Characteristic Transition Temperature Research Articles

Mixed‐alkali effect in the thermal collapse and melting kinetics of Zeolite X

AbstractThe thermal stability of zeolites underlies their many applications. Structural collapse usually occurs through a series of reactions, involving an initial low‐density amorphous state (LDA), a high‐density melt (HDA), and, eventually, a dense recrystallization product. The LDA–HDA transition resembles a glass melting process; the HDA phase can sometimes be quenched into a glass. Using isothermal as well as nonisothermal in situ observation methodology on the faujasitic zeolite X and its potassium‐for‐sodium ion‐exchanged derivatives, we find a pronounced mixed‐alkali effect in the characteristic nonisothermal transition temperatures as well as in the isothermal reaction timescale of the LDA–HDA transition. The latter is taken as being directly related to the viscosity of the liquid into which the zeolite framework is melting; the apparent viscosity associated with this melting process was found to reach as high as 1015 Pa.s at 740°C. The observed mixed‐alkali effect is similar to the one observed in the dynamics of common oxide glasses and their corresponding melts.

Magnetic and electrical transport properties in GdAlSi and SmAlGe

Abstract In this work, we conduct a detailed examination of the magnetic and electrical transport properties in GdAlSi and SmAlGe crystals, which possess a LaPtSi-type structure (space group I41 md). The magnetic susceptibility data unambiguously reveal magnetic ordering below a characteristic transition temperature (T N ). For GdAlSi, a hysteresis loop is observed in the magnetization and magnetoresistance curves within the ab plane when the magnetic field is applied below T N , which is around 32 K. Notable specific heat anomalies are detected at 32 K for GdAlSi and 6 K for SmAlGe, confirming the occurrence of magnetic transitions. Besides, the extracted magnetic entropy at high temperatures is consistent with the theoretical value of Rln(2J+1) for J = 7/2 in Gd3+ and J = 5/2 in Sm3+, respectively. SmAlGe also exhibits Schottky-like specific heat contributions. Additionally, both GdAlSi and SmAlGe exhibit positive magnetoresistance and a normal Hall effect.

Interaction between synthetic elastin-like polypeptide and collagen: Investigation of miscibility and physicochemical properties

Poly(GVGVP), where G-Glycine, V-Valine, and P-Proline, is a synthetic elastin-like polypentapeptide that has been studied for its interaction with collagen in blends using viscometry, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and X-ray diffractogram (XRD) techniques. Additionally, the thermal characteristics such as glass transition temperature (Tg) and thermal stability of the blends were studied respectively by Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA). The results showed that amide A and B band's positions in FTIR spectra of collagen were shifted correspondingly to higher and lower wavenumbers after blending with polypentapeptide. DSC study unveiled characteristic glass transition temperatures (Tg) for the blends and the particular components. All the blends show thermal stability in between the pure polymers. Viscosity evaluations also showed a strong association between collagen and poly(GVGVP). Collagen and poly(GVGVP) together may provide the opportunity to assemble novel, promising materials for biomedical purposes.

Molecular Dynamics Simulation of NiTi Shape Memory Alloys Produced by Laser Powder Bed Fusion: Laser Parameters on Phase Transformation Behavior.

In this study, the deposition, powder spreading, and laser fusion processes during the laser powder bed fusion (L-PBF) process were studied using molecular dynamics (MD) simulation. The effect of Ni content on the characteristic phase transformation temperatures was also investigated. Shape memory effect and superelasticity of NiTi alloys with Ni content ranged from 48.0% to 51.0% were analyzed. By employing MEAM potentials, the effects of the laser power, spot diameter, and scanning speed on the molten pool size and element evaporation were studied. Simulation results showed that a larger spot diameter renders a higher Ni content in the molten pool, also a larger molten pool. A faster scanning speed leads to a higher Ni content in the molten pool, and a smaller molten pool. The element is difficult to evaporate using small laser power and a large spot diameter. The element in the molten pool expresses a great evaporation effect when the Es is larger than 0.4 eV/ų. According to Ni content within the molten pool during laser fusion, characteristic phase transition temperatures in single crystalline NiTi alloys with variant Ni content were investigated by employing a 2NN-MEAM potential. Characteristic phase transition temperature changes as the Ni content increases from 48.0% to 51.0%. Austenite boundaries and Ni content in the boundary were found to be the keys for controlling the characteristic phase transformation temperature.

