Differential Thermal Analysis Analysis Research Articles

Evaluation of Sample Preparation Practices Common with Differential Thermal Analysis of Grapevine Bud Cold Hardiness

<h3>Background and goals</h3> Differential thermal analysis (DTA) is a popular semi-automated method to determine the temperature at which plant tissues freeze. It is used to evaluate effects of environmental variables, genotypes, and agronomic practices on cold hardiness, and as an Extension tool to monitor cold hardiness and provide decision support for growers of many specialty crops. <h3>Methods and key findings</h3> This study evaluated common approaches in sampling and preparation of dormant grapevine compound buds for DTA to provide a reference point as to which adjustments might cause excessive variation in subsequent data. Common adjustments in sample preparation, such as using foil packets, moistened tissue paper, or bud orientation, had no consistent effects on DTA values, typically resulting in a variation of &lt;1°C. The same was true for storage (or shipping conditions) of 24 hrs or less, provided samples were maintained at low, but above-freezing temperatures (1.6 to 4°C). Finally, influence of bud position along the length of the cane was also inconsistent. <h3>Conclusions and significance</h3> The robust nature of DTA for estimating grapevine cold hardiness offsets the potential impact of variation introduced from different sample preparation methods. These results can help those wishing to develop DTA protocols or expand their capacity to conduct DTA analysis to design protocols to best suit their individual program needs. Consistency in DTA approach is likely more important than the specific methods used, especially when comparing relative differences in observed lethal temperatures.

New Clayey Deposit and Their Potential as Raw Material for Red or Structured Ceramics: Technological Characterization.

Mineralogical and technological characterization of ceramic raw materials from a new deposit located at Caxias city, Maranhão State—Brazil, was accomplished to determine their potential as raw materials for the ceramics industry in northeastern Brazil. The ceramic raw materials were collected from three different locations on the site and characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), differential thermal analysis (DTA), and thermogravimetry (TG). The XRF analysis of the fraction < 2 μm revealed that most samples had SiO2 (35–51 wt%), Al2O3 (19–29 wt%), Fe2O3 (2–21 wt%), MgO (0.7 to 4.5 wt%) and K2O (0.9 to 5 wt%) as components. Quartz, kaolinite, illite, hematite and montmorillonite were the main mineral phases identified. DTA and TG analysis confirmed the mineral identification. The technological potential of the ceramic raw materials was investigated by: cation exchange capacity (CEC), plastic behavior (Atterberg Limits), linear shrinkage at 950 °C (LSF), flexural strength (FS), apparent porosity (AP), water absorption (WA) and bulk density (BD). The main experimental results—WA (9–17%), AP (19–31%), FS (2.0–23 MPa), and the Atterberg limits—indicated that the ceramic raw materials investigated have high potential to be used to develop mass for red or structured ceramics, such as bricks and roof tiles.

The Effect of ZnO on the Physicochemical and Mechanical Properties of Aluminosilicate Dental Cements

In this study, the effect of the addition of various amounts of ZnO (0, 1, 2, and 3 wt. %) to aluminosilicate bioactive glass (BGs) network (SiO2-Al2O3- P2O5-CaF2-CaO-K2O-Na2O) on the mechanical properties of the fabricated glass ionomer cement (GIC) samples was studied. The GIC samples were fabricated by mixing the synthesized aluminosilicate BGs with Rivaself cure liquid. The synthesized aluminosilicate glass was characterized using differential thermal analysis (DTA), X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Besides, the mechanical properties of GICs were evaluated using Vickers microhardness and Diametral tensile strength (DTS) test. According to DTA analysis, the glass transition temperature (Tg) of aluminosilicate BGs was decreased from 575 to 525 °C. According to the results, the aluminosilicate BGs with an amorphous state (~90%) and the grain size of 36 μm were synthesized. Doping of the ZnO to glass network up to 3 wt. % could increase the amorphous phase up to 95% and decrease the grain size of the particles up to 28 μm. The microhardness and DTS of the GIC samples containing the aluminosilicate BGs were about 677 Hv and 8.5 MPa, respectively. Doping of ZnO to the glass network increased the mentioned values up to 816 Hv and 12.1 MPa, respectively.

Thermal Analysis and Selected Properties of CuNi2Si Alloy Used for Railway Traction.

