Restructuring butterfat through blending and chemical interesterification. 3. Rheology

Interesterified and noninteresterified butterfat-canola oil blends, ranging from 100% butterfat to 60∶40 butterfat-canola oil (w/w) in 10% increments, were evaluated for hardness index (HI), dropping point, viscosity, and viscoelastic properties at small deformation. Both blending and chemical interesterification diminished HI in a nonlinear fashion. HI changes in interesterified blends were more pronounced than in noninteresterified blends. Dropping points yielded information on the structure of the blends. Butterfat’s dropping point (DP) was 34.4°C, whereas that of interesterified butterfat was 37.0°C, which is indicative of a more structured network for the latter. DP values of blends with 60–90% butterfat (interesterified vs. noninteresterified) were not significantly different (P<0.05). Interesterified blends had a higher crystallization onset temperature than did noninteresterified blends. All blends in the liquid state displayed Newtonian behavior. Oscillatory frequency sweep measurements at small amplitude showed that interesterified blends generally had lower storage moduli (G′) than their noninteresterified counterparts. BothG′ andG″ were frequency-dependent. Replacement of 30% butterfat by canola oil led to notable changes in small deformation measurements, whereas replacement of 20% butterfat led to big changes in large deformation measurements.     

Restructing butterfat through blending and chemical interesterification. 1. Melting behavior and triacylglycerol modifications

Chemical interesterification of butterfat-canola oil blends, ranging from 100% butterfat to 100% canola oil in 10% increments, decreased solid fat content (SFC) of all blends in a nonlinear fashion in the temperature range of 5 to 40°C except for butterfat and the 90∶10 butterfat/canola oil blend, whose SFC increased between 20 and 40°C. The sharp melting associated with butterfat at 15–20°C disappeared upon interesterification. Heats of fusion for butterfat to the 60∶40 butterfat/canola oil blend decreased from 75 to 60 J/g. Blends with >50% canola oil displayed a much sharper drop in enthalpy. Heats of fusion were 30–50% lower on average for interesterified blends than for their noninteresterified counterparts. Both noninteresterified and interesterified blends deviated substantially from ideal solubility, with greater deviation as the proportion of canola oil increased. The change in the entropy of melting was consistently higher for noninteresterified blends than for interesterified blends. Chemical interesterification generated statistically significant differences for all triacylglycerol carbon species (C) from C₃₀ to C_56′ except for C_42′ and in SFC at most temperatures for all blends.     

Investigation of the chemical versatility in high-entropy pyrochlores

This article reports on the exploration of the chemical versatility of entropy-stabilized pyrochlores (A₂B₂O₇) with large chemical disorder introduced on the B site, as well as the study of isovalent and aliovalent substitution on the B site and of Ca²⁺-doping on the A site. Among all the 20 new compounds obtained in this study, 8 are entropy-stabilized: RE₂(TiZrHfGeSn)₂ (with RE = Gd–Ho and Y), Pr₂(TiZrHfScNb)₂O₇, and RE₂(TiGeSnAlNb)₂O₇ (with RE = Er and Y). Moreover, some physical properties (magnetic, electrical, thermal, and optical properties) of these high-entropy pyrochlores have been screened, and some of them could be potentially interesting for applications. For example, we observed low thermal diffusivity values (between 0.4 and 0.7 m² s⁻¹) making them interesting for thermal barrier coating or tunable optical bandgaps in the visible region that could make them appealing as photocatalysts or in optical applications. Furthermore, single-phased compounds were obtained for almost all the rare earths (REs) on the A site. Therefore, when five nonmagnetic cations are used for the B site, it enables to study the magnetic properties and, more specifically, the influence of the local chemical and structural disorder on the exotic ground states observed in monocationic RE pyrochlores.     

Effect of processing conditions on physical properties of a milk fat model system: Microstructure

