Display omitted
•A high entropy interlayer (TiZrHfNb)95Al5 was successfully designed for diffusion bonding of GH4169 to Ti2AlNb.•The relationships between grain characteristics, lattice mismatch and ...mechanical properties, fracture mechanisms were revealed.•The major cracks located at the elastic modulus dramatically changed interface, i.e., the no-coherent interface.•The highest shear strength reached 384 MPa at 980 °C for 90 min.
A high entropy interlayer (TiZrHfNb)95Al5 was successfully designed for vacuum diffusion bonding of GH4169 superalloy to Ti2AlNb alloy. The relationships between grain size, grain boundary, lattice mismatch and microhardness, elastic modulus, shear strength and fracture behaviors were revealed. The typical microstructure was Ti2AlNb/B2/Solid solution/(Ti, Zr, Hf)2(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb) + Solid solution/(Ti, Zr, Hf)(Ni, Nb) + (Cr, Ni, Fe)ss/(Cr, Ni, Fe)ss/Cr-rich(Cr, Ni, Fe)ss/Ni-rich(Cr, Ni, Fe)ss/GH4169. With the holding time increased, the shear strength overall increased and decreased sharply, and the highest shear strength reached 384 MPa at 980 °C for 90 min. The microstructure had anisotropic crystal orientation, and the joints of Zone Ш for 90 min consisted of 92.08 % HAGBs and 7.92 % LAGBs. The residual strains and stresses decreased when the holding time increased. Meanwhile, recrystallisation appeared in Zone Ш, and the increase in the recrystallisation rate led to grain refinement. The lattice mismatch between (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe)ss phases was 25.05 %, indicating that the interface was non-coherent, and (Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe)ss phases were located at an elastic modulus dramatically changed interface. Thus, the cracks easily formed in this interface and led to joint fracture. Moreover, the fracture mechanism was brittle fracture.
This paper prepared cBN-Ti and cBN-Ti-Al system composites by high-temperature and high-pressure method using cubic boron nitride powder, titanium powder, and aluminum powder as raw materials. The ...phase composition, microstructure, and mechanical properties of the two systems based on varying holding time and synthesis pressure were studied and analyzed. The results showed that when the holding time was <480 s, the mechanical properties of the composites worsened for the intermediate products remained. The composites of the cBN-Ti and cBN-Ti-Al systems exhibited their highest bending strengths of 779 MPa and 957 MPa, respectively, after being held for 480 s. Both composites' hardness and bending strength increased as the synthesis pressure increased. At a synthesis pressure of 6 GPa, the hardness and bending strength of the cBN-Ti system composite were 33.3 GPa and 804 MPa, respectively. Similarly, the cBN-Ti-Al system composite showed a hardness of 33.3 GPa and a bending strength of 994 MPa at the same pressure.
•Brief holding time may limit intermediate product involvement in the reactions.•Improving synthesis pressure is crucial for improving the hardness and strength.•The cBN-Ti-Al system has better mechanical properties than the cBN-Ti system.
Herein, alumina green bodies are fabricated by three dimensional (3D) printing technology, then, the influence of debinding holding time under vacuum and argon on mechanical properties is ...systematically investigated by comparing the changes in microstructure, bulk density, open porosity, grain connection situation and flexural strength of ceramics. The flexural strength of alumina ceramics acquired the maximum values of 26.4 ± 0.7 MPa and 25.1 ± 0.5 MPa after debinding under vacuum and argon for 120 min and 180 min, respectively. However, the alumina ceramics rendered the flexural strength of 19.4 ± 0.6 MPa and 9.5 ± 0.4 MPa under vacuum and argon without extended holding time, respectively. The relatively low mechanical properties can be mainly attributed to the weak interlayer binding force, which is caused by layer-by-layer forming mode during 3D printing process and anisotropic shrinkage during the sintering process. Moreover, the alumina ceramics exhibited moderate bulk density and open porosity of 2.4 g/cm3 and 42% after the sintering process, respectively, which are mainly influenced by the microstructural evolution of alumina ceramics during thermal treatment. Also, the diffusion of gases is achieved by curing of photosensitive resin and influenced by different holding times during debinding, affecting the mechanical properties of sintered ceramics. The mechanical properties of as-sintered ceramics are suitable for the utilization of ceramic cores in the manufacturing of hollow blades.
