Heat Treatment Period Research Articles

Bacillus cereus in refrigerated milk submitted to different heat treatments.

The possibility of the survival, germination, and multiplication of Bacillus cereus in extended-shelf-life milk prompted research into the occurrence of the bacteria in refrigerated milk submitted to different heat treatments. Samples were submitted to ultrapasteurization (138 degrees C for 2 s), "superpasteurization" (96 degrees C for 13 s), and pasteurization (74 degrees C for 15 s) and stored under refrigeration at 4 +/- 2 degrees C for up to 6 weeks. The milk was analyzed for its sensory quality and for the quantitative determination of mesophilic and psychrotrophic B. cereus in the vegetative form at incubation temperatures of 7 and 30 degrees C, in addition to standard plate counts and psychrotrophic counts. In the three experimental trials, the psychrotrophic B. cereus counts were below the detection limit of the methodology (<10 CFU/ml) in all of the samples analyzed, independent of the heat treatment and storage period. The count of mesophilic B. cereus was restricted to samples of superpasteurized and pasteurized milk from a single trial, reaching 4.0 x 10(1) and 7.0 x 10(5) CFU/ml, respectively. Although the pasteurized milk had higher populations of mesophilic B. cereus after the second week of storage, flavor defects resulting in sensory rejection of the product did not appear before the fourth week of storage. The results of this research indicate that superpasteurization and ultrapasteurization are adequate for maintaining the product at refrigeration temperatures for 6 weeks. Pasteurized milk produced under clean conditions should have a shelf life limited to less than 2 weeks.

The influence of annealing temperature on the graphitisation of CK 45 Steel

Graphitization in steels is a subject which has been studied temporarily in past decades. The importance of this phenomenon is due to the fact that graphite formation in steels can ease machining treatment and increase cold-work capability of steels. Weight reduction of the parts and the dedicated bioenvironmental properties of these steels are considered as a valuable replacement for lead containing steels for researchers. Anyway there has been always the assumption that this operation is long and not economically cost effective. For this reason due to the different conditions of applied heat treatments, the effects of the temperature and the time period of heat treatment on the graphitization of CK45 steel is investigated in present research.

Evolution of Special Grain Boundaries in Austenitic Steels

AISI 304 type austenitic stainless steel samples were subjected to different thermomechanical treatments in order to investigate the effect of thermo-mechanical treatment on the grain boundary structure of the material. Electron back scatter diffraction measurements have been carried out in order to obtain information about the boundaries of the treated specimen. The measurements showed that achieving the same deformation with the same number of deformation cycles and same heat treatment temperature, the application of shorter heat treatment holding time was advantageous in aspect of grain boundary structure comparing to the thermo-mechanical treatments with longer holding time. The frequency of the special Σ3n type CSL-boundaries excluding coherent twin boundaries was significantly decreased by increasing the heat treatment holding time of the samples from the very short heat treatment periods. Extending the holding time further, the frequency of the special Σ3n type CSL-boundaries excluding coherent twin boundaries increased and reached the results applying the shorter heat treatment periods.

Second-Generation Aluminium Extraction Residue Used as Devitrification Aid for Glass-Ceramics

Brazil has one of the world’s most important Bauxite deposits, the raw material for the aluminium extraction metallurgy. This work is focused on finding a suitable application for the white dross residue (WDR), a second-generation waste material produced during the metal recovery from the slag left after the primary extraction of aluminium from the ore. A commercial lime-silica based glass frit was used, to which WDR additions were made (up to 30 wt.%), aimed at studying the devitrification process of the glasses produced. Such mixtures were melted at temperatures varying from 1100 to 1500°C and the resulting fritted glasses were heat treated at 900°C. The starting materials and the mixtures thereof were characterized before and after thermal treatment by differential thermal analysis, X-ray diffraction and fluorescence, and scanning electron microscopy. The results obtained showed that the WDR is easily incorporated into the glass matrix and causes easy devitrification after short heat treatment periods at low temperature.

Close−Open−Close Evolution of Holes at the Tips of Conical Graphenes of Single-Wall Carbon Nanohorns

We previously reported that holes opened at the tips of conical single-graphenes of single-wall carbon nanohorns were closed during heat treatment at 1200 °C in an argon atmosphere. Here, we report phenomena related to the behavior of these holes: the holes closed quickly at first, then reopened, and then slowly closed again as the heat treatment period increased. This close−open−close evolution occurred only when the initial hole size was medium (0.7−0.9 nm). Smaller and larger holes did not reopen after they thermally closed. We discuss the close−open−close mechanism by considering the functions of oxygenated groups existing at the edges of the holes.

