Thermal Processing Conditions Research Articles

Processing chemically amplified resists on advanced photomasks using a thermal array

A thermal array, which consists of a dense distribution of multivariate controlled heat/chill elements, is developed to achieve temperature uniformity of a quartz photomask throughout the processing temperature cycle of ramp, hold and quench. The thermal array spatially tunes the uniformity in response to calibrated feedback provided by temperature sensor instrumented masks or by linewidth data. The system can stabilize to decreases in temperature setpoints at fast rates, about 40 °C/min, to improve the throughput of the tool for situations requiring switching between operating temperatures. The thermal array is a likely aid to improve critical dimension distribution on expensive photomasks by providing uniform thermal processing conditions.

Application of Transfer Functions to the Thermal Processing of Sweet and Sour Cherries Preserves: Influence of Particle and Container Sizes

The conditions of thermal processing of fruit preserves packed in transparent glass containers have great importance from the point of view of the final product appearance. Process simulation can allow to predict the quality of the product and its possible degradation. This work applied the transfer function method to simulate the pasteurisation of whole sweet and sour cherries canned in glass containers, with a 25 °Brix sucrose solution as covering liquid, and the predicted results were experimentally tested. The influence of fruit and container diameters on the treatment times was analysed. Kinetic models for enzyme degradation were coupled to the prediction model as examples of the possibilities of optimising the whole pasteurisation process. The accuracy (average error in predicted temperatures: 2.1%) of the simulation method was satisfactory for practical purposes, its use resulted simple and fast, and it allowed adjusting of pasteurisation times, even during the process.

Intrinsic Strain Modeling and Residual Stress Analysis for Thin-Film Processing of Layered Structures

Residual stresses develop due to intrinsic and extrinsic strains that form during the processing. Extrinsic strains can be determined using coefficient of thermal expansion, material properties, and processing conditions. An “Equivalent Reference Temperature (ERT)” technique is described and used to model and evaluate the intrinsic strains. piezoelectric microelectromechanical systems (P-MEMS) are considered in this work. Laminate theory with three-dimensional state of stress and strain is used to evaluate residual stresses using the ERT model. In finite element analysis (FEA), the residual stresses and strains of multi-layer P-MEMS structures deposited layer-by-layer during processing, are simulated using the “element birth-and-death” approach. The evaluated residual stresses for a simplified geometry using ANSYS three-dimensional FEA and analytical analysis employing three-dimensional laminate theory are presented along with their corresponding experimental results. A user-friendly software based on the 3-D laminate theory is developed and installed on the Internet. The “equivalent reference temperature” as well as residual stresses and strains can be determined using this software. The level of residual stresses and strains of P-MEMS depend upon various factors such as geometrical design, material selection, and process conditions.

Effects of powder preparation and sintering procedure on microstructure and dielectric properties of PLZT ceramics

PLZT ceramics belong to one of the very important groups of functional materials that make a basis for the production of a large range of electronic devices. The microstructure and properties of ceramics depend on the powder preparation and thermal processing conditions. Various techniques have been used to obtain chemically homogeneous and fine starting powders PLZT powders have been prepared by two different production routes: by a modified Pechini method, using a polymeric precursor method (PMM) and by a partial oxalate method. A two-step sintering process, including a hot pressing, was carried out at 1100 and 1200?C. Distinct phases obtained during the sintering process have been investigated by SEM and EDS techniques and dielectric properties such as permittivity and dielectric loss were measured in a frequency range from 1 to 20 kHz. A significant difference in microstructure and dielectric properties, depending on powder origin and sintering procedure, has been noticed.

Changes in the odors of squeezed apple juice during thermal processing

Effects of processing temperature and time on the odors of squeezed apple juice were investigated by the combined of sensory and analytical method. Freshly squeezed apple juice was treated by a flow system under the conditions of residence time 2–320 s and treatment temperature 80–120 °C. The odors of the juices were evaluated by a paired-comparison test and quantitative descriptive analysis. There was a complex change in the nature of the odors with treatment temperature and residence time. The quality optimum points were observed around 45 s for 90 °C, 20 s for 100 °C and 20 s for 110 °C. Changes in the volatility of aroma compounds were extremely complicated with respect to thermal processing conditions. Principal component analysis indicated that the treatment temperature more affected the volatility than the treatment time. Present data demonstrated the existence of optimum conditions in the thermal processing of squeezed apple juice.

