Heat Resistance Capacity Research Articles

Development of polymer/carbon nanotubes incorporated sustainable materials for manufacturing of autobrake pad

AbstractAlthough asbestos fiber is used for autobrake pad production due to its heat resistance capacity, it is associated with a challenge of health risk (cancerogenic in nature). This health risk associated with asbestos-based autobrake pads has presented polymeric materials as a better candidate for the application due to their eco-friendliness, lightweight, chemical inertness, easy of processing, etc. However, polymers are associated with low wear and low mechanical properties, which are vital properties for autobrake pads. Therefore, this study developed EP nanocomposites reinforced with a low content of carbon nanotubes (CNTs) and eggshell (ES) attached cow bone (CB) particles denoted as (ES@CB) as agro-waste/sustainable materials for the manufacturing of autobrake pads. The hybrid ternary nanocomposites were developed via solution mixing and casting. Scanning electron microscope (SEM) revealed the 1-D structure of the CNTs, and relatively spherical shapes of ES and CB particles, and microstructures of the developed nanocomposites. The nanocomposite showed a low coefficient of friction and a reduction in wear rate in the range of 1.14 × 10−4 mm3/Nm for pure EP to 5.45 × 10−6 mm3/Nm for EP/0.4wt%CNTs-10wt%ES@CB nanocomposite, while the elastic modulus and hardness increased from 1.84 GPa and 128.64 MPa for pure EP to 4.41 GPa and 252.88 MPa for EP/0.2wt%CNTs-20wt%ES@CB nanocomposite, respectively. The comparison of the wear response of the developed nanocomposites with the current asbestos-based brake pads show that the developed epoxy nanocomposites from agro-waste materials are potential option for the manufacturing of autobrake pads, which will ensure sustainability, health risk-free, and environmentally friendly.

One-step preparation and ablation behavior of ZrC-SiC-Si coating for nose-shaped ZrC/C composites with gradient pore structure by vapor silicon infiltration

To improve the ablation resistance of the nose-shaped ZrC/C composites with gradient pore structure (ZrC/CGS), a ZrC-SiC-Si coating was prepared by one-step vapor silicon infiltration. The bonding strength between the ZrC-SiC-Si coating and the ZrC/CGS composite was 21.2 MPa. The hardness and elastic modulus of the ZrC-SiC-Si coating were 1650.5 ± 30.5 HV and 176.7 ± 3.2 GPa. As the temperature increased from 200 to 1500 ℃, the CTE of the ZrC-SiC-Si coated ZrC/CGS composites increased from 4.9 × 10−6 K−1 to 6.18 × 10−6 K−1. After ablation for 40 s using oxyacetylene torch with a heat flux 2.4 MW/m2, the linear ablation rate of the ZrC-SiC-Si coated ZrC/CGS composites decreased by 54.8% compared with that of the ZrC/CGS composites, and it could be maintained at 97.4% of the original heat resistance capacity. The finite element simulation results showed that the residual thermal stresses at the coating/matrix interface were in the range of 10.7–20.2 MPa. After ablation for 40 × 3 s, the ZrC-SiC-Si coating failed.

Prediction of Machining Characteristics of Wire Electrical Discharge Machined Hastelloy-X using Artificial Neural Network

Due to extensive mechanical load bearing capability under high temperature and pressure, Nickel based super alloys are widely incorporated in aerospace and aviation industries in various sections like chemical, fuselage, engine, combustor components, etc. Hastelloy-X is a Ni-based super alloy consisting mainly Ni, Cr, Fe, Mo and Co, which has good corrosion and heat resistance capacity. Since Hastelloy-X is a difficult-to-machine material, a non-conventional Wire Electric Discharge Machining is used. This work aims at machining characteristics study of WEDM of Hastelloy-X and prediction of major machining performances using Artificial Neural Network (ANN). At first, full factorial design of experiments was set using Minitab which includes four input machining parameters namely pulse-on time (T-on), pulse-off time (T-off), wire feed (WF) and servo voltage (SV); kept at three levels; high, medium and low. Total 81 experimental runs were performed. After machining on WEDM, machining performances MRR (material removal rate) and SR (surface roughness) were measured. There after the neural network is trained in nntool in MATLAB to predict the MRR and SR. The predicted model has mean absolute percentage error (MAPE) of 6.371% for MRR prediction and 5.92% for SR prediction while the MSE (Mean Square Error) was found to be 0.389 and 0.129 for MRR and SR respectively. The trained network has training, validation and testing regression coefficient (R) values of 0.9756, 0.9916 and 0.9662 respectively. And the overall R value was 0.97746. After prediction, the samples with extreme values of actual and predicted outputs were studied for other machining responses like recast layer, surface cracks and kerf width. Out-turn of this research can be utilized for machining hard to machine materials in a high precision WEDM for different applications.