Thin films of Cu 2Sb and Cu 9Sb 2 as anode materials in Li-ion batteries

Thin Cu 2Sb films have been prepared by heat-treating Sb films, electrodeposited on Cu substrates. The influence of the electrodeposition conditions and the heat-treatment period on composition and morphology of the films were investigated (SEM and XRD) and the obtained films were tested as anode materials for Li-ion batteries. The Cu 2Sb material showed a stable capacity of 290 mAh g −1 (close to the theoretical capacity of 323 mAh g −1) during more than 60 cycles. The presence of 9–11% (w/w) Sb 2O 3 in the electrodeposited films resulted in smaller particles but also slowed down formation of Cu 2Sb during the heat-treatment step. The presence of Sb 2O 3 was found to decrease the cycling stability although structural reversibility of Cu 2Sb was obtained both with and without Sb 2O 3. Longer heat-treatments of pure Sb films resulted in the formation of Cu 9Sb 2 which was shown to be reduced at a lower potential than Cu 2Sb. The Cu 9Sb 2 was converted to Cu 2Sb during repeated cycling and the capacity of the latter Cu 2Sb material was found to be 230 mAh g −1. While reduction of the materials was complicated by simultaneous formation of an SEI layer, three plateaus could be identified during the oxidation of Li 3Sb, indicating the presence of three separate one-electron oxidation reactions.

Modern electric furnaces for heat-treatment of ceramic articles and art glass

The enterprise “TermIKS” manufactures a new generation of electric furnaces for mollification and fusing of glass as well as for drying and firing ceramic articles. The minimum admissible temperature differential is maintained throughout the entire period of heat treatment of an article in the furnaces.

Torsion Fracture Behavior of Drawn Pearlitic Steel Wires with Different Heat Treatments

In this paper, torsion fracture behavior of drawn pearlitic steel wires with different heat treatments was investigated. Samples with different heat treatment conditions were subjected to torsion and tensile tests. The shear strain along the torsion sample after fracture was measured. Fracture surface of wires was examined by Scanning Electron Microscopy. In addition, the method of Differential Scanning Calorimetry was used to characterize the thermodynamic process in the heat treatment. A numerical simulation via finite element method on temperature field evolution for the wire during heat treatment process was performed. The results show that both strain aging and recovery process occur in the material within the temperature range between room temperature and 435 °C. It was shown that the ductility measured by the number of twists drops at short heating times and recovers after further heating in the lead bath of 435 °C. On the other hand, the strength of the wire increases at short heating times and decreases after further heating. The microstructure inhomogeneity due to short period of heat treatment, coupled with the gradient characteristics of shear deformation during torsion, results in localized shear deformation of the wire. In this situation, shear cracks nucleate between lamella and the wire breaks with low number of twists.

真空後熱処理を組み合わせた Ar-5%CO ガスを利用したチタン材料の表面硬化処理法

Surface hardening using solute oxygen formed by dissociation of oxidation film on C.P. (commercially pure) titanium, α+β type Ti-4.5Al-3V-2Fe-2Mo (SP-700) alloy and β type Ti-15Mo-5Zr-3Al (Ti-15-53) alloy was investigated. This method consists of two processes at 1073 K; surface hardening in use of Ar-5%CO gas with a short period of time and subsequent heat treatment under vacuum. The maximum surface hardness and hardening layer depth of C.P. titanium obtained by surface hardening for 1.8 ks were 420 Hv and 30 μm, respectively and these values increased to 820 Hv and 70 μm, respectively, by post heat treatment for 14.4 ks. The extra-surface hardening obtained by post heat treatment was yielded by solid solution hardening of oxygen with the following steps; the solute oxygen is continuously formed at oxide/titanium interface by the dissociation of oxidation film formed by the surface hardening treatment, and then it diffuses into titanium matrix. The maximum surface hardness was the highest in C.P. titanium and the lowest in Ti-15-53. On the other hand, the hardening layer depth was the deepest in Ti-15-53 and the shallowest in C.P. titanium. These results could be explained by the difference of solubility and diffusivity of solute oxygen between titanium α and β phases. This two-step process seems to be a beneficial industrial surface hardening method for titanium materials because it enables to remove the oxide film, achieving the very high maximum surface hardness comparable to that obtained by one-step surface hardening under the same total processing time.