This paper investigates the effect of high-temperature aging (600 °C and 650 °C) on the microstructure and functional properties of copper CuNi2Si alloy. The paper also presents the results of elastomeric tests performed by means of the Gleeble 3800 heat and plastic treatment simulator, as well as DTA (Differential Thermal Analysis) analysis carried out for the investigated alloy aged for 1, 2, 4 and 7 h. Corrosion resistance tests were performed by means of the potentiodynamic method with Atlas Sollich Atlas 0531 potentiostat/galvanostat in a 3% sodium chloride solution. Based on the tribological tests, it was confirmed that the CuNi2Si alloy was solution heat treated from the temperature of 1000 °C and gradually aged at the temperature of 600 °C and 650 °C for 1–7 h, characterized by a stable wear resistance. The alloy aged at the temperature of 600 °C was characterized by a lower mass loss compared to the one aged at 650 °C. Based on the DTA analysis, it was found that for the alloy aged for 2, 4 and 7 h, at the temperatures of 401 °C, 411 °C and 412 °C, respectively, the decomposition of a supersaturated solid solution took place by spinodal transformation accompanied by a sequence of phase transitions DO22 [(Cu, Ni)3Si],→ δ-Ni2Si → (Cu, Ni)3Si. The results of these investigations have proved that the CuNi2Si alloy can be widely used for electric traction. The use of alloys that replace elements made entirely of copper and, in this way influencing its lower demand, is in line with the global policy of economical management of natural resources.

Synthesis and characterization of dialdehyde cellulose/amino‐functionalizedMCM‐41 core‐shellmicrospheres as a new eco‐friendly flame‐retardant nanocomposite

AbstractUsing proper flame‐retardant materials when constructing buildings or fabricating devices is the most important fire safety guidelines. The halogen and phosphorus‐based compounds are among the most effective flame retardants. However, most of these compounds are recognized to have a harmful effect on human body and the environment during combustion. In this context, we designed and synthesized a new eco‐friendly flame‐retardant nanocomposite by combining dialdehyde cellulose (DAC) and amino‐functionalized mesoporous silica MCM‐41 (N‐M41). Spherical N‐M41 nanoparticles have been successfully prepared in one‐pot reaction using tetraethyl orthosilicate and (3‐aminopropyl)triethoxysilane (APTES), and then coated with different amounts of DAC through Schiff base reaction between the carbonyl group of DAC and NH2of APTES. The resulted DAC@N‐M41 nanocomposite was characterized by XRD, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, differential thermal analysis (DTA) and thermogravimetry analysis (TGA). TEM micrographs revealed that this nanocomposite was made up of core‐shell nanospheres structure with narrow size distribution (ca. 140 nm). DTA and TGA analysis revelated that the presence of silica within the nanocomposite can effectively increase the char yield, decrease the heat release, and improve the fire performance of the prepared nanocomposite. A mechanism of the reduction in flammability of this nanocomposite has been proposed.

Thermodynamic Investigation of New High-Strength Low-Alloy Steels with Heusler Phase Strengthening for Welding and Additive Manufacturing: High-Throughput CALPHAD Calculations and Key Experiments for Database Verification

High-strength low-alloy (HSLA) steels often comprise of Cu clusters and M2C (M: Mo, Cr) carbides as strengthening particles. In this work, three new HSLA steels with alternative strengthening phases, Fe2SiTi and Ni3Ti, are investigated by using HSLA-115 steel as the reference. To evaluate the weldability for potential fabrication using casting, welding, and additive manufacturing, freezing ranges are studied using differential thermal analysis (DTA), and CALPHAD (Calculation of Phase Diagrams) approach under equilibrium and nonequilibrium conditions. While the cooling signals in the DTA analysis are not pronounced enough for thermal analysis, the trend of freezing range change based on the nonequilibrium and equilibrium calculations are consistent with the heating signals. High-throughput calculations are performed to deduce the effect of variation of each alloying element on the freezing range. Moreover, the experimental and calculated phase fractions and compositions of the as-cast and heat-treated alloys were compared. Though CALPHAD model-prediction can provide valuable insights into the phase stability of these new alloys, there is a remarkable difference regarding phase fraction and composition of individual phases. Therefore, this study indicates that the application of the CALPHAD approach in new alloy discovery requires a careful model-validation and database calibration.