The effect of processing conditions on the microstructure of three blends of 30, 40, and 50% high-melting fraction [Mettler dropping point (MDP)=47.5°C] in the lowmelting fraction (MDP=16.5°C) of milk fat was studied. The effect of cooling and agitation rates, crystallization temperature, chemical composition of the blends, and storage time on crystalline microstructure (number, size, distribution, etc.) was investigated by confocal laser scanning microscopy (CLSM). To improve resolution, a mix of Nile blue and Nile red dyes was dissolved in the melted samples in proportions that did not modify the nucleation kinetics. Samples were then crystallized by cooling (0.2 or 5.5°C/min) to crystallization temperature (25, 27.5, and 30°C). After 2 h at crystallization temperature, a slurry was placed on a microscope slide and samples were stored 24 h at 10°C. During this period, more material crystallized. Slowly crystallized samples (0.2°C/min) formed different structures from rapidly crystallized samples (5.3°C/min). Crystals were sometimes diffuse and hard to distinguish from the liquid. Samples were darker as a result of this solid-mass distribution. However, rapidly crystallized samples had well-defined crystals and seemed to be separated by a distinct liquid phase. These crystals were not in touch with each other as was the case for slowly crystallized samples. Higher agitation rates led to smaller crystal size due to enhanced nucleation. Larger crystals were formed when crystallization occurred at higher temperatures. Storage time resulted in an increase of crystal size. Larger crystal size and structures with more evident links had a more elastic behavior with higher elastic modulus E’.     

铝、铝硅溶胶及其粉末的合成

以硝酸铝为铝源、硅溶胶为硅源、柠檬酸为稳定剂,采用溶胶凝胶法制备出了稳定的铝溶胶及铝硅溶胶,分析了硝酸铝与柠檬酸的摩尔比(N/C比)、反应温度、保温时间对铝溶胶形成的影响,确定N/C比3:1、100℃及保温1h是铝溶胶较优的工艺参数。XRD分析表明,经1200℃煅烧2h后,铝凝胶粉转变成了α-Al2O3晶相,铝硅凝胶粉末经1200℃煅烧2h后,样品主要为正交莫来石结构,SEM显示所得粉末为无规则形态。     

A comparative study on the magnetic properties of MFe12O19 and MAlFe11O19 (M = Sr, Ba and Pb) hexaferrites with different morphologies

M-type nano hexaferrites MFe₁₂O₁₉ and MAlFe₁₁O₁₉ (M = Sr, Ba and Pb) have been prepared by the sol-gel method to investigate the shielding effect of inorganic ions KCl, KBr and KI on the phase growth of ferrites. FTIR frequency bands in the range 560-580 cm⁻¹ and 430-470 cm⁻¹corresponds to the formation of tetrahedral and octahedral clusters of metal oxides in ferrites, respectively. X-ray powder diffractographs do not show any peaks for the as obtained samples showing the amorphous nature of the samples, however regular peaks for M-type structure have been obtained for all the annealed samples. There is negligible small change in the lattice parameters ‘a’ and ‘c’ with substitution of the hexagonal ferrites with aluminium. Magnetic measurements showed that the coercivity (Hc) values of all the samples with KCl and KBr enhance due to KCl and KBr to act as deactivators. However, the coercivity value decreases with KI as it oxidise to I₂ during annealing. The saturation magnetization of the hexaferrites decreases with Al³⁺ ion substitution for Fe³⁺ ion due to preferential occupancy of aluminium in octahedral sites.     

Microstructure and properties of high alumina castables containing calcium alumino‐titanate

Calcium alumino‐titanate (CAT)‐containing high alumina castables were prepared using bauxite, CAT, and α‐Al₂O₃ as starting materials, and subsequently heat treated at various temperatures ranging from 1400°C to 1600°C. The thermo‐mechanical properties of the specimens as a function of the temperature were characterized in terms of linear shrinkage, bulk density, apparent porosity, cold crushing strength (CCS), modulus of rupture (MOR), residual ratio of MOR, and coefficient of thermal expansion (CTE). X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were used to determine the phase composition and microstructural evolution, respectively. Sintering at temperatures between 1450 and 1500°C promoted normal grain growth, with the formation of a granular surface contact, and abnormal grain growth occurred at higher temperatures (≥ 1550°C). The cold strength of the specimen initially increased and subsequently decreased with temperature, whereas the residual ratio of MOR initially decreased with increasing temperature to 1550°C, then increased above 1550°C. In addition, the CTE of the specimen was only minimally influenced by the firing temperature.     

Sintering and characterization of in situ formed porous cordierite ceramics with nano boehmite additions

In this study, we investigated the effect of sintering temperature and nano boehmite additions on the phase composition, densification, and mechanical properties of porous cordierite ceramics. Ceramic samples were sintered at temperatures ranging from 1200 to 1400°C. Carbon powder was used as a pore forming agent to improve the porosity of the ceramic structure. Nano boehmite and carbon additions significantly enhanced ceramic porosity and average pore size in sintered samples. The bulk density and apparent porosity of the sintered samples were found to be 0.96–1.53 g/cm³ and 42.3%–65.6%, respectively. Sintered samples had cold crushing strengths of 1.5–14.3 MPa. The microstructure obtained by scanning electron microscopy was used to measure average pore size in sintered samples and was found to be 41.93 µm for stoichiometric composition (SC), 67.72 µm for SC and nano boehmite, and 102.98 µm for SC, nano boehmite, and carbon. The microstructure of the sintered samples revealed that the crystallinity of the in situ formed phases increased with the increase in nano boehmite additions.     

