Orientador: Eugênio José Zoqui / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T00:04:00Z (GMT). No. of bitstreams: 1 Naldi_MarcosAntonio_M.pdf: 15438226 bytes, checksum: ccd17a2befec608057948a418e6317b5 (MD5) Previous issue date: 2011 / Resumo: A tecnologia de semi-sólidos normalmente utiliza ligas de alumínio de baixo silício, como AA356 (Al-7,0wt%Si) como matéria-prima. Ligas contendo alto teor de silício com uma composição quasi-eutética diminuem a faixa semi-sólida, tornando difícil controlar a temperatura de tixoconformação. Entretanto, ligas de alumínio com alto teor de silício apresentam excelentes propriedades mecânicas. Este trabalho tem por objetivo avaliar a tixoconformabilidade da liga Al-9,5wt%Si- 2,5wt%Cu (AA332) abrangendo as etapas de caracterização em termos de micro e macroestrutura, caracterização do comportamento viscoso até o processo de tixoforjamento em prensa do tipo excêntrica em matriz do tipo aberta. Através das simulações do software Thermo-Calc e técnicas experimentais de DSC a temperatura de transição de sólido para líquido foi mapeada a fim de obter o melhor comportamento semi-sólido e, conseqüentemente, a melhor temperatura de tixoconformação. Amostras de 20 mm de diâmetro por 15 mm de altura foram aquecidas foram aquecidas a três temperaturas, 562oC, 567oC e 572oC, pra se obter cerca de 30%, 45% e 60% da fração sólida por tempos de permanência de 0s, 30s, 90s e 210s. A evolução morfológica e o comportamento semi-sólido das amostras para estas temperaturas foram determinados através do teste de compressão a quente. A despeito das temperaturas e tempos usados a estrutura se mostrou bastante estável sendo que o melhor comportamento semi-sólido ocorreu à temperatura de 572º C, com uma viscosidade aparente de até 1.5E+5 Pa.s / Abstract: The thixoforming technology typically uses semi-solid aluminium alloys low silicon, as the AA356 (Al-7wt%Si-0.5wt%Mg) as raw material. Alloys with high content of silicon, with a quasi-eutectic composition decreases semi-solid range, making it difficult to control the thixoforming temperature. However, aluminium alloys with high silicon content present excellent mechanical properties. The goal of this work was to evaluate the thixoformability of Al-9,5wt%Si- 2,5wt%Cu(AA332) alloys, including the following stages process: characterization in terms of microstructure and macrostructures; characterization of the viscous behavior; and the tixoforging process in an eccentric press using a matrix-type open. Simulations using Thermo-Calc software and DSC experimental technique were used to map the transition temperature from solid to liquid to obtain the best semi-solid behaviour and, consequently, the best thixoforming temperature. Samples 20mm diameter, 15mm height were heated were heated at three distinct temperatures, 562oC, 567oC and 572oC, to obtain circa 30, 45 and 60% of solid fraction for soaking times of 0s, 30s, 90s and 210s. The morphological evolution and the behaviour of the semi-solid samples at these temperatures were determined by the hot compression test. Despite the different temperatures and times used, the structure proved to be quite stable and the best semi-solid behaviour occurred at a temperature of 572°C with an apparent viscosity of up to 1.5E+5 Pa.s / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Le traitement thermique est un procédé très largement utilisé dans l'industrie automobile et en particulier sur les pièces à dentures. Appliqué en général après usinage, il permet d'améliorer les propriétés mécaniques des pièces. Dans le même temps, plusieurs phénomènes physiques conduisent à des déformations, qui peuvent conduire au non-respect des tolérances dimensionnelles et géométriques. Ces déformations sont certes liées au traitement thermique mais également à l'ensemble de la gamme de fabrication en amont de celui-ci.L'objet de ce travail de recherche est d'améliorer d'une part la connaissance des phénomènes physiques mis en jeu au traitement thermique et d'autre part l'identification des déformations géométriques. Dans un premier temps, les déformations propres à chaque étape de fabrication sont identifiées. Puis au sein de la gamme, les sources d'origine dans la signature géométrique finale sont séparées. Une gamme de fabrication numérique illustre cette méthode.D'autre part, les « contraintes résiduelles » sont identifiées comme influentes sur l'évolution de la géométrie. Leur impact sur les déformations au traitement thermique est obtenu grâce à plusieurs campagnes d'essais sur site industriel. De cette façon, chaque caractéristique géométrique est reliée à une ou plusieurs étapes de fabrication en particulier. Ces résultats fournissent une aide au diagnostic des causes de non-conformités au traitement thermique. En parallèle, des modifications sur la gamme de fabrication sont proposées. / Heat treatment is widely used in automotive industry, especially in the case of gears. This process is habitually used after machining and increases mechanical properties of work pieces. In the meantime, several phenomena lead to distortions and sometimes to geometrical non-conformities. Distortions are due to heat treatment but also to previous manufacturing processes.The objective of this study is to improve both the understanding of physical phenomena occurring during heat treatment and the identification of distortion. First, distortions of each single manufacturing step are identified. Then, causes of final geometry amongst the overall process are ranked. A numerical manufacturing process is used as an example to illustrate this method.Secondly, residual stress influence on heat treatment distortion is revealed thanks to several industrial experiments. Thus, each single geometrical criterion is linked to a manufacturing step. These results provide a diagnosis tool helping to determine distortion causes. Moreover, evolutions on industrial process are proposed.