Properties of Linear Low Density Polyethylene

As result of the modification of polyolefin, composite materials based on them were obtained for the use in special equipment in order to entrain their heat resistance. Data analysis DTA (differential thermal analysis) of the DTA curve of this polyethylene sample suggests a bimodal nature of their MWD (molecular weight distribution) which differs from polyethylene with unimodal MWD and a series of endo oxidation effects with a maximum temperature of 245, 335, 358 and 435 °С. X-ray structural studies showed that the crystal system and the size of the unit cells of the crystal lattice of LLDPE practically does not differ from those of LDPE. LLDPE as well as LDPE and HDPE has a layered structure with dense packing of macromolecules. In terms of crystallinity and crystallite sizes, LLDPE are on par with HDPE and significantly differ from LDPE. These data are in agreement with published data. The parameters of the unit cells of the crystal structure of UHMWPE are close to those of LLDPE, and by crystallinity it occupies middle ground between HDPE and LLDPE.

Deterioration of CA mortar filling layer under cyclical thermal loading

Cement and emulsified asphalt mortar (CA mortar) has been widely used as a filling layer between concrete bed plates and track slabs for high-speed railways. This study analyses the cracking mechanism of the interface between CA mortar and the concrete under CT treatment (cyclical temperature from −40 °C to 60 °C) and CTI treatment (cyclical temperature from −40 °C to 60 °C then immersed in water) by means of scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), thermos-gravimetric analysis (TG) and differential thermal analysis (DTA). Results showed that cracks were observed on the interface after 16 CT cycles, while 25 cycles were required to observed cracks for sample under CTI treatment. The samples subjected to the CT treatment had a larger length difference between the CA mortar and concrete at high temperature. The volume proportion of 2–10 μm-level pore in CA mortar was declined after CT or CTI treatment, which was caused by removal of asphalt component in CA mortar from the matrix to the capillary porosity as confirmed by SEM results. CT treatment made it clear that the substance of low melting point in the asphalt either volatilized or turned into the substance of high melting point from TG and DTA analysis.

Precipitation kinetics of γ″ phase and its mechanism in a Nb-bearing nickel-based superalloy during aging

While understanding the precipitation kinetics of gamma double prime (γ″) phase is of vital importance in Inconel 718 superalloy, kinetics studies by Johnson–Mehl–Avrami–Kolmogorov (JMAK) and thermoanalysis techniques have not been conducted so far, and hence, investigating the mechanism of γ″ formation deserves more attention. In response, in the present work, the precipitation kinetics of γ″ phase was studied by JMAK analysis based on the hardness measurements during aging and differential thermal analysis (DTA) during continuous heating. Average Avrami exponent of 0.64 was obtained, which was interpreted as precipitation on dislocations on the theoretical front. Moreover, the activation energy of precipitation (Q) was found to be close to the activation energy for the diffusion of niobium in the matrix, which was also confirmed by the Kissinger's plot obtained from DTA analysis. As a result, the present work contributes to the kinetics and mechanism of the γ″ phase formation.

Thermal analysis of W-free Co\u2013(Ni)\u2013Al\u2013Mo\u2013Nb superalloys

In this investigation, the thermal analysis of W-free cobalt-based superalloys based on Co–Al–Mo–Nb and Co–Ni–Al–Mo–Nb systems was performed. The analysis was performed at different stages of heat treatment process. The differential thermal analysis (DTA) was utilized for the determination of characteristic temperatures related to microstructural changes. First of all, the DTA analysis was carried out for discussing as-cast alloys in the temperature range of 40–1500 °C. The results showed thermal effects connected with melting and important order–disorder transition. The temperature range of 1200–1250 °C was chosen for performance of a first heat treatment operation for the investigated alloys. Specimens were annealed at selected temperature for 5 h. The microstructure of alloys after solution heat treatment was analyzed as well. Afterward, the solutionized specimens were subjected to the further thermal analysis in order to select the aging temperature according to the order–disorder transformation related to formation of γ′ phase with overall formula Co3(Al,X). Five aging variants were performed in the temperature range of 800–1000 with a step of 50 °C. After each stage of heat treatment, SEM/EDS analysis and hardness measurements were performed.

