Microstructural evolution and characterisation of interfacial phases in Al<inf>2</inf>O<inf>3</inf>/Ag-Cu-Ti/Al<inf>2</inf>O<inf>3</inf> braze joints

Alumina ceramics with different levels of purity have been joined to themselves using an active braze alloy (ABA) Ag–35.3Cu–1.8Ti wt.% and brazing cycles that peak at temperatures between 815 °C and 875 °C for 2 to 300 min. The microstructures of the joints have been studied using scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. A limited number of joints prepared with the ABA Ag–26.7Cu–4.5Ti wt.% have also been studied. In terms of characterising the interfacial phases, efforts were made to understand the interfacial reactions, and to determine the influence of various brazing parameters, such as the peak temperature (Tp) and time at Tp (τ), on the microstructure. In addition, the extent to which impurities in the alumina affect the interfacial microstructure has been determined. Ti3Cu3O has been identified as the main product of the reactions at the ABA/alumina interfaces. At the shortest joining time used, this phase was observed in the form of a micron-size continuous layer in contact with the ABA, alongside a nanometre-size layer on the alumina that was mostly composed of γ-TiO grains. Occasionally, single grains of Ti3O2 were observed in the thin layer on alumina. In the joints prepared with Ag–35.3Cu–1.8Ti wt.%, the interfacial structure evolved considerably with joining time, eventually leading to a high degree of inhomogeneity across the length of the joint at the highest Tp. The level of purity of alumina was not found to affect the overall interfacial microstructure, which is attributed to the formation of various solid solutions. It is suggested that Ti3Cu3O forms initially on the alumina. Diffusion of Ti occurs subsequently to form titanium oxide at the Ti3Cu3O/alumina interface.The authors acknowledge the financial support for this study provided by AWE.This is the author accepted manuscript. The final version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S1359645415003791

Interfacial reactions between sapphire and Ag-Cu-Ti-based active braze alloys

The interfacial reactions between two commercially available Ag–Cu–Ti-based active braze alloys and sapphire have been studied. In separate experiments, Ag– 35.3Cu–1.8Ti wt.% and Ag–26.7Cu–4.5Ti wt.% alloys have been sandwiched between pieces of R-plane orientated sapphire and heated in argon to temperatures between 750 and 900 °C for 1 min. The phases at the Ag–Cu– Ti/sapphire interfaces have been studied using selected area electron diffraction, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy. Gradual and subtle changes at the Ag–Cu–Ti/sapphire interfaces were observed as a function of temperature, along with the formation of a transient phase that permitted wetting of the sapphire. Unequivocal evidence is shown that when the active braze alloys melt, titanium first migrates to the sapphire and reacts to dissolve up to ~33 at.% oxygen, forming a nanometre-size polycrystalline layer with a chemical composition of Ti₂O₁₋ₓ (x<<1). Ti₃Cu₃O particles subsequently nucleate behind the Ti₂O₁₋ₓ layer and grow to become a continuous micrometre-size layer, replacing the Ti₂O₁₋ₓ layer. Finally at 845 °C, a nanometre-size γ-TiO layer forms on the sapphire to leave a typical interfacial structure of Ag–Cu/Ti₃Cu₃O/γ-TiO/sapphire consistent with that seen in samples of polycrystalline alumina joined to itself with these active braze alloys. These experimental observations have been used to establish a definitive bonding mechanism for the joining of sapphire with Ag–Cu alloys activated by small amounts of titaniumWe are grateful for the financial support for this study provided by AWE.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.actamat.2015.11.01

Evolution of the interfacial phases in Al2_{2}O3_{3}–Kovar joints®^{®} brazed using a Ag–Cu–Ti-based alloy

A systematic investigation of the brazing of Al$_{2}$O$_{3}$ to Kovar$^{®}$ (Fe–29Ni–17Co wt.%) using the active braze alloy (ABA) Ag–35.25Cu–1.75Ti wt.% has been undertaken to study the chemical reactions at the interfaces of the joints. The extent to which silica-based secondary phases in the Al$_{2}$O$_{3}$ participate in the reactions at the ABA/Al$_{2}$O$_{3}$ interface has been clarified. Another aspect of this work has been to determine the influence of various brazing parameters, such as the peak temperature, $\textit{T}$$_{p}$, and time at $\textit{T}$$_{p}$, $\tau$, on the resultant microstructure. As a consequence, the microstructural evolution of the joints as a function of $\textit{T}$$_{p}$ and $\tau$ is discussed in some detail. The formation of a Fe$_{2}$Ti layer on the Kovar$^{®}$ and its growth, along with adjacent Ni$_{3}$Ti particles in the ABA, dominate the microstructural developments at the ABA/Kovar$^{®}$ interface. The presence of Kovar$^{®}$ next to the ABA does not change the intrinsic chemical reactions occurring at the ABA/Al$_{2}$O$_{3}$ interface. However, the extent of these reactions is limited if the purity of the Al$_{2}$O$_{3}$ is high, and so it is necessary to have some silica-rich secondary phase in the Al$_{2}$O$_{3}$ to facilitate the formation of a Ti$_{3}$Cu$_{3}$O layer on the Al$_{2}$O$_{3}$. Breakdown of the Ti$_{3}$Cu$_{3}$O layer, together with fracture of the Fe$_{2}$Ti layer and separation of this layer from the Kovar$^{®}$, has been avoided by brazing at temperatures close to the liquidus temperature of the ABA for short periods of time, e.g. for $\textit{T}$$_{p}$ between 820 and 830 °C and $\tau$ between 2 and 8 min.We are grateful for the contribution and support for this study by AWE plc