Push and Pull Effect of Methoxy and Nitro Groups Modifies the Spin-State Switching Temperature in Fe(III) Complexes.

We have explored the impact of electron-donating (methoxy) and electron-withdrawing (nitro) substituents on SalEen ligand based spin crossover (SCO) behavior of Fe(III) complexes. Thus, 3-X-substituted SalEen ligands were employed to prepare [Fe(3-X-SalEen)2]·NCSe, where X = OMe (1), H (2), and NO2 (3) (3-X-SalEen is the condensation product of 3-substituted salicylaldehyde and N-ethylethylenediamine). The characteristic spin transition temperature (T 1/2) is shown to shift to a lower temperature when an electron-donating substituent (OMe) is used and to a higher temperature when an electron-withdrawing substituent (NO2) is used. We used experimental and theoretical methods to determine the reasons for this behavior. The solid-state magnetic data revealed the transition temperatures for complexes 1, 2, and 3 to be 219, 251, and 366 K, respectively. The solution-state magnetic data also support this trend in T 1/2 values. UV-vis spectra analysis indicates that there is greater delocalization in the π-manifold of the ligand when the nitro group is the substituent. Theoretical studies through density functional theory methods suggest the methoxy substituent decreases the energy gap between the t2g and eg orbitals (explaining the lower T 1/2 value), while the nitro substituent increases the energy gap between the t2g and eg orbitals and thus increases the T 1/2 value.

Evolution of electrical, superconducting, crystallinity and structural features with aliovalent Nd/Sr replacement in Bi-2223 ceramics

This paper blazes the trail for the understanding of fundamental characteristic features for Bi-2223 ceramic with aliovalent Nd/Sr replacement in Bi1.8Pb0.35Sr1.9-yNdyCa2.2Cu3Ox superconducting matrix (0.00 ≤ y ≤ 0.10). Full characterization of superconductors is performed by conventional experimental methods, viz. X-ray diffraction (XRD), dc electrical resistivity based on temperature (ρ-T), electron dispersive X-ray (EDX) and scanning electron microscopy (SEM) examinations. Measurement results display that the trivalent Nd+3 ions may partially be substituted by Sr+2 impurities in the Bi-2223 crystal structure. EDX results illustrate that the local elemental composition distributions of Nd atoms increase systematically depending on substitution level. However, it is noted that the replacement mechanism damages seriously fundamental electrical, superconducting, crystallinity and structural features. Dc electrical findings present that the superconducting and electrical properties reduce remarkably with the increment of aliovalent Nd/Sr substitution due to deviation in the mobile holes, inhomogeneities of oxidation states in the copper-oxide layers, and formation of new internal and microscopic problems in the crystal system, confirmed by SEM examination. Besides, the characteristic transition temperatures diminish harshly from 116.59 K to 108.74 K for onset and 108.40 K until 78.81 K for offset transition temperature. The dramatic decrements stem from the degradation in bipolaron formations in the superconducting clusters, phonon modes and especially the gap coefficient. Similarly, the presence of Nd impurity damages the amplitude of pairing wave function. In fact, at maximum replacement level the ceramic compound exhibits a slight trace of pseudo-critical transition. The XRD results indicate that both the appearance or disappearance of characteristic diffraction peaks and the reduction of average crystallite size and c lattice cell constant confirm the reduction of high-Tc superconducting phase due to the suppression in the structural quality. The SEM pictures indicate that the appearances of surface morphology and crystallinity quality remarkably deteriorate depending on Nd/Sr replacement level as a consequence of non-uniform grain alignment distributions, structural problems, microvoids, internal defects, porosity, misoriented grain coalescences and microcrystals in the superconducting system. Additionally, the negative effect of Nd/Sr substitution is extensively discussed on the activation energy for the crystallization, thermodynamic stability, reaction kinetics, surface nucleation and growth mechanisms for the first time.

The Thermal Characteristics, Sorption Isotherms and State Diagrams of the Freeze-Dried Pumpkin-Inulin Powders.

