Oxidation kinetics of boron carbide ceramic under high gamma irradiation dose in the high temperature

In the presented work, high purity boron carbide (purity of 99.9%, and bulk density 1.8 g/cm³ at 20 °C) compounds were gamma-irradiated at dose rate of D = 30 rd/sec using Co⁶⁰ gamma source. The irradiation of the samples at different gamma doses (5·10⁹; 1·10¹⁰; 1.5·10¹⁰ and 2·10¹⁰ Mrd) was carried out at room temperature and atmospheric pressure. The Differential Scanning Calorimetry (DSC) was used to study the solvothermal chemical reaction mechanisms of boron carbide from room temperature up to 900 K and the oxidation kinetics, rate of oxidation diffusion (plots of Jander), depth of oxidation and activation energy from 900 ≤ T ≤ 1250 K after gamma irradiation at different gamma absorption doses. The depth of the gamma irradiation dose on the surface determined the “critical limit” for the thin oxide layer for boron carbide. Also, depths of gamma irradiation dose is calculated activation energy by the Arrhenius plots. The activation energy was found to increase from 99.59 J mol⁻¹ to 102.93 J mol⁻¹ as the gamma irradiation dose increased from 5·10⁹ to 2·10¹⁰ Mrad.     

Effect of gamma irradiation on optical and chemical properties of cellulose nitrate thin films

In this work, cellulose nitrate films were irradiated with different doses of gamma irradiations. The gamma irradiation doses were 25, 55, 120, and 170 kGy. The compositional transformation, optical properties, and morphological changes resulted from the gamma irradiation were obtained using different spectroscopic methods. These methods were Fourier transform infrared spectrometry, UV/visible spectrometry, and scanning electron microscope. The surface roughness, as well, for pristine and gamma-irradiated polymer films was determined. The obtained results exhibit changes in the absorbance intensities of the function groups of the irradiated cellulose nitrate films. An induced increase in the UV/visible absorption spectra with increase in the gamma irradiation was observed. A noticeable shifting in the UV/visible spectra toward higher wavelength and decrease in the optical band gap were observed as the gamma irradiation increases. As well, the number of carbon clusters and the activation energy were discussed. The morphological investigation indicates the decrease in the roughness surface with increasing of gamma irradiation.     

The irradiation impacts of high gamma doses on optical features and degradation of Makrofol DE 1-1

The induced impacts of high doses of gamma irradiations on the optical features of the Makrofol DE 1-1 detector were studied in the ultraviolet and visible range (from 270 to 500 nm). Makrofol DE 1-1 detector specimens were irradiated separately for different doses from 200 to 1000 kGy; step 200. The optical absorbance spectra of the pristine Makrofol DE 1-1, as well as the irradiated gamma-ray samples display two main features: (i) A redshift with further gamma-ray irradiation doses from 200 to 1000 kGy. This redshift can be ascribed to irradiation-induced defects in polymer material. (ii) A remarkable increment in the optical absorbance for irradiated Makrofol DE 1-1 specimens compared to the pristine one. This increment can be ascribed to the creation of some electronic levels within the forbidden gap resulting from the irradiation process. Moreover, this absorbance increment was employed to assess the degradation percent produced by gamma-ray irradiations. The degradation percent of the Makrofol DE 1-1 increased from 31.73% at 200 kGy to 78.08% at 1000 kGy. The optical band gap, Fermi level and metallization criterion showed decrement behaviors with further doses of gamma-ray irradiations. Also, the percent of changes in optical band gap values were employed to evaluate the degradation of Makrofol DE 1-1 under gamma-ray irradiations. This percent augmented from 15.19% at 200 kGy to 20.25% at 1000 kGy proving the obvious degradation of Makrofol DE 1-1 under gamma-ray irradiations. On the other hand, the number of carbon atoms per cluster, linear and nonlinear refractive indices showed increasing behaviors with further doses of gamma-ray irradiations.     

