Effect Of Thermal Treatment Temperature Research Articles

Study of the Biocompatibility and Corrosion Resistance of Hydroxyapatite Sol-Gel Thin Coatings on Ti6Al4V Alloy

The aim of this work was to prepare hydroxyapatite thin films (HAp) by a sol-gel method and to study the effect of thermal treatment temperature upon the biocompatibility and corrosion protection of these coatings on Ti6Al4V alloy. The HAp sol was obtained by hydrolysis and condensation of a mixture of triethyl phosphite and calcium nitrate tetrahydrate in stoichiometric amounts (i.e. maintaining a Ca/P ratio of 1.67) adapting a water-based route. The crystallite size and degree of crystallinity of the HAp sol-gel derived coatings strongly depends on the thermal treatment applied. Based on this knowledge, the HAp sol-gel films were annealing in air during 2h at 400ºC, 600ºC, 800ºC and 1200ºC, respectively. As an alternative to conventional thermal treatments, a set of samples was prepared by applying a modification of the Controlled Rate Thermal Analysis (CRTA) developed by Rouquerol, with the aim of obtaining HAp ceramic thin films with controlled textural characteristics at lower temperatures. The basis of this thermal treatment is to control temperature and pressure system, keeping constant the decomposition speed. The application of Thermogravimetric/Differential Thermal Analyses (TG/DTA) and X-ray Diffraction (XRD) has provided valuable information about the phase transformation, mass loss, identification of the phases developed, crystallite size and degree of crystallinity of the obtained HAp powders. Fourier Transformer Infrared Spectroscopy (FTIR) has been utilized for studying the functional groups within the prepared structures. The surface morphology and nature of the prepared HAp coatings was studied by Scanning Electron Microscopy (SEM) with energy dispersive spectroscopy (EDS). The specific surface (BET) and porosity of the material were determined starting from isotherms of adsorption for N2 at a temperature of 77 K. The corrosion protection behaviour of the HAp-coatings/Ti6Al4V in Kokubo’s Simulated Body Fluid (SBF) has been studied by Electrochemical Impedance Spectroscopy (EIS). Inductively Coupled Plasma (ICP) has been used to detect the concentration of Ca2+ and PO4 3- ions released and re-precipitated upon the HAp coatings submitted to soaking test in SBF. The quantification of the in vitro cytotoxicity of the HAp sol-gel coatings was made with human osteoblast cultures and a tetrazolium dye (MTT) based assay (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide)). Finally the analysis of the adhesion and cellular proliferation on the surface of the materials was also carried out. In these last studies Alamar Blue assays and human osteoblast cultures have been used. In summary hydroxyapatite nano-crystalline coatings on Ti6Al4V alloy have been obtained by a water-based sol-gel route. The crystallite size and degree of crystallinity of the HAp sol-gel derived coatings strongly depends on the thermal treatment applied. HAp films have been successfully obtained by annealing sol-gel-derived coatings in air during 2h at 600ºC and 800ºC. As an alternative to these conventional thermal treatments it has been possible to crystallize pure hydroxyapatite at 100°C of temperature of control for the pressure and 300°C as maximum temperature by applying controlled rate thermal analysis (CRTA) conditions. The obtained results have shown that the prepared coatings are nanocrystalline HAp with little deviations from that present in the human bone. All these HAp coating/Ti6Al4V systems have shown to have good bioactivity upon immersion in SBF, good biocompatibility and corrosion protection properties. Acknowledges The authors would also like to acknowledge the Ministerio de Economía y Competitividad of Spain (Projects MAT2012-38541-C02-02 and MAT2015-65445-C2-1-R) and Comunidad de Madrid (Project S2013/MIT-2862-MULTIMAT-CHALLENGE) for funding this research.