Le traitement thermique du bois est une industrie qui se développe depuis une dizaine d'années, mais est freinée par l'absence de certifications. Le bois traité thermiquement est un matériau nouveau dont les propriétés mécaniques et de durabilité sont modifiées grâce aux réactions chimiques des biopolymères avec l'apport de chaleur. Cette étude vise à trouver des indicateurs non destructifs permettant d'apporter des garanties sur les performances des bois chauffés. La caractérisation de plusieurs essences chauffées chez Bois Durables de Bourgogne permet d'abord d'apprécier l'influence du traitement thermique sur des échantillons variés avec de petites éprouvettes sans défaut. Cette première campagne montre une amélioration prononcée de la durabilité permettant des usages en classe d'emploi 4, et des variations de propriétés mécaniques qui dépendent des sollicitations étudiées. Les propriétés apparaissant comme les plus importantes à estimer en vue d'une certification sont celles de la résistance en flexion et de la perte de masse due au traitement thermique, directement reliée à la durabilité grâce aux travaux du LERMAB. A ce stade, l'analyse vibratoire apparaît comme un bon indicateur de l'intensité de traitement. Dans un second temps, l'essence de frêne est étudiée à quatre intensités de traitement entre 170 et 228 °C sur des éprouvettes en dimensions d'emploi. Cette deuxième campagne permet de confirmer que l'analyse vibratoire est un bon indicateur pour la perte de masse, mais ne permet pas cette fois d'estimer la résistance en flexion. La composition élémentaire du bois mis en évidence comme indicateur par d'autres travaux ne semble pas utilisable dans un contexte industriel. En revanche, l'aire sous la courbe de traitement est une mesure globale et disponible qui est bien corrélée avec les valeurs moyennes de résistances en flexion et de pertes de masse. / The heat treatment of wood has been a growing industry in the last decade, but its development is curbed by the lack of certifications. Heat-treated wood is a new material whose mechanical properties and durability are modified by heat transfer and chemical reactions of biopolymers. This study aims at finding non-destructive indicators that can guarantee heat-treated wood quality. The characterization of several species heated by Bois Durables de Bourgogne first enables to assess the influence of heat treatment on various samples using small specimens free from defects. This first approach shows a marked improvement of durability ensuring uses in hazard class 4, and variations of mechanical properties depending on studied reaction. Properties that appear as the most relevant in terms of certifications are bending strength and mass loss due to heat treatment. The latter is directly linked to durability owing to studies previously led by LERMAB. At this stage vibration analysis seems to be a proper way to estimate treatment intensity. In a second part ash wood is studied under four treatment intensity, between 170 and 228 °C on large specimens. This second approach confirms that vibration analysis is an appropriate indicator to estimate mass loss, but does not predict bending strength. Wood elemental composition which has been already highlighted as an indicator by other studies is not suitable for an industrial application. On the other hand the area under the treatment chart is a global measurement which is easily available and well correlated with mean values of bending strength and mass loss.