Experimental investigation of tensile properties in banana fibre composites

This paper proposed the methodology for investigating the tensile properties of banana fibre. For the high tensile strength, and good heat resistance capacity the banana fibre is preferred in garments and making yarn. The epoxy resin and extracted banana fibre were selected as the matrix and reinforced materials. The composites were produced with the various ratios of epoxy and banana fibre The present work spotlighted the study of mechanical properties of banana fibre/epoxy resin composite at 30%, 40% and 50% volume fractions of banana fibre and different fibre directions 00, 450 & 900. The mechanical property like tensile strength is experimentally evaluated. The results indicate the high tensile strength was achieved due to the proper ratio selection of banana fibre and epoxy resin.

Effect of Nano SiO2on Mechanical and Thermal Properties of Polymer Matrix Nanocomposites

ABSTRACT In this paper, the mechanical and thermal properties of epoxy/nano-SiO2 polymer composites have been investigated. The ultrasonic vibration-assisted hand layup process was used for the preparation of composites with different weight percent (1%, 2%, 3%, and 4%) of nano-SiO2 particles. The density of polymer composite has been calculated by both theoretical and experimental methods. The mechanical properties were measured by the tensile tests, hardness tests, impact tests, and flexural tests. For the evaluation of morphological analysis, field emission scanning electron microscopy, XRD, and FT-IR tests were performed. A heat deflection temperature test was also performed for testing the thermal characteristic of the polymer composites. The results indicate the improvement of mechanical, thermal, and morphological properties with increasing wt.% of nano-silica particles in polymer composites. The results of field emission scanning electron microscopy, X-RD, and FT-IR tests also show the enhancement of morphological and physical properties of the polymer matrix composites with the addition of nanoparticles. Heat deflection temperature tests have shown the improvement in heat resistance capacity of composites with high wt.% of nano-silica particles. The experimental results have shown improvement in tensile strength, hardness, and impact strength by 48%, 18%, and 64%, respectively. The heat deflection temperature improved up to 25%.

Ablation and heat insulation performances of nose-shaped ZrC-C composites with gradient pore structure

Nose-shaped ZrC-C composites with gradient pore structure (ZrC-CGS) were successfully prepared by isothermal chemical vapor infiltration using ZrC skeleton as preform. Pyrolytic carbon with medium texture was deposited around ZrC skeleton. From the top to back, the porosity of the ZrC-CGS composites increased gradually from 0% to 62.9%. Compared with the ZrC-C composites with dense structure (ZrC-CDS), the mass ablation rate of the ZrC-CGS composites decreased by 15.3% and the heat resistance capacity increased by 45.6%, and their coefficients of thermal expansion decreased obviously in the temperature range of 200–1500 °C. The simulation results showed that the residual thermal stress and back temperature of the ZrC-CGS composites are lower than those of the ZrC-CDS composites. This work provides an effective strategy for designing and preparing ultra-high temperature composites having both ablation and heat insulation performances by controlling the pore structure and distribution.

