Antioxidant properties of kilned and roasted malts

Compounds possessing antioxidant activity play a crucial role in delaying or preventing lipid oxidation in foods and beverages during processing and storage. Such reactions lead to loss of product quality, especially as a consequence of off-flavor formation. The aim of this study was to determine the antioxidant activity of kilned (standard) and roasted (speciality) malts in relation to phenolic compounds, sugars, amino acids, and color [assessed as European Brewing Convention units (degrees EBC) and absorbance at 420 nm]. The concentrations of sugars and amino acids decreased with the intensity of the applied heat treatment, and this was attributed to the extent of the Maillard reaction, as well as sugar caramelization, in the highly roasted malts. Proline, followed by glutamine, was the most abundant free amino/imino acid in the malt samples, except those that were highly roasted, and maltose was the most abundant sugar in all malts. Levels of total phenolic compounds decreased with heat treatment. Catechin and ferulic acid were the most abundant phenolic compounds in the majority of the malts, and amounts were highest in the kilned samples. In highly roasted malts, degradation products of ferulic acid were identified. Antioxidant activity increased with the intensity of heating, in parallel with color formation, and was significantly higher for roasted malts compared to kilned malts. In kilned malts, phenolic compounds were the main identified contributors to antioxidant activity, with Maillard reaction products also playing a role. In roasted malts, Maillard reaction products were responsible for the majority of the antioxidant activity.

A study of the relationship between process conditions and mechanical strength of mineralized red algae in the preparation of a marine-derived bone void filler

Bone void fillers that can enhance biological function to augment skeletal repair have significant therapeutic potential in bone replacement surgery. This work focuses on the development of a unique microporous (0.5-10 mu m) marine-derived calcium phosphate bioceramic granule. It was prepared fro Corallina officinalis, a mineralized red alga, using a novel manufacturing process. This involved thermal processing, followed by a low pressure-temperature chemical synthesis reaction. The study found that the ability to maintain the unique algal morphology was dependent on the thermal processing conditions. This study investigates the effect of thermal heat treatment on the physiochemical properties of the alga. Thermogravimetric analysis was used to monitor its thermal decomposition. The resultant thermograms indicated the presence of a residual organic phase at temperatures below 500 degrees C and an irreversible solid-state phase transition from mg-rich-calcite to calcium oxide at temperatures over 850 degrees C. Algae and synthetic calcite were evaluated following heat treatment in an air-circulating furance at temperatures ranging from 400 to 800 degrees C. The highest levels of mass loss occurred between 400-500 degrees C and 700-800 degrees C, which were attributed to the organic and carbonate decomposition respectively. The changes in mechanical strength were quantified using a simple mechanical test, which measured the bulk compressive strength of the algae. The mechanical test used may provide a useful evaluation of the compressive properties of similar bone void fillers that are in granular form. The study concluded that soak temperatures in the range of 600 to 700 degrees C provided the optimum physiochemical properties as a precursor to conversion to hydroxyapatite (HA). At these temperatures, a partial phase transition to calcium oxide occurred and the original skeletal morphology of the alga remained intact.

Influence of preparation conditions on the characteristics of activated carbons produced in laboratory and pilot scale systems

The central theme of this investigation is to evaluate the feasibility of using bituminous coal as a precursor material for the production of chars and activated carbons using physical and chemical activation processes. The chemical activation process was accomplished by impregnating the raw materials with different dehydrating agents in different ratios and concentrations, prior to heat treatment (ZnCl2, KCl, KOH, NaOH and Fe2(SO4)3·xH2O). Steam activation of the precursor material was adopted for the preparation of activated carbon using physical activation technology. Different types of bituminous coal; namely, contaminated Columbian (contaminated with pet. coke), pure Columbian, Venezuelan and New Zealand bituminous coal were used in the production processes. BET surface area, micropore area, pore size distribution and total pore volume of the chars and activated carbons were determined from N2 adsorption/desorption isotherm, measured at 77 K. Charring conditions, charring temperature of 800 °C and charring time of 4 h, proved to be the optimum conditions for preparing chars. Contaminated Columbian were found to be the best precursor material for the production of char with reasonable physical characteristics (surface area = 138.1 m2 g-1 and total pore volume of 8.656 × 10-0.2 cm3 g-1). An improvement in the physical characteristics of the activated carbons was obtained upon the treatment of coal with dehydrating agents. Contaminated Columbian treated with 10 wt% ZnCl2 displayed the highest surface area and total pore volume (surface area = 231.5 m2 g-1 and total pore volume = 0.1227 cm3 g-1) with well-developed microporisity (micropore area = 92.3 m2 g-1). Venezuelan bituminous coal using the steam activation process was successful in producing activated carbon with superior physical characteristics (surface area = 863.50 m2 g-1, total pore volume = 0.469 cm3 g-1 and micropore surface area = 783.58 m2 g-1).

