Influence of calcium aluminate cement in magnesia castable on total oxygen content of interstitial free steel

Abstract

Samples of interstitial free (IF) steel buried in MgO castable bonded by calcium aluminate cement (CA) in graphite crucibles were heated at 1600°C for 90 min. Total oxygen content (TOC) of the steel was examined after heating and the refractory was investigated by SEM and EDS. It was found that TOC was higher in IF steel samples in contact with MgO castables containing 3 or 5 wt-% CA than with castables containing 7 wt-% CA or without CA. A liquid layer formed between refractory oxide and molten steel separates the refractory oxides from molten steel and inhibits direct dissolution of oxides in the molten steel. Transfer of oxygen between the refractory oxide and molten steel occurs by the formation of CaO.Fe₂O₃ at the boundary between the refractory oxide and the liquid layer, diffusion of CaO.Fe₂O₃ in the liquid phase layer, decomposition of CaO.Fe₂O₃ and dissolution of FeO into the molten steel. W ith increasing CA content in MgO based castables the CaO content in molten steel increases, but iron oxide content decreases, leading to the result mentioned above.     

Surface modification of bioceramics by grafting of tailored allyl phosphonic acid

Abstract

A new route to interfacial bonding between ceramic and matrix in biocomposites is identified. A tailored allyl phosphonic acid is used as a coupling agent bound to the surface of a bioceramic to form a 'grafted' calcium phosphate (CAP). The allyl phosphonic acid coupling agent is synthesised by reaction of allyl halide and trialkyl phosphite. Successful synthesis was confirmed by nuclear magnetic resonance and Fourier transform infrared spectroscopy (FTIR). The allyl phosphonic acid was incorporated onto calcium phosphate using a wet chemical coprecipitation synthesis route. The resulting 'grafted' CAP was characterised using FTIR coupled with photoacoustic sampling, and Fourier transform Raman spectroscopy (FTR). The spectroscopic data suggest an interaction between the allyl phosphonic acid and calcium phosphate resulting from observed reductions in intensity of the hydroxyl (3570 cm^?1) and phosphate ν ₃ (1030 cm^?1) peaks. The continued presence of C=C functionality on the surface of the grafted CAP was indicated by FTIR and FTR spectra (peaks at 1650 and 1635 cm^?1 respectively) and confirmed by X-ray photoelectron spectroscopy (XPS). On the basis of these results, it is concluded that grafted CAP may be used to produce a chemically bonded composite with superior mechanical properties.     

Preparation and characterisation of porous calcium phosphate bone cement as antibiotic carrier

Abstract

This study investigated the release of cephalexin monohydrate (CMH) antibitic from macroporous calcium phosphate cement (CPC) over 0·5–300 h in simulated body fluid. Macroporosity was introduced into the cement matrix by using sodium dodecyl sulphate molecules as air entraining agents. The effect of both surfactant and CMH on basic properties of the CPC has been also elaborated. The results showed that the release rate of the drug from a porous CPC was higher than that of the non-porous CPC; however the same release patterns observed for both morphologies indicated a time dependent controlled release. Incorporation of CMH into the cement composition increased the setting time, while the crystallinity of the formed apatite decreased and injectability of the paste improved. In addition, the rate of hydraulic reactions, leading to conversion of the reactants into apatite phase, did not influenced by incorporating both CMH and surfactant into the cement.     

The Effects of Incorporated Silicone Oils and Calcium Carbonate on the Resistance to Settlement and the Antifouling Performance of a Silicone Elastomer

The surfaces of elastomeric coatings based on poly(dimethylsiloxane), unfilled or containing calcium carbonate filler or with filler and silicone oils, have been characterised from topographic and surface indentation measurements by atomic force microscopy. The resistance of the coatings to marine biofouling has been assessed in a sea-exposure trial, in which the strengths of attachment of some barnacles and tubeworms have been measured. In laboratory experiments, the materials have been challenged with oyster larvae (Crassotrea gigas), barnacle cyprids (Balanus amphitrite) and brown algal embryos (Sargassum muticum). Using a linear stress flow cell, the stresses required to detach settled larvae and embryos by fluid flow have been measured. The attachment of barnacles to the coatings was promoted by the microscopic surface roughness produced by protruding particles of filler. Oyster larvae and algal embryos were more readily displaced from surfaces that had been characterised as relatively soft, or from oil-bloomed surfaces.     