Partially hydrolyzed polyacrylamide–poly(N-vinylpyrrolidone) copolymers as superabsorbents synthesized by gamma irradiation

Partially hydrolyzed polyacrylamide-co-poly(n-vinyl pyrrolidone) used as a superabsorbent was prepared from acrylamide monomers exposed to γ-rays to become polyacrylamide that was subsequently partially hydrolyzed and was then copolymerized with n-vinylpyrrolidone to obtain a terpolymeric superabsorbent with a water retention value of 1100 times its dried weight. The total dose and dose rate along with the appropriate degree of hydrolysis were investigated for percentage conversion in each polymerization and the extent of water absorption. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:191–203, 1998     

Effect of gamma irradiation on structural,morphological and optical properties of thermal spray pyrolysis deposited CuO thin film

This study reports the influences of gamma irradiation (GI) in the range of 20–100 kGy on CuO thin films via thermal spray pyrolysis technique on the glass substrates. The results demonstrate significant influences of GI on the crystallographic, microstructural and optical characteristics of CuO thin films. The obtained XRD results showed that the crystallinity of the films deteriorates by gradually decreasing crystallite size (from 59.13 to 46 nm) as applied gamma doses increases. However, the basic monoclinic crystal structure remains same. The dislocation density and lattice strain increased with the rise of GI absorbed dose due to the creation of defects. The values of number of crystallites per unit surface area increased as dose increased indicating the abundance of crystallization of nano CuO thin films. A UV–Vis–NIR spectrophotometer was utilized to determine the optical properties and obtained results indicated that the optical energy band gap (OBG) energies reduced from 2.00 to 1.72 eV as the doses increased from 0 to 100 kGy. No distinctions of the monoclinic phase of virgin CuO thin film have been perceived under applied absorbed doses, notwithstanding the slight deterioration of the crystallinity and narrowing the OBG.     

Effect of gamma irradiation on the interpenetrating networks of gelatin and polyacrylonitrile: Aspect of crosslinking using microhardness and crosslink density measurements

The present article reports the effect of gamma irradiation on the hardness behavior of the interpenetrating polymer networks (IPNs) of gelatin and polyacrylonitrile (PAN). Various compositions of gluteraldehyde‐crosslinked gelatin and N, N′‐methylene bis acrylamide (MBA)‐crosslinked PAN were prepared and investigated for microhardness studies. The pre‐ and post‐irradiated IPNs were characterized for their crosslinking density, determined with swelling ratio measurements. It was found that the crosslinked IPNs get further hardened because of radiational hardening at specific doses in the range from 2 to 250 kGy. The role of acrylonitrile and crosslinker (MBA) in the IPNs, as a consequence of irradiation, has also been explained. A fair consistency has been observed between the microhardness results and crosslinking density measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2581–2586, 2006     

Study on antibacterial activity of silver nanoparticles synthesized by gamma irradiation method using different stabilizers

Colloidal solutions of silver nanoparticles (AgNPs) were synthesized by gamma Co-60 irradiation using different stabilizers, namely polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), alginate, and sericin. The particle size measured from TEM images was 4.3, 6.1, 7.6, and 10.2 nm for AgNPs/PVP, AgNPs/PVA, AgNPs/alginate, and AgNPs/sericin, respectively. The influence of different stabilizers on the antibacterial activity of AgNPs was investigated. Results showed that AgNPs/alginate exhibited the highest antibacterial activity against Escherichia coli (E. coli) among the as-synthesized AgNPs. Handwash solution has been prepared using Na lauryl sulfate as surfactant, hydroxyethyl cellulose as binder, and 15 mg/L of AgNPs/alginate as antimicrobial agent. The obtained results on the antibacterial test of handwash for the dilution to 3 mg AgNPs/L showed that the antibacterial efficiency against E. coli was of 74.6%, 89.8%, and 99.0% for the contacted time of 1, 3, and 5 min, respectively. Thus, due to the biocompatibility of alginate extracted from seaweed and highly antimicrobial activity of AgNPs synthesized by gamma Co-60 irradiation, AgNPs/alginate is promising to use as an antimicrobial agent in biomedicine, cosmetic, and in other fields.     