Precipitation, microstructure and mechanical properties of low nickel maraging steel

A maraging steel with a composition of Fe–12·94Ni–1·61Al–1·01Mo–0·23Nb (wt-%) was investigated. Optical, scanning electron and transmission electron microscopy and X-ray diffraction analysis were employed to study the microstructure of the steel after different aging periods at temperatures of 450–600°C. Hardness and Charpy impact toughness of the steel were measured. The study of microstructure and mechanical properties showed that nanosized precipitates were formed homogeneously during the aging process, which resulted in high hardness. As the aging time is prolonged, precipitates grow and hardness increases. Fractography of the as forged steel has shown mixed ductile and brittle fracture and has indicated that the steel has good toughness. Relationships among heat treatment, microstructure and mechanical properties are discussed. Further experiments using tensile testing and impact testing for aged steel were carried out.

SEM-EDX of morphology of electroless nickel coatings with tin and tungsten

Electroless plating of binary Ni-P, ternary Ni-Sn-P and Ni-W-P, and quaternary Ni-W-Sn-P alloy coatings was carried out in alkalicitrate baths. After the plating, several kinds of test were carried out to determine the improvement in the characteristics and properties due to the additional elements as well as to study the change in behaviour when heat treatment was applied to these coatings. The coatings were subjected to X-ray diffraction analysis where it was found that all the coatings were amorphous. Interesting surface morphology features were examined using scanning electron microscopy. Addition of a third element improved the hardness.

Relationship between microstructure and deformation behaviour during dynamic compression in Ti-3Al-5Mo-5V alloy

The relationship between microstructure and deformation and damage behaviour during dynamic compression in Ti-3Al-5Mo-5V alloy has been studied using several experimental techniques, including optical microscopy, scanning electron microscopy and microhardness measurements. It was found that the deformation behaviour during dynamic compression was closely related to deformation parameters. After dynamic deformation, the deformation shear band that formed in the titanium alloy had microhardness similar to that of the matrix. However, the microhardness of the white shear band was much higher than the matrix microhardness. The effects of deformation parameters, including deformation rate and deformation degree, on deformation localisation were investigated. Based on the results from the present work, the microstructure and deformation processing parameters can be optimised. In addition, treatment methods after dynamic compression were explored to restore alloy properties. Using post-deformation heat treatment, the microstructure and property inhomogeneity caused by shear bands could be largely removed.

Microstructure and mechanical properties of low nickel maraging steel

Austenitization with lower temperature and intercritical annealing were introduced in the treatment of a maraging steel with a composition of Fe–12.94Ni–1.61Al–1.01Mo–0.23Nb (wt.%). Scanning electron microscopy was employed to study the microstructure after austenitization at 950 °C and intercritical annealing, followed by aging at 485 and 600 °C. X-ray diffraction (XRD) analysis was applied to evaluate the formation of retained or reverted austenite. Thermodynamic calculation was employed to calculate equilibrium phase mole fractions. Hardness and Charpy impact toughness of the steel were measured. Intercritical annealing treatments did not result in significant increase of hardness either before or after aging. The Charpy impact toughness of the alloy in aged condition was enhanced after austenitization at 950 °C. No austenite was observed in XRD. However, suspected reverted austenite was found after austenitization at 950 °C followed by aging at 600 °C for 4 h. Relationships among heat treatment, microstructure and mechanical properties are discussed.

Fracture surface, impact energy and hardness of Ni-free high-Mn steels

Two manganese steels were investigated: Fe-19.7%Mn (VM339A) and Fe-19.7%Mn stabilized with 0.056%C, 0.19%Ti and 0.083%Al (VM339B). The toughness of VM339A was higher than VM339B, but VM339B had higher hardness. Tempering does not affect the toughness of the alloys. SEM images of the fracture surface for both the alloys revealed ductile fractures. A further alloy with a lower manganese content, Fe-8.46%Mn-0.24%Nb-0.038%C, and thus even lower cost than the conventional 3.5Ni cryogenic steel, was tested for its impact toughness after heat treatment at 600°C, giving promising results.

PHOTOMINERALISATION OF 4-CHLOROPHENOL SENSITIZED BY TITANIUM-DIOXIDE - A STUDY OF THE EFFECT OF ANNEALING THE PHOTOCATALYST AT DIFFERENT TEMPERATURES

The results of a study of the variation in photocatalytic activity of TiO2, as measured by its ability to photomineralise 4-chlorophenol, as a function of temperature used to anneal the TiO2, are reported. Heat treatment of the TiO2 leads to a marked decrease in its photocatalytic activity at annealing temperatures above 600-degrees-C. This decrease is associated with a concomitant drop in the specific surface area of the TiO2, owing to particle sintering, rather than the anatase to rutile transformation, which occurs largely at temperatures above 700-degrees-C. There is a reasonable correlation between photocatalytic activity and the surface area of the aggregate particles in the dispersions of the different heat-treated TiO2 samples.