Starch/silver nanocomposite: Effect of thermal treatment temperature on the morphology, oxygen and water transport properties

The present work reports a strategy involving the preparation of nanostructured starch based film containing silver nanoparticles (AgNPs) using a completely green chemistry process. The nanocomposite films were prepared by solution cast process. The AgNPs were in situ generated inside the polymer film by thermal treatment at different temperatures (25, 40 and 85°C). The influence of the presence and the amount of reducing agent (glucose) were also investigated. For all nanocomposite films, the AgNPs were spherical with a diameter less than 15nm. Contrary to the presence of glucose, thermal treatment condition was a key factor for the AgNPs structure. Crystalline AgNPs were obtained only after thermal treatment at 85°C. Improvements of water and oxygen barrier properties near to one decade were observed in this last case and were explained by the formation of crystalline AgNPs associated to the establishment of strong interactions between AgNPs and starch polymer matrix.

Characteristics of bulk liquid undercooling and crystallization behaviors of jet electrodeposition Ni–W–P alloy

The undercooling of Ni–W– P ternary alloy coating melt was investigated by in situ differential scanning calorimeter (DSC) with the flux processing technique. The results showed that the highest undercooling of Ni–W–P ternary alloy with 359 K was obtained as the thermal treatment temperature of the melt being 1679 K and the cooling rate being 50 K min−1. When cooling rate is fixed, the change of undercooling depends on the melt processing temperature, and the undercooling will increase rapidly at the first stage. The effects of thermal treatment temperature and cooling rates on the undercooling were discussed.

Green synthesis of zeolites from a natural aluminosilicate mineral rectorite: Effects of thermal treatment temperature

This article reports the effects of thermal treatment temperature on the physicochemical properties of a rectorite mineral and the chemical reactivity and crystallization behavior of the activated rectorite products for zeolite synthesis purposes. The raw rectorite mineral and its thermal activation products were systematically characterized by XRF, XRD, FTIR and 29Si and 27Al MAS NMR techniques and the resultant zeolites were characterized by XRD technique. The results showed that after being thermally treated in the temperature range of 25–1300°C, the rectorite experienced the following four stages: dehydration at 150–300°C, dehydroxylation at 600–700°C, structure collapse at 1000°C, and new phase formation at above 1100°C. Moreover, it was found that after being thermally treated at ca. 1000°C, the SiO4 tetrahedral units in the rectorite mineral are distorted, while the AlO6 octahedral units are decomposed and thus the maximum contents of active SiO2 and Al2O3 can be simultaneously achieved, and as a result, zeolite P is obtained when using the rectorite calcined at 1000°C as the starting material for fabricating zeolites. Our results further revealed that like kaolin rectorite after thermal activation at a suitable temperature can be used for zeolite synthesis and thus demonstrates itself a promising feedstock for the green synthesis of zeolites directly from natural aluminosilicates without experiencing intermediate chemicals.

Effect of thermal treatment temperatures on the reinforcing and interfacial properties of recycled carbon fiber–phenolic composites

Carbon fiber reinforced plastic (CFRP) chips were thermally treated to clean their surfaces and their use as reinforcing materials in composites explored. The interfacial properties were dependent on the thermal treatment temperature. Electrical resistance measurements, by the 4-probe method, were used to evaluate the state of dispersion of the recycled carbon fibers (RCFs) in the RCF–phenolic composites. FE-SEM and AFM were used to study the surfaces of the recycled carbon fibers and the fracture surfaces of the RCF–phenolic composites, for the different treatment temperatures (200–600°C). There were differences in the nature and amount of residual epoxy resin on the surface of recycle CF subsequent to different thermal treatments. Mechanical and thermal properties of RCF–phenolic composites were affected by the presence of residual epoxy resin. SEM and AFM investigations indicated that the optimal treatment temperature was approximately 400°C, where the surface was clean of the residual epoxy matrix material and still relatively free of thermal damage. The decrease in diameter as well as damage to the fibers at the higher temperatures was accompanied by a decrease in the mechanical properties for composites manufactured with the recycled chips. The interfacial properties of the CFRP chips were generally improved by the appropriate thermal treatment, resulting in better interfacial adhesion between the recycled fibers and the phenolic resin.