Powders based on plant raw materials have low storage stability due to their sorption and thermal properties and generate problems during processing. Therefore, there is a need to find carrier agents to improve their storage life as well as methods to evaluate their properties during storage. Water adsorption isotherms and thermal characteristics of the pumpkin powder with various inulin additions were investigated in order to develop state diagrams. Differential scanning calorimetry (DSC) was used to obtained glass transition lines, freezing curves and maximal-freeze-concentration conditions. The glass transition lines were developed using the Gordon–Taylor model. Freezing data were modeled employing the Clausius–Clapeyron equation and its development–Chen model. The glass transition temperature of anhydrous material (Tgs) and characteristic glass transition temperature of maximum-freeze-concentration (Tg′) increased with growing inulin additions. Sorption isotherms of the powders were determined at 25 °C by the static-gravimetric method and the experimental data was modeled with four different mathematical models. The Peleg model was the most adequate to describe the sorption data of the pumpkin–inulin powders. Guggenheim-Anderson-de Boer (GAB) monolayer capacity decreased with increasing inulin concentration in the sample.

Функциональные свойства сегнетоэлектрических материалов на основе цирконата-титаната свинца и триглицинсульфата на макро- и микромасштабе размеров

Samples of ferroelectric functional materials based on lead zirconate titanate with the chemical formula PbTiO3-PbZrO3-PbNb2/3Zn1/3O3-PbNb2/3Mg1/3O3 and triglycine sulfate (NH2CH2COOH)3•H2SO4 were manufactured and characterized. The dielectric spectroscopy and differential scanning calorimetry confirmed the presence of phase transitions in them, and the characteristic transition temperatures were determined. Thermomechanical analysis method has been used to study thermally induced deformations in them, near phase transitions. The shape memory effect (SME) and electrocaloric effect in macro samples were studied. Methods of studying the SME on the microscale of sample sizes have been worked out. The process of formation of microstructures in these materials in the form of «micropillars» («micropillars») by selective ion etching with a focused ion beam is investigated. The process of deformation of «micro-pillars» with a diameter from 120 nm to 1 micron from ferroelectric materials using a microneedle mounted on a Kleidiek nanomanipulator in the vacuum chamber of a two-beam scanning microscope CrossBeam 1540 EsB has been studied.

Multi-functional epoxy vitrimers: Controllable dynamic properties, multiple-stimuli response, crack-healing and fracture-welding

Vitrimers, a new generation of polymeric materials, have been widely investigated to resolve the intersection of thermoplastics and thermosets, relying on the exchange reactions in networks. However, it is still a challenge to develop multi-functional vitrimer materials. Herein, multi-functional epoxy vitrimers that exhibited controllable dynamic properties, multiple-stimuli response, crack-healing and fracture-welding were prepared by introducing Fe3O4 nanoparticles into the networks of dual dynamic epoxy vitrimers. It was revealed that the typical dynamic parameters of vitrimer including the characteristic relaxation time (τ), activation energy (Ea), Arrhenius prefactor (τ0) and topology freezing transition temperature (Tv) could be readily adjusted in the multi-functional epoxy vitrimers. Moreover, the multi-functional epoxy vitrimers were simultaneously responsive to temperature, near infrared and magnetic field, while they could be driven by magnets, heated by near infrared and healed or welded by heating. Upon heating or near infrared, the cracks in samples could be successfully healed. Besides, by the cooperation of heating and magnet or near infrared and magnet, the multi-functional epoxy vitrimers were able to achieve non-touch welding of factures. These multi-functional epoxy vitrimers might have potential application in improving the reliability and extending the lifetime of polymeric materials. Meanwhile, the facile way to functionalize the epoxy vitrimers is estimated to be suitable for other vitrimer materials.

Ultrastrong behaviors of a non-equiatomic Ti-Zr-Ni-Cu-Be high entropy metallic glass with ultrahigh glass forming ability

We studied the thermodynamics and kinetics of a non-equiatomic Ti32.8Zr30.2Ni5.3Cu9Be22.7 high entropy metallic glass (HEMG, ΔSconfig.∼1.44R) with a critical size for glass formation over 50 mm. The characteristic transition temperature, enthalpy of transition and specific heat capacity along with the relaxation time at different heating rate were determined using differential scanning calorimeter (DSC) measurements. It reveals that the present HEMG supercooled liquid shows the lowest thermodynamic driving force against the nucleation and growth of crystalline phases with comparing to other typical MG formers. Meanwhile, it exhibits the ultrastrong behavior near glass transition in terms of the Angell's fragility concept. The alloy has a fragility index of D* = 45.2, higher than all the typical MG formers reported so far. Both thermodynamic and kinetic factors are responsible for the ultrahigh glass-forming ability of the HEMG alloys.