La fabrication directe et additive regroupe un ensemble de technologies de mise en forme des matériaux en rupture avec les procédés conventionnels. L'industrie aéronautique et aérospatiale s'intéresse fortement à ces nouveaux procédés, dont la fusion sélective par laser de lits de poudre métallique (SLM). Cette thèse présentera les enjeux de la fabrication additive ainsi que certains procédés. Une étude bibliographique a été menée sur deux alliages aéronautiques utilisés dans ces travaux : l'alliage de titane TA6V et le superalliage base nickel Nimonic 263. Les travaux présentés dans ce rapport comprennent l'étude de la poudre métallique brute d'atomisation (morphologie, granulométrie, composition chimique). D'autre part, l'étude de la recyclabilité de la poudre utilisée en SLM est présentée pour le TA6V, tant en ce qui concerne l'évolution de la poudre elle-même que celle des propriétés mécaniques des pièces qui en sont issues. Par ailleurs ce travail traite d'un modèle de consolidation du lit de poudre permettant également d'évaluer la productivité du procédé. Enfin, une étude paramétrique et thermique menée sur le Nimonic 263 en vue de l'établissement d'une solution de contrôle procédé est présentée. / Direct and additive manufacturing regroups several new technologies that are very different from conventional manufacturing processes such as casting. Aeronautic and space industries are really interested in those new processes such as the selective laser melting of metallic powder beds know as the SLM process. This PhD thesis report will show the issues of additive manufacturing and will describe some processes. A bibliography study has been done on two aeronautical alloys used in this work: titanium alloy TA6V and nickel-based superalloy Nimonic 263. This work also presents powder characterization (granulometry, morphology chemical composition) for the gas atomized powder. Besides, study has been done on the recyclability of the TA6V powder for the SLM process, for the powder itself and the mechanical properties of parts built from recycled powder. Moreover, this works deals with a powder bed consolidation model to estimate the productivity of the process. Then, a parametric and thermal study has been done on the Nimonic 263. The coaxial system for thermal visualization is described such as the image processing algorithm used. Finally, this reports deals with the study of thermal signature of typical SLM defects.

La conservation des mangues 4ème gamme est limitée par le brunissement enzymatique et la perte de fermeté dus aux différentes opérations de transformation. Cette thèse propose un nouvelle approche pour améliorer la conservation de mangues 4ème gamme : l’application de traitements thermiques par immersion et/ou la conservation sous atmosphère modifiée : passive ou active (5% O2 – 5 % CO2) ou des enrobages (chitosane). Ce travail a permis tout d’abord de déterminer un couple température / temps optimal: 50 °C / 30 min qui permet de maintenir la qualité de plusieurs variétés de mangue (Keitt, Kent, Tommy Atkins). Les effets du traitement thermique sur l’intensité respiratoire, la couleur, la fermeté, les teneurs en antioxydants : vitamine C, caroténoïdes et phénols totaux, et sur l’activité de plusieurs enzymes (pour la fermeté : PME, PG, b-GAL ; et pour la couleur : PPO et PAL) ont été étudiés. Ces travaux ont montré que durant 9 jours à 6 °C, le traitement thermique maintient principalement la couleur par réduction de l’activité de la PPO et réduit la perte en fermeté par réduction de l’activité des enzymes pectolytiques (PME et b-GAL). Par ailleurs, les atmosphères modifiées semblent moins efficaces pour le maintien de la couleur et de la fermeté des mangues 4ème gamme. L’association du traitement 50°C/ 30 min avec une conservation sous atmosphère modifiée apporte peu d’effets additionnels et a même parfois un effet inhibiteur / The storage of fresh-cut mangoes is limited by the enzymatic browning and the loss of firmness due to the various operations of process. This work proposes a new approache to improve the storage of fresh-cut mangoes by: application of heat treatments by dipping with, or not, a storage under modified atmosphere: passive or active (5% O2 - 5% CO2) or using coatings (chitosane). The first step of this work was to determine the traitement 50 °C/30 min as an optimal treatment which maintian the quality of several varieties of mango (Keitt, Kent, Tommy Atkins). Effects of the heat treatment on