Preparation, Physicochemical Characterization and In-Vitro Dissolution Studies of Ketoprofen Solid Dispersion with PEG 6000 and HPMC 6 cps

Ketoprofen [2-(3-benzoylphenyl)-propionic acid], a non-steroidal anti-inflammatory drug exhibits poor dissolution pattern. Solid dispersion (SD) techniques were used because it is particularly promising to improve the oral absorption and bioavailability of BCS Class II drugs. This investigation entails solid dispersion of ketoprofen which was formulated and characterized for better release profile and immediate action of the drug. Melting method was applied to prepare solid dispersion by using two immediate release (IR) polymer PEG 6000 and HPMC 6 cps at different weight ratios. In the formulation, a fixed amount of lactose was used as adsorbent. The solid dispersions were investigated for drug entrapment efficiency and dissolution behavior. In vitro dissolution study was performed in phosphate buffer (pH 7.4) medium for one hour. Percent cumulative drug release from solid dispersion was found to be minimum 92.19% and maximum 98.95% within one hour, which showed a better dissolution compared to the active drugs. Evaluation of the properties of the solid dispersion was also performed by using Scanning Electron Microscopy (SEM) study and Differential Thermal Analysis (DTA). SEM results indicated that ketoprofen crystallinity in SDs was significantly reduced, and that the majority of ketoprofen was in amorphous form. No interaction was found between drug and polymers from DTA and Fourier-transform infrared (FTIR) spectroscopy analysis. So, solid dispersion technique may be an effective technique to enhance dissolution rate of ketoprofen.&#x0D; Bangladesh Pharmaceutical Journal 23(1): 44-53, 2020

Thermal and structural characterization of the kidney stone

In the present study, the thermal and structural properties of a kidney stone, which was passed out of the body naturally by a 29-year-old woman who was 4 months pregnant, were investigated by using the experimental analysis methods of the differential thermal analysis (DTA), thermogravimetric analysis (TG) and X-ray diffraction. The DTA and TG analyses were taken in the temperature range of 25–1000 °C. After reaching the temperature of 680 °C, the decomposition of calcium carbonate to calcium oxide was detected. In the TG curve, the total mass loss of 26.2% was detected. The as-used kidney stone is fully composed of the single phase of calcium oxalate monohydrate (C2H2CaO5), also known as the whewellite, with the tetragonal crystal structure. The crystallinity percent of the as-used kidney stone was found to be 91.3%. The crystallite size was computed to be 107.22 ± 4.79 nm and 79.69 ± 3.63 nm from Scherrer and Williamson–Hall equations, respectively.

Single solid source precursor route to the synthesis of MOCVD Cu-Cd-S thin films

Bis-(morpholinodithiato-s,s′)-Cu-Cd was synthesized from appropriate reagents as a single solid source precursor and characterized using particle induced x-ray emission (PIXE), Fourier transform infrared (FTIR) spectroscopy and differential thermal analysis (DTA). Cu-Cd-S thin films were deposited on sodalime glass substrate using MOCVD technique at temperatures in the range 360 °C–450 °C. The films were further characterized using Rutherford backscattering spectroscopy (RBS), x-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy and four-point probe technique. PIXE revealed that the synthesized precursor contained the expected elements which led to the successful deposition of the Cu-Cd-S thin films. FTIR ascertained that the organic ligand actually attached to the metals. DTA analysis showed that the synthesized precursor was thermally stable and could pyrolyzed around 300 and 500 °C. RBS of the deposited films showed that the stoichiometry and the thickness depended on deposition temperature. XRD analysis revealed that the films deposited at 360 and 380 °C are amorphous while those deposited at 400 °C to 450 °C showed peaks, which supported the possible co-existence of CuS and CdS as Cu-Cd-S, with an improvement in the crystallinity as substrate temperature increased. SEM showed that the films are uniform and crack-free, in which the morphology strongly depended on substrate temperature. Optical analysis revealed that the films have high absorbance in the UV region and high transmittance in the visible and near infrared region, in which direct band gap energy of 2.36 to 2.14 eV was obtained as deposition temperature increased. Other optical parameters such as Urbach energy, refractive index, extinction coefficient, dielectric constant also increased as the deposition temperature increased. Electrical analysis showed that resistivity is temperature dependent as it reduced as deposition temperature increased.

Differential Thermal Analysis of ‘Elberta’ and ‘Flavorich’ Peach Flower Buds to Predict Cold Hardiness in Georgia