Processing‐induced changes in total phenolics and procyanidins in clingstone peaches

AbstractClingstone peaches contain a wide array of complex secondary plant metabolites and polyphenolics, and increasing evidence indicates that many of these components are important in human health. Oligomeric flavan‐3‐ol metabolites (procyanidins) are particularly interesting owing to their potent antioxidant activity and protective cardiovascular effects. To date, little information is available on how postharvest and processing conditions impact levels of phenolics and procyanidins in fruit. This research addresses the impact of lye peeling, freezing, storage temperature (4 and 30 °C) and three different time–temperature sterilisation combinations on levels of total phenolics (TPs) in Ross clingstone peaches. Additionally, we describe the profile of procyanidin oligomers (monomers through heptamers) in clingstone and freestone peaches and demonstrate a dramatic decrease in procyanidins in thermally processed peaches. TP levels ranged between 316 and 397 mg kg−1 in peeled peaches and between 376 and 609 mg kg−1 in unpeeled peaches. Cold storage at 4 °C for 14 days or freezing and storing at −12 °C for 3 months produced no loss in TPs. Peaches stored at 30 °C for 24 h resulted in a 1.7‐fold increase in TPs. Studies of TPs in peaches processed at temperatures of 213 °F for 40 min, 220 °F for 10 min and 230 °F for 2.4 min indicate that processing above 213 °F decreases levels of both TPs (up to 21%) and procyanidins (up to 100%). Processing at 213 °F for 40 min produced no significant loss in TPs. Furthermore, studies reveal that a 30–43% loss in phenolic levels occurs during the first 3 months in storage after canning. It is clear that both storage and thermal processing conditions profoundly impact the levels of polyphenolics in peaches. More interestingly, these studies indicate that peaches are a rich source of procyanidins, having profiles similar to those found in cocoa, apples, wine and tea.© 2002 Society of Chemical Industry

Alicyclobacillus acidoterrestris spores as a target for Cupuaçu ( Theobroma grandiflorum) nectar thermal processing: kinetic parameters and experimental methods

The kinetic parameters of thermal inactivation of a spore former, Alicyclobacillus acidoterrestris, in a tropical fruit nectar [25% of Cupuaçu ( Theobroma grandiflorum) pulp and 15% sugar] were determined by the isothermal method (IM), under batch heating, and by the paired equivalent isothermal exposures (PEIE) method, under non-isothermal continuous conditions. The isothermal experiments were repeated three times, every 4 months, with the same spore suspension kept frozen between experiments. The aging of spores, under frozen storage, seemed to produce a notorious increase in the z-value from experiment to experiment: Experiment 1 ( z=7.8±2.6 °C, D 95 °C=5.29±0.96 min), Experiment 2 ( z=22±5 °C, D 95 °C=5.99±0.63 min), and Experiment 3 ( z=29±10 °C, D 95 °C=3.82±0.48 min). The evaluation of the kinetic parameters by the PEIE method was carried out in parallel with Experiment 3, with the same aged spores, and the results ( z=31±6 °C, D 95 °C=5.5±1.2 min) were close to the ones obtained in this experiment. From this work, it seems that the PEIE method can also be applied to evaluate the reduction parameters of a spore-forming microorganism, and in a more realistic way, since the continuous system eliminates the errors caused by come-up and cool-down times (CUT and CDT) that are unavoidable in isothermal experiments. Therefore, when designing a thermal process for a continuous system, the PEIE method should be used, or the chances are that the process would be underdesigned, risking that the desired level of spore inactivation would not be achieved. An optimization of the thermal processing conditions was next performed for Cupuaçu nectar, considering a 5 D reduction in A. acidoterrestris spores. If a pasteurization process is considered, the conditions that ensure safety (9 min at 98 °C) only allow a 55% retention of ascorbic acid (AA). If sterilization is considered, 8 s at 115 °C will ensure a safe product and retain 98.5% of the original ascorbic acid. Therefore, if A. acidoterrestris is considered as the target microorganism, the nectar should undergo an aseptic high temperature short time principle (HTST) process to achieve a 5 D reduction in this acidophilus spore former. However, if the hot-fill-and-hold pasteurization process is preferred, the product should be fortified with ascorbic acid.