Effect of cold rolling on the pressure coefficient of glass transition temperature in bulk metallic glasses

Vitreous alloys exhibit changes in the specific heat capacity (Δcp) as well as configuration at the characteristic glass transition temperature (Tg). A wide variety of bulk metallic glasses (BMGs) such as, Zr47.5Cu47.5Al5, Zr55Cu30Ni5Al10, Zr52.5Cu17.9Ni14.6Al10Ti5 and Zr41.2Ti13.8Cu12.5Ni10Be22.5 were rolled at room temperature, and the variation of Tg, Δcp at Tg, configurational entropy (ΔSconf.), pressure coefficient of Tg (dTg/dP) and bending strength were measured to understand the configurational change in BMGs upon cold rolling. The normalized bending moment during yielding of a cold rolled Zr55Cu30Ni5Al10 has increased by 43.4% than the as-cast specimen. The ΔSconf. of the Zr55Cu30Ni5Al10 plate increased upon rolling from 0.537±0.041 J/mol∙K for as-cast to 0.654±0.032 J/mol∙K for 70% cold rolled sample. A relaxed glassy state with low Tg exhibits high dTg/dP value and vice versa.

Urea induces (unexpected) formation of lamellar gel-phase in low concentration of cationic surfactants

HypothesisThe unexpected formation of a lamellar structure with concomitant gelation in solutions containing high urea concentration (40 wt%) and relatively low amount of cationic surfactant (3 wt%), indicates that a hierarchically structured complex is formed by both molecules. ExperimentsGels formed by combination of aqueous solutions of urea and C12TAB, C14TAB or C16TAB were prepared in different proportions and their structures at microscopic and mesoscopic levels were investigated using XRD and SAXS, respectively. The elastic and viscous moduli and yield stress of the samples were determined and correlated with the composition and structuration of the gels. The lamellar structure is reversibly thermically destroyed and this process was investigated using DSC. FindingsXRD revealed that, at microscopic scale, the gels are formed through crystallization of adducts containing surfactant molecules loaded into the cavities of honeycomb-like urea assemblies. Such crystalline phase arranges itself in lamellae with interplanar distance around ∼20–30 nm, which were observed by SAXS. This hierarchical structure is independent of the chain length of the cationic surfactants. The blocks of lamellae dispersed in the continuous phase form a three-dimensional rigid particulate network structure, giving the characteristic rheological behavior of a hydrogel. DSC revealed a reversible thermal transition at around 20–25 °C, beyond which the adducts and the lamellar phase are destroyed and micelles are formed. The characteristic transition temperature is independent of the chain length of the surfactant, and thus, it is not associated with their Krafft temperatures. The structures of the gels indicate that they resemble alpha-gels formed by fatty-alcohols and surfactants, although they self-assemble by different driving forces.

CA Modeling of Microsegregation and Growth of Equiaxed Dendrites in the Binary Al-Mg Alloy.

A two-dimensional model based on the Cellular Automaton (CA) technique for simulating free dendritic growth in the binary Al + 5 wt.% alloy was presented. In the model, the local increment of the solid fraction was calculated using a methodology that takes into account changes in the concentration of the liquid and solid phase component in the interface cells during the solidification transition. The procedure of discarding the alloy component to the cells in the immediate vicinity was used to describe the initial, unstable dendrite growth phase under transient diffusion conditions. Numerical simulations of solidification were performed for a single dendrite using cooling rates of 5 K/s, 25 K/s and 45 K/s and for many crystals assuming the boundary condition of the third kind (Newton). The formation and growth of primary and secondary branches as well as the development of component microsegregation in the liquid and solid phase during solidification of the investigated alloy were analysed. It was found that with an increase in the cooling rate, the dendrite morphology changes, its cross-section and the distance between the secondary arms decrease, while the degree of component microsegregation and temperature recalescence in the initial stage of solidification increase. In order to determine the potential of the numerical model, the simulation results were compared with the predictions of the Lipton-Glicksman-Kurz (LGK) analytical model and the experimental solidification tests. It was demonstrated that the variability of the dendrite tip diameter and the growth rate determined in the Cellular Automaton (CA) model are similar to the values obtained in the LGK model. As part of the solidification tests carried out using the Derivative Differential Thermal Analysis (DDTA) method, a good fit of the CA model was established in terms of the shape of the solidification curves as well as the location of the characteristic phase transition temperatures and transformation time. Comparative tests of the real structure of the Al + 5 wt.% Mg alloy with the simulated structure were also carried out, and the compliance of the Secondary Dendrite Arm Spacing (SDAS) parameter and magnesium concentration profiles on the cross-section of the secondary dendrites arms was assessed.

