Effects Of Various Heat Treatments Research Articles

The surface structure of platinum catalyst particles

For many metal-catalysed reactions, activity and selectivity depend strongly on the structure of the metal surface. However, surprisingly little is known about the surface structures of supported ultrafine metal particles of the type used in practical catalysts. Transmission electron microscopy can play an important role in this area, and is beginning to produce results which could have a major impact on our understanding of processes such as catalyst poisoning and promotion.In this study, which builds on previous work, the effect of various heat-treatments on the shapes and surface structures of alumina-supported platinum particles has been investigated using both conventional bright field TEM and high-resolution imaging. It has been found, for example, that heating in hydrogen tends to produce almost spherical particles with little faceting, as shown in Figure 1. Heating in sulphur-containing atmospheres, on the other hand, produces sharp (100) faceting so that the particles often display square or rectangular profiles, as shown in Figure 2. It is well known that sulphur poisoning can produce changes in catalytic selectivity without deactivating the catalyst completely.

Heat Treatment Effects on Warmed‐Over Flavor in Chicken Breast Meat

ABSTRACTThe effects of various heat treatments on warmed‐over flavor (WOF) in ground chicken breast meat were examined. WOF was measured by thiobarbituric acid test and taste panel. Integral temperature‐time history functions (TTH) were used to quantify constant and variable temperature‐time heat treatments. The effect of processing on WOF was modeled as a modified first‐order kinetic absolute reaction. A reaction threshold temperature of 74°C and an activation energy of 15,000–20,000 Cal/g‐mole were calculated. The accumulated TTH value above 74°C was found to have a major effect on WOF development. WOF in precooked chicken breast meat can be controlled by choice of processing conditions.

The morphology of platinum catalyst particles studied by transmission electron microscopy

The effect of various heat treatments on the surface structure of supported platinum particles was studied using transmission electron microscopy. Heating in a vacuum furnace resulted in the formation of sharp (111) facets, probably as a consequence of carbon deposition, while heating in the presence of hydrogen sulphide induced (100) faceting. In contrast, heat treatments in hydrogen tended to reduce the degree of faceting, resulting in particles with almost circular profiles.

The morphology of platinum catalyst particles studied by transmission electron microscopy

The effect of various heat treatments on the surface structure of supported platinum particles was studied using transmission electron microscopy. Heating in a vacuum furnace resulted in the formation of sharp (111) facets, probably as a consequence of carbon deposition, while heating in the presence of hydrogen sulphide induced (100) faceting. In contrast, heat treatments in hydrogen tended to reduce the degree of faceting, resulting in particles with almost circular profiles.

Optimization of yield and properties of silken tofu from soybeans.

SummaryThe effect of various heat treatments on the yield, protein content and physical form of silken tofu was investigated. Better yields and quality were obtained when the macerated bean slurry was filtered prior to heating and a defined rate of heating was used with stirring. The optimum coagulation temperature was 75–80°C.

Devitrification and subsequent effects on the leach behavior of a simulated borosilicate nuclear waste glass

The effects of various heat treatments on the devitrification and subsequent leach behavior of a simulated alkali-borosilicate nuclear waste glass containing trace levels of Cs, Sr, and U are examined. Samples were held at 500, 525, 550, and 575°C for 1, 2, 4, and 10 days and then air cooled. The volume percent of the crystalline phase was determined by a statistical point-count of petrographic thin sections for 2 samples, and by normalized x-ray diffraction for the remainder of the samples. Samples from each heat treatment schedule were corroded in static-leach tests. Post-heat-treatment and post-corrosion samples were examined by optical microscopy, scanning electron microscopy-energy dispersive spectroscopy, electron spectroscopy for chemical analysis (x-ray photoelectron spectroscopy), and fourier-transformed infrared reflection spectroscopy (FTIRRS), and results were correlated with the crystalline volume and solution data. Leach behavior degrades with increasing crystalline volume fraction by as much as 40 ×. Devitrification is not observed below 525°C and appears to be more time-sensitive than temperature-sensitive within the range of treatments studied. The principal crystalline phases identified by x-ray diffraction and FTIRRS are solid solution variations of acmite, augite, and aegir ne. The range of solid solution variation is fairly large and is likely due to the limited diffusion rates at the heat treatment temperatures and glass inhomogenity prior to heat treatment.