the respiratory intensity, the color, firmness, the contents antioxydants: vitamin C, carotenoids and phenols total, and on the activity of several enzymes (PME, PG, b-GAL: for firmness; and PPO and PAL for colour changes) were studied. This work showed that during 9 days at 6 °C, the heat treatment maintains mainly the color by reduction of the activity of PPO and reduces the loss in firmness by reduction of the activity of the pectolytic enzymes (PME et b-GAL). In addition, the modified atmospheres seem less effective for the maintenance of the color and the firmness of freshcut mangoes. Combination of heat treatment with a modified atmosphere storage and have less additional effects and has even sometimes an inhibiting effect

Denna uppsats beskriver sökandet efter en metod för att genomfärga trä utan att tillföra pigment. Ett test av fördjupad ammoniakrökning beskrivs i uppsatsen. Ammoniakrökning är en förenklad variation av kembetsning där virke med höga halter garvsyra utsätts för ammoniakånga. Detta gör virkets kulör betydligt mörkare. I detta test värms virket innan ammoniakångan tillförs för att se om det är möjligt med en mer djupgående kulörförändring. Två olika metoder för att hetta upp trävirke kommer att beskrivas, eftersom en ändrad kulör är en av de egenskapsförändringar som följer dessa metoder beslutade jag mig för att fördjupa mig i dessa. Uppvärmningen görs i en syrefri miljö (termisk modifiering och oljeuppvärmning) och därigenom ändrar virket kulör. De övriga egenskapsändringarna i virket, vid termisk modifiering och oljeuppvärmning, kommer att beskrivas och förtydligas. Båda metoderna har i stort sett samma inverkan på trä men processen skiljer sig åt. Därför behövdes ett begripligt underlag över de egenskapsändringar som sker i virket efter behandlingarna, för att se om dessa genomfärgningsmetoder är lämpliga som möbelvirke.

This dissertation investigates microstructure/property relations in ultrahigh carbon steel (UHCS) with the aim of improving toughness while retaining high hardness. Due to high C contents (ranging from 1 to 2 wt%), UHCS exhibit high strength, hardness, and wear resistance. Despite this, applications for UHCS are currently limited because they typically contain a continuous network of proeutectoid cementite that greatly reduces ductility and toughness. In previous research, thermomechanic processing had seen considerable success in breaking up the network. However, the processing is difficult and has thus far seen very limited industrial application. Chemical modification of the steel composition has also seen some success in network break-up, but is still not well understood. There have been relatively few fundamental studies of microstructure evolution in UHCS; studies in the literature typically focused on lower C steels (up to 1 wt% C) or on cast irons (>2.1 wt% C). Thus, this work was undertaken to gain a better understanding of microstructural changes that occur during heat treatment and/or chemical modification of UHCS with a focus on the distribution of proeutectoid cementite within the microstructure. This dissertation is composed of eight chapters. The first chapter presents an introduction to phases found in UHCS, descriptions of research materials used in each chapter, and the hypotheses and objectives guiding the work. The second chapter describes a study of the microstructure found in a 2C-4Cr UHCS before and after an industrial-scale austenitizating heat treatment that increased hardness and toughness and also produced discrete carbide particles in the matrix. The third chapter establishes and demonstrates a metric for measuring connectivity in carbide networks. The fourth chapter describes a series of heat treatments designed to investigate kinetics of spheroidization and coarsening of carbide particles and denuded zones near cementite network branches in 2C-4Cr UHCS. The fifth chapter describes an additional series of heat treatments comparing coarsening kinetics in 2C-1Cr and 2C-4Cr UHCS. Lowering the Cr content caused clustering of cementite particles near grain boundaries, in contrast to the denuded zones observed in the higher Cr UHCS. The fifth chapter details four in situ confocal laser scanning microscopy heat treatments of 2C-4Cr UHCS. The seventh chapter investigates the effects of a 2wt% Nb addition on 2C-4Cr UHCS. The eighth and final chapter summarizes the findings of all the experiments of the previous chapters and revisits the objectives and conclusions.