Thermal characterizations of basalt fiber-reinforced poly(aryl-ether-ketone) biomedical composites

This research article deals with the development and characterization of poly(aryl-ether-ketone) (PAEK) reinforced with 10 mass%, 20 mass% and 30 mass% of basalt fibers; the samples are titled as PABA 1, PABA 2 and PABA 3, respectively. The composite samples are prepared by hot compression molding process, and test specimens are prepared to ASTM standards. The prepared specimens are subjected to various thermal analyses. The results reveal that differential scanning calorimetry curve shows high crystallization temperature and melting enthalpy for 20 mass% basalt fiber in PAEK composite compared to other composites. The percentage of crystallinity is also higher, which indicates the purity of PABA 2. The same composite shows low mass loss with increase in degradation temperature in the thermogravimetric analysis, due to high heat resistance capacity and thermal barrier of PAEK/basalt fiber at this particular mass%. Dynamic mechanical analysis of 20 mass% basalt fiber PAEK composite shows better storage modulus and low loss modulus compared to 10 and 30 mass% basalt fiber/PAEK composites. The PABA 2 composite has minimum damping coefficient which indicates better stiffness and suitability for high-performance applications. The scanning electron microscope images show a good affinity between the matrix and the fiber in all the composites. Agglomeration of fibers in matrix is observed when loaded beyond 20 mass%; this may be due to lack of melt flow during hot compression.

Investigation on the accurate calculation of the temperature field of permanent magnet governor and the optimization method of heat conduction

Since the heat resistance capacity of permanent magnet governor's key components is poor and high temperature will affect the governor's lifespan, it is extremely necessary to conduct the study on temperature field. Taking the 250 kW permanent magnet governor which is researched and developed independently as an example, the present paper focuses on the present problem of magnetic-thermal unilateralism coupling field's failure of precisely calculating the transmission torque and temperature distribution. The paper proposes adopting bidirectional coupling calculation method, considering temperature's effect on the performance of magnetizer as well as permanent magnet's magnetic field and magnetic characteristics’ influence on temperature field, so as to realize the accurate calculation of magnetic field and thermal field. In addition, simulation results of unilateralism and bidirectional coupling have been verified through experiments. It turns out that the magnetic-thermal bidirectional coupling calculation is closer to the temperature value measured in the experiment, with an error only within 2%, which proves that the bidirectional coupling calculation is more accurate and is of great importance to guiding the design of permanent magnet governor's magnetic field. Meanwhile, as most of the current simulation models neglect the air gap of the connection between the actual magnetizer and the steel disc's rigging screw, the calculation of temperature field is not precise enough. The present paper has conducted a temperature simulation comparison between no air film and air films of varying thicknesses. In this way, it is discovered that the thickness of air film exerts an apparent effect on temperature field, with the highest temperature difference up to 22 ℃. Aiming at the issue of air film's reduction of heat conduction performance, the present paper proposes that the magnetizer disc and steel disc employ explosive welding to form composite board craft, so as to optimize heat condition. In addition, experiments have been conducted for verification. It has been proved that the temperature in the situation where explosive welding heat conduction optimization method is used is lower than the temperature when air film's thickness is 0.15 mm by 7–10 ℃, thereby greatly increasing the efficiency of heat conduction and guaranteeing the steady as well as reliable operation of permanent magnet governor.

Field study of thermal comfort in non-air-conditioned buildings in a tropical island climate

The unique geographical location of Hainan makes its climate characteristics different from inland areas in China. The thermal comfort of Hainan also owes its uniqueness to its tropical island climate. In the past decades, there have been very few studies on thermal comfort of the residents in tropical island areas in China. A thermal environment test for different types of buildings in Hainan and a thermal comfort field investigation of 1944 subjects were conducted over a period of about two months. The results of the survey data show that a high humidity environment did not have a significant impact on human comfort. The neutral temperature for the residents in tropical island areas was 26.1 °C, and the acceptable temperature range of thermal comfort was from 23.1 °C to 29.1 °C. Residents living in tropical island areas showed higher heat resistance capacity, but lower cold tolerance than predicted. The neutral temperature for females (26.3 °C) was higher than for males (25.8 °C). Additionally, females were more sensitive to air temperature than males. The research conclusions can play a guiding role in the thermal environment design of green buildings in Hainan Province.