Reactions of nitrogen and oxygen surface groups in nanoporous carbons under inert and reducing atmospheres

The reactions of surface functional groups have an important role in controlling conversion of char nitrogen to NOx during coal combustion. This study involved an investigation of the thermal stability and reactions of nitrogen surface functional groups in nanoporous carbons. Four suites of carbons, which were used as models for coal chars, were prepared with a wide range of nitrogen and oxygen contents and types of functional groups. The porous structures of the carbons were characterized by gas adsorption methods while chemical analysis, X-ray photoelectron spectroscopy, and X-ray near edge structure spectroscopy were used to characterize the surface functional groups. Temperature programmed desorption and temperature programmed reduction methods were used to study the reactivity of the surface functional groups during heat treatment under inert and reducing conditions. Heat treatment studies show that the order of stability of the functional groups is quaternary nitrogen > pyridinic > pyrrolic > pyridine N-oxide. Pyridine N-oxide surface groups desorb NO and form N-2 via surface reactions at low temperature. Pyrrolic and pyridinic functional groups decompose and react with surface species to give NH3, HCN, and N-2 as desorption products, but most pyrrolic groups are preferentially converted to pyridinic and quaternary nitrogen. The main desorption product is N-2. Approximately 15-40 wt % of the original nitrogen was retained in the carbons mainly as quaternary nitrogen after heat treatment to 1673 K. The results are discussed in terms of decomposition ranges for surface functional groups and reaction mechanisms of surface species.

Laser welding of thin foil nickel–titanium shape memory alloy

In this study, two L27 Taguchi experiments were carried out to study the effect of fibre laser welding parameters and their interactions upon the weld bead aspect ratio of nickel–titanium thin foil. The optimum parameters to produce full penetrated weld with the largest aspect ratio and desirable microstructure were successfully obtained by the Taguchi experimental design. The corrosion property of the optimized NiTi weld in Hank’s solution at 37.5 °C was studied and compared with the as-received NiTi. To improve the corrosion properties of the weld, the effect of post-weld-heat-treatments ranging from 573 to 1173 K was investigated. The corrosion properties, surface morphology, microstructure and Ti/Ni ratio of the heat-treated NiTi weld were analysed. It was found that a post-weld heat treatment at 573 K for 1 h provided the best pitting corrosion resistance at the weld zone.

Evaluation of Cyclic Deformation Behavior of Laser-welded Shape Memory NiTi Alloys at Different Working Temperatures

Post-weld heat-treatment (PWHT) has been established as one of the cost-effective ways to improve the functional properties, namely shape memory and super-elastic effects (SME and SE), of laser-welded NiTi alloys. However, the functional performance of the laser-welded joint at different working temperatures has not been explored yet. The purpose of this study is to investigate the effect of different working temperatures on the functional properties of the laser-welded NiTi alloys before and after PWHT by applying cyclic deformation tests. Two laser-welded samples: as-welded and heat-treated sample (after PWHT at 350 oC or 623 K) were tested in this work at room temperature, 50 oC (or 323 K) and 75 oC (or 348 K) respectively. The samples were cyclically loaded and unloaded for 10 cycles up to 4 % strain. The critical stress to induce the martensitic transformation and the residual strain after the cyclic tests were recorded. The results indicate that the heat-treated sample exhibited better functional properties than the as-welded sample at room temperature and 50 oC (or 323 K). However, both the as-welded and heat-treated samples failed in the cyclic tests at 75 oC (or 348 K). These findings are important to determine the feasible working temperature range for the laser-welded NiTi components to exhibit desirable functional properties in engineering applications involving cyclic loading.

Photocatalytic organic synthesis in an NMR tube:CC coupling of phenoxyacetic acid and acrylamide

NMR was used to study the semiconductor photocatalytic (SPC) CC coupling of phenoxyacetic acid (PAA) with acrylamide (ACM) in an NMR tube photoreactor. Using an NMR tube with a sol-gel titania inner coating as a photoreactor, this reaction is relatively clean, forming only 1 product, 4-phenoxybutanamide (4-PB), in yields up to 78%. This SPC reaction is used to assess the activity of the sol-gel titania coating as a function of their annealing temperature, which alters the surface area and phase of the titania, and the general reusability of the TiO coated NMR tubes. The optimum temperature range for annealing the sol-gel titania films is between 450 °C and 800 °C, with the maximum yield and rate attained at 450 °C. Despite a decrease in the initial rates of formation of 4-PB above an annealing temperature of 450 °C, the final product yields remained similar, giving maximum yields within 60 min of irradiation. The reusability study reveals that the activity of the sol-gel titania can quickly deteriorate with repeated use due to the adsorption of yellow/brown coloured, insoluble, most likely organic polymeric, material and its screening effect on the underlying photocatalyst. The titania can, however, be restored to its original activity by a simple heat treatment at 450 °C for 30 min.