Effects of Various Heat Treatments on Structure and Solubility of Whey Proteins

Structure and solubility of whey proteins are interrelated and affected by commonly used heat treatments. The relation between these characteristics, however, varies with the nature of the protein and the composition of the protein solution.After a brief analysis of structure and properties of the major whey proteins in the native state, attention is given to effects of thermal treatments (up to 150°C) on structure and solubility of the different whey proteins. It is pointed out that mild heat treatments up to 60°C may affect reversibly the solubility and foaming properties of whey proteins. Conformational changes, as reflected by differential scanning calorimetry and observed above 60°C for α-lactalbumin and near 80 and 140°C for β-lactoglobulin, however, exert more serious effects on the functional properties of whey proteins. Modifications of cystine-residues in the polypeptide chain are detected by amino acid analysis upon heat treatments above 100°C under identical heating conditions as used for differential scanning calorimetry.Special attention is given to the effect of changes of environmental conditions such as pH and the presence of lactose and calcium salts, to get more information on the complicated relation between structure and properties of proteins in whey.

チタン合金粉（Ｔｉ‐６Ａｌ‐４ＶおよびＴｉ‐６Ａｌ‐２Ｓｎ‐４Ｚｒ‐６Ｍｏ）の通電抵抗焼結

Two types of commercial Ti alloy powders (Ti-6AI-4V and Ti-6A1-2Sn-4Zr-6Mo, <500 μmφ) made by a rotating electrode process (REP) have been resistance-sintered in air. The relation between physical and mechanical properties of sintered specimens and their resistance-sintering conditions have been studied. The effects of various heat treatments on the properties of resistance-sintered specimens have been also examined.These powders in a die insulated by mica were resistance-sintered under a pressure (1.2 t/cm2). The condition of resistance-sintering was as follows: electric current; 7.6-15 kA, voltage; 2.5-4.7 V, time; 0.6-2.0 sec (30-100 C, C; cycles) and power input; 45-190 kVAC/g (1 kVAC=9.8 J).By the resistance-sintering with a power input higher than 140 kVAC/g, specimens having high density-ratio (>98% theoretical) and high tensile strength could be obtained (Ti-6A1-4C; 120 kg/mm2, Ti-6A1-2Sn-4Zr-6Mo; 100 kg/mm2). Resistance-sintered specimens of both alloys were strengthened by the solu-tion-treatment and the aging (STA) heat treatment (tensile strength-130 kg/mm2). Tensile strength of resistance-sintered Ti alloys was almost comparable to that of those water-quenched.

The effect of heat treatment on unpassivated and passivated gallium arsenide surfaces

The effects of various heat treatments on the surface of GaAs crystals have been studied using Rutherford scattering and channelling of alpha particles. The heat treatment was in the form of isochronal anneals in the temperature range 350–750°C. The crystals were heated in both flowing dry nitrogen and in vacuum (∼ 10 −6 torr). The changes in surface-stoichiometry and surface disorder were measured and the results, for both free and silicon oxide passivated surfaces, are discussed. It is shown that preferential loss of As occurs for the unpassivated surfaces heated in nitrogen. However, the unpassivated surfaces heated in vacuum show no degradation, even up to 750°C. The behaviour of the passivated surfaces was dominated by the mechanical properties of the silicon oxide layer, which suffered from adhesion and blistering problems. Only for annealing in nitrogen at 550°C did the silicon oxide behave successfully as a passivating layer and prevent the out-diffusion of Ga and the evaporation of As.