Effect of Chemical History and Thermal Processing Conditions on the Surface Fractality of Iron(III) Oxide

Effect of Chemical History and Thermal Processing Conditions on the Surface Fractality of Iron(III) Oxide

A Study of the Decomposition of GaN during Annealing over a Wide Range of Temperatures

ABSTRACTAnnealing experiments were carried out on gallium nitride layers, which were grown on sapphire through Metal Organic Chemical Vapor Deposition (MOCVD). Rutherford Backscattering Spectrometry (RBS) was performed on as-grown and annealed GaN samples using a 2 MeV proton beam to study the stoichiometric changes in the near-surface region (750 nm) with depth resolution better than 50 nm. No decomposition was measured for temperatures o up to 800 °C. Decomposition in the near-surface region increased rapidly with a further increase o of temperature, resulting in a near-amorphous surface-region for annealing at 1100 °C. The depth profiles of nitrogen and incorporated oxygen in the decomposed GaN are extracted from the nanoscale RBS data for different annealing temperatures. The surface roughness of the GaN layers observed by atomic force microscopy (AFM) is consistent with RBS decomposition measurements. We describe the range of annealing conditions under which negligible decomposition of GaN is observed, which is important in assessing optimal thermal processing conditions of GaN for both conventional and nanoscale optoelectronic devices.

Dielectric Properties of (Ba,Sr)TiO3 Thin Film Capacitors Fabricated on Alumina Substrates

ABSTRACTDouble layer (DL) Ba0.7Sr0.3TiO3 (BST) capacitors with Pt electrodes have been fabricated with similar growth conditions on different substrates. The substrates used in the present study were r-plane sapphire, polycrystalline alumina Al2O3 (99.6% and 96%), and glazed polycrystalline alumina. BST films were grown by metal-organic decomposition (MOD) method. By varying the annealing conditions which affects the formation of the crystalline structure, significant changes in the dielectric properties of the BST films have been observed. BST films were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Powder X-ray Diffractometer (PXRD). These observations showed that BST films grown at lower temperatures on alumina substrates exhibited the smallest grain size. BST films of the same thickness prepared under the same thermal processing conditions showed higher capacitance when grown on all types of alumina-based substrates compared to those deposited on control SiO2/Si. The higher capacitance on alumina was always associated with larger dissipation factor, and lower or similar leakage current density. The final tuning, of the dielectric properties of BST DL capacitors on non-silicon substrates, was correlated to the initial film formation temperature and post-annealing conditions of the BST films. The leakage current density, of DL BST capacitors fabricated on glazed alumina, becomes smallest when the BST processing temperature was lowered by 100 °C compared to the control SiO2/Si. The typical achieved leakage current density for 1500×1500 μm2 DL capacitors on glazed alumina was 3.8×10-9 A/cm2 at 250 kV/cm (36.5 fF/μm2), about 3 times lower than on SiO2/Si substrates (1.1×10-8 A/cm2 at 250 kV/cm, 31 fF/μm2).

Characterization of cold-rolled and aged MP35N alloys

Systematic research has been undertaken on the effects of deformation and aging on the mechanical properties and microstructures of MP35N alloys. A relationship among the aging time, aging temperatures and mechanical properties has been established and the optimum aging conditions were critically assessed by evaluation of the variations of hardness with the thermal processing conditions. Aging of 65% cold-rolled MP35N alloys at 550 °C for 8 h produced materials with hardness values of 5647±78 MPa (580 HV) and yield strength of 2125 MPa at room temperature. At −196 °C, the yield strength reached 2511±1 MPa and the work hardening rate was higher than that at room temperature. Assisted by electropolishing, light microscopy and scanning electron microscopy (SEM) revealed the microstructure changes in the materials, whereas the detailed microstructure introduced by cold deformation and aging was studied by transmission electron microscopy (TEM). Deformation results in production of {110}〈1̄12〉 and {110}〈1̄11〉 textures, rotation of the annealing twin boundaries and introduction of very fine platelets that strengthen the face-centered-cubic (fcc) matrix.