A study of Eu-doped La2Zr2O7 nanocrystals prepared by salt-assistant combustion synthesis

Nanocrystalline (La1−xEux)2Zr2O7 series solid solutions were prepared by a simple and controllable salt-assisted combustion process. The samples were characterized by XRD, TEM and EDS. The results showed the partial substituted products were single-phase solid solutions. The effect of thermal treatment temperature on the crystal size of nanocrystals and the activation energy of crystal growth during calcinations were studied. And the activation energy of (La1−xEux)2Zr2O7 series with x=0.05, 0.1, 0.25, 0.5, and 0.75 was 25.4, 27.8, 28.0, 32.4, and 30.6kJ/mol, respectively. TEM images revealed that the products were composed of well-dispersed cubic-like particles with the range of size at 20–50nm. EDS results furtherly confirmed that the composition of the obtained compound was in agreement with the stiochiometric formular. The emission spectra of (La1−xEux)2Zr2O7 nanocrystals at 385nm upon excitation showed that there were some intense and prevailing emission peaks located at 590–650nm.

Investigation on the undercooling and crystallization of pure zinc melt by DSC

The undercooling of pure zinc melt was in situ investigated by differential scanning calorimeter (DSC) with the flux processing technique. The highest undercooling of pure zinc with 23.9 K was obtained as the thermal treatment temperature of the melt being 903 K and the cooling rate being 30 K min−1. When cooled rate is fixed, the undercooling depends on the melt processing temperature, and increases rapidly at the first stage. The effects of thermal treatment temperature and cooling rates on the undercooling were discussed.

Effect of Temperature and CaO Addition on the Removal of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Fly Ash from a Medical Waste Incinerator

The effects of thermal treatment temperature and CaO addition on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) content in the fly ashes from a medical waste incinerator with high chlorine content (7.5%) were investigated. Two kinds of batch mode were examined: without CaO addition under the temperature range of 50–850°C, and with CaO addition at various Ca/Cl molar ratios (CCR = 0.8–44.3) at 250°C. The results show that the PCDD/F content in raw fly ash was 6.20 ng I-TEQ/g. When elevating the temperature from 50 to 400°Cwithout CaO addition, the PCDD/F content dramatically increased from 5.38 to 575 ng I-TEQ/g. Even at 850°C, the PCDD/Fs were not destructed apparently and were still with a concentration of 401 ng I-TEQ/g. However, with the addition of CaO at CCR = 17.7 at only 250°C, the removal ratio of PCDD/Fs reached to 87.2% and the PCDD/F content was significantly reduced to 0.889 ng I-TEQ/g, which meets the soil pollution standard of Taiwan EPA (1 ng I-TEQ/g) and could be considered as backfill. CaO addition was proven efficiently to enhance the reduction rate of PCDD/Fs in fly ashes during the thermal treatment at a low temperature, as well as inhibit the formation of PCDD/Fs.

Synthesis and Properties of Cerium Oxide Nanoparticles

Cerium oxide(CeO2)nanoparticles were synthesized via a precipitation method using cerous sulfate, ammonia water and cetyl three methyl brominated ammoniu(CTAB) as raw materials. The effect of thermal treatment temperature and dispersing agent on the crystal structure and morphology were discussed. The structural evolutions and morphological characteristics of the nanoparticles were investigated using X-ray diffractometery, scanning electron microscopy, Fourier transform infrared spectroscopy. The results showed that the broadening of CeO2peaks decreases by the increasing in heat-treatment temperature and the dispersing agent playes key roles in microstructure of the CeO2.

