and Titanium-zirconium alloys on conductive and non-conductive substrates coated with low, medium, or high phosphate electroless nickel. Two methods of titanium deposition were designed and optimized. One was a conventional electroplating method—which used constant current—and another one was a nanocrystalline electrodeposition (we refer to as the “turbo method”), which uses pulse plating. In both methods electrodeposition of the titanium alloys proceeded from the sulfuric acid solution. The advantages of the method of plating titanium include a) low cost, b) relatively low number of process steps, thus posing minimal effect on the environment (safer and zero discharge process) and c) very broad application. Moreover, Produced materials are characterized by a) light weight, b) high corrosion resistance c) high yield strength, d) wear resistance, e) high resilience, stiffness at room temperature as well as at elevated temperature (e.g. up to 200C). This makes the titanium coating an attractive technology for a variety of industries including: high efficiency batteries, medical applications, biotechnology, aerospace, defense, sports and automotive.

Scale-dependent failure of stereolithographic polymer microtrusses in three-point bending

Microtrusses fabricated by a combination of stereolithography and nanocrystalline electrodeposition are composites at both a global architectural scale and at an individual strut scale. This fabrication route is especially attractive in producing high performance lightweight materials because the key stages of forming optimally efficient templates and depositing ultra high strength material are fully decoupled. Using novel 3-D printing techniques, this study analyzes microtrusses built bottom-up from photopolymerizable polymer where the complex structure can be constructed of unit cells a few millimeters in length. While the predicted failure mechanisms matched the experimental observations, deterministic energetic size effects were needed to account for the critical loads. For strut radii &lt;5 × the 3-D printer layer thickness, stochastic size effects became important.

Co-W nanocrystalline electrodeposits as barrier for interconnects

This study was performed in order to investigate a possibility to obtain Co-W microbumps via electrochemical routes, because this alloy recently has gained attraction as a novel barrier against copper diffusion. In order to be applied in flip-chip technology, barrier layers should be void-free and uniformly deposited on the entire area of a die to ensure high reliability and high performance of wafer bump-solder interface. To meet these requirements, a set of potentiostatic and galvanostatic electrodeposition was carried out from a citrate electrolyte, at pH 5 and at room temperature. The tests done confirm that void-free Co-W bumps with a uniform tungsten content along the bump can be obtained by potentiostatic and galvanostatic electrodeposition. Successful electrodeposition of Cu/Co-W/Sn layers with good adhesion between them and uniformity on the entire array of bumps also was obtained. The XPS data confirm that electrodeposited Co-W layers can act as a good barrier between Sn and Cu.

Enhanced Rate Performance of Mesoporous Co3O4Nanosheet Supercapacitor Electrodes by Hydrous RuO2Nanoparticle Decoration

Mesoporous cobalt oxide (Co3O4) nanosheet electrode arrays are directly grown over flexible carbon paper substrates using an economical and scalable two-step process for supercapacitor applications. The interconnected nanosheet arrays form a three-dimensional network with exceptional supercapacitor performance in standard two electrode configuration. Dramatic improvement in the rate capacity of the Co3O4 nanosheets is achieved by electrodeposition of nanocrystalline, hydrous RuO2 nanoparticles dispersed on the Co3O4 nanosheets. An optimum RuO2 electrodeposition time is found to result in the best supercapacitor performance, where the controlled morphology of the electrode provides a balance between good conductivity and efficient electrolyte access to the RuO2 nanoparticles. An excellent specific capacitance of 905 F/g at 1 A/g is obtained, and a nearly constant rate performance of 78% is achieved at current density ranging from 1 to 40 A/g. The sample could retain more than 96% of its maximum capacitance even after 5000 continuous charge-discharge cycles at a constant high current density of 10 A/g. Thicker RuO2 coating, while maintaining good conductivity, results in agglomeration, decreasing electrolyte access to active material and hence the capacitive performance.

Effects of processing on texture, internal stresses and mechanical properties during the pulsed electrodeposition of nanocrystalline and ultrafine-grained nickel

The mechanical properties of nanocrystalline and ultrafine-grained metals strongly depend on grain size, grain boundary segregation, texture and internal stresses. In this paper a thorough systematic analysis is given on the influence of different pulsed electrodeposition processing parameters and grain refiners on the grain size, texture and segregation of Ni and thus on internal stresses. The grain refiner content of the electrolyte, mainly the saccharin content, and the pulse parameters on- and off-time as well as the pulse current density were varied systematically. The combination of different methods of stress and texture analysis allows, among other things, a careful discussion of the influence of saccharin on stress and texture development. Massive tensile specimens were produced with different grain sizes and deformed in incremental load tests. These tests clearly demonstrate the strong effect of the production process on the deformation behavior under constant load.

