Application of Dynamic Temperature-Humidity Chamber for Measuring Moisture Sorption Isotherms of Biomaterials as Compared to the Conventional Isopiestic Method

Measurement of water activity and moisture sorption isotherms of foods and biomaterials are important to determine the state of water. In this work, a dynamic temperature-humidity (DTH) controlled chamber was used to measure water sorption isotherm and compared with the conventional isopiestic method. Temperature and relative humidity of DTH chamber can be controlled in the range of -15 to 100°C and 0 to 98%, respectively; thus, measurement of water activity at any point can be measured within the above ranges. The DTH chamber method showed high reproducibility as compared with the conventional isopiestic method when measured isotherms of cellulose, lignin, and hemicellulase were compared at 30°C. Finally, isotherm data of cellulose, lignin, and hemicellulase were generated in the temperature range of 10-90°C using DTH chamber, and these were modelled by BET and GAB equations. The model parameters were correlated with the temperature.

Ageing of laser sintered glass-filled Polyamide 12 (PA12) parts at elevated temperature and humidity

Additive manufacturing is traditionally used to manufacture either prototypes or very small-scale demonstrators. In recent years though, it is being increasingly used to make low volume parts for the aeronautical and defence industry. One concern with laser sintered parts is that their relatively porous nature, means that they may be more susceptible to ageing than injection moulded parts. Parts were aged for 6 months in at different temperatures (18°C, 40°C, 50°C, 60°C, 80°C and 100°C) and in a humidity chamber at 60°C and 80% relative humidity. Each month samples were removed for characterisation. The testing included tensile testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and gas pycnometry. During ageing the samples displayed visible discolouration and embrittlement over the 6-month test period. This embrittlement was not observed in those samples aged at room temperature or an elevated humidity. The observed yellowing in the samples aged above ambient temperature is likely a result of the build-up unsaturated degradation products. No significant differences as a result of ageing were observed via DSC, TGA, SEM or gas pycnometry.

Tin Whiskers’ Behavior under Stress Load and the Mitigation Method for Immersion Tin Surface Finish

Since the use of the most stable Pb-based materials in the electronic industry has been banned due to human health concerns, numerous research studies have focused on Pb-free materials such as pure tin and its alloys for electronic applications. Pure tin, however, suffers from tin whiskers’ formation, which tends to endanger the efficiency of electronic circuits, and even worse, may cause short circuits to the electronic components. This research aims to investigate the effects of stress on tin whiskers’ formation and growth and the mitigation method for the immersion of the tin surface’s finish deposited on a copper substrate. The coated surface was subjected to external stress by micro-hardness indenters with a 2N load in order to simulate external stress applied to the coating layer, prior to storage in the humidity chamber with environmental conditions of 30 °C/60% RH up to 52 weeks. A nickel underlayer was deposited between the tin surface finish and copper substrate to mitigate the formation and growth of tin whiskers. FESEM was used to observe the whiskers and EDX was used for measuring the chemical composition of the surface finish, tin whiskers, and oxides formed after a certain period of storage. An image analyzer was used to measure the whiskers’ length using the JEDEC Standard (JESD22-A121A). The results showed that the tin whiskers increased directly proportional to the storage time, and they formed and grew longer on the thicker tin coating (2.3 μm) than the thin coating (1.5 μm). This is due to greater internal stress being generated by the thicker intermetallic compounds identified as the Cu5Sn6 phase, formed on a thicker tin coating. In addition, the formation and growth of CuO flowers on the 1.5 μm-thick tin coating suppressed the growth of tin whiskers. However, the addition of external stress by an indentation on the tin coating surface showed that the tin whiskers’ growth discontinued after week 4 in the indented area. Instead, the whiskers that formed were greater and longer at a distance farther from the indented area due to Sn atom migration from a high stress concentration to a lower stress concentration. Nonetheless, the length of the whisker for the indented surface was shorter than the non-indented surface because the whiskers’ growth was suppressed by the formation of CuO flowers. On the other hand, a nickel underlayer successfully mitigated the formation of tin whiskers upon the immersion of a tin surface finish.