Multifunctional sol-gel derived thin film based on nanocrystaline hydroxyapatite powders

The aim of this work was to prepare bioactive hydroxyapatite coatings by sol-gel method and to study the effect of thermal treatment temperature upon the bioactivity and corrosion protection of these coatings on Ti6Al4V alloy. The application of (DTA/TGA) and (XRD) has provided valuable information about the phase transformation, mass loss, identification of the phases developed, crystallite size and degree of crystallinity. (SEM/EDX) has been applied to study the surface morphology of coated samples before and after immersion in simulated body fluid (SBF) to detect the biomimetic precipitation of the bonelike apatite. The obtained results show that all the prepared samples are ceramic nanocrystalline with crystal structure and composition like hydroxyapatite, with little deviations from that present in the human bone. The bioactivity of the studied samples is found to be closely related to the thermal treatments applied. That is, the bioactivity decreases as the temperature of the thermal treatment increase. Coatings from such prepared hydroxyapatite sol have been accomplished by dip-coating technique on non-toxic Ti6Al4V alloy for biomedical applications. The corrosion behaviour of the resulting hydroxyapatite coatings in a (SBF) has been studied by electrochemical impedance spectroscopy (EIS). The hydroxyapatite coated Ti6Al4V alloy displayed excellent bioactivity when soaked in the (SBF) and acceptable corrosion protection behaviour.

Evaluation on the property of sewage sludge cake by thermal treatment

The sewage sludge cake (SSC) used in this study was provided by a K-wastewater treatment plant in Kyonggi-Do, Korea. The characteristics of the SSC, such as particle size, water content, and composition were analyzed. Both the Korea extraction test (KET) and the toxicity characteristic leaching procedure (TCLP) were used to estimate whether the SSC was hazardous. In thermal experiments, the temperature was varied in the range 400° to 900°C and the heating time was varied from 1 to 6 h. The effects of thermal treatment temperature and time were evaluated by turbidity tests on the resultant SSC. On a dry basis, SSC mainly consisted of combustible content (60.2%) and phosphorous (25.9%). The turbidity of SSC was initially estimated in terms of the sedimentation time. The turbidity of SSC decreased exponentially from 9873 FAU at 0 h to 986 FAU at 6 h, so that the sedimentation time of SSC was established as 6 h. From the results of the thermal treatment at 600°C, thermal time can be determined by 2h because the turbidity of SSC is decreased dramatically within 1h and is stabilized after 2h. The turbidity of SSC decreased when the thermal treatment temperature increased from 400° to 900°C. The turbidity after thermal treatment at 400°C for 2 h was 29 FAU and this became almost 10 FAU at 600°C. The SSC was not hazardous, because KET and TCLP analysis produced values that were smaller than the regulatory levels. Hence, it was concluded that SSC can be stabilized by thermal treatment and can be used as a recycled material.

Synthesis and characterization of nanosized Ce1−xbixo2−δ solid solutions for catalytic applications

This study consists of elaborating and characterizing some nanometric materials in basic of rare-earth oxides by the soft chemistry technique. the first step of this work consists of synthesizing nanometric pure ceria by sol-gel process. In the second one, the Bismuth doped ceria by co-precipitation method was realized in order to obtain ceria-based solid solution, to improve its catalytic property by creation of oxygen vacancies. The solubility limit of Bi2O3 in CeO2 was determined to be around 20 atom %. The effect of thermal treatment temperatures on the average crystallite sizes and lattice parameters was done for pure ceria and Ce1−xBixO2−x/2 (x = 0.15 and 0.2). The different elaborated samples are subject of structural characterization (XRD). Catalytic reactivity of these materials in presence of “air- toxic gas” mixtures is studied by Fourier Transform Infra-Red Spectroscopy (FTIR).