Characterization of electron beam irradiated polypropylene: Influence of irradiation temperature on molecular and rheological properties

The aim of the investigations was to analyze the influence of the temperature during the irradiation process of polypropylene on the molar mass, the formation of long chain branching and the final branching topology. A linear isotactic polypropylene homopolymer was modified by electron beam irradiation at different temperatures, with two irradiation doses to insert long chain branching. The samples were analyzed by size exclusion chromatography coupled with a multiangle laser light scattering detector, by differential scanning calorimetry, and by shear and elongational rheology. The shear and elongational flow behavior is discussed in terms of the influence of molecular parameters and used to analyze the topology of the irradiated samples. With increasing temperature, a slight reduction of the molar mass, an increase of long chain branching and an increase of crystallization temperature were found. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2770–2780, 2006     

Preparation of high sensitive colorimetric sensing film for detection of iron ions using gamma irradiation

ABSTRACT

Poly(vinyl alcohol)/2–poly(hydroxyethylmethacrylate)/tannic acid (PVA/PHEMA/TA) sensor film was prepared by gamma irradiation. The optimum irradiation dose for preparation is 10 kGy and 1wt% of TA concentration. The film has suitable water uptake and the equilibrium is obtained at 300 min where the water uptake is 98%. The colorimetric sensing of (PVA/PHEMA/TA) film towards Fe(III) was investigated. It was found that when the film was exposed to a Fe(III) solution 50 mg/L the film color turned rapidly from colorless to black after 1 min. The color intensity increased with increasing Fe(III) concentration in the solution. A remarkable change in color was observed at pH 4.5 and 6.2 due to the association of carboxylate anion that can chelate Fe(III). It was found that the activity of (PVA/PHEMA/TA) sensor towards Fe(III) remained ~ 100% after seven repeated cycles. (PVA/PHEMA/TA) sensor film and PVA/PHEMA/TA-Fe(III) complex film were characterized by using (FTIR) and (SEM).     

Formation of blisters in kapton polymer by the effect of 1.25 MeV gamma irradiation

The surface morphology, chemical, optical, and structural response of 1.25 MeV gamma rays irradiation at various doses ranging from 16 to 300 kGy on Kapton polymer samples were studied by using scanning electron microscope (SEM), Fourier Transform Infrared (FTIR), ultraviolet/visible absorption (UV/VIS) and X‐ray diffraction (XRD). The morphology study shows the blisters formation on the Kapton polymer surface due to 1.25 MeV gamma rays irradiation at ambient temperature. This observation provides a basis for the quantitative evaluation of FTIR results obtained for thermally stable polymer on the chemical bond deterioration with increasing gamma irradiation. The blistering mechanism is correlated with the internal gases (CO, H₂) released due to gamma radiation induced damages. The recorded UV–VIS spectrum shows a maximum absorption around the wavelength 540 nm. However, the nature of the spectra does not change due to gamma irradiation but a shift in absorption edge towards the higher wavelength side has been observed with increasing dose. The optical data shows an increase in the calculated band gap at the highest dose. The diffraction pattern of virgin sample shows that polymer is semicrystalline, but due to irradiation, a decrease in the peak intensity and FWHM and an increase in the crystallite size at the highest dose level of 300 kGy have been observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effect of some fluoropolymers' structures on their response to UV irradiation

The response of three commercial fluoropolymer films, untreated and γ-irradiated poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVDF), and poly(ethylene-co-tetrafluoroethylene) (ETFE), to ultraviolet (UV) irradiation was studied. The changes in tensile properties, thermal behavior, and chemical structure were investigated. The UV resistance of the PVF film is the lowest, and that of ETFE is the highest among the studied films. The biaxially oriented PVF films undergo massive chain scission under the UV irradiation. The chain scission process in both oriented PVF and PVDF films, although at different levels, is accompanied by increased solubility, increased upper glass transition temperatures, and decreased elevated temperature shrinkage. The UV exposure at 50°C, above the polymers' T_g has annealing effects, mainly reflected by a shift to higher temperatures of their upper glass transition. PVF films are unaffected by a low-dose ionizing radiation. However, the γ-irradiated films show reduction of their UV resistance. PVDF films undergo both chain scission and crosslinking by γ radiation, and the addition of UV exposure mainly causes further chain scission. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1471–1481, 1998     

The effect of microwave irradiation on poly(vinyl alcohol) dissolved in ethylene glycol