Physical and physicochemical evaluation of calcium phosphate cement made using human derived blood plasma

Abstract

In the present work, calcium phosphate cement was made by mixing a solid phase and blood plasma as liquid phase. The basic properties of the cement (called BPC) were compared with those of conventional calcium phosphate cement (c-CPC) where distilled water was used as liquid. BPC had better consistency and injectability than c-CPC but longer setting time. In both cements, the reactants were converted into apatite phase after immersing in simulated body fluid but the phase formed in BPC had lower crystallinity than the phase formed in c-CPC. The set BPC was stronger than c-CPC, having a compressive strength (CS) of about 2–6 MPa after 24 h incubation at 37°C. The CS reduced during soaking at early stage but was relatively improved at the end of soaking period (day 7). In contrast, an increase in CS was observed in c-CPC during soaking period.     

Influences of scaffold and coal injection on gas and liquid flow distributions in blast furnace: experimental study

Abstract

A laboratory investigation of the gas dynamics and studies using a water–electricity analogue were carried out to clarify the influences of scaffold formation and high coal powder injection on the distribution of gases and liquid slag in the blast furnace. A better understanding of the gas and liquid flow patterns under these conditions was acquired. The applicability of the water–electricity analogue approach to the investigation of liquid slag flow in the blast furnace was proven.     

Audio acoustic plant condition monitoring of spiral bevel gearbox

Abstract

Plant condition monitoring (PCM) is widely used by a variety of industries as part of a condition based maintenance programme. This replaces the previous ‘schedule’ based maintenance programme, in which individual components of a machine are replaced at specified intervals. With PCM the condition of the individual components is monitored, and they are only replaced when their performance is deemed unsatisfactory. PCM techniques are often capital and/or labour intensive, and their use limited to critical machines only. The objective of the present research is to develop a system comprised of microphones and accelerometers which is able to screen industrial environments, such as the hot rolling mill at Corus's Port Talbot plant, for machine faults. The system would use the minimum number of transducers to remotely screen the maximum number of machines, but is not required to provide detailed diagnostic information. To date, an omnidirectional microphone has been used successfully to detect badly damaged gear teeth. The method does not require the use of a soundproof enclosure to filter out background noise. A finite element analysis model of the test rig has been created to determine the eigenfrequencies and eigenmodes of the test rig and to improve the understanding of the vibration behaviour of the faults.     

Preparation and characterisation of calcium phosphate cement made by poly(acrylic/itaconic) acid

Abstract

In this study, the compressive strength and bioactivity of strong polymeric calcium phosphate cement (PCPC), made by mixing a calcium phosphate powder (a mixture of tetracalcium phosphate and dicalcium phosphate dihydrate) and an aqueous solution of poly(acrylic/itaconic) acid, were investigated. The characteristics of the cement such as phase composition, setting reaction products and microstructure were analysed and compared to those of a control sample made by the same solid phase and water as a liquid. The hard tissue healing capability of PCPC was tested in a rabbit model by radiographical observations of the healing process as well as the cement condition. The results showed that the compressive strength of the set PCPC was ~35 MPa before soaking in a simulated body fluid (SBF), which was much higher than that of the control specimen. However, it sharply decreased when the cement was immersed in the SBF. X-ray diffraction analysis revealed that tricalcium phosphate was formed in the set PCPC and only a small amount of hydroxyapatite was produced after seven days soaking. In contrast, hydroxyapatite was almost the only phase of the control specimen after the soaking period. Radiography tests showed a cement (PCPC) with an irregular macrostructure after three months implantation, with a decreased radiopacity, and without any periosteal or intercortical callus formation.     

Study of biodegradable ceramic bone graft substitute

Abstract

The aim of the present study was to obtain a biodegradable porous calcium phosphate implants as a synthetic bone graft substitute. The calcium phosphate used in the present study consisted of hydroxyapatite (HA) and dicalcium phosphate anhydrous (DCP). Porous bioceramic was fabricated by a foam casting method. By polyurethane foam and slurry containing HA/DCP (3 : 1 weight ratio) powder, water and additives a high porous structure with ～70% was created. The X-ray diffractometry revealed that the β-tricalcium phosphate (β-TCP) formation is major phase. Surface morphology analysis and porosity evaluations were performed. The variation in the compressive strength, elastic modulus and dissolution behaviour of immersed synthetic bone graft in simulated physiological solution investigated.     

Surface tension and specific volume of copper–titanium melts measured by the sessile drop method

By using non-wetted and inert calcium fluoride substrates as plates or crucibles (cups), it is possible to extend the sessile drop method and its more precise version 'large drop' method for surface tension measurement of highly chemically active alloys. The surface tension and density of copper-titanium alloys over a wide range of titanium concentration (up to 70 at%) at temperatures between 1000 and 1250°C were measured. The surface tension-concentration dependence for Cu-Ti melts deviates positively from the Zhychovitsky theoretical isotherm for ideal solutions. The compression of alloys is observed. The copper-titanium melts deviate negatively from Raoult's law. The work of adhesion of Cu-Ti melts to CaF₂ was also determined and it was found to be 820 ± 65 mJ/m² for Cu + 70 at% Ti.