Complete dissolution temperature of magnesium and silicon in commercial 6000 series aluminum alloys

Mg and Si contents in mass% written as {Mg} and {Si} was read out from solid solubility isotherms in Al rich corner of Al–Mg–Si phase diagram recommended by Willey. The Mg richer side than locus of apex for (Al) –Mg2Si– (Si) three phases region was named as region A and another side richer in Si than the locus as region B. Relation between complete dissolution temperature TCD and the Mg and Si contents in the region A can be written asln [ {Mg} 1.73 {Si} ] = (12.1±0.2) − (1.06±0.01) ×104/TCD .In the region B, writing linear relation between {Mg} and {Si} as {Mg} =α {Si} +βand under assumption that the β shows an Arrhenius type temperature dependence, a relationln [ {Mg} +2.43 {Si} ] = (8.16±0.03) − (5.77±0.03) ×103/TCDwas obtained. Tracing change in resistivity with temperature of heat treatment, the TCD of commercial alloys was experimentally estimated. Experimental TCD values well coincided with calculated values in 6N01, 6151 and previously investigated 6063 alloys which are low contents in the region A. However, perhaps because of existence of coarse Mg2Si particles which require long period of high temperature heat treatment to dissolution, high contents 6061 in the region A and 6022 in the region B showed experimental values about 20 K lower than the calculated values.

Qualidade sanitária e fisiológica de sementes de milho submetidas a termoterapia e condicionamento fisiológico

A termoterapia é uma medida de controle tradicionalmente utilizada com sucesso para eliminação de patógenos em sementes de espécies hospedeiras. Trata-se, no entanto, de uma medida que provoca alterações fisiológicas e bioquímicas nas sementes em diferentes intensidades, podendo comprometer o desempenho das mesmas nas condições de cultivo. Objetivou-se com este trabalho avaliar a eficácia da termoterapia no controle de alguns fungos associados a sementes de milho e do condicionamento osmótico, após o tratamento térmico, no sentido de reparar danos nas sementes provocados nestas circunstâncias. Os fungos associados às sementes foram avaliados por meio do método de incubação em substrato de papel com congelamento, e a qualidade fisiológica das sementes pelos testes de germinação, primeira contagem, condutividade elétrica, e padrões eletroforéticos das enzimas esterase (EST), malato desidrogenase (MDH) e álcool desidrogenase (ADH). O tratamento térmico utilizado foi por imersão em água aquecida a 60°C por 5, 10 e 20 minutos. Após o tratamento, uma fração das sementes foi submetida ao condicionamento fisiológico em rolo de papel embebido em solução de PEG 6000 a -1,2 MPa. Todos os tratamentos térmicos reduziram ou eliminaram Acremonium strictum das sementes. A incidência de Fusarium verticillioides foi reduzida significativamente pelo tratamento térmico nos períodos de 10 e 20 minutos. À medida que se aumentou o tempo de exposição ao tratamento térmico, houve aumento dos valores de condutividade elétrica e redução significativa da primeira contagem e germinação das sementes. O tratamento térmico durante 20 minutos alterou os padrões eletroforéticos das enzimas esterase e malato desidrogenase. O condicionamento fisiológico das sementes não foi capaz de reverter os danos causados pela termoterapia.

The effects of heat treatment on physical properties and surface roughness of red-bud maple ( Acer trautvetteri Medw.) wood

Heat treatment is often used to improve the dimensional stability of wood. In this study, the effects of heat treatment on physical properties and surface roughness of red-bud maple ( Acer trautvetteri Medw.) wood were examined. Samples obtained from Düzce Forest Enterprises, Turkey, were subjected to heat treatment at varying temperatures and durations. The physical properties of heat-treated samples were compared against controls in order to determine their; oven-dry density, air-dry density, and swelling properties. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements, using the stylus method, were made in the direction perpendicular to the fiber. Three main roughness parameters; mean arithmetic deviation of profile ( R a), mean peak-to-valley height ( R z), and maximum roughness ( R max) obtained from the surface of wood, were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Significant differences were determined ( p > 0.05) between surface roughness parameters ( R a, R z, R max) at three different temperatures and three periods of heat treatment. The results showed that the values of density, swelling and surface roughness decreased with increasing temperature treatment and treatment times. Red-bud maple wood could be utilized successfully by applying proper heat treatment techniques without any losses in investigated parameters. This is vital in areas, such as window frames, where working stability and surface smoothness are important factors.