Design and Manufacturing of Low Relative Humidity Chamber for Laser Processing of Lithium Metal

In order to overcome the energy density limitations of lithium-ion batteries consisting of graphite anodes, studies on lithium metal batteries (LMBs) have been actively conducted. However, most LMBs related studies focus on suppressing the growth of unpredictable dendrites. Research for production processes has been rarely conducted. In the paper, laser processing is introduced to improve the drawback of conventional processing for Li metal. Moreover, a low humidity maintenance chamber is manufactured to prevent oxidation of Li metal during laser processing because Li metal easily reacts with moisture. The chamber has a closed space that does not allow outside air to enter, and a glass that allows the laser beam to pass through is installed at the upper part. In addition, silica gel is installed to maintain low relative humidity. The dew point inside the chamber drops to -17.4 ℃ in 1 hour. This result implies that the chamber can prevent Li metal oxidation. Next, we analyze the effect of transparent plate glass on laser beam with Gaussian distribution. Finally, it is confirmed through experiments that lithium metal is not contaminated by moisture during laser processing using a manufactured chamber.

Humidity-Sensing Chipless RFID Tag with Enhanced Sensitivity Using an Interdigital Capacitor Structure

An eight-bit chipless radio frequency identification tag providing humidity sensing and identification information is proposed. A compact, enhanced-sensitivity resonator based on an interdigital capacitor (IDC) structure is designed for humidity sensing, whereas seven electric-field-coupled inductor capacitor (ELC) resonators are used for identification information. These eight resonators are placed in a two-by-four array arrangement. A step-by-step investigation for the effect of varying the number of elements and array configuration on the resonant frequency and radar cross-section (RCS) magnitude of the IDC resonator is conducted. The RCS value of the resonant peak frequency for the IDC resonator increases as the number of array elements placed nearby increases due to the mutual coupling among the elements, and the increase in the RCS value becomes larger as the number of arrays increases in the vertical direction. Polyvinyl alcohol (PVA) is coated on the IDC-based resonator at a thickness of 0.02 mm. A non-reflective temperature and humidity chamber is fabricated using Styrofoam, and the relative humidity (RH) is varied from 50% to 80% in 10% intervals at 25 °C in order to measure a bistatic RCS of the proposed tag. The humidity sensing performance of the IDC resonator in the proposed tag is measured by the shift in the resonant peak frequency and the RCS value, and is compared with a single ELC resonator. Experiment results show that when RH increased from 50% to 80%, the sensitivities of both the resonant peak frequency and the RCS value of the IDC resonator were better than those of the ELC resonator. The variation in the RCS value is much larger compared to the resonant peak frequency for both IDC and ELC resonators. In addition, the resonant peak frequency and RCS value of the PVA-coated IDC-based resonator change, whereas those of the other seven resonators without a PVA coating do not change.

Rapid Simultaneous Testing of Multiple Antibiotics by the MALDI-TOF MS Direct-on-Target Microdroplet Growth Assay

Accelerating antimicrobial susceptibility testing (AST) is a priority in the development of novel microbiological methods. The MALDI-TOF MS-based direct-on-target microdroplet growth assay (DOT-MGA) has recently been described as a rapid phenotypic AST method. In this proof-of-principle study, we expanded this method to simultaneously test 24 antimicrobials. An Enterobacterales panel was designed and evaluated using 24 clinical isolates. Either one or two (only for antimicrobials with the EUCAST “I” category) breakpoint concentrations were tested. Microdroplets containing bacterial suspensions with antimicrobials and growth controls were incubated directly on the spots of a disposable MALDI target inside a humidity chamber for 6, 8 or 18 h. Broth microdilution was used as the standard method. After 6 and 8 h of incubation, the testing was valid (i.e., growth control was successfully detected) for all isolates and the overall categorical agreement was 92.0% and 92.7%, respectively. Although the overall assay performance applying short incubation times is promising, the lower performance with some antimicrobials and when using the standard incubation time of 18 h indicates the need for thorough standardization of assay conditions. While using “homebrew” utensils and provisional evaluation algorithms here, technical solutions such as dedicated incubation chambers, tools for broth removal and improved software analyses are needed.