Survival and heat resistance of Listeria monocytogenes after exposure to alkali and chlorine.

A strain of Listeria monocytogenes isolated from a drain in a food-processing plant was demonstrated, by determination of D values, to be more resistant to the lethal effect of heat at 56 or 59 degrees C following incubation for 45 min in tryptose phosphate broth (TPB) at pH 12.0 than to that of incubation for the same time in TPB at pH 7.3. Cells survived for at least 6 days when they were suspended in TPB at pHs 9.0, 10.0, and 11.0 and stored at 4 or 21 degrees C. Cells of L. monocytogenes incubated at 37 degrees C for 45 min and then stored for 48 or 144 h in TPB at pH 10.0 were more resistant to heat treatment at 56 degrees C than were cells stored in TPB at pH 7.3. The alkaline-stress response in L. monocytogenes may induce resistance to otherwise lethal thermal-processing conditions. Treatment of cells in 0.05 M potassium phosphate buffer (pH 7.00 +/- 0.05) containing 2.0 or 2.4 mg of free chlorine per liter reduced populations by as much as 1.3 log(10) CFU/ml, while treatment with 6.0 mg of free chlorine per liter reduced populations by as much as 4.02 log(10) CFU/ml. Remaining subpopulations of chlorine-treated cells exhibited some injury, and cells treated with chlorine for 10 min were more sensitive to heating at 56 degrees C than cells treated for 5 min. Contamination of foods by L. monocytogenes cells that have survived exposure to processing environments ineffectively cleaned or sanitized with alkaline detergents or disinfectants may have more severe implications than previously recognized. Alkaline-pH-induced cross-protection of L. monocytogenes against heat has the potential to enhance survival in minimally processed as well as in heat-and-serve foods and in foods on holding tables, in food service facilities, and in the home. Cells surviving exposure to chlorine, in contrast, are more sensitive to heat; thus, the effectiveness of thermal processing in achieving desired log(10)-unit reductions is not compromised in these cells.

Phase formation and thermal treatment optimisation in uranium compound doped (Bi,Pb) 2Sr 2Ca 2Cu 3O x/silver superconducting tapes

A combination of uranium doping with thermal neutron irradiation has been well demonstrated to be one of the most effective means to introduce pinning centres in Bi-2223/Ag tapes. A substantial improvement in flux pinning and reduction of anisotropy in uranium-doped Bi-2223/Ag tapes has been achieved due to thermal neutron irradiation. However, the radioactivity of silver sheath is too high for practical application of this technique. In the current study, a number of U-containing compounds, U 3O 7, UCa 2O 5, and UCa 1.5Sr 1.5O 6 have been used as dopants. The compatibility and interaction between U-compound and Bi-2223 matrix was systematically studied with various thermal processing conditions. UCa 1.5Sr 1.5O 6 shows a remarkable compatibility with Bi-2223 phase, with critical current density reduced by about 15% at a doping level of 1.1 at.%, compared with the 85% reduction in critical current density at the same doping level for pure U-oxide doping. XRD results show that UCa 1.5Sr 1.5O 6 has no effect on Bi-2223 formation while U 3O 7 caused degradation of Bi-2223 phase up to 50% at doping level of 1.1 at.%. The U-compound doping also widens the processing window to 15°C.