A Galvanostatic Modeling for Preparation of Electrodeposited Nanocrystalline Coatings by Control of Current Density

The correlation between the grain size of electrodeposited coatings and the current densities was modeled by considering galvanostatic conditions. In order to test the model by experimental results, nanocrystalline (NC) nickel samples were deposited at different current densities using a Watts bath. The grain size of the deposits was evaluated by X-ray diffraction (XRD) technique. Model predictions were validated by finding a curve being the best-fit to the experimental results which were gathered from literature for different NC coatings in addition to those data measured in this research for NC nickel coatings. According to our model, the variation of grain size with the reciprocal of the current density follows a power law. A good agreement between the experimental results and model predictions was observed which indicated that the derived analytical model is applicable for producting the nanocrystalline electrodeposits with the desired grain size by controling current density.

Effects of cis-2-butene-1,4-diol additive and pulse current imposition on production of Ni nanocrystalline coatings

Nickel nanocrystalline electrodeposits were produced from a Watts type bath with the addition of cis-2-butene-1,4-diol and simultaneous application of either direct or pulse current conditions. The surface morphology, the preferred orientation, grain size and microhardness of Ni deposits were determined as functions of the concentration of the additive in bath, the type of imposed current and the frequency of imposed current pulses. The combined imposition of predefined pulse current conditions (pulse frequency) and specific additive concentration in the bath leads to specific textural modifications ([211] and [100] preferred crystal orientations) accompanied by considerable nanosized grain refinement of the coatings. The overall experimental data indicate that the production of hard and bright nanostructured deposits could be obtained under pulse current regime and reduced amounts of cis-2-butene-1,4-diol compared to direct plating.

Reinforcement of microtruss cellular materials by nanocrystalline electrodeposition

Compositionally graded microtruss cellular materials can be created by electrodepositing ultrahigh-strength sleeves of nanocrystalline material over precursor microtruss cores. Due to their position relative to the neutral axis of the struts, even relatively thin coatings can provide significant strength and weight benefits to the precursor assembly. Using nanocrystalline nickel as an example, the questions of strength prediction, performance increase, sleeve/core delamination and sleeve fracture are discussed.

Mechanical anisotropy in electrodeposited nanocrystalline metal/metal composite foams

Electrodeposition can be used to create new types of nanocrystalline metal/metal composites. In addition to increasing the strength and stiffness of conventional metal foams, electrodeposition also has the effect of introducing mechanical anisotropy to the cellular architecture. Because of electromagnetic shielding effects, outer ligaments receive more electrodeposited material than inner ligaments, creating a gradient in structural reinforcement. This study provides a first examination of the compressive strength and stiffness anisotropy introduced by nanocrystalline electrodeposition.

Residual stress in electrodeposited nanocrystalline nickel-tungsten coatings

Abstract

Electrodeposited Nanocrystalline Ni-Fe with Banded Structure

The microstructure of a Ni–18 wt.% Fe electrodeposits having a banded structure is described in detail. The aim is to investigate the influence of the banded structure on grain growth behaviour and texture and to elucidate if there are other mechanisms operative in the stabilization of nanocrystalline electrodeposits. Spectroscopy techniques have been used to characterize the variations in alloy/impurity concentration perpendicular to the growth direction. The influence of these chemical variations on the microstructural evolution has been monitored by in-situ annealing treatments in the TEM. Local texture of the annealed material has been determined by use of the electron backscatter diffraction (EBSD) technique. SEM and TEM investigations have shown that the banded structure is not related to phase changes and that grain growth is not affected by the banded structure, i.e. there is no preferred growth along bands. The first grown grains have &lt;100&gt;, &lt;112&gt; and &lt;111&gt; orientations with the growth direction and upon further grain growth a &lt;111&gt; fibre texture with respect to the growth direction of the electrodeposits is formed. The banded structure seems not to affect the general behaviour of nanocrystalline electrodeposits.