Determination of Possible Maximum Critical Transition Temperatures with Empirical Model Depending on Structural Disorders-Defects for Bi2.1Sr2.0Ca1.1Cu2.0Oy System

In this study, we find a strong link depending on the preparation annealing ambient conditions between structural disorders-defects and characteristic transition temperature parameters (offset, Tc offset and onset, Tc onset) of bulk Bi2.1Sr2.0Ca1.1Cu2.0Oy system for the first time. The superconducting samples are prepared at various annealing temperatures intervals 830°C -850°C with the temperature step of 10°C for annealing time ranging between 24 h and 48 h via traditional solid-state reaction route. The temperature-dependent resistivity measurements are conducted at temperature range of 30-140 K. The most ideal annealing ambient is obtained to be the combination of annealing temperature of 840 °C and annealing time of 24 h because of the enhancement in the formation possibility of strong cooper-pairs and optimization of itinerant charge carrier concentrations in the valence band. Similarly, the positive contributions are observed in the overlapping mechanism of wave functions between Cu-3d and O-2p electrons and especially logarithmic distribution of electronic state densities. The optimum annealing ambient makes the Bi-2212 system refine the structural problems and especially connectivity between the grains in the crystal structure. Conversely, the excess annealing ambient leads to increase considerably the grain misorientation, defects and grain boundary couplings due to the induced permanent problems in the crystal system. The highest correlated model shows that the Bi-2212 superconducting compounds with the minimum structural disorders in the short-range-ordered antiferromagnetic Cu-O2 layers exhibit the maximum Tc onset and Tc offset values of about 85.347 K (R2adj=0.9882) and 87.421 K (R2adj=0. 97465).

Effect of Temperature and Concentration on the Physical Properties of Cholesteryl Pelargonate Near Transition Temperatures

Thermodynamic and acoustical study of cholesteric liquid crystal (CLC) was carried out near phase transition temperatures using an ultrasonic interferometer. The study of ultrasonic waves and related thermo-acoustical parameters provides information in understanding the nature of molecular interactions associated with liquid crystals. A statistical mechanical approach is used to calculate the viscosity of samples. The characteristic textures and phase transition temperatures are obtained with Polarizing Microscopy (POM). Fabry Perot scattering studies (FPSS) are used to ascertain the phase transition temperatures of CLC. The thermo-acoustical parameters have been calculated using experimental data with well-known formulae. The acoustical parameters show variation with temperature as well as with concentration of CLC. Anomalous behavior of these parameters is noticed at the clearing temperature of CLC. The variation of the parameters is explained in terms of solute-solvent molecular interactions in the solution. The molecular behavior, structural changes, and intermolecular interactions between CLC and solvent are discussed in detail.

Modeling the Glass Transition and Glassy Dynamics of Random Copolymers Using the TS2 Mean-Field Approach

Understanding the glass transition and glassy dynamics in random copolymers and miscible polymer blends is crucial for both fundamental and applied polymer science. While there are multiple models describing the dependence of the glass transition temperature on the copolymer or blend composition (Fox, Gordon-Taylor, Kwei, and others), it is still not easy to describe or predict the broader temperature dependence of relaxation times in these systems. Here, we expand our TS2 (two states, two (time)scales) mean-field model to random copolymers and formulate simple and intuitive mixing rules for the model parameters as a function of composition. We obtain a new equation for the characteristic transition temperature, T*, that can serve as an approximate predictor for the glass transition temperature, Tg. The model then allows us to refine the prediction and calculate Tg based on the standard criterion (τα(Tg) = 10² s). We can also calculate the temperature-dependent α- and β-relaxation times for different copolymer compositions. To test the theory, we computed the glass transition temperatures and relaxation times for random styrene-methylmethacrylate (PS-r-PMMA) and statistical styrene-butylmethacrylate (PS-stat-PnBMA) copolymers and found good qualitative and semi-quantitative agreement with published literature data. The described approach can be easily extended to blends and copolymers with multiple components.