Philosophiae Doctor - PhD / In this thesis, intrinsic hydrogenated nanocrystalline silicon thin films for solar cells application have been deposited by means of the hot – wire chemical vapour deposition (HWCVD) technique and have been characterised for their performance. It is noticed that hydrogenated nanocrystalline silicon is similar in some aspects (mainly optical) to its counterpart amorphous silicon actually used as the intrinsic layer in the photovoltaic industry. Substantial differences between the two materials have been found however in their respective structural and electronic properties. We show that hydrogenated nanocrystalline silicon retains good absorption coefficients known for amorphous silicon in the visible region. The order improvement and a reduced content of the bonded hydrogen in the films are linked to their good stability. We argue that provided a moderate hydrogen dilution ratio in the monosilane gas and efficient process pressure in the deposition chamber, intrinsic hydrogenated nanocrystalline silicon with photosensitivity better than 102 and most importantly resistant to the Staebler Wronski effect (SWE) can be produced. This work explores the optical, structural and electronic properties of this promising material whose study – samples have been exclusively produced in the HWCVD reactors based in the Solar Cells laboratory of the Physics department at the University of the Western Cape. / South Africa

The aim of the present study was to investigate the bioavailability of selenium (Se) from milled soya beans, a plant protein, to lambs after various degrees of heat treatment. Thirty Dohne Merino lambs (ca. 25 kg live weight, 4 months old) were allocated randomly within sex and weight groups into three treatment groups. During the experimental period, they were fed a diet consisting of a large proportion of milled soya beans as their main source of Se and other feeds low in Se to balance the diet. Blood was drawn during this period and analysed for Se and glutathione peroxidase (GSH-Px) activity. Chemical and Se analyses were performed on the feed and soya bean samples as well as on the organs, wool and rumen fluid of the lambs. Although the ADIN concentration of the soya beans increased with increasing heat treatments, more heat damage could have been inflicted on it to differentiate the different soya bean fractions in comparison to each other. On average, the in sacco disappearance of the dry matter (DM), crude protein (CP) and Se was higher for the unprocessed soya beans compared to the two processed soya beans fractions. As a result, the lambs receiving the unprocessed soya beans (control group- C-group) had a significant higher rumen bacterial Se concentration than the lambs receiving the heat¬treated soya beans. Despite this higher concentration, the liver Se concentration of this group was statistically significantly lower compared to the two heat-treated groups. This can be interpreted that the heat processing of the soya beans enhanced its Se fraction to be taken up by the liver. However, those differences were biologically not significant. The average liver Se concentration between the lambs receiving the over- ¬processed- (a-group) and those receiving the ideal treated soya beans (I-group), did not differ, indicating that the excessive heat treatment did not influence the amount of Se reaching the lower digestive tract of the a-group. Although the Se concentration of the heart muscle of the a-group was statistically significantly lower than for the I-and C-groups, those differences biologically were not significant. Despite an increase in the erythrocyte GSH-Px activity over the duration of the trial in all three the treatment groups, no significant differences between the three treatment groups were observed at any stage. It is concluded from this study that the heat treatment of soya beans has not influenced the incorporation and the bioavailability of its Se fraction to any significant degree. / Dissertation (MSc (Agriculturae))--University of Pretoria, 2006. / Animal and Wildlife Sciences / unrestricted

La datte Deglet-Nour est traditionnellement récoltée et consommée au stade de maturité complet Tamar caractérisée par une faible activité en eau (aw< 0,76). Cette datte est stable dans des conditions ambiantes. En revanche, à un stade de maturité précoce (Routab), la Deglet-Nour est intéressante sur le plan organoleptique, mais susceptible de développement microbien en raison de son activité en eau intermédiaire (aw = 0,80−0,85). Ce travail s'est intéressé à d'une part, réduire la charge microbienne initiale des dattes par une opération de traitement thermique de surface post-récolte, puis d'autre part, à prolonger la durée de vie des dattes en inhibant le développement fongique par l'effet (seul ou combiné) de trois facteurs environnementaux que sont la température, l'aw et l'atmosphère enrichie en CO2 (emballage sous atmosphère modifiée). Les souches fongiques présentent à la surface des dattes ont été isolées et identifiées sur des dattes collectées dans trois régions du sud algérien ; il s'agit d'Aspergillus niger, d'Alternaria alternata et de Candida apicola. La charge fongique varie entre 