Activity of paracin C from lactic acid bacteria against Alicyclobacillus in apple juice: Application of a novelty bacteriocin

AbstractOne of the common bacteria to cause spoiling of fruit juices, is Alicyclobacillus acidoterrestris. Control of A. acidoterrestris in apple juice by paracin C, a bacteriocin produced by Lactobacillus paracasei CICC 20241, has been described in the present work. The spectrum of paracin C activity was investigated which resulted in identification of seventeen strains of A. acidoterrestris as sensitive. Bacteriocin absorption to different A. acidoterrestris resulted in variations based on differences in strain and testing environments Increase in absorption was observed with increasing temperature while it decreased with increasing pH. Presence of NaCl (1%) propelled the absorption of bacteriocin while Tween 20 and Tween 80 reduced the absorption. Results of electron microscopy examination clearly pointed out extensive cell damage and destruction of bacteria on treatment with bacteriocin. Although the endospores cannot be killed by paracin C in apple juice, upon addition of this bacterioicin, reduction in the thermal resistance of A. acidoterrestris spores was clearly observed. There was no unpalatable favor when the addition of paracin C was less than 100 μg/ml.Practical uses–actual or potential–of the researchOne of the common bacteria to cause spoiling of fruit juices, is Alicyclobacillus acidoterrestris. The heat resistance capacity in its spores is very high and the normally pasteurization in industry may not be able to kill all the spores. This situation calls for development of an effective method to control the germination and outgrowth of Alicyclobacillus acidoterrestris and it is an urgent need in the beverage industries. Traditional chemical preservatives may be harmful to health if used in over‐dose or in long‐time use. Paracin C produced by Lactobacillus paracasei CICC 20241 is a safe and efficient bacteriocin active against A. acidoterrestris. It is able to inhibit and kill the cells of A. acidoterrestris present in apple juice and has a broad activity spectrum. These factors along with other characterization made it a promising potential preservative in apple juice industrial.

Variability in DPA and Calcium Content in the Spores of Clostridium Species.

Spores of a number of clostridial species, and their resistance to thermal treatment is a major concern for the food industry. Spore resistance to wet heat is related to the level of spore hydration, which is inversely correlated with the content of calcium and dipicolinic acid (DPA) in the spore core. It is widely believed that the accumulation of DPA and calcium in the spore core is a fundamental component of the sporulation process for all endospore forming species. We have noticed heterogeneity in the heat resistance capacity and overall DPA/calcium content among the spores of several species belonging to Clostridium sensu stricto group: two C. acetobutylicum strains (DSM 792 and 1731), two C. beijerinckii strains (DSM 791 and NCIMB 8052), and a C. collagenovorans strain (DSM 3089). A C. beijerinckii strain (DSM 791) and a C. acetobutylicum strain (DSM 792) display low Ca and DPA levels. In addition, these two species, with the lowest average Ca/DPA content amongst the strains considered, also exhibit minimal heat resistance. There appears to be no correlation between the Ca/DPA content and the phylogenetic distribution of the C. acetobutylicum and C. beijerinckii species based either on the 16S rRNA or the spoVA gene. This finding suggests that a subset of Clostridium sensu stricto species produce spores with low resistance to wet heat. Additionally, analysis of individual spores using STEM-EDS and STXM revealed that DPA and calcium levels can also vary amongst individual spores in a single spore population.

Effects of chitosan as biopolymer coupling agent on the thermal and rheological properties of polyvinyl chloride/wood flour composites

Chitosan (CS) was opted as a novel biopolymer coupling agent for wood flour polyvinyl chloride composites (WF/PVC) to improve interfacial adhesion. This study mainly aimed at investigating the effects after adding CS of different addition amounts and particle sizes on the thermal and rheological properties of WF/PVC composites by the analyses of vicat softening temperature test (VST), differential scanning calorimetry (DSC), thermogravimetry (TGA) and torque rheometry. The results indicated that an optimum addition amount (30phr) with the particle size (180–220mesh) could elevate heat resistance capacity, glass transition temperature of composites as well as thermal stability at the early stage of degradation more effectively. In the aspect of rheological characteristics, longer fusion time, lower fusion torque and higher fusion temperature were showed as the CS addition amount increased and the particle size declined. In order to obtain sufficient compaction and ensure proper blending to compounds during extrusion, the higher pressure needed to be supplied when the addition amount of CS exceeded 20phr.