Theoretical Analysis of Hysteresis and Characteristic Transition Temperatures of Iron-Based Memory Metals

The correlation between valence electrons per atom (ev/a) and the characteristic transition temperatures of quaternary and quinary Fe-based shape memory alloys (SMAs) is investigated. Regression equations relating their transformation temperatures (Ms, As) to composition and ev/a are obtained. On adding alloying elements to the SMAs, their transformation temperatures get altered and this is correlated to their ev/a ratio. Three distinct trends between the ev/a ratio and transformation temperatures are found. The correlation between the transformation hysteresis and the atom diameter of the alloying elements is also analysed.

Evaluation of machine learning algorithms to predict the hydrodynamic radii and transition temperatures of chemo-biologically synthesized copolymers

Elastin-like polypeptides (ELP) belong to a family of recombinant polymers that shows great promise as biocompatible drug delivery and tissue engineering materials. ELPs aggregate above a characteristic transition temperature (Tt). We have previously shown that the Tt and size of the resulting aggregates can be controlled by changing the ELP's solution environment (polymer concentration, salt concentration, and pH). When coupled to a synthetic polyelectrolyte, polyethyleneimine (PEI), ELP retains its Tt behavior and gains the ability to be crosslinked into defined particle sizes. This paper explores several machine learning models to predict the Tt and hydrodynamic radius (Rh) of ELP and two ELP-PEI polymers in varying solution conditions. An exhaustive design of experiments matrix consisting of 81 conditions of interest with varying salt concentration (0, 0.2, 1 M NaCl), pH (3, 7, 10), polymer concentration (0.1, 0.17, 0.3 mg/mL), and polymer type (ELP, ELP-PEI800, ELP-PEI10K) was investigated. The five models used in this study were multiple linear regression, elastic-net, support vector regression, multi-layer perceptron, and random forest. A multi-layer perceptron model was found to have the highest accuracy, with an R2 score of 0.97 for both Rh and Tt. This was followed closely by the random forest model, with an R2 of 0.94 for Rh and 0.95 for Tt. Feature importance was determined using the random forest and linear regression models. Both models showed that salt concentration and polymer type were the two most influential factors that determined Rh, while salt concentration was the dominant factor for Tt.

Molecular orientation and thermal stability of thin-film organic semiconductors

Molecular orientation in organic semiconductors plays a critical role in maximizing external quantum efficiencies of organic light-emitting diodes. It was generally believed that the molecular packing of organic semiconductors is either amorphous or liquid-crystal-like with a preferred molecular orientation distributed uniformly throughout the film. In this paper, however, we report that the orientation of organic molecules in physical-vapor deposited films varies drastically depending on thickness. The thermal stability of the molecular network, measured by its characteristic glass transition temperature, also varies as a function of the film thickness. Based on a two-layered film-structure model, we propose a simple function to quantify the molecular dipole orientation S parameter as a function of film thickness. This function describes well experimental data. In addition to contributing to external quantum efficiency, the molecular orientation parameter S is found to have a strong impact on disruptive change in material density after thermal anneal and glass transition.

Sorption properties, glass transition and state diagrams for pumpkin powders containing maltodextrins

The state diagrams of freeze-dried pumpkin powders with different maltodextrin additions were developed using glass transition line, freezing curve and maximal-freeze-concentrations conditions. The freezing curve was plotted employing Clausius – Clapeyron equation and glass transition lines were developed using Gordon – Taylor model. The ultimate maximum-freeze-concentration conditions of the powders were observed in range from 0.685 to 0.745 g solids/g sample. Characteristic glass transition temperature of maximum-freeze-concentration (Tg’) of the pumpkin was equal to - 83.7 °C and was increase with increasing maltodextrin addition. Adsorption isotherms of pumpkin – maltodextrin powders were determined at 25 °C by static - gravimetric method and the experimental data was modelled with BET and GAB equations. Monolayer moisture content of the pumpkin powder decreased with increasing maltodextrin additions. The state diagram and water adsorption isotherms of the pumpkin – maltodextrin powders are useful for predicting suitable storage and processing conditions.