Thermal process calculations using artificial neural network models

In this study, artificial neural network (ANN) models were evaluated as potential alternatives to conventional thermal process calculations methods. ANN is a computing system capable of processing information by its dynamic response to external inputs. ANNs learn from examples through iteration by adjusting the internal structure to match the pattern between input and output variables. Finite difference simulations, which are widely recognized as practical alternatives to experimental methods, were used to generate temperature profiles under thermal processing conditions for a wide range of can sizes and operating conditions. Time-temperature data so gathered were used to evaluate the heat penetration parameters, f h, j ch, f c and j cc as well as to compute process lethality and process time. These data were used for developing the ANN models. Selected Formula methods were also used to calculate the respective process times/process lethalities. The accuracy and ability of ANN models were compared with the Formula methods, both with respect to process time and process lethality computations using data from the finite difference model as the reference. Process calculation results from ANN model were comparable to, and sometimes better and more flexible than, the currently available Pham and Stumbo methods.

Aqueous base development and acid diffusion length optimization in negative epoxy resist for electron beam lithography

A new aqueous base developable, chemically amplified negative resist based on epoxy chemistry is evaluated for high-resolution, high-speed e-beam lithography. This resist is formulated using partially hydrogenated poly(hydroxy styrene) and epoxy novolac polymers. Degree of hydrogenation controls the aqueous base solubility and microphase separation phenomena. Reduction of edge roughness compared to the pure epoxy systems is observed whereas the absence of swelling phenomena allows lithography up to 100 nm regime and a sensitivity of 4–8 μC/cm2 at 50 keV. The diffusion coefficient has been evaluated both from high-resolution line and dot exposures and it is found to be 5×10−14 cm2/s for the optimal thermal processing conditions selected.

A modified laboratory canning protocol for quality evaluation of dry bean (Phaseolus vulgaris L)

The effects of calcium (Ca2+) level in the soak water, blanch water and brine, blanching temperature, and total seed solids on dry bean canning quality were investigated to optimise a laboratory canning protocol. A linear increase in the Ca2+ level of soak water, blanch water and brine resulted in a linear decrease in hydration coefficient and percent washed drained weight but a linear increase in texture. Low Ca2+ level (10 mg kg−1) reduced the hydration time for dry bean seed from 14 to 1 h. Blanching temperatures of 50, 70 and 88 °C had non-significant effects on canning quality traits. Blanching for 30 min at 70 °C for black bean or at 88 °C for navy bean and pinto bean resulted in percent washed drained weight ≥ 60, as required by the Canada Agricultural Products Standards Act. Seed solids levels of 95–97 g per 300 × 407 (14 fl oz) can were sufficient to attain a percent washed drained weight of 60. It was confirmed that the thermal processing conditions (115.6 °C retort temperature, 45 min) used in this study were sufficient to achieve commercial sterility. The optimised lab protocol for evaluation of the canning quality of dry bean breeding lines is as follows. Seed containing 95 g of solids for pinto bean, 96 g for navy bean and 97 g for black bean is soaked in water for 30 min at 20 °C and blanched for 30 min at 70 °C for black bean and 88 °C for navy bean and pinto bean in water containing 10 mg kg−1 of Ca2+. The seed is then transferred to a 300 × 407 can, filled with brine containing 10 mg kg−1 of Ca2+, 1.3% (w/v) of NaCl and 1.6% (w/v) of sugar. The can is then sealed, processed in steam at 115.6 °C for 45 min and cooled at 20 °C for 20 min. Cans are stored for at least 2 weeks prior to quality evaluation of the canned product. Canning of dry bean seed according to this protocol results in precise estimation of canning quality traits, particularly percent washed drained weight. © 2000 Society of Chemical Industry

A modified laboratory canning protocol for quality evaluation of dry bean (Phaseolus vulgaris L).