Evaluation of Corrosion Fatigue Characteristics of Artificially Sensitized Austenitic Stainless Steel Using the DCPD Method

Austenitic stainless steel has a large problem to decrease its corrosion resistance and mechanical properties by sensitization in the welding process. Thus, in this paper, corrosion fatigue characteristics of artificially sensitized STS304 were investigated. According as heat treatment period for sensitization increases, the Cr-carbide deposition in the grain boundary and degree of sensitization (Ia/Ir) increased. From the results, corrosion fatigue strength of sensitized STS304 was remarkably reduced compare to non-sensitized ones.

Phase transformation in doped Y–Ba–Cu–O superconductors obtained by different melt processing techniques

In order to produce superconductors with improved properties the better understanding of the phase transformations taking place during the heat treatments in the melt processing techniques seems to be important. For the examination of the phase transformation in the Y–Ba,K–Cu–O,F superconductors a Philips PW 3710 type X-ray diffractometer equipped with a HTK 16 Anton Paar type heating chamber was used. It was established, that in the melted, Y 2O 3 particles containing materials the most part of the Y123 phase crystallizes during the heating period of the subsequent heat treatment, but in the samples presintered at lower (900 °C) temperature the formation of Y123 phase occurs mainly on cooling. The partial substitution of Ba for K influences favourably on the crystallization of Y123.

Sol–hydrothermal preparation and photocatalysis of titanium dioxide

Nanosized TiO 2 with controlled crystal phase/structure was prepared by a sol–hydrothermal process using titanium (IV) n-butoxide as a precursor of TiO 2. After hydrothermal processing at 200 °C for 1 h, the granulous anatase phase with average crystal size of 5 nm was formed. Upon increasing the heat treatment period to more than 5 h, the rod-like rutile phase with particle size of 19 × 70 nm became predominant. The structure evolution from X-ray diffraction (XRD), particle size/morphology from transmission electron microscopy (TEM), surface area from Brunauer–Emmitt–Teller (BET) analysis, and photocatalytic activity of TiO 2 products show strong correlation with the hydrothermal conditions.

Isolation of hydrogen generating microflora from cow dung for seeding anaerobic digester

The effectiveness of using cow dung as a source for isolating hydrogen generating microflora was investigated under varying isolating conditions based on viz.: pH adjustment and pH adjustment coupled with heat treatment. The viability of the isolated microflora was tested in an anaerobic jar with respect to biogas generation, hydrogen content and pH. The results showed that for pH adjusted microflora isolated from cow dung with solids content at 10% resulted in a cumulative biogas generation of 1494, 2404 and 3327 ml, whereas the corresponding cumulative hydrogen generation was found to be 424, 701 and 47 ml during the anaerobic fermentation for 120 h at a pH of 4, 5 and 6, respectively. The biogas was free from methane when operated at pH 4 and 5, whereas at pH 6 methane generation was observed. In the case of microflora isolated from cow dung with 10% solids, by subjecting to pH adjustment coupled with heat treatment resulted in biogas free from methane content during the fermentation at pH 4, 5 and 6, respectively. At the end of 120 h of fermentation for a reactor pH at 4, 5 and 6 the cumulative biogas generation was 1685, 2610 and 2353 ml, whereas the cumulative hydrogen generation was 509, 1198 and 1165 ml, respectively. A maximum of 41% and 62% hydrogen was obtained at pH 5 for microflora isolated based on pH adjustment and pH adjustment coupled with heat treatment. The effect of initial solids content of the cow dung on the isolating efficiency of hydrogen generating microflora was also investigated at pH 5 and 6 coupled with heat treatment. The results revealed that with the increase in initial solids content of the cow dung the optimum heat treatment period also increased as the pH increased from 5 to 6.