Rapid Synthesis of Eu<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> Nanocrystals via Salt-Assistant Combustion Method

Eu2Zr2O7 nanocrystals with cubic structure were successfully synthesized by salt-assistant combustion method. The Eu2Zr2O7 nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Emission/ excitation spectra. The effect of thermal treatment temperature on the crystal size of nanocrystals was studied. The results indicated that Eu2Zr2O7 nanocrystals obtained by this method were well-dispersed and uniform in particle size distribution with average size of 20 nm. By comparison, it was found that the introduction of KCl in the solution combustion reaction process can effectively prevent nanocrystallites from sintering and forming inseparable three-dimensional network, and result in the formation of well-dispersed nanoparticles. The method provides a convenient, low-cost and nontoxic route for the synthesis of nanostructures of oxide materials. Moreover, the strong fluorescent property of the Eu2Zr2O7 nanocrystals obtained by salt-assistant combustion method at 385 nm upon excitation was measured at room temperature. The results showed that Eu2Zr2O7 nanocrystals obtained by salt-assistant combustion method put up excellent fluorescent properties.

Synthesis and characterization of Er 2Sn 2O 7 nanocrystals by salt-assistant combustion method

Er 2Sn 2O 7 nanocrystals were successfully synthesized by salt-assistant combustion method (SACM) at a relatively low temperature (600 °C). The Er 2Sn 2O 7 nanocrystals were characterized by XRD, FT-IR, TEM and HRTEM. The effect of thermal treatment temperature on the crystal size of nanocrystals was studied and the activation energy of Er 2Sn 2O 7 nanocrystals formation during calcination was calculated to be 88.1 kJ/mol. TEM results showed that the Er 2Sn 2O 7 nanoparticles obtained by SACM were well-dispersed and uniform in particle size distribution. The interplanar distance of d 222 measured from the HRTEM images was 0.301 nm, coinciding with the theoretical value.

Investigation on the undercooling and crystallization of Ni–Fe alloy coating melt by DSC

The undercooling of Ni–Fe alloy coating melt was in situ investigated by differential scanning calorimeter with flux processing technique. The highest undercooling of Ni–Fe alloy with 426 K was obtained as the thermal treatment temperature of the melt being 1904 K and the cooling rate being 50 K min−1. When cooling rate is fixed, the undercooling depends on the melt processing temperature, and increases rapidly at the first stage. The effects of thermal treatment temperature and cooling rates on the undercooling were discussed.

Preparation and characterization of Y 2Zr 2O 7 nanocrystals and their photocatalytic properties

The yttrium zirconate (Y 2Zr 2O 7) nanocrystals with cubic structure in the size range of 50 nm were prepared by stearic acid method (SAM) using zirconium nitrate and yttrium nitrate as raw materials, stearic acid as solvent and dispersant. The synthesis process was monitored by TG–DTA. The product was characterized by XRD, FT-IR, TEM, HRTEM, EDS and BET. The effect of thermal treatment temperature on crystal size and lattice distortion of the nanocrystals was studied. Y 2Zr 2O 7 nanocrystals obtained by SAM were well dispersed with average size of 20–40 nm. The interplanar distances measured from the HRTEM image were 0.294 and 0.185 nm, respectively, coinciding with the theoretical values. Moreover, the photocatalytic properties of Y 2Zr 2O 7 nanocrystals were measured and discussed.

Preparation and characterization of pyrochlore La2Zr2O7 nanocrystals by stearic acid method

Pyrochlore La2Zr2O7 nanocrystals with cubic structure were prepared by stearic acid combustion method using zirconium nitrate and lanthanum nitrate as raw materials, stearic acid as solvent and dispersant. The La2Zr2O7 was characterized by XRD, Raman, FT-IR, BET, TEM, HRTEM and Emission/excitation spectra. The effect of thermal treatment temperature on crystal size of the nanocrystals was studied and a single phase of La2Zr2O7 was completely formed at 900 °C. The interplanar distances of d222 and d400 measured from the TEM images were 0.322 nm and 0.263 nm, respectively, coinciding with the theoretical values. Moreover, the strong fluorescent property of the La2Zr2O7 was measured, with the maximum emission peak at ca. 389 nm upon excitation at ca. 324 nm.