State of dispersion of platinum in alumina-supported catalysts

A study of the effects of various heat treatments on the state of dispersion of platinum in alumina-supported catalysts has shown that during heat treatments in hydrogen and air the hydrogen-chemisorption capacity (expressed as the H Pt ratio) of the catalysts decreases. The mechanism by which this occurs, however, is not the same in the two cases. During heat treatment in an oxygen-containing atmosphere above 500 °C agglomeration of platinum takes place. This results in a bimodal size distribution of Pt crystallites: Besides well-dispersed platinum (crystallites below 3 nm), a fraction of particles of about 10–15 nm is formed. There are practically no particles of intermediate size. A carefully controlled oxidation at low temperature (below 500 °C) is not capable of redispersing the “big” crystallites. During heat treatment in hydrogen hardly any agglomeration of platinum takes place. However, a certain amount of platinum becomes “inaccessible” and causes the observed decrease in the H Pt ratio. The actual mechanism by which this occurs still needs further investigation. Oxidation at a carefully controlled, low temperature (below about 500 °C) restores the original contribution to the H Pt value of the platinum fraction which has become “inaccessible” as a result of heat treatment in a hydrogen atmosphere. These results suggest that it is generally incorrect to derive the average platinum crystallite size solely from H 2-chemisorption data: the existence of a direct link between “decrease in H Pt ratio” and “sintering” is often highly debatable. For this reason the conclusions of various published studies are suspect.

DTA-EGA Observations of vanadium precipitates in low alloy steel

Differential thermal analysis-evolved gas analysis (DTA-EGA) has been used, along with x-ray diffraction and microchemical techniques, to study the effect of varying the concentrations of vanadium, carbon, and nitrogen added to steels upon the composition of the second-phase compounds isolated. It was thus possible to identify and quantitatively measure vanadium carbide, nitride, and carbonitride in the presence of one another in the isolated residues. The effect of various heat treatments of the steels upon the composition of the second-phase compounds will also be presented.

Effects of Heat Treatment on Infra-red Reflection Spectra of Phase Separable PbO-B&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-SiO&lt;sub&gt;2&lt;/sub&gt; Frit

Effects of various heat treatments on the peak shift and the change of contour of infra-red spectra of frits in PbO-B2O3-SiO2 system were investigated. The infra-red reflection peak due to Si-O-Si streching vibration in the range of 900-1300cm-1 shifted to higher wave number and the width of it decreased rapidly in the transformation range.When the temperature was elevated to the deformation range the contour of the band became broad again. The peak shift to higher wave number was attributed to the increase of Si-O-Si bond strength in the silica rich phase after phase separation. It was considered that the decrease of peak width in the transformation range was due to the temporary good arrangement of Si-O-Si bond during phase separation. The increase of peak width in the deformation range was dependent on the development of the shoulder at 1050cm-1 and 1150cm-1 of the main reflection peak.

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

Low temperature specific heat of Ni3Al and Ni3Ga

Results of specific heat measurements between 1.5 K and 15 K on a large number of alloys in the range of existence of the Ni3Al and Ni3Ga intermetallic phases are reported. For four Ni3Ga samples the measurements were extended down to 0.2 K, and the effect of various heat treatments on the specific heat was measured on two Ni3Ga samples. The results, especially their concentration dependence, definitely exclude the presence of any appreciable contribution of the form predicted for paramagnon enhancement, but an interpretation in terms of superparamagnetic clusters also runs into serious difficulties.

BaSO 4CaSO 4 solid solutions isotypic with BaSO 4

The effect of various heat treatments on BaSO 4 (60 mole per cent)/CaSO 4 (40 mole per cent) was studied by i.r. spectroscopy and X-ray diffraction. Under specific conditions a solid solution of the above composition, isotypic (isostructural) with BaSO 4 (barite) was found to occur. X-ray diffraction analysis gave the following unit cell parameters: a = 8·480 ± 0·009, b = 5·397 ± 0·008 and c = 6·965 ± 0·008 A ̊ .