形态学实验和分析方法在高分子研究中的意义与应用

论述了形态学实验分析方法（X射线衍射、电子显微镜和光学显微镜）的概况及其在高分子研究中的应用，为在高分子材料与工程实践中合理运用该实验方法。掌握正确的图象分析方法提供理论依据。     

Structural, thermal and crystallization kinetics of ZnO–BaO–SiO2–B2O3–Mn2O3 based glass sealants for solid oxide fuel cells

Glass compositions in the system 40SiO₂–30BaO–20ZnO–(x)Mn₂O₃–(10 − x)B₂O₃ glasses have been synthesized and the thermal, structural and crystallization kinetic properties characterized. The lower concentration of Mn₂O₃ in place of B₂O₃ acts as a network former and suppressed the tendency of phase separation in glasses. On the other hand, concentration of Mn₂O₃ > 7.5 mol% induce phase separation in the glass matrix. The highest activation energy for crystallization is observed in the composition without B₂O₃ (INM4) (355 kJ/mol). The values of thermal expansion coefficient (TEC) and viscosity of this glass is 8 × 10⁻⁶ K⁻¹ and 10^4.2dPa s (850 °C), respectively. After long heat treatment (800 °C for 100 h), thermodynamically stable hexacelsian and monoclinic phases are formed. These phases are not detrimental to SOFC application.     

Structural studies of poly[(2S,3S)-2,3-dimethoxybutylene alkanamide]s

The structural characterization of a series of stereoregular polyamides 4,n (n=8, 10, 12), which were obtained from polycondensation of (2S,3S)-2,3-dimethoxy-1,4-butanediamine with aliphatic dicarboxylic acids, has been carried out. X-ray diffraction of powder and fiber samples were analyzed together with electron diffraction patterns of single crystals obtained by isothermal crystallization in solution. Experimental results based on lattice parameters data were used to build a preliminary crystal model using the Cerius program. The main characteristic of the proposed model is the presence of intermolecular hydrogen bonds along the crystal a direction, similarly arranged to conventional nylons.     

在以EDTA和柠檬酸为配位剂的酸性硫代硫酸盐-亚硫酸盐镀液中电沉积金

以乙二胺四乙酸或柠檬酸作配位剂,在无氰的硫代硫酸盐–亚硫酸盐体系中研究了金在镀镍铜基底上的电沉积。在温度为60°C,pH为6和电流密度为2A/dm2的条件下,研究了不同配位剂对电流效率、镀速、镀层硬度及镀液分散能力的影响。最佳的镀液组成为0.5mol/L硫代硫酸钠–亚硫酸钠 0.2mol/L乙二胺四乙酸(或0.3mol/L柠檬酸)。该镀液具有良好的分散能力及高达98%的电流效率。采用扫描电镜、原子力显微镜及X射线衍射分析了镀态金镀层的表面形貌和晶体结构。所得的金镀层几乎无孔(孔隙率<2~4个/cm2),结合力良好,硬度适中(80~130HV)。     

TEM and electron tomography studies of carbon nanospheres for lithium secondary batteries

The structure of carbon nanospheres of 100-200 nm diameter, which showed superior high-speed charge-discharge behavior as the negative electrode in a lithium ion battery, was investigated with XRD, SEM and TEM with an electron tomography attachment. Observation of carbon 0 0 2 lattice images, as well as electron diffraction patterns, illustrated that heterogeneous microtexture was formed as the polyhedronization of the particle proceeded with heat-treatment. The outside region of the particle heat-treated at 2800 °C has stacking structure of aromatic layers with some distribution of d₀₀₂, while the center region consisted of non-graphitic. Structure defects seemed to be concentrated along the ridgelines of the polyhedronized particles after heat-treatment. The electron tomography technique clarified the morphology of the graphitized particles, although the images should be understood with other crystallographic measurements. A slice image computed in the 3D-reconstruction process showed the inner texture of the graphitized particles more clearly than the conventional TEM bright-field image.     