Biohydrogen generation from jackfruit peel using anaerobic contact filter

A novel method of anaerobic digestion using contact filter was adopted for treating solid waste generated from the fruit processing industry, namely jackfruit, with the intention of generating energy free from greenhouse gases. A new source of microflora was isolated from cow dung by subjecting it to pH adjustment at 5 ± 0.2 coupled with heat treatment at 105 ∘ C for 1 h, and not less than three consecutive periods of heat treatment. The isolated microflora exhibited their capability to generate hydrogen while treating solid waste consisting of jackfruit peel. The biogas generation was found to be 0.72 l/g VS (jackfruit peel) destroyed. The hydrogen content in the biogas was found to be consistent resulting in 55 ± 2 % , while the biogas was free from methane content. The effect of hydraulic retention time (HRT) on volatile solids destruction efficiency was investigated for an influent volatile solids content of 33 g/l at an HRT of 7 and 12 d. The results showed a volatile solids destruction efficiency of 22% and 50%, respectively, for the above said conditions. The efficiency of anaerobic digestion was also investigated for varying influent volatile solids content viz: 22.5, 17.1 and 11.3 g/d at 12 d HRT. The anaerobically digested jackfruit peel waste having an initial volatile solid content of 22.5 g/d was subjected to filtration test at 15 psi for a period of 1.3 h. The sludge resulting from the filtration test had a solids content of 12%, whereas the filtrate had the following characteristics viz: pH 5.3 ± 0.2 , COD 1700 mg/l, BOD 1175 mg/l and TKN 120 mg/l.

STRUCTURE AND PROPERTIES OF (La2-xSrx)MnO4 COMPOUNDS

Polycrystalline single phase ( La 2-x Sr x) MnO 4 (1.10≤ x ≤1.40) samples were prepared by a citrate precursor method. They have tetragonal K 2 NiF 4 structure with a space group of 14/mmm, increasing x, unit-cell a-axis increases and c-axis decreases, which is a result of decreasing of the Jahn-Teller effect due to the increase of the Mn ( IV ) ion. Spin glass state exists at low temperature and a hump observed from the susceptibility (χ) measurement is probably caused by the interactions of several magnetic phases. Among them, ( La 0.6 Sr 1.4) MnO 4 has the largest magnetoresistance ratio ([ρ(H)-ρ(0)]/ρ(0)), which reaches to 78.4% at 48 K. It is not possible to obtain single phase materials with 0.60≤ x ≤1.00 in the heat treatment temperature range of 1000-1600°C. Impurities were easily observed under SEM and X-ray diffraction patterns. Increasing the heating period and decreasing the temperature, the amount of ABO3 perovskite phase increases. In order to extend the solubility range, of the SrO in the ( La 2-x Sr x) MnO 4, it probably needs a higher temperature (&gt;1600°C) and a shorter heat treatment period (&lt;1 h).

Chemical and mechanical stabilization of martensite

An algorithm of quantitative analysis of two basic contributions to the stabilization of martensite – atomic reordering (“chemical” stabilization component) and pinning of interfaces (“mechanical” contribution) – has been developed. The algorithm uses data obtained by routine calorimetry measurements. The possibility to quantitatively separate contributions of “chemical” and “mechanical” stabilization components stems from the fact that they affect the first reverse transformation of stabilized martensite through thermodynamically reversible and irreversible factors, respectively. Analysis of the thermodynamics of the thermoelastic martensitic transformations allowed us to conclude that stabilization of martensite should be described in terms of pure shift and broadening of the reverse transformation. These parameters are shown to have a clear physical meaning. Namely, pure shift of the reverse transformation as a result of martensite stabilization provides an upper estimate for the atomic reordering or “chemical” contribution to the stabilization, whereas broadening of the reverse transformation represents a lower limit for pinning-induced or “mechanical” stabilization component. Experimental data on stabilization of a Cu–Zn–Al alloy are analyzed, indicating that contributions of “chemical” and “mechanical” stabilization components are comparable but depend on martensite ageing period and details of the initial heat treatment of samples.

Crosslinking of Poly(vinyl alcohol) via Bis(β-hydroxyethyl) Sulfone

Poly(vinyl alcohol) (PVA) was crosslinked via bis(β-hydroxyethyl) sulfone (BHES) at elevated temperatures to improve the water resistance. The best conditions for the crosslinking such as temperature, heat-treatment period, and amount of BHES or catalyst were screened out. Water resistance of the crosslinked PVA was characterized in terms of swelling and weight loss in water. The addition of BHES into PVA followed by heating at elevated temperature resulted in successful formation of crosslinking structure. The crosslinking occurs above 160 °C and takes shorter period at high temperature than low temperature. The crosslinking catalyst, sodium carbonate, acts more effectively at 160 °C than at 200 °C. The results from thermal analysis using a differential scanning calorimetry revealed that the catalyst functions against BHES to lower the temperature for the crosslinking reaction and that even the crosslinked films have the PVA crystalline. The crosslinking procedure using BHES and sodium carbonate is applicable to form ion-exchange fibers based on PVA with high water resistance.