Evolution of the interfacial phases in Al2_{2}O3_{3}–Kovar joints®^{®} brazed using a Ag–Cu–Ti-based alloy

A systematic investigation of the brazing of Al$_{2}$O$_{3}$ to Kovar$^{®}$ (Fe–29Ni–17Co wt.%) using the active braze alloy (ABA) Ag–35.25Cu–1.75Ti wt.% has been undertaken to study the chemical reactions at the interfaces of the joints. The extent to which silica-based secondary phases in the Al$_{2}$O$_{3}$ participate in the reactions at the ABA/Al$_{2}$O$_{3}$ interface has been clarified. Another aspect of this work has been to determine the influence of various brazing parameters, such as the peak temperature, $\textit{T}$$_{p}$, and time at $\textit{T}$$_{p}$, $\tau$, on the resultant microstructure. As a consequence, the microstructural evolution of the joints as a function of $\textit{T}$$_{p}$ and $\tau$ is discussed in some detail. The formation of a Fe$_{2}$Ti layer on the Kovar$^{®}$ and its growth, along with adjacent Ni$_{3}$Ti particles in the ABA, dominate the microstructural developments at the ABA/Kovar$^{®}$ interface. The presence of Kovar$^{®}$ next to the ABA does not change the intrinsic chemical reactions occurring at the ABA/Al$_{2}$O$_{3}$ interface. However, the extent of these reactions is limited if the purity of the Al$_{2}$O$_{3}$ is high, and so it is necessary to have some silica-rich secondary phase in the Al$_{2}$O$_{3}$ to facilitate the formation of a Ti$_{3}$Cu$_{3}$O layer on the Al$_{2}$O$_{3}$. Breakdown of the Ti$_{3}$Cu$_{3}$O layer, together with fracture of the Fe$_{2}$Ti layer and separation of this layer from the Kovar$^{®}$, has been avoided by brazing at temperatures close to the liquidus temperature of the ABA for short periods of time, e.g. for $\textit{T}$$_{p}$ between 820 and 830 °C and $\tau$ between 2 and 8 min.We are grateful for the contribution and support for this study by AWE plc

Active metal brazing of Al2_{2}O3_{3} to Kovar® (Fe–29Ni–17Co wt.%) using Copper ABA® (Cu–3.0Si–2.3Ti–2.0Al wt.%)

The application of an active braze alloy (ABA) known as Copper ABA® (Cu–3.0Si–2.3Ti–2.0Al wt.%) to join Al$_{2}$O$_{3}$ to Kovar® (Fe–29Ni–17Co wt.%) has been investigated. This ABA was selected to increase the operating temperature of the joint beyond the capabilities of typically used ABAs such as Ag–Cu–Ti-based alloys. Silica present as a secondary phase in the Al$_{2}$O$_{3}$ at a level of ~5 wt.% enabled the ceramic component to bond to the ABA chemically by forming a layer of Si$_{3}$Ti$_{5}$ at the ABA/Al$_{2}$O$_{3}$ interface. Appropriate brazing conditions to preserve a near-continuous Si$_{3}$Ti$_{5}$ layer on the Al$_{2}$O$_{3}$ and a continuous Fe$_{3}$Si layer on the Kovar® were found to be a brazing time of ≤15 min at 1025 °C or ≤2 min at 1050 °C. These conditions produced joints that did not break on handling and could be prepared easily for microscopy. Brazing for longer periods of time, up to 45 min, at these temperatures broke down the Si$_{3}$Ti$_{5}$ layer on the Al$_{2}$O$_{3}$, while brazing at ≥1075 °C for 2–45 min broke down the Fe$_{3}$Si layer on the Kovar® significantly. Further complications of brazing at ≥1075 °C included leakage of the ABA out of the joint and the formation of a new brittle silicide, Ni$_{16}$Si$_{7}$Ti$_{6}$, at the ABA/Al$_{2}$O$_{3}$ interface. This investigation demonstrates that it is not straightforward to join Al$_{2}$O$_{3}$ to Kovar® using Copper ABA®, partly because the ranges of suitable values for the brazing temperature and time are quite limited. Other approaches to increase the operating temperature of the joint are discussed.We are grateful for the financial support for this study provided by AWE