Poly(vinyl alcohol) (PVA) dissolved in ethylene glycol is subjected to microwave (MW) irradiation for 1 h to determine possible degradation. Fourier transform infrared spectroscopy results show that MW treatment produces a minor effect on the solutions. Ultraviolet–visible spectroscopy suggests that PVA could undergoes loss of hydroxyl groups followed by formation of unsaturated conjugated bonds although the extent of degradation is limited, whereas size exclusion chromatography indicates that MW irradiation do not cause significant changes in PVA molar mass and neither chain cleavage nor crosslinking reactions are observed. Hence, polymer degradation induced by MWs in solution can be considered as negligible for prospective applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effect of phase transition of methanol on the reaction rate in the alkylation of hydroquinone

An O-alkylation reaction of hydroquinone with excess methanol was carried out by using alkaline metal ion-exchanged zeolite catalysts at various phases of methanol in a slurry type reactor. The amount of methanol, used as a methylating agent and also a solvent, significantly affected the reaction rate. When the amount of methanol was decreased from 2 mol to 0.6 mol, the reaction rate was increased more than nine times. These changes in the reaction rate could be explained by the pressure change and the phase transition of the reactant, methanol, depending on the temperature and the elimination of a diffusion limitation of reactants through the zeolite pores in a gas phase condition. Thus, higher than 89% selectivity to 4-methoxyphenol was obtained at 80% conversion of hydroquinone at a gas phase reaction condition using 1 mol of methanol for 2 hours.     

环氧树脂室温固化体系的研制及性能研究

以兼具引发剂和稀释剂功能的自制BH-1为固化剂,通过引入低黏度活性稀释剂,制备室温固化EP(环氧树脂)胶粘剂;然后以EP/BH-1/活性稀释剂为基体、单向玻璃纤维为增强材料,制备相应的复合材料。研究结果表明:当w(BH-1)=4%时,EP浇铸体的室温(25℃)凝胶时间约为8.5 h和玻璃化转变温度(Tg)为130.9℃,并具有优异的力学性能,其冲击强度为50.0 kJ/m2、拉伸强度和模量分别为0.075 GPa和2.80 GPa、弯曲强度和模量分别为0.136 GPa和3.02 GPa;当m(EP)∶m(BH-1)∶m(活性稀释剂)=100∶4∶10时,复合材料的弯曲强度(0.984 GPa)和层间剪切强度(56.1 MPa)分别提高了26.4%和15.2%。     

Co γ-Initiated polymerization of vinyl monomers in room temperature ionic liquid/THF mixed solutions

Radiation induced polymerization of styrene (St), methyl methacrylate (MMA) and n-butyl methacrylate (BMA) is carried out in a room temperature ionic liquid (RTIL), [Me₃NC₂H₄OH]⁺[ZnCl₃]⁻, and in its mixed solutions with THF. The presence of ionic liquid (IL) leads to a significant increase in monomer conversion and polymer's molecular weight. Molecular weight distribution (MWD) of resulting polymer varies with the IL fraction in the RTIL/THF solutions and is also dependent on the monomer used. For polystyrene (PSt) and poly(n-butyl methacrylate) (PBMA), multi-modal broad MWD is observed at IL >50 v% while single-modal narrow MWD is observed at IL <40 v%. For poly(methyl methacrylate) (PMMA), however, nearly a single-modal MWD is observed at THF >20 v%. The measured miscibility of polymer with RTIL is in the order: PMMA>PBMA>PSt. Here we propose that the difference in MWD is due to the inhomogeneous nature of the ionic liquid in micro-region and the immiscibility of polymer with medium.     

Structure of trickle-to-pulse flow regime transition and pulse dynamics at elevated temperature in slow-mode cyclic operation