LITERATURE ABSTRACTS

‘Rheological and Other Physical Terms Relating to the Structure‐Sensitive Properties of Butter’, by J. C. Novello‘Food Rheology Today’, by A. L. Elder and R. J. Smith‘Acceptance and Consumer Preference Testing’, by B. H. Ellis‘Textural Discrimination Sensitivity as Measured by Frequency Spectrographic Analysis of Chewing Sounds’, by K. K. Kapur, W. Dorr, E. Loftus, and R. Feller‘The Relevance of Correlating Objective and Subjective Data’, by A. Kramer‘Relationship between Chemical Structure and Rheological Properties of Gluten Proteins’, by R. Lasztity‘Application of Stress‐Strain Behavior to Thermally Contracted Collagen from Epimysial Connective Tissues’, by P. E. McClain, E. Kuntz and A. M. Pearson‘Perceiving Visual Texture: A Literature Survey’, by R. M. Pickett‘Relationship between Structure and Rheological Properties of Gluten Proteins (A review)’, by J. S. Wall and A. C. Beckwith‘Dessert Gel (Gelatin) Strength Testing. If: Collaborative Study’, by E. Borker and K. G. Sloman‘Determination of Potato Texture’, by J. M. De Man‘A Recording Micro‐Penetrometer, Design and Application’, by M. Jacobson and G. Armbruster‘Possibilities of Accurate Assessment of the Quality of Fish’, by O. M. Mel'nikova‘Measuring Apparent Viscosity of Organic Slurries’, by B. W. Mitchel and R. M. Peart‘Konsistometrische Untersuchungen an Rindfleisch’ (‘Consistometric Investigations of Beef) by E. Scharner (Leipzig, D.D.R.)‘An Automatic and Recording Torsion Measuring Apparatus’, by H. J. Scherr and W. E. Palm‘Penetrometry ‐ Practical Uses’, by J. Kleinert‘Objective Methods for Estimating the Texture of Foodstuffs’, by G. Thomas‘Objective Methods for Measurement of Consistency in Solid Foods’, by R. Heiss and H. WitzelA. FOODS‘Objective Measurements for Baked Products’, by K. Funk, M. E. Zabik, and D. A. Elgidaily‘Brookfield Develops Reliable Measurement of Chocolate Viscosity’, by David H. Howard‘Studies on the Quality Characteristics of Canned Grapefruit Segments. I. Factors Affecting the Drained Weight and Texture’, by A. Ludin, Z. Samish, A. Levi, and E. Hershkowitz‘Studies on the Quality Characteristics of Canned Grapefruit Segments. II. Additives Improving Their Drained Weight and Texture’, by A. Levi, Z. Samish, A. Ludin, and E. Hershkowitz‘Use of Penetrometer for Assessing the Tenderness of Meat’, by G. T. Pagens and C. Autino‘The Interrelationship of the Viscosity, Fat Content, and Temperature of Cream between 40° and 80° C, by L. W. Phipps‘Objective Measurements of French Fried Potato Quality. Laboratory Techniques for Research Use’, by L. R. Ross and W. L. Porter‘Interpretation of Multiple‐Peak Shear Force Curves Obtained with French Fried Potatoes’, by L. R. Ross and W. L. Porter‘Effect of Moisture Content on Mechanical Properties of Shelled Corn’, by Leora Shelef and Nuri N. Mohsenin‘Physical Properties of the Potato Tuber’, by P. W. Voisey, N. W. Tape, and M. Kloek‘The Control of Oil‐in‐Water Emulsion Consistency Using Mixed Emulsifiers’, by B. W. Barry‘Quality in Frozen Cod and Limiting Factors on Its Shelf Life’, by T. R. Kelly‘The Effect of Low Temperature Freezing on Quality Changes in Cold Stored Cod’, by T. R. Kelly and J. S. Dunnett‘Mechanical Properties of Beef during the Freezing Process’, by N. Kulmanova‘Phospholipid Concentration in Cocoa Butter and its Relationship to Viscosity in Dark Chocolate’, by J. G. Parsons and P. G. Keeney‘Influence of Emulsifiers on the Emulsion System of Creams’, by E. Nuernberg‘The Effect of Level of Skin on the Quality of Chicken Frankfurters’, by R. C. Baker, J. M. Darfler, and M. C. Bourne‘Type and Level of Fat and Amount of Protein and Their Effect on The Quality of Chicken Frankfurters’, by R. C. Baker, J. Derfler, and D. V. Vadehre‘Texture Studies on Mushrooms’, by T. R. Gormley‘Photomicrograph of Studies of Dynamic Changes in (Beef) Muscle Fiber fragments. 1: Effect of Various Heat Treatments on Length, Width and Birefringence’, by R. L. Hostetler and W. A. Landmann‘Comparison of Sarcomere Length to Other Predictors of Beef Tenderness’, by R. D. Howard and M. D. Judge‘Pectic Substances and the Texture of French Fried Potatoes’, by A. S. Jaswal‘Texture, Colour and Chemical Composition of Cling Peaches as Affected by Potassium Fertilization’, by B. S. Luh and F. W. Liao‘Some Effects of Process Treatment on the Body of Cream’, by J. H. Prentice and H. R. Chapman‘Deterioration of Frozen Par‐Fried Potatoes upon Holding after Thawing. 2. Composition, Histology and Objective Measurements of Texture’, by R. M. Reeve, B. Feinberg, F. P. Boyle, and G. K. Notter‘Chocolate Particle Size and Its Organoleptic Influences’, by W. Rostagno‘Hardening Ice Cream by Immersion in Liquid Nitrogen’, by A. W. Rudnick, I. J. Ross, and J. D. Fox‘The Influence of the Composition of the Fatty Phase of Margarine on Its Consistency’, by E. Sambuc and M. Naudet‘Properties and Chemical Characterization of a ‘Bloom’ on Process Cheese Slices’, by L. G. Scharpf Jr. and T. P. Kichline(Wheat) Hour Constituents Affecting MacMichael Viscosities, by W. b. Sollars‘Relation of Trimethylsilyl Derivatives of Fruit Tissue Polysaccharides to Apple Texture’, by M. Tavakoli and R. C. Wiley‘The Rheology of Meat. IV. Changes in the Rheological Properties of Meat after Slaughter’, by L. Toth and R. Hamm