Fat Bloom Caused by Partial De-Oiling on Chocolate Surfaces after High-Temperature Exposure

Fat bloom in chocolate is a substantial problem that affects its sensory properties, such as texture and appearance. This phenomenon is because of diffuse light reflection on a roughened surface of chocolate, caused by structural changes of fat crystals subjected to various temperature conditions. The purpose of this study is to characterize the fat bloom formed through gradual two-step cooling after exposure to temperatures (35–37 °C) slightly above the cocoa butter Form βV melting point (33.8 °C). To clarify the fat bloom formation process, the structural changes in cocoa butter and on the chocolate surface, at the dynamic thermal condition for bloom formation, was investigated using X-ray diffraction (XRD), fluorescence light microscopy, and scanning electron microscopy (SEM). The results revealed that an entirely light brown fat bloom occurred, even in the absence of the Form βVI or other polymorphic transformation. Microscopic observation showed that the light brown appearance was because of the porous structure on the chocolate surface. This porous structure was formed by liquid oil moving inside of chocolate from the surface. The formation of a coarse network and the subsequent de-oiling, because of movement of unsolidified liquid fat into the chocolate, appeared to be the main causes of bloom formation. Therefore, a coarsened fat network and oil movement besides the conventional principles of polymorphic transformation of cocoa butter should be considered.     

Determination of organic sulphur in raw and chemically cleaned coals by scanning electron microscopy and energy dispersive X-ray spectrometry

Scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) is a useful method to evaluate chemical cleaning processes and to obtain values of the organic sulphur remaining in cleaned coals. Pressed pellets can be used when the cleaning process has made the coal too heterogeneous to analyse by the conventional epoxy mounting method. The SEM-EDS analysis time is the same for both methods, whereas the preparation of pellets is much easier than that of epoxy mounts. The overall analysis time should therefore be decreased by using the pellet technique.     

Selective Deposition of Mo2C-Containing Coatings on {100} Facets of Synthetic Diamond Crystals

An efficient way to improve the properties of metal–diamond composites (mechanical strength, wear resistance, thermal conductivity) is the preliminary modification of the diamond surface to improve its wettability by the metal matrix. In the present work, Mo₂C-containing coatings were deposited on the diamond crystals under different conditions: hot pressing (atmosphere of argon), spark plasma sintering (forevacuum), and annealing in air. The influence of the sintering parameters on the morphology and phase composition of the coatings deposited on diamond was studied. Mo₂C-containing coatings were selectively deposited on the facets of synthetic diamond microcrystals by annealing of the latter with a molybdenum powder. Experiments were carried out to deposit coatings under different conditions: during hot pressing (argon atmosphere), spark plasma sintering (forevacuum), and annealing in air. The process parameters were the temperature, holding time, and concentration of molybdenum in the initial mixture. Experiments with a pre-oxidized molybdenum powder were also conducted. The coated diamond crystals were investigated by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The deposition was enabled by the gas phase transport of molybdenum dioxide, MoO₂, contained in the starting powder. The following sequence of the coating formation stages was proposed. First, MoO₂ sublimes and is adsorbed mainly on the {100} facets of diamond. Then, it is reduced to metallic molybdenum by carbon of the diamond, which further reacts with carbon to form the Mo₂C carbide phase. These processes occurred during treatment of the mixtures in the hot press and the spark plasma sintering facility. When the mixture was annealed in air, no selective deposition was observed. During annealing, MoO₃ particles adhered to the diamond surface.     

Solid Solutions of Lindbergite–Glushinskite Series: Synthesis,Ionic Substitutions,Phase Transformation and Crystal Morphology

To clarify the crystal chemical features of natural and synthetic oxalates Me²⁺(C₂O₄)∙2H₂O (Me²⁺ = Fe, Mn, Mg, Zn), including minerals of the humboldtine group, solid solutions of lindbergite Mn(C₂O₄)∙2H₂O–glushinskite Mg(C₂O₄)∙2H₂O were precipitated under various conditions, close to those characteristic of mineralization in biofilms: at the stoichiometric ratios ((Mn + Mg)/C₂O₄ = 1) and non-stochiometric ratios ((Mn + Mg)/C₂O₄ < 1), in the presence and absence of citrate ions. Investigation of precipitates was carried out by powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Thermodynamic modelling was performed in order to evaluate the lindbergite–glushinskite equilibrium. It was shown that glushinskite belongs to the orthorhombic β-modification (sp. Gr. Fddd), while lindbergite has a monoclinic α-modification (sp. gr. C2/c). Mg ions incorporate lindbergite in much higher quantities than Mn ions incorporate glushinskite; moreover, Mn glushinskites are characterized by violations of long-range order in their crystal structure. Lindbergite–glushinskite transition occurs abruptly and can be classified as a first-order isodimorphic transition. The Me²⁺/C₂O₄ ratio and the presence of citric acid in the solution affect the isomorphic capacity of lindbergite and glushinskite, the width of the transition and the equilibrium Mg/Mn ratio. The transition is accompanied by continuous morphological changes in crystals and crystal intergrowths. Given the obtained results, it is necessary to take into account in biotechnologies aimed at the bioremediation/bioleaching of metals from media containing mixtures of cations (Mg, Mn, Fe, Zn).     