Solid-state synthesis and electrochemical property of SnO 2/NiO nanomaterials

SnO 2/NiO nanomaterials were successfully synthesized through a solid-state reaction of NiCl 2·6H 2O, SnCl 4·5H 2O and NaOH with NaCl as a diluter. The precursor and SnO 2/NiO nanomaterials were investigated using X-ray diffraction (XRD), infrared spectrum (IR) and scanning electron microscopy (SEM). Effect of the calcination temperature on the microstructure of the products was discussed. Electrochemical property of SnO 2/NiO nanomaterials was tested by cyclic voltammetry (CV) technique and effect of thermal treatment temperatures for the precursor on the electrochemical property of SnO 2/NiO nanomaterials was investigated. It was found that potentials of oxidation peaks shift towards positive whereas those of reduction peaks shift towards negative when the scanning rate was increased. The maximum specific capacitance was 357.45 F/g according to the CV results of SnO 2/NiO nanomaterials at a scanning rate of 10 mV/s.

Photoinduced charge property of nanosized perovskite-type LaFeO 3 and its relationships with photocatalytic activity under visible irradiation

In this paper, ABO 3-type perovskite LaFeO 3 nanosized photocatalysts were synthesized by a sol–gel method, using citric acid (HOOCCH 2C(OH)(COOH)CH 2COOH) as complexing reagent and La(NO 3) 3·6H 2O and Fe (NO 3) 3·9H 2O as raw materials. The as-prepared samples also were characterized by several testing techniques, such as thermogravimetry–differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET), infrared spectrum (IR), ultraviolet–visible diffuse reflection spectrum (UV–vis DRS), photoluminescence spectrum (PL), surface photovoltage spectroscopy (SPS) and electrical field induced surface photovoltage spectroscopy (EFISPS). The sample activity of different LaFeO 3 nanoparticles for degrading Rhodamine B solution under visible irradiation ( λ > 400 nm) was evaluated. The effects of thermal treatment temperature on photoinduced charge property and photocatalytic activity were mainly investigated, together with their relationships. The results show that the LaFeO 3 sample calcined at 500 °C exhibits higher activity, and the activity decreases with increasing calcination temperature, which is in good agreement with the characterization results. The weaker is the PL and SPS signal, the higher is the photocatalytic activity. Moreover, the activity of all as-prepared LaFeO 3 samples is higher than that of international P-25 TiO 2 under visible irradiation.

アルキルトリメトキシシランによるＴｉＯ２の乾式疎水化における固着に及ぼす熱処理の影響

In the present work, the authors studied the effects of thermal treatment temperature and thermal treatment duration on endowment of a hydrophobic property to TiO2 treated with alkyltrimethoxysilane solutions by a dry method. Also, the relationship between M value, a parameter of hydrophobic property, and fixation of ATMS onto TiO2 was examined. The main results obtained are as follows :(1) M values of TiO2 treated with n-BTMS and n-PTMS solutions increase with the increase in time elapsed, in another words, average polymerization degree, and finally reach a stagnant stage. The elevation of thermal treatment temperature and its duration also positively affect the M value of TiO2. On the other hand, the M value of TiO2 treated with n-DTMS was kept constant despite the change in thermal treatment conditions.(2) Amounts of fixed n-BTMS or n-PTMS onto TiO2 treated with these solutions increase with the increase in average polymerization degree. Since M value increases with the elevation of temperature even at the same level of fixation amount of coupling agent, it is assumed that the elevation of temperature affects the condensation onto the TiO2 surface.(3) ATMS Oligomer of lower molecular weight evaporated during the mixing and thermal treatment processes of TiO2 and ATMS solutions. This phenomenon was suppressed with the increase in average polymerization degree, resulting in the increase of fixed amount of ATMS onto TiO2. The decreasing sequence is expressed as n-PTMS>n-BTMS>n-DTMS. However, thermal treatment temperature is almost independent of vaporization amount.