The effects of temperature and pressure on the structure of the trickle-to-pulse flow regime transition in slow-mode cyclic operation in trickle-bed reactors were reported. The relationship between liquid holdup and liquid velocities at the trickle-to-pulse flow transition in cyclic operation, the shock wave behavior as a function of bed depth, as well as the pulsing flow regime properties were investigated for Newtonian (air-water) and non-Newtonian (air-0.25% carboxymethylcellulose (CMC)) liquids. At a given temperature, the breakthrough, plateau and decay times of the shock wave were found to decrease with bed depth. The pulse velocity and pulse frequency for pulsing flow regime both in cyclic operation and in natural pulsing (constant-throughput operation) were observed to increase with temperature. However, increasing the reactor pressure led to increased pulse frequency and decreased pulse velocity. Analysis of the transition liquid holdups for natural pulse flow and cyclic operation revealed that the liquid holdup decreased with temperature and pressure. The transition liquid holdups and superficial liquid pulse velocities in symmetric peak-base cyclic operation surpassed those in constant-throughput operation for given temperature, pressure and gas velocity, giving rise to wider trickle flow regime area in cyclic operation. The behavior of both Newtonian and power-law non-Newtonian fluids was similar regarding the effect of temperature, pressure and gas velocity.     

室温自交联功能单体N,N'-二双丙酮丙酰胺基乙二胺的合成与应用

利用乙二胺与双丙酮丙烯酰胺间的Michael加成反应合成了含酮羰基的新型扩链剂N,N'-二双丙酮丙酰胺基乙二胺,用¹H NMR和¹³C MNR证实了结构。聚己二酸新戊二醇酯、异佛尔酮二异氰酸酯(IPDI)、二羟甲基丙酸(DMPA)预聚后加入N,N'-二双丙酮丙酰胺基乙二胺扩链得到含酮聚氨酯预聚物,预聚物经分散、乙二胺扩链后得到聚氨酯分散体。研究了含酮扩链剂用量对分散体及其膜性能的影响。结果表明随N,N'-二双丙酮丙酰胺基乙二胺的增加,聚氨酯分散体的粒径增大、黏度减小。己二酸二酰肼交联后能明显提高WPU胶膜的力学性能。     

Change of the properties of nanostructured MoO3 thin films using gamma-ray irradiation

Thin films of Molybdenum trioxide (MoO₃) were deposited on glass substrates by the spray pyrolysis at 500?°C and the samples were then exposed to gamma γ radiation doses by ⁶⁰Co radioisotope at different doses (0.1, 10 and 50 kGy). The effects of gamma irradiation on the properties of MoO3 thin films were investigated. The XRD pattern and Raman spectroscopy of as-deposited MoO₃ samples show an orthorhombic structure related to α-MoO₃ with (0k0) preferred orientations. Uv‐vis spectra were studied to investigate the transmission measurements of MoO₃ films. The optical energy band gap and Urbach energy were found to be gamma-dose dependent. Photoluminescence measurements at room temperature using 300?nm wavelength excitation were investigated. SEM images indicate the formation of α-MoO₃ nanorods.     

化学镀镍金及其温度的影响

介绍了化学镀镍金工艺流程和工艺控制,探讨了温度对镀层沉积速率、渗金漏镀、镀层厚度的影响。提出选用高精度、高灵敏度、温度场更均匀的恒温控制设备可以显著提高化学镀镍金的品质。     

The effect of benzenesulfonamide plasticizers on the glass transition temperature of an amorphous aliphatic polyamide

The plasticizing effect of benzenesulfonamides (BSAs) on an amorphous aliphatic polyamide (AAPA) has been studied using dynamic mechanical analysis of copper‐supported spin‐coated mixtures. It follows that N‐(n‐butyl)BSA (BBSA), an amorphous liquid hydrogen bonding BSA, is fully miscible with AAPA because their mixtures are characterized by a single glass transition (T_g) throughout the compositional range. The T_g–composition dependence, however, is not linear because experimental results suggest a 20 K fall in T_g occurring around 0.65 BBSA units per amide unit, which coincides with the system shifting from a polymer‐like to a liquid‐like glass‐forming material. When considering a crystallizable hydrogen‐bonding plasticizer such as ethylBSA (EBSA), AAPA/EBSA mixtures become fully crystalline at a 1.3 EBSA unit per amide group. Nevertheless, melting point depression together with the single T_g observed throughout the compositional range on quenched (and therefore amorphous) samples confirms the miscibility of AAPA chains with the plasticizer. N,N‐DialkylBSAs, which lack the sulfonamide proton and therefore the possibility of hydrogen bonding with amide groups, quickly phase separate from AAPA, the glass transition of the latter staying mainly unaffected apart from a small (9 K) decrease at 10–15 mol% plasticizer. © 2001 Society of Chemical Industry