Photomicrographic Studies of Dynamic Changes in Muscle Fiber Fragments. 1. Effect of Various Heat Treatments on Length, Width and Birefringence

SUMMARY– Photomicrographs were made of muscle fiber fragments as the stage of the microscope was heated from room temperature to 80°C, or as fibers were held at 37, 45, 53, 61, 69, or 77°C on the heated stage for an hour. The possible relationship of changes in width, length and in birefringence brought about by heating to loss of moisture, water‐holding properties, loss of acidic groups, and changes in tenderness are discussed. Changes in width appeared to be related to changes in water‐holding capacity. Changes in length and loss of birefringence were related to loss of acidic groups, to coagulation of proteins, to volume change in cooked meat, and to changes in tenderness.

Quantitative studies on methyl ketone formation in butteroil: effect of temperature.

AbstractA quantitative study of the effect of various heat treatments on methyl ketone formation in butteroil was conducted. Methyl ketone formation was found to follow first‐order reaction kinetics. The energy of activation was calculated to be approximately 26.55 kcal/mole. The ketones were formed in a fairly constant molar ratio approximating to the following C15,2蝘C13,1蝘C11,1蝘C9,1蝘C7,2蝘C5,1. The temperature‐time conditions had little or no effect on the ratio.

The effects of thermal history on the kinetics of the β → α phase change in uranium and uranium-chromium alloys

The effects of various heat treatments on the kinetics of the β → α phase change in pure uranium and two uranium-chromium alloys has been examined using an electrical resistivity technique. The heat treatments were arranged to enable the effects associated with β grain size to be separated from those due to submicroscopic effects determined by the quenching temperature. Transformation at temperatures near to the equilibrium transition temperature is retarded by increasing the β quenching temperature. In the alloys this retardation is shown to be due to an increase in β grain size; in the pure metal the position is less clear but the results suggest that whilst β grain size is the most important factor it is not the only one. Transformation at temperatures in the martensitic and bainitic ranges is accelerated by increasing the quenching temperature because of the removal of the β grain boundaries, which arrest growth of α crystals.

Modern Methods of Dyeing and Finishing Ladies' Nylon Hose

The methods available for the dyeing and finishing of ladies' nylon hosiery are described and reviewed. These include “conventional” methods— preboard and machine finish, postboard, and tray dry or tray fold. Dyeing techniques are discussed with particular emphasis on the practical effects of various heat treatments upon the yarn or hosiery, particularly in relation to the dye uptake of the nylon. Combined dyeing and finishing machines, or dyoboarders, are then described, with their main advantages and disadvantages, in the form of a chronological survey. The machines referred to are the Electrocolorset, the Dyotherm, the Heliot Teintofix, the Colorplast, the Turbo Dyeboarder, the Pegg Dyeboarder, the Girland Dyeboarder, and the Hydroset machine.