During runoff process, the urban road dust (URD) passes through the road-side gutters and detention tanks, where it gets hold for a certain period of time, hours to weeks, before making its way into ...the water bodies. A part of the water-exchangeable toxicants are leached by the water, and some strongly bound toxicants remain attached to the URD. Toxicity of urban runoff is dependent on holding time, water volume, and the type and composition of the wet road dust (WeRD) and leachate. However, there are no studies that have elucidated the manner in which toxicities of the WeRD and leachate vary during prolonged holding in the runoff processes. The main objectives of this research were to, i) identify the distribution of toxicants in the WeRD and leachate, and ii) evaluate the change in toxicity during prolonged holding. The URD samples that were collected from residential road, arterial road and highways in Tokyo, Japan, were mixed with moderately hard water in varying ratios (1:2 to 1:16) and were held for a certain time (1h to 5days) before centrifuging into the WeRD and leachate. Toxicity test was conducted with ostracod Heterocypris incongruens direct contact test. Toxicity of both the WeRD and leachate from residential area was not significantly greater than the 20% lethal limit. Toxicity of the WeRD from other stations initially decreased, further reached a minimum corresponding to the critical holding time, and it subsequently increased again. Toxicity of the arterial leachate gradually increased, whereas that of the highway leachate gradually decreased during 5days holding. Unionized ammonia and zinc were confirmed as one of the possible toxicants. This study proposes and verifies a model for the toxicity change of the WeRD during prolonged holding.
Display omitted
•Toxicity change of road dust during runoff process is elucidated.•Toxicity of wet road dust (WeRD) decreased initially and gradually increased.•Unionized ammonia and Zinc were confirmed as one of the toxicants.•Model for the toxicity change of the WeRD during prolonged holding is proposed and verified.
The inorganic solid electrolytes Li6.25-xAl0.25La3Zr2-xTaxO12 (LALZT) with various Ta contents (x) are synthesized using conventional solid-state reaction method at 1200 °C for different holding ...times. The effect of holding time and Al/Ta co-doping on the crystal structure, microstructure and ionic conductivity of the LALZT solid electrolytes is discussed. The LALZT powder with a fine particle size and narrow particle distribution is prepared by the high-energy ball milling. Suitable Al/Ta doping stabilizes the cubic phase and enhances the ionic conductivity of the LALZT. The short holding time is 6 h due to the equal ionic conductivity for the LALZT samples sintered for 6 h or 10 h by the solid-state reaction method. The highest ionic conductivity can be obtained for the optimized composition of Li5.85Al0.25La3Zr1.6Ta0.4O12. The excellent ionic conductivity indicates that Al/Ta co-doped LALZT could be a promising electrolyte candidate for all-solid-state Li-ion batteries in practical application.
Display omitted
•Cubic-phase LALZT powder shows a fine particle size and narrow particle distribution.•The optimized holding time is 6 h for the conventional solid-state method.•The optimized composition of Li5.85Al0.25La3Zr1.6Ta0.4O12 shows better ionic conductivity of 4.59 × 10-4 S cm-1 at 20 °C.
The relationship of functional parameters such as lung mechanics, chest kinematics, metabolism and peripheral and respiratory muscle function with the level of exercise tolerance remains a ...controversial subject. While it has been previously shown that pulmonary rehabilitation is capable of improving exercise tolerance in patients afflicted by COPD, as expressed by values of 6-minute walking test (6MWT), the degree of contribution to this change by each of the aforementioned parameters remains unclear.
To investigate the correlation between changes in exercise capacity and other functional markers following pulmonary rehabilitation in COPD and to determine which parameters are more closely related to improvements of exercise tolerance.
Three hundred and twenty-seven patients with COPD (with average, 95% CI for forced expiratory volume in the first second FEV
: 45% 25%-83% predicted, age: 64 48-80 years, and BMI: 27 13.5-40.4 kg/m
) participated in this study. Thirty percent of the patients had pulmonary hypertension as comorbidity. Patients underwent a pulmonary rehabilitation program with 20-30 minutes sessions two to three times per day for 4 weeks. The program was composed of chest wall-stretching, controlled breathing exercises, and a personalized training schedule for cycling and treadmill use. Measurements of 6MWT, lung function, chest wall expansion, grip strength, maximal inspiratory pressure, and breath holding time were taken. The Body mass index, airflow Obstruction, Dyspnea and Exercise capacity (BODE-index), body mass index BMI, FEV
, 6MWT, modified Medical Research Dyspnea Scale score, and an alternative scale score (for BMI, FEV
, 6MWT, and COPD Assessment Test) were calculated.
Rehabilitation resulted in a generalized improvement in 6MWT among patients (average: 360 95% CI: 178-543 m vs average: 420 95% CI: 238-601 m,
<0.05). Improvements in exercise tolerance were found to be most closely associated with changes in composite BODE-index (
=-0.6), Alternative Scale (
=-0.56), dyspnea score (modified Medical Research Dyspnea Scale
=-0.54), and health status (COPD Assessment Test
=-0.4,
<0.05). In addition, improvements in exercise tolerance were found to moderately correlate with improvements in inspiratory vital capacity (IVC,
=0.34,
<0.05). Post-rehabilitation changes in IVC displayed a connection with grip strength (
=0.6) and chest expansion (
=0.48).
Enhancements in exercise tolerance had correlation with changes in IVC, BODE-index, and the new Alternative Scale. However, comprehensive assessment needs to include considerations of chest kinematics and peripheral and respiratory muscle function as well.