2,4 et 5,8 10^2 UFC/g et est localisée uniquement à la surface des dattes. Un modèle d'inactivation thermique des souches a été développé. La thermosensibilité des souches a été évaluée avec un D_50 de 2,3 ± 0,4 min et 22,1 ± 2,1 min, pour C. apicola et Asp. niger respectivement. Les valeurs de sont 9,4 ± 2,6°C et 9,6 ± 0,1°C, pour C. apicola et Asp. niger, respectivement. Ce modèle cinétique a été validé en condition de traitement thermique instationnaire. Un modèle numérique de transfert d'énergie en 2D axisymétrique a été conçu et résolu par la méthode des éléments finis. Il prend notamment en compte, les diverses parties d'une datte (pulpe, lame d'air, noyau) et permet d'estimer la réduction de charge des levures et l'impact sur la qualité. Ces informations ont permis de rationaliser les barèmes de pasteurisation en surface des dattes tout en limitant le brunissement non-enzymatique. Les effets de la température (10−40°C), de l'aw (0,993−0,818) et de la concentration en CO2 (9,4−55,1%, v/v) sur les vitesses de croissance des deux souches ont été quantifiées et modélisées par un modèle primaire linéaire à deux phases et le modèle secondaire du γ-concept. Il inclue les interactions entre l'aw et le CO2. Les limites de croissance/non-croissance ont été prédites par une approche déterministe, et l'évaluation de la performance du modèle a été menée sur une pâte de datte. Asp. niger manifeste une plus grande vitesse de croissance et tolérance aux faible aw que Alt. alternata, tandis que Alt. alternata est plus tolérantes aux fortes concentrations en CO2 et aux basses températures (respectivement pour Asp. niger et Alt. alternata : µ_opt = 28,6 et 12,1 mm jour^–1 ; aw_min= 0,786 et 0,808 ; CO2_max= 79,8 et 95,1% ; T_min = 4,4°C et 1,6°C). Le modèle γ-concept surestime les vitesses de croissance sur la pâte de datte, en revanche le modèle reste optimiste avec des prédictions conservatrices. Cette étude a mis en évidence l'intérêt d'un traitement thermique pour pasteuriser la surface des dattes tout en limitant le brunissement non-enzymatique ; de plus l'effet inhibiteur CO2 sur la croissance des deux moisissures est très efficace et un conditionnement enrichi en CO2 semble pertinent pour la conservation de ces dattes immatures. / The Deglet-Nour date is traditionally harvested and consumed at full ripeness stage (Tamar) characterized by a reduced water activity (aw<0.76). This date is stable under ambient storage conditions. In contrast, unripe Deglet-Nour (Routab stage) has interesting organoleptic properties, but is prone to microbial contamination due to its intermediate water activity levels (aw = 0.80−0.85). On the one hand, this work focused on the reduction of the initial microbial load by post-harvest surface heat treatment operation and, on the other hand, extending the shelf life of the dates by the inhibition of fungal growth using three environmental factors: temperature, aw and CO2-enriched atmosphere (modified atmosphere packaging). The fungal strains initially present on the Deglet-Nour dates surface were isolated from three districts in Algeria (Biskra, Tolga and Doucen). These strains were identified at the molecular level as Aspergillus niger, Alternaria alternata and Candida apicola. The fungal load ranged from 2.4 to 5.8 10^2 CFU/g. A thermal inactivation model for these strains was developed. Decimal reduction times at 50°C (D_50) were 22,1 ± 2,1 min and 2.3 ± 0.4 min for A. niger and C. apicola, respectively. The z-values were 9.6 ± 0.1°C and 9.4 ± 2.6°C for A. niger and C. apicola, respectively. This kinetic model was validated in unsteady heat treatment conditions. In parallel, a 2D axial-symmetric model of heat transfer was designed and solved by the finite element method. It takes into account the various sub-domains of date (pulp, air layer and pit) and assesses the yeast inactivation rate and the impact on quality. These data allowed for streamlining pasteurization schedules on dates surface. The effect of temperature (10−40°C), aw (0.993−0.818) and CO2 concentrations (9.4-55.1%, V/V) on the growth rates of Asp. niger and Alt. alternata have been quantified and modeled using the two-phase linear model and the γ-concept. The boundary between growth/no-growth was predicted using a deterministic approach and the model performance evaluation was conducted on pasteurized date past. A significant effect of the environmental factors on the growth of both strains has been found. Asp. niger displayed a faster growth rate and higher tolerance to low aw than Alt. alternata, which in turn proved more resistant to CO2 concentration and low temperature (respectively for Asp. niger and Alt. alternata: µ_opt = 28.6 and 12.1 mm day^–1; aw_min= 0.786 and 0.808; CO2_max= 79.8 and 95.1% ; T_min = 4.4°C and 1.6°C). The γ-concept model overestimated growth rates on date past; however, it is optimistic and provides somewhat conservative predictions. This study highlights the benefit of heat treatment to pasteurize dates surface while minimizing the color date degradation. In addition, the inhibitory effect of CO2 on the growth of both molds is very efficient, and CO2-enriched atmosphere seems relevant for the preservation of unripe dates.