Differential thermal analysis (DTA) has great potential as a quick and convenient cold hardiness determination method in plants. It measures freezing events inside of plant samples by detecting exotherm(s) produced when water changes from liquid to solid phase. DTA is highly sensitive to the experimental conditions and it has been reported to be ineffective among different fruit crops after acclimation of floral buds has occurred. The objective of this project was to establish DTA as a rapid and accurate method to predict peach floral bud cold hardiness from acclimation to deacclimation as compared with the traditional standard artificial freezing test. Floral buds of ‘Elberta’ and ‘Flavorich’ peach cultivars were subjected to DTA and artificial freezing tests throughout the winters of 2015–16 and 2016–17. Before deacclimation, two distinct exotherms, low-temperature exotherms (LTE) and high-temperature exotherms (HTE), were normally detected from floral bud DTA analyses. After deacclimation, DTA tests yielded only a few LTEs. However, incubation of floral buds at −2 °C overnight before the cooling process of DTA tests yielded an increased number of LTEs for both seasons in comparison with samples directly run using DTA without incubation. Similarly, after deacclimation started, the temperature in which LTE occurred was correlated (r = 0.59–0.86) with LT50 (lethal temperature that damaged 50% of floral buds) when DTA samples were treated overnight at −2 °C. In our study, pretreatment of floral buds at −2 °C overcame the inability of DTA to detect LTEs after deacclimation, which improved the ability and reliability of DTA to detect LTEs for more than 50% of the buds used per date per cultivar. DTA is a promising method to predict cold hardiness of peach plants.

Preparation Structure and Magnetic Properties of Mn-Doped ZnO Nanoparticles Prepared by Hydrothermal Method

In this research, manganese-doped ZnO (Zn0.99-xMnxO) nanoparticles were synthesized by hydrothermal method using the chemicals. The samples were annealed at 500 and 600 °C to figure out the optimum annealing temperature characterized by differential thermal analysis (DTA) method. Simultaneously with DTA analysis, the possible weight loss was observed by thermal gravimetric (TG) method and categorized the lost chemicals with varying temperature regions. The crystal structure with lattice parameters and the phases were determined by X-ray diffraction method. Microstrain (e), stress (σ), the dislocation density (δ), the locality of the atoms and their displacements (u), and the bond length (L) values were calculated by making use of lattice parameters. The particle morphologies were monitored by scanning electron microscope (SEM) technique and the elemental compositions of the samples were investigated and found that all peaks belong to Zn, Mn, and O elements. The magnetic properties of the samples were revealed using Quantum design PPMS measurement system and correlated with structural properties.

Thermal, Physico-Chemical, and Mechanical Behaviour of Mass Concrete with Hybrid Blends of Bentonite and Fly Ash.

Mass concrete has been commonly known for its thermal stresses which arise due to the entrapment of hydration temperature susceptible to thermal cracking. The utilization of mineral additives is a promising and widely adopted technique to mitigate such effects. This paper presents the thermal, physico-chemical, mechanical, and morphological behaviour of mass concrete with blends of bentonite (BT) and fly ash (FA). Apart from the rise in temperature due to hydration, the compressive strength, ultrasonic pulse velocity (UPV), differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) analysis, and microstructure were studied. The results of this study revealed that the substitution of BT and FA significantly improved the compressive strength and development rate of UPV in the mass concrete samples. The FA concrete (FC) specimen presented the lowest temperature during the peak hours compared to all other concrete mixes studied in this research. Bentonite concrete (BC) was also found to be more effective in controlling the escalation of temperature in mass concrete. Scan electron microscopy (SEM) micrographs presented partially reacted FA particles in a mix. XRD and DTA analysis indicated that the concentration of calcium hydroxide (CH) declined by substituting FA and BT, specifically in ternary blends, which was due to the dilution effect and consumption of CH through the pozzolanic reaction.

КРИСТАЛЛИЗАЦИЯ КВАЗИБИНАРНОЙ ЭВТЕКТИКИ bnss-tss В СИСТЕМЕ Cu-Fe-Ni-S

Исследование посвящено изучению процессов зональной кристаллизации в четырехкомпонентной системе Cu-Fe-Ni-S, являющейся базовой при формировании медно-никелевых сульфидных руд. Образец исходного состава (мол. %): Cu = 17.19, Fe = 19.05, Ni = 19.66, S = 44.10 синтезирован с применением метода квазиравновесной направленной кристаллизации. Результаты микроскопического исследования показали, что полученный слиток образован из 6 зон с разным фазовым и химическим составом. Основная часть слитка представлена зоной IV. Образцы, вырезанные из этой зоны, исследовались методами дифференциального термического анализа (ДТА), растровой электронной микроскопии (СЭМ) и рентгено-спектрального микроанализа (РСМА). Микроскопические исследования позволили предположить, что слиток состоит из твердых растворов tss и bnss, но при дальнейшем охлаждении tss разложился на дочерние фазы. Однако эти данные можно трактовать и как кристаллизацию четверной эвтектики. Результаты ДТА исследования образцов позволили измерить температуры фазовых эффектов и однозначно установить образование бинарной эвтектики bnss-tss. Температура бинарной эвтектики (L → tss + bnss) составляет 578±1 °С (851±1 K). Температуры ликвидуса незначительно повышаются от 857±2 °С до 862±2 °С (1130±2 K - 1135±2 K). Указанное изменение объясняется небольшими изменениями состава исследуемых образцов. Полученные результаты подтвердили адекватность и согласованной предложенной методики, сочетающей методы направленной кристаллизации, дифференциального термического анализа, растровой электронной микроскопии и рентгеноспектрального микроанализа при исследовании фазовых равновесий в многокомпонентных системах.&#x0D; &#x0D; Исследование выполнено в рамках госзадания (проект 0330-2016-0001) и при частичной финансовой поддержке комплексной программы фундаментальных научных исследований СО РАН II.1. № 303.&#x0D;