Low temperature synthesis of ZrB2-SiC powders by molten salt magnesiothermic reduction and their oxidation resistance

Herein, we prepare phase-pure ZrB₂-SiC composite powders by molten-salt-mediated reduction of ZrSiO₄/B₂O₃/activated carbon mixtures with Mg, showing that the phase composition and morphology of the above composites is influenced by firing temperature, B:Zr and C:Si molar ratios, and the amount of excess Mg. Notably, phase-pure ZrB₂-SiC powder with a ZrB₂:SiC weight ratio of ~75:25 could be obtained by 3-h firing at 1200?°C, i.e., at a temperature lower than that used for conventional carbothermal reduction by at least 200?°C. As-prepared ZrB₂-SiC composites exhibited grain sizes of several microns and comprised SiC nanoparticles well distributed in the ZrB₂ matrix. Finally, the oxidation activation energies of the prepared ZrB₂ and ZrB₂-SiC powders were determined as 326 and 381?kJ/mol, respectively, which demonstrated that the introduction of SiC improved the oxidation resistance of monolithic ZrB₂.     

Recycling bagasse and rice hulls ash as a pore-forming agent in the fabrication of cordierite–spinel porous ceramics

Bagasse and rice hulls ash are both waste materials. In recent years, in order to meet environmental protection, these materials have been recycled in the production of porous ceramics. A solid-state reaction mechanism of calcined alumina and talc was used to prepare cordierite–spinel porous ceramics. Talc was added from 30 to 60 wt.% at the expense of alumina and sintered at 1400°C for 2 h. The effect of bagasse and rice hulls ash (as a pore forming agent) on the densification parameters, cold crushing strength (CCS), and pore size distribution was also studied. The phase composition (X-ray diffraction) and microstructure (scanning electron microscopy) of sintered samples were investigated. The results showed that the main phases present in the samples are cordierite, corundum, spinel, and sapphirine. In the sample with a higher amount of talc additions (60 wt.%), only the formation of the cordierite and spinel phases was observed. The bulk density of the samples and the apparent porosity ranged from 1.77 to 2.26 g/cm³ and from 28.6% to 48.21%, respectively. The CCS of the samples ranges from 13.9 to 36.3 MPa. The microstructures of the sintered samples were observed for the formation of cordierite phase, alumina phase, and spinel phase in an excellent crystallization and phase arrangement.     

Sloughing and limited substrate conditions trigger filamentous growth in heterotrophic biofilms—Measurements in flow-through tube reactor

The aim of this study was to investigate the interaction between biofilm structure and sloughing in a flow-through tube reactor exposed to constant, limiting and non-limiting substrate conditions. Biofilm development and detachment were analysed by means of gravimetrical methods and confocal laser scanning microscopy (CLSM). This study revealed the impact of sloughing on biofilm structure. After six weeks of cultivation all biofilms were dominated by filamentous growth. In three out of four cultivations fungal networks developed after the first or second major sloughing event. In one biofilm, experiencing the highest substrate limitations, filamentous bacteria dominated the biofilm community prior to the first sloughing. Despite structural changes the overall biofilm substrate conversion rates remained rather constant. Several factors were identified, which possibly led to the first major sloughing event. For example, all biofilms had a density less than 40 kg m⁻³, a biofilm thickness above 80 μm, an increased surface roughness and presence of protozoa prior to sloughing. The observed fungal development may have several reasons: (1) small colonies dormant in the base biofilm adapted rapidly towards new conditions after sloughing, (2) spores attached after sloughing within the remaining base biofilm and (3) the absence of bacterial reseeding as a result of no recirculation of the bulk-fluid containing planktonic bacteria. Filamentous bacterial growth was due to the combination of limited substrate availability and high flow rates. These results can be significant for industrial systems where biofilm stability and sloughing as well as community composition are critical factors for process stability.