Effect of Wood Flour Addition on Warm/Cool Feeling of Green Composite

In this study, effect of wood flour addition on warm/cool feeling of green composite using wood flour and poly(lactic acid) was investigated for comfortability of interior product. Additive amounts of wood flour were 10 – 40 wt.%. Measurement of initial maximum values of heat flux of green composite using wood flour was conducted under constant temperature and humidity chamber. Surface of green composite using wood flour was observed by Scanning Electron Microscope (SEM). Following conclusions were obtained. The initial maximum value of heat flux of green composite decreased with an increase of wood flour additive amount until 20 wt.%. But, initial maximum value of heat flux of green composite at more than wood flour additive amount 30 wt.% almost did not change. From SEM observation, the appearance void area on surface of green composite at wood flour additive amount 20 wt.% was larger than that of green composite at wood flour additive amount 10 wt.%. Therefore, initial maximum value of heat flux of green composite was mainly affected because of increase of void area and wood flour until wood flour additive amount 20 wt.%.

Autogenous Self-Healing Capacity of Early-Age Ultra-High-Performance Fiber-Reinforced Concrete

This paper analyzes the autogenous self-healing capacity of early-age Ultra-High-Performance Fiber-Reinforced concretes (UHPFRCs) by measuring the crack closure and the possible mechanical recovery on healed specimens. The main parameters considered in this research were the healing exposure conditions (humidity chamber, immersion in tap water, immersion in seawater and heat curing) and the precracking levels (microcracks and macrocracks). For the microcrack level, four-point bending tests were performed on prismatic specimens (100 × 100 × 500 mm3) obtaining a multiple cracking pattern characterized by crack widths ranged from 10 to 20 µm. Whereas for the macrocrack level (behavior after crack localization), splitting tests were carried out on notched cubic specimens (100 × 100 × 100 mm3) obtaining crack widths of up to 0.4 mm. For both precracking levels, specimens were precracked at two days and were cured for one month in the mentioned exposure conditions. Healing products were analyzed on the specimen surface and also inside the cracks; to this purpose, their microstructure was analyzed by means of SEM and EDS analyses. The results have shown that the highest crack closure values were obtained for the heat-cured specimens and for the specimens immersed in water (tap water and seawater) whereas the less efficient condition was the humidity chamber.

Filmwise Condensation From Humid Air On a Vertical Superhydrophilic Surface: Explicit Roles of the Humidity Ratio Difference and the Degree of Subcooling

The process involving heat and mass transfer during filmwise condensation (FWC) in presence of non-condensable gases (NCG) has great significance in a large variety of engineering applications. The vapor mass flux leading to condensation and the resulting condensation heat transfer coefficient (CHTC) are dependent on the gradients of temperature and vapor mass fraction established near the condenser plate. The effects of the two most influencing thermodynamic parameters, i.e., the degree of subcooling and the difference of humidity ratio (between the free stream environment and on the condenser plate), have been characterized in this work both experimentally and through a mechanistic model. The vapor mass flux during condensation on a subcooled vertical superhydrophilic surface under a free convection regime is experimentally measured in a controlled environment (temperature and humidity) chamber. A mechanistic model, based on the similarity of energy and species transports, is formulated for the thermogravitational boundary layer over the condenser plate and tuned against the experimental results. Further, the model is used to obtain comprehensive data of the condensate mass flux and CHTC as functions of the salient thermal operating conditions over a wide parametric range. Results indicate that humidity ratio difference has a more pronounced influence on the condensation mass transfer rather than the degree of subcooling. The mechanistic model lends to the development of empirical correlations of condensate mass flux and CHTC as explicit functions of these two parameters for easy use in practical FWC configurations.

Should black carbon concentration from aethalometer measurements onboard of UAVs be additionally corrected? - What is the impact of rapid relative humidity changes on our measurements?

<p>Relative humidity and rates of its change are relevant parameters in atmospheric sciences. Observations of output data of AE-51 aethalometer operating in ACS1000 humidity chamber reveal strong dependence of attenuation on rapid relative humidity changes. Data collected in winter 2020/21 suggests a probability of similar effect occurring during UAV measurements as thermodynamic parameters could change fast during such runs. Two AE-51 devices were connected in the WET and DRY ACS1000 humidity chamber's channels. During periodic relative humidity oscillations, incident negative peaks of equivalent black carbon mass concentration coincide with high negative derivatives of relative humidity. In most extreme cases values of -1000 ng/m3 equivalent black carbon mass concentration were recorded in parallel with relative humidity derivative of -1.5 %/min. These correlations seem to play an important role in atmospheric measurements as vertical profiles of aerosol parameters such as attenuation are collected using UAV runs during which relative humidity varies significantly. Our goal is to propose a correction method to minimise these anomalies.</p>