S. A. Impey

Microstructural characterization of sol–gel lead–zirconate–titanate thin films

The techniques of x-ray diffraction, x-ray photoelectron spectroscopy (XPS), Auger analysis, and transmission and scanning transmission electron microscopy (TEM) have been applied to the analysis of thin films of Pb(Zr0.30Ti0.70)O3 (PZT30/70) deposited at low temperatures (510 °C) by a sol–gel process onto Pt/Ti electrodes on SiO2/Si 100 substrates. It is found that the platinum film is highly oriented with the [111] axis perpendicular to the substrate plane. The ferroelectric film tends to crystallize epitaxially upon this as columnar crystals. There are indications from the TEM of the existence of a second metallic phase at the interface between the platinum and the PZT30/70 film, which may be associated with its nucleation. The TEM shows the boundaries between the individual sol–gel layers, although the growing crystallites of the PZT30/70 propagate through these boundaries unhindered. The XPS and Auger analyses have shown that Pb penetrates through the Pt layer to the underlying Ti layer, even at the ...

Nickel oxide sol–gel films from nickel diacetate for electrochromic applications

Abstract Nickel diacetate tetrahydrate, [Ni(acetate)2·4H2O] and nickel diacetate dimethylaminoethanol, [Ni(acetate)2(dmaeH)2] were successfully used to deposit NiOx thin films on conductive glass substrates by sol–gel techniques for large area electrochromic applications. Homogeneous one layer films 100 nm thick were deposited by spin coating 0.5 M [Ni(acetate)2·4H2O] in dmaeH at 1000 rpm and by dip coating methods. The NiOx films were characterised by X-ray diffraction, transmission electron microscopy and atomic force microscopy. The thin film electrochromic performances were characterised by means of optical (transmittance) and electrochemical (cyclic voltammetry) methods. On early cycling NiOx thin films present an activation period, related to an increase in capacity. The electro-optical data show an increase in the electrochromic response (i.e. an increase in contrast and colouration efficiency) upon cycling. Following this initial activation period a steady state is reached in which the thin films reversibly switch from transparent to brown. The anodically coloured NiOx thin films are therefore suitable for use in a complete electrochromic cell with tungsten oxide as the cathodic colouring layer. However, the films are not fully stable with long cycling.

A TEM and neutron diffraction study of the local structure in the rhombohedral phase of lead zirconate titanate

Transmission electron microscopy and neutron diffraction have been used to characterize ceramics and single crystals from the rhombohedral region of the (x = 0.06-0.45) phase diagram. Electron diffraction patterns showed the existence of superlattice reflections of the type , where h = k = l, and , which are not observed by neutron powder diffraction. The analysis of these reflections also revealed satellite spots around the , which are associated with periodic antiphase boundaries. The origin of these superlattice reflections is explained by the existence of local regions presenting antiparallel cation displacements, and models for this are suggested

Synthesis and crystal structures of dimethylaminoethanol adducts of Ni(II) acetate and Ni(II) acetylacetonate. Precursors for the sol–gel deposition of electrochromic nickel oxide thin films

The reaction between N,N-dimethylaminoethanol (dmaeH) and nickel(II) acetylacetonate, [Ni(acac)2]3 or Ni(II) acetate tetrahydrate, [Ni(CH3CO2)2(H2O)4] yields the new complexes [Ni(acac)2(dmaeH)] (1) and [Ni(CH3CO2)2(dmaeH)2] (2). Complexes (1) and (2) are mononuclear, containing six-coordinate Ni(II) atoms in slightly distorted octahedral environments. Complex (1) contains two bidentate and chelating acetylacetonate groups with a chelating dmaeH ligand. Complex (2) contains two monodentate acetate groups in a cis configuration and two chelating dmaeH ligands. Both complexes dissolve readily in dmaeH to form stable solutions, and are good precursors for the deposition of NiO thin films by sol–gel techniques. (1) and (2) were successfully used to grow electrochromic NiO thin films on conductive glass substrates. The surface morphology of the films was characterised by scanning electron microscopy (SEM) and atom force microscopy (AFM). The thin film performances were characterised by means of optical (transmittance) and electrochemical (cyclic voltammetry) methods. Upon cycling, the NiO thin films switch from brown to transparent in a reversible way exhibiting anodic electrochromic performance.