An experimental study on fire resistance of medical modular block

Fire performance and fire safety of high-rise buildings have become major concerns after the disasters of World Trade Center in the U.S. in 2001 and Windsor tower in Spain in 2005. Performance based design (PBD) approaches have been considered as a better method for fire resistance design of structures because it is capable of incorporating test results of most recent fire resistance technologies. However, there is a difficulty to evaluate fireproof performance of large structures, which have multiple structural members such as columns, slabs, and walls. The difficulty is mainly due to the limitation in the testing equipment, such as size of furnace that can be used to carry out fire tests with existing criteria like ISO 834, BS 476, and KS F 2257. In the present research, a large scale calorie meter (10 MW) was used to conduct three full scale fire tests on medical modular blocks. Average fire load of 13.99 kg/m2 was used in the first test. In the second test, the weighting coefficient of 3.5 (the fire load of 50 kg/m2) was used to simulate the worst fire scenario. The flashover of the medical modular block occurred at 62 minutes in the first test and 12 minutes in the second test. The heat resistance capacity of the external wall, the temperatures and deformations of the structural members satisfied the requirements of fire resistance performance of 90 minutes burning period. The total heat loads and the heat values for each test are calculated by theoretical equations. The duration of burning was predicted. The predicted results were compared with the test results, and they agree quite well.

KSR-III 축소형(I) 엔진의 연소 시험

KSR-III 축소(I) 기본형 엔진에 대한 연소 시험을 실시한 결과 분사면의 내열 특성이 불량한 것으로 판명되었으며, 이에 기본형 엔진의 설계를 다각도로 수정한 축소(I) 수정형 엔진을 제작하게 되었다. 주요 설계 파라미터는 주분사기의 배열, 주분사기의 충돌각, 열차폐코팅이었으며 이들에 대한 시험적 연구를 수행하고 각 디자인에 대한 엔진 성능 및 내열 성능을 비교하였다. 내열 성능은 직교배열의 경우, 주분사기 충돌각이 작은 경우, 열차폐 코팅이 있는 경우 향상되는 경향을 보였으며, 일부는 30초 시험을 통해서 적절한 내열 성능을 보여주었다. 그에 따른 엔진 성능의 변화를 살펴보면 5% 범위 이내에서 성능 차이를 보이는데, 방사배열의 경우가 직교배열의 경우보다 성능이 높고, 주분사기 충돌각 <TEX>$15^{\circ}$</TEX>의 경우가 <TEX>$20^{\circ}$</TEX>의 경우보다 오히려 높게 나타났다. 또한, 저주파 연소불안정성의 측면에서는 충돌각이 작을수록, 방사형 배열보다는 직교형 배열의 경우 불안정 특성이 큰 것으로 판명되었다. 이러한 내열 성능 및 엔진 성능의 변화는 분무 특성의 변화 및 이에 의한 화염 구조의 변화에 기인하는 것으로 보이며, 보다 심도 있는 분석을 위해 추가적인 연구가 필요하다. In the preceding tests using the KSR-III Sub.(I) engines, it was observed that the heat resistant capability of the engines was not enough for the mission. So Sub.(I) Mod. engines were designed and tested. The Sub.(I) Mod. engines have three major design parameters - the arrangement of main injectors, the impinging angle of main injectors and thermal barrier coating. More than twenty experiments were carried on to evaluate engine performance and heat resistance capability with respect to design parameters. In this study, the test results are introduced. Analysing the result of Sub.(I) engine tests, it is found that decreasing the impinging angle, adopting the H-type arrangement(rather than radial type arrangement) and adopting the thermal barrier coating can increase heat resistance capacity substantially. Also, engine performance evaluation is conducted using specific impulse and characteristic velocity parameter. The results show that the performance variation is small(about 5%) and the performance is better in the case of radial arrangement. It is suspected that these phenomena are caused by the change of flame structure atomization mixing characteristic of sprays and the distortion of recirculation zone. Also from the low frequency instability point of view, it is observed that reducing the impinging angle and adopting the H type arrangement can increase the instability characteristics.