Use of a Non-Penetrating Captive Bolt for Euthanasia of Neonate Goats

A non-penetrating captive bolt device, powered by a 1 grain 0.22&Prime; cartridge delivering a calculated kinetic energy of 47 Joules was tested as a euthanasia method on 200 neonate goats (Capra aegagrus hircus) of mean dead weight = 4.425 kg (SD (Standard deviation) &plusmn; 0.4632), to assess effectiveness and shot position. Evaluation of the method was conducted using behavioural indicators of brain dysfunction followed by post mortem examination of the heads. Once correct shot position had been established, 100% of 158 kids (95% confidence interval 97.5% to 100%) were successfully stunned/killed with a shot positioned on the midline, between the ears, with the chin tucked into the neck. The use of the Accles and Shelvoke CASH Small Animal Tool can therefore be recommended for the euthanasia of neonate goats with a 1 grain cartridge and a specific shooting position

Optical and photocatalytic behaviours of nanoparticles in the Ti-Zn-O binary system

Continuous hydrothermal flow synthesis (CHFS) has been used as a rapid and clean, synthetic method to produce a range of crystalline nanoparticles in the Ti-Zn-O binary system. The nanopowders were prepared from aqueous solutions of titanium(iv) bis(ammonium lactato)dihydroxide (TIBALD) and hydrated zinc nitrate, respectively, using a CHFS reactor which uses superheated water (at 400°C and 24.1 MPa) as a reagent and crystallizing medium. The resulting nanopowders were heat-treated at 850°C for five hours in air to give photoactive semiconductor mixtures of rutile and zinc oxide and/or zinc titanates. The as-prepared powders and their corresponding heat-treated mixed phase photocatalysts were characterized using powder X-ray synchrotron diffraction, transmission electron microscopy, BET surface area measurement, X-ray photoelectron spectroscopy and UV-Vis spectrophotometry. Because of the interest for these materials in UVA and UVB attenuating materials, the UV-Vis profiles of the nanocomposites and solid solutions were studied. Photocatalytic activity of the samples towards the decolourisation of methylene blue dye was also assessed. © 2014 the Partner Organisations

The Use of a Mechanical Non-Penetrating Captive Bolt Device for the Euthanasia of Neonate Lambs

A non-penetrating captive bolt device, powered by a 1-grain 0.22&Prime; cartridge delivering a calculated kinetic energy of 47 Joules was tested as a euthanasia method on 200 neonate lambs (Ovis aries) of 4.464 kg (SD (Standard deviation) &plusmn; 1.056) mean dead weight, to assess effectiveness and shot position. Every lamb (n = 200) was effectively stunned when the weapon was applied powered by a brown, 1-grain cartridge but 10/200 (5%) of the lambs displayed rhythmic or agonal breathing and were subsequently euthanased using euthatal (Merial, UK, GTIN: 03661103015550). Evaluation of the method was conducted using behavioural indicators of brain dysfunction followed by post-mortem examination of the heads. A second trial was conducted using a higher velocity 1.25-grain cartridge and a specific shot position on 48 lambs (mean dead weight = 6.21 kg, SD &plusmn; 1.24) averaging 5 days old. One hundred percent of the lambs in the second trial were immediately stun-killed. Given this complete kill rate and the sample size of the study, the study provides a statistical 95% confidence interval of 92.6% to 100%. The use of the Accles &amp; Shelvoke &ldquo;CASH&rdquo; Small Animal Tool (Birmingham, UK) can therefore be recommended for the euthanasia of neonate lambs with a 1.25-grain cartridge and a specific shooting position

The Use of a Non-Penetrating Captive Bolt for the Euthanasia of Neonate Piglets

The most common method for the on-farm euthanasia of neonate piglets is reported to be manual blunt force trauma. This paper presents the results of research to evaluate a mechanical non-penetrating captive bolt (the Accles and Shelvoke CASH small animal tool, Birmingham, UK) to produce an immediate stun/kill with neonate piglets. One hundred and forty-seven piglets (average dead weight = 1.20 kg ± 0.58 (standard deviation, SD), mean age = 5.8 days (median = 3)) were euthanized with the device and demonstrated immediate loss of consciousness, subjectively assessed by behavioural signs and no recovery. The result that 147 out of 147 animals were effectively stun/killed gives a 95% confidence interval for the true percentage of animals that would be effectively stun/killed of 97.5–100% with the use of the CASH small animal tool under the conditions of the current study. This research concludes that the CASH small animal tool, using a 1 grain brown coded cartridge, is suitable for producing a stun/kill in neonate piglets when applied in a frontal/parietal position