The Causes and Prevention of Smut on Etched AISI 300 Stainless Steels

Abstract During the fabrication of stainless steel parts by photochemical machining (PCM), a seemingly random occurrence of a partially-adherent, brown/black deposit, known as smut, can occur. This quality problem has plagued the PCM industry for over 30 years. In the past, the problem has been attributed to “poor etch-quality” stainless steel. However, an extensive investigation by the authors, comprising some 7 person-years of effort, has established that while the metallurgy of the stainless steel has some influence on the formation of smut, by far the most important factor is the condition of the ferric chloride etchant used for etching the parts. The influences of etchant concentration, free hydrochloric acid content, temperature, atmosphere and hydrodynamic flow have now been assessed quantitatively for the first time. The investigation has led to the development of a theory outlining the causes of smut formation, thus providing solutions for its prevention.

Structure zone diagram and particle incorporation of nickel brush plated composite coatings

This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%.

Single point diamond turning of ferroelectric materials

Abstract One of the most important ferroelectric ceramics materials used in a wide range of applications is the lead zirconate titanate solid solution series (PZT). The possibility of machining brittle materials using single point diamond turning in a ‘ductile mode’ has been investigated by many researchers in recent years. The ability to machine ferroelectrics in a ductile manner and by so doing reduce sub-surface damage, could eliminate the need for subsequent lapping and polishing and thus reduce production costs. Fracture mechanics techniques were used to investigate the localised elastic/plastic behaviour. PZT ceramics in the poled and unpoled state were single point diamond turned under different machining conditions and ductile machining has been achieved. X-ray diffraction indicates the degree of domain reorientation caused by machining, and it is suggested that the strain generated by reorientation accounts for brittle damage. Appropriate poling can have a marked effect on the brittle/ductile mac...

FEA Simulation Model in Support of the Mechanical Reliability of Automotive Exhaust Gas Temperature Sensors

Automotive exhaust gas temperature sensors are fitted to monitor the performance of a vehicle emission control system. The aggressive working environment is a big challenge in sensor design. This paper introduces an FEA simulation model developed to support the mechanical reliability of new sensor designs. The simulation model was validated by laboratory tests. Suggestions for optimising sensor reliability are given based on the simulation results.

Analysis of infrared optical polishing effluents and reduction of COD and TSS levels by ultrafiltration and coagulation/flocculation

AbstractSamples of polishing effluent produced during infrared optics manufacture were analyzed. Their particle size, composition, Zeta potential, chemical oxygen demand (COD), total suspended solids (TSS), and settleable solids were determined. Feasibility of treatment methods such as ultrafiltration (UF) and coagulation/flocculation was investigated to reduce both COD and TSS. It was found that effluents consisted of a suspension of micro- and nanoparticles. Effluent particle size distribution reflected the removal rate of the originating polishing process. Their composition was primarily germanium and other polished substrates as well as polishing abrasives. The effluent Zeta potential was highly negative and prevented particle settling. COD of all specimens was very high, which prevented sewage discharge. Laboratory-scale trials using UF showed substantial COD abatement of up to 74.1%. TSS was reduced to zero after UF. Comparable coagulation/flocculation COD abatement was demonstrated for the highest ...

Nature and influence of surface layers and films on the chemical and electrochemical micromachining of NiTi shape memory alloys

Shape memory alloys are used in the manufacture of microactuators and stents. This paper discusses (1) the nature of the surface oxide layer on NiTi shape memory alloys; (2) its role in protecting the underlying base metal from chemical and electrochemical etchants; (3) how the oxide can be removed and;; (4) the necessity of rapid by- product removal from the metal-etchant interface to achieve even the etching of the underlying alloy.