Sintering, crystallization and properties of 2(Mg1−xMnx)O·2Al2O3·5SiO2 ceramics

Mn-substituted cordierites, 2(Mg1−xMnx)O·2Al2O3·5SiO2 (x = 0–1), were prepared from natural components (talc, clay, alumina) and MnO2. Sintering behavior, phase transformation, and microstructural features of the samples were investigated using X-ray diffraction (XRD), differential thermal analysis (DTA), dilatometric measurements and scanning electron microscopy (SEM) with energy dispersive analysis (EDS). The results of DTA and XRD analysis indicate that MnO2 is successively reduced to Mn2O3 and MnO in the sintering process. Mn2+ ions incorporate into the crystal structure of α-cordierite substituting Mg2+ ions in octahedral sites and thus increasing the cordierite unit cell volume. Mn promotes the sintering process: the crystallization temperature, melting point, density and open porosity of Mn-substituted cordierites lowered, whereas the shrinkage and medium pore diameter enlarged with an increase in MnO2 content in the mixture of raw materials. Surface enrichment with Mn with the formation of manganese oxide crystallites was found for the samples with high substitution degree.

In-situ high temperature XRD and TEM study of the thermal stability and sintering behavior of octacalcium phosphate

Currently, the characteristics of solid-state phase transformation corresponding to octacalcium phosphate (OCP) sintering is still not completely understood. Although it was known that Ca-deficient (Ca-def) hydroxyapatite (HA) is usually unstable at high temperature, the thermal stability and sintering behavior of OCP have been rarely reported. The objective of this study is to systematically investigate the thermal stability and sintering behavior of OCP powders by comprehensive characterization techniques including in-situ high temperature X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA) and scanning electron microscopy (SEM). In-situ XRD results showed that the “collapsed OCP”, Ca-def HA and β-tricalcium phosphate (TCP) crystal structures formed by heating OCP at 200–250 °C, 300–600 °C and 800–900 °C, respectively. Furthermore, DTA analysis revealed that the peak temperatures of the phase transitions of OCP to Ca-def HA and Ca-def HA to β-TCP were ∼170 °C and ∼720 °C, respectively. SEM examination indicated that a large number of pores were introduced during sintering OCP powders due to the release of structurally contained water at 200–250 °C. Therefore, a porous β-TCP ceramic can be directly prepared by sintering OCP powders at 900 °C. This phase transition induced foaming method may be extended for preparing porous bioceramics by sintering calcium phosphate phases as long as they contain crystalline water, which could provide guidelines for better utilizing the phase transformations of calcium phosphate to produce special bioceramics for biomedical applications.

Structural, Thermal and Optical Modifications of Chitosan due to UV-Ozone Irradiation

The present work focused on modifying the chitosan structure which has noticeable places in advanced research. The effect of UV-ozone irradiation with different exposure doses (9.68 x 10-14, 19.35 x 10-14, 29.03 x 10-14 and 38.75 x 10-14 J/m2) on the microstructural, thermal stability and optical properties of chitosan was studied. X-ray diffraction (XRD), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), optical parameters techniques as well as Differential thermal analysis (DTA) and thermogravimetric analysis (TGA and DTG), were performed. The obtained results indicated that, effects on semi-crystalline structures have occurred. Detected variations in XRD, SAED, HRTEM, DTA and TGA analyses under investigation may be attributed to the different degrees of crystallinity, induction of structural changes and molecular configuration of chitosan upon exposure to UV-ozone. The results confirmed that the UV-ozone irradiation plays a role in refining the microstructure and changes occurring in chitosan matrix for future biomedical applications.