The effects of calcium (Ca2+ ) level in the soak water, blanch water and brine, blanching temperature, and total seed solids on dry bean canning quality were investigated to optimise a laboratory canning protocol. A linear increase in the Ca2+ level of soak water, blanch water and brine resulted in a linear decrease in hydration coefficient and percent washed drained weight but a linear increase in texture. Low Ca2+ level (10 mg kg-1 ) reduced the hydration time for dry bean seed from 14 to 1 h. Blanching temperatures of 50, 70 and 88 °C had non-significant effects on canning quality traits. Blanching for 30 min at 70 °C for black bean or at 88 °C for navy bean and pinto bean resulted in percent washed drained weight ≥ 60, as required by the Canada Agricultural Products Standards Act. Seed solids levels of 95-97 g per 300 × 407 (14 fl oz) can were sufficient to attain a percent washed drained weight of 60. It was confirmed that the thermal processing conditions (115.6 °C retort temperature, 45 min) used in this study were sufficient to achieve commercial sterility. The optimised lab protocol for evaluation of the canning quality of dry bean breeding lines is as follows. Seed containing 95 g of solids for pinto bean, 96 g for navy bean and 97 g for black bean is soaked in water for 30 min at 20 °C and blanched for 30 min at 70 °C for black bean and 88 °C for navy bean and pinto bean in water containing 10 mg kg-1 of Ca2+ . The seed is then transferred to a 300 × 407 can, filled with brine containing 10 mg kg-1 of Ca2+ , 1.3% (w/v) of NaCl and 1.6% (w/v) of sugar. The can is then sealed, processed in steam at 115.6 °C for 45 min and cooled at 20 °C for 20 min. Cans are stored for at least 2 weeks prior to quality evaluation of the canned product. Canning of dry bean seed according to this protocol results in precise estimation of canning quality traits, particularly percent washed drained weight. © 2000 Society of Chemical Industry.

Application of 13C NMR to the selection of the thermal processing conditions of canned fatty fish

13C nuclear magnetic resonance spectroscopy has been applied to select the processing conditions for tuna sterilisation. The work aimed to determine the heating times and retort temperatures required to guarantee a particular degree of microbiological sterility, but also to provide maximum nutrients and/or the retention of quality factors. Quality assessment was made on the basis of lipid degradation, hydrolysis and oxidation, and the estimation of the nutritional value (n-3 fatty acid content). Treatments involving the highest temperatures for the shortest times led to a final food with the highest n-3 fatty acid content and the lowest lipid degradation.

Process integration issues for doping of ultrashallow junctions

Process integration and in-line metrology are now the key agenda items for formation of ultrashallow junctions for ultralarge scale integration devices. Integration of the complete process sequence from selection of the device layer material through introduction and activation of dopants involves dozens of interacting decisions. This article highlights some issues associated with the control of channeling, damage annealing of preamorphized and molecular ion implants, outgassing of oxygen from product wafers during rapid thermal processing cycles and conditions for control of beam divergence and doping microuniformity near gate stack structures.

Effects of pelleting and storage of a complex nursery pig diet on lysine bioavailability.

The effects of pelleting and storage of a complex nursery pig diet (28% lactose and 1.4% lysine) on lysine bioavailability were assessed in a chick bioassay. The nursery diet was steam-conditioned at 60 degrees C for 45 s and then pelleted through a 5-mm die with a depth of 38 mm. Samples of meal and pelleted diet were placed in metallic feeders in an occupied nursery facility for 1 wk (warm) or were stored at 4 degrees C (cool). For the standard-curve bioassay, a total of 144 8-d-old chicks were offered the following dietary treatments: 1 to 3) a basal diet (lysine deficient) and two levels (.08 and .16%) of added lysine (from L-lysine-HCl); 4 and 5) two positive controls (.7% added lysine with or without 10% of the nursery diet); and 6 to 9) basal diet plus 10% of one of the four nursery diet samples (meal or pellet stored cool or warm for 1 wk). Pelleting had no effect (P>.10) on lysine bioavailability, probably because pelleting conditions (temperature, humidity, and pellet size) were not aggressive enough to result in detectable effects on lysine utilization. However, storage in the nursery facility for 1 wk reduced (P<.03) lysine bioavailability by an average of 10%. No significant (P>.10) interactions were observed. Furthermore, true digestibility of lysine in the four pig diet samples was estimated in a cecectomized cockerel digestibility assay using 15 adult Single-Comb White Leghorn cockerels. Lysine digestibility in all samples was high (average of 94%) and was not affected (P>.10) by treatment. We conclude that the pelleting conditions used in our experiments did not decrease lysine utilization. More research is needed to define thermal processing conditions that might cause protein quality deterioration. However, typical warm and humid environmental conditions encountered in modern nursery facilities have a negative effect on protein quality of diets rich in reducing sugars and lysine.