Authors:S. Cheng, J. Tseng, S. Lin, J. Gupta, and C. Shu
Tert-butyl peroxybenzoate (TBPB) is one of the sensitive and hazardous chemicals which have been popularly employed in petrifaction
industries in the past. This study attempted to elucidate its unsafe characteristics and thermally sensitive structure so
as to help prevent runaway reactions, fires or explosions in the process environment. We employed differential scanning calorimetry
(DSC) to assess the kinetic parameters (such as exothermic onset temperature (T0), heat of reaction (ΔH), frequency factor (A)), and the other safety parameters using four different scanning rates (1, 2, 4 and 10°C min−1) combined with curve-fitting method.
The results indicated that TBPB becomes very dangerous during decomposition reactions; the onset temperature and reaction
heat were about 100°C and 1300 J g−1, respectively. Through this study, TBPB accidents could be reduced to an accepted level with safety parameters under control.
According to the findings in the study and the concept of inherent safety, TBPB runaway reactions could be thoroughly prevented
in the relevant plants.
A method of elemental analysis based on the detection of prompt γ-rays produced by the inelastic scattering of fast monoenergetic
neutrons has been investigated. Time-of-flight discrimination techniques and the use of Ge(Li) detectors provide significant
advances over previous studies. This method is multielemental, non-destructive, and essentially free of interferences and
matrix effects. Sample analysis is rapid and selective excitation of various elements is possible. Many elements have been
examined by this technique and minimum detection limits have been established. This method has been applied to the analysis
of metal alloys.
Authors:X. Zeng, Y. Chen, S. Cheng, X. Meng, and Q. Wang
A novel method for the determination of rate constants of reactions, the time-variable method, is proposed in this paper. The method needs only three time points (t), peak heights () and pre-peak areas (), obtained from the measured thermoanalytical curve. It does not require the thermokinetic reaction to be completed. It utilizes data-processing on a computer to give the rate constants. Four reaction systems, including a first-order reaction, second-order reactions (with equal concentrations and with unequal concentrations) and a third-order reaction, were studied with this method. The method was validated and its theoretical basis was verified by the experimental results.
Authors:T. Cheng, J. Morris, S. Koirtyohann, V. Spate, and C. Baskett
Toenail samples were collected from 129 carpenters (average age 47). The bone and blood lead data for these carpenters have shown a broad range of lead-level exposure in this population. A total of 28 elements were measured in the sample set by a combination of instrumental neutron activation analysis (INAA) and graphite furnace atomic absorption spectrometry (GFAAS) methods. Of the elements measured, only Co, Cr, Fe, Na, Cd, Cu, F, and Ni were significantly correlated with lead. A statistical treatment of the overall data set, including principal component analysis, was further applied in an attempt to correlate the elements in the samples.
Authors:Y. Chou, J. Huang, J. Tseng, S. Cheng, and C. Shu
Organic peroxides have caused many serious explosions and fires that were promoted by thermal instability, chemical pollutants,
and even mechanical shock. Cumene hydroperoxide (CHP) has been employed in polymerization and for producing phenol and dicumyl
peroxide (DCPO). Differential scanning calorimetry (DSC) has been used to assess the thermal hazards associated with CHP contacting
sodium hydroxide (NaOH). Thermokinetic parameters, such as exothermic onset temperature (T0), peak temperature (Tmax), and enthalpy (ΔH) were obtained. Experimental data were obtained using DSC and curve fitting using thermal safety software (TSS) was employed
to obtain the kinetic parameters. Isothermal microcalorimetry (thermal activity monitor, TAM) was used to investigate the
thermal hazards associated with storing of CHP and CHP mixed with NaOH under isothermal conditions.
TAM showed that in the temperature range from 70 to 90°C an autocatalytic reaction occurs. This was apparent in the thermal
curves. Depending on the operating conditions, NaOH may be one of the chemicals or catalysts incompatible with CHP. When CHP
was mixed with NaOH, the T0 is lower and reactions become more complex than those associated with assessment of the decomposition of the pure peroxide.
The data by curve fitting indicated that the activation energy (Ea) for the induced decomposition is smaller than that for decomposition of CHP in the absence of hydroxide.
Authors:L. Wu, K. Chen, S. Cheng, B. Lee, and C. Shu
Hydrogen peroxide (H2O2) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By
using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition
reaction of H2O2 mixed with sulfuric acid (H2SO4) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic
onset temperature (T0), heat of decomposition (ΔHd), pressure rise rate (dP/dt), and self-heating rate (dT/dt), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations
of H2SO4, the experimental data of T0, ΔH, dP/dt, and dT/dt were obtained. Comparisons of the reactivity for H2O2 and H2O2 mixed with H2SO4 (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems.
Authors:Y. Wang, S. Feng, X. Feng, Y. Lei, L. Cheng, Q. Xu, Z. Zhuo, and D. Xue
Yaozhou Kiln at Lidipo and Shangdian are two independent porcelain kiln groups of Yaozhou kiln series in Shanxi Province.
Both of them were consisted of some individual porcelain kilns. The samples of 20 pieces of porcelain sherds produced in Shangdian
and 43 pieces of porcelain sherds made in Lidipo sites which produced in Kin Dynasty (1115–1234 A.D.) have been collected.
The main chemical compositions in body were determined by X-ray fluorescence (XRF). The contents of trace elements were measured
using neutron activation analysis (NAA). Principal component analysis (PCA) and stepwise discriminant analysis were used to
study the provenance characteristic of these samples. The results indicated that the main components and trace elements in
the specimen can be used to reveal the provenance characteristic.
Authors:S. Yu, A. Ren, J. Cheng, X. Song, C. Chen, and X. Wang
Effects of pH, ionic strength and fulvic acid on sorption of radiocobalt on montmorillonite and its Al-pillared and cross-linked
samples were studied using batch technique. The results indicate that the sorption of cobalt is strongly dependent on pH values
and independent of ionic strength. Fulvic acid enhances the sorption of cobalt slightly at low pH, but has no influence at
high pH values. Surface complexation is considered the main mechanism of cobalt sorption to montmorillonite. The sequences
of FA/Co2+ additions to the system did not affect cobalt sorption.
Authors:G. Zhang, X. Li, S. Tian, J. Li, J. Wang, X. Lou, and Q. Cheng
The stability of β-cyclodextrinethyl benzoate6H2O(β-CDC6H5COOC2H56H2O) was investigated by TG and DSC. The mass loss takes place in three stages: the dehydration occurs at 50-120C; the dissociation
of β-CDC6H5COOC2H5occurs at 200-260C; the decomposition of β-CD begins at 280C. The kinetics of the dissociation of β-CDC6H5COOC2H5in a dry nitrogen flow was studied by means of thermogravimetry both at constant temperature and linearly increasing temperature.
The results show that the dissociation of β-CDC6H5COOC2H5is dominated by a three-dimensional diffusion process (D3). The activation energy E is 116.19 kJ mol-1and the pre-exponential factor A 6.5358109min-1.
Cyclodextrin is able to form inclusion complexes with a great variety of guest molecules, and the studies focus on the energy
of binding between cyclodextrin and the guest molecule. In this paper, the β-cyclodextrinethyl benzoate inclusion complex
was studied by fluorescence spectrophotometry and infrared absorption spectroscopy, and the results show that the stable energy
of inclusion complexes of β-CD with weakly polar guest molecules consists mainly of van der Waals interaction.