Pruned apple tree branches are abundant and ideal raw material for biomass carbonization due to less ash. It would provide valuable guide to study the effect of carbonization conditions on the ...biochar characteristics for high-efficiency energy utilization of pruned branches. In this study, we systematically investigated the effects of carbonization conditions on yield and fixed carbon content by using the reaction temperature, heating rate, and holding time as factors in an experiment. The results were evaluated through a single-factor test and response surface analysis. Based on the results of single-factor experiments, the following conditions were determined to be appropriate for the carbonization of pruned apple tree branches: a temperature of 500 °C, heating rate of 4 °C/min, and holding time of 120 min. According to the central composite design test of the response surface methodology, the temperature, heating rate, and holding time had an extremely significant effect on yield and fixed carbon content. The effects of the main factors influencing yield decreased in the order temperature > holding time > heating rate, whereas that on the fixed carbon content was temperature > heating rate > holding time. In the range of the factor levels studied, the interaction between temperature and holding time has a significant effect on yield and an extremely significant effect on the fixed carbon content. The interactions between pairs of the other factors did not significantly affect the yield or fixed carbon content.
Display omitted
•Pruned apple trees branches are abundant and ideal raw material for biomass carbonization.•The appropriate carbonization conditions of pruned apple tree branches were determined.•The effects of interactions between factors on yield and fixed carbon content were analyzed.•This study provides valuable guidance for biochar production of pruned apple tree branches.
The effects of the current density and holding time on the densification and microstructure of flash-sintered (FS-ed) magnesium aluminate (MgAl2O4) ceramic discs were investigated. The results showed ...that the MgAl2O4 discs exhibited typical flash characteristics at a furnace temperature of 1350 °C and required a critical electric field of 6500 V/cm. Compared with pressureless sintering, the densification and grain growth were distinctly accelerated in the case of flash sintering. The relative density and grain size of the FS-ed samples increased with increasing current density and holding time; the relative density attained a value of 99.66% when the current density was increased to 50 mA/mm2 and the holding time was 150 s. Additionally, the grain sizes on the positive side were found to be larger than those on the negative side, and the microstructure gradients increased with an increasing holding time.
Most hydrogen is derived from fossil fuels. Therefore, more environmentally friendly methods for hydrogen production have been investigated. The present report describes a hot compressed water (HCW) ...pretreatment to increase hydrogen production using sake lees, which is an industrial waste of sake production. The inoculum is obtained from treated biogas slurry. The temperatures of HCW are 130 (0.3 MPa), 150 (0.5 MPa), and 180 °C (0.8 MPa) for 15–120 min. Gas production was analyzed using gas chromatography; fermentation liquid analyses were performed using HPLC. The modified Gompertz model was used to determine hydrogen potential, lag time, and production rate. Results show an increase in the degradation of sake lees with longer holding time and higher temperature. Total sugar and organic acids also are influenced by HCW pretreatment. The maximum hydrogen yield was obtained at 130 °C for 60 min with the result 112.07 mL H2/g COD. The HCW pretreatment successfully decreased the lag phase of biohydrogen production and increased the degree of acidification. Clostridium butyricum, C. acetobutylicum, and other Clostridium sp. were identified in all samples, while Pantoea agglomerans was detected in two samples.
•The Hot Compressed water (HCW) treatment increase biohydrogen production.•The high HCW temperature and long holding time increase the degradation rate.•HCW treatment lessen the lag time of fermentation & increase the acidification degree.•P. agglomerans and Clostridium sp. synergize in the biohydrogen fermentation.
In present paper, effect of holding time at 600 °C during the brazing cooling process on creep life of solid oxide fuel cell (SOFC) with bonded compliant seal (BCS) is investigated by the finite ...element method. The research indicates that creep crack initiation time in BCS structure increases significantly with the holding time increasing. Compared with that the traditional cooling method during the brazing process, the creep crack initiation time can be prolonged more than twice by the holding time of 150 h with the operating temperature of 600 °C, it increases from 14,949 h to 31,911 h. When the operating temperature is 800 °C, the creep crack initiation time of SOFC can hardly be affected if the holding time exceeds 10 h. Based on the creep damage analysis and considering the cost of the SOFC manufacturing process, it is recommended that the holding time should not be exceeded 300 h if the operating temperature is below 750 °C. And when the operating temperature is 800 °C, the recommended holding time should not be longer than 10 h. The research of the present paper can provide theoretical guidance for the long life manufacturing and reliability operation of SOFC.
•Effect of holding time in brazing process on creep life of SOFC is investigated.•Creep life of SOFC increases significantly with the holding time increasing.•Holding time should not exceed 300 h if the operating temperature is below 750 °C.•Recommend holding time is 10 h when operating temperature is higher than 800 °C.
PDF
