High Temperature-high Humidity Research Articles

Grey image recognition-based mold growth assessment on the surface of typical building materials responding to dynamic thermal conditions

Mold growth on building materials poses a threat to both the building structural integrity and occupants’ well-being. However, it is generally studied under suitable conditions in laboratory; the assessment is based on visual inspection but lacks an objective criterion. This research explored the effects of simulated dynamic thermal conditions on mold growth on three typical building materials artificially contaminated with Aspergillus niger spores. Test specimens were assessed based on a developed digital image-based method, where image segmentation, processing, and greyscale recognition via the OpenCV visual library were introduced. The results showed that the high temperature-high humidity condition in a 24-h cyclic change facilitated mold growth on the surfaces of three materials, especially for gypsum board, with an identified area proportion of 1.13% on the 80th day. This was consistent with the changes of the counted number of mold colonies, and no significant differences were found among the gypsum board, latex paint, and wallpaper. The growth extents of mold spores were objectively evaluated by the mean greyscale values; the values decreased gradually with time, and the decrements were different compared high-temperature to low-temperature conditions. The mold growth models were developed, where the area proportion of mold growth was linearly related to the counted colonies and greyscale values under different material surfaces. This novel grey image recognition-based method provides an accurate means of evaluating mold growth abilities and extents, overcoming the inaccuracy of visual observation. The findings have significant implications for visual inspection, mold prediction, and building management.

9.2: Mechanism of H2O‐induced Instability of Self‐Aligned Top‐Gate Amorphous InGaZnO TFTs

The influence of H2O on self‐aligned top‐gate (SATG) a‐ InGaZnO thin‐film transistor (TFT) was systematically investigated by performing the high‐temperature high‐humidity (HTHH) test (50 °C, 80% RH). Though initial electrical characteristics were well maintained, the stability under positive bias stress (PBS) was considerably deteriorated, including an abnormal negative Vth shift, degraded SS, and increased off current. The mechanism of H2O‐induced instability was proposed to be the dissociation of H2O molecules and the migration of hydrogen (H) atoms into the a‐IGZO channel. The hydrogen diffusion and doping effects in SATG a‐IGZO TFTs were further proved by SiNx‐passivated TFTs with regulated H content in SiNx layers.

MADS-box protein AGL8 interacts with chromatin-remodelling component SWC4 to activate thermotolerance and environment-dependent immunity in pepper.

Pepper (Capsicum annuum) employs distinct defence responses against Ralstonia solanacearum infection (RSI); however, the mechanisms by which pepper activates these defence responses in a context-dependent manner is unclear. Here we study pepper plants defence response to RSI under room temperature-high humidity (RSRT, 28 °C / 90%) and high temperature-high humidity (RSHT, 37 °C / 90%) conditions, and non-infected plants under high temperature-high humidity (HTHH, 42 °C / 90%) stress. Herein, we found that the MADS-box transcription factor CaAGL8 was up-regulated by HTHH stress and RSRT or RSHT, and its silencing significantly reduced pepper thermotolerance and susceptibility to infection under both room and high temperature-high humidity (RSRT and RSHT). This was coupled with down-regulation of CaSTH2 and CaDEF1 upon RSRT, down-regulation of CaMgst3 and CaPRP1 upon RSHT, and down-regulation of CaHSP24 upon HTHH. In contrast, the ectopic overexpression of CaAGL8 significantly increased the resistance of Nicotiana benthamiana plants to RSRT, RSHT, and HTHH. In addition, CaAGL8 was found to interact with CaSWC4, which acted as a positive regulator of the pepper response to RSRT, RSHT, and HTHH. Silencing of either CaAGL8 or CaSWC4 blocked the hypersensitive response (HR) cell death and context-dependent up-regulation of defence-related genes triggered by the other. Importantly, enrichment of H4K5Ac, H3K9Ac, H3K4me3, and H3K9me2 on the tested defence-related genes was context- and gene-specifically regulated through synergistic interaction between CaSWC4 and CaAGL8. Our results indicate that pepper employs CaAGL8 to modulate chromatin remodelling by interacting with CaSWC4, thereby activating defence responses to RSRT, RSHT, and HTHH.

Effects of high temperature, high humidity, and cold storage on structure and qualities of whole oat flour noodles during processing

Gelation and structure of oat starch significantly affect qualities of whole oat flour noodles. During extrusion, the structure of noodles is loose, resulting in high cooking loss and poor texture. Therefore, oat noodles were treated with high temperature, high humidity (HTH), and cold storage (CS), and their structure and qualities were analyzed. The results showed that compared with CS, HTH could reduce the cooking loss of noodles from 10.12% to 6.13%, increase the hardness (65.59g) and chewiness (20.67) of noodles, and effectively improve the sensory quality of noodles. The change in texture and sensory of noodles was due to HTH by accelerating the retrogradation of starch in noodles, promoting the cross-linking of starch molecules to form an ordered structure, causing an increase in the ordered degree and crystallinity of starch and making the structure of noodles denser. It made the mobility of water in the noodles decrease, and more tightly bound water was transformed into weakly bound water and free water. HTH can be applied to industrial production of whole oat flour noodles. This study could effectively guide the production of high-quality whole oat flour noodles without any food additives.

Impact of storage conditions and premix type on water-soluble vitamin stability.

Mitigation options to reduce the risk of foreign animal disease entry into the United States may lead to degradation of some vitamins. The objective of Exp. 1 was to determine the impact of 0, 30, 60, or 90 d storage time on water-soluble vitamin (riboflavin, niacin, pantothenic acid, and cobalamin) stability when vitamin premix (VP) and vitamin trace mineral premix (VTM) were blended with 1% inclusion of medium-chain fatty acid (MCFA) (1:1:1 blend of C6:C8:C10) or mineral oil (MO) with different environmental conditions. Samples stored at room temperature (RT) (approximately 22 °C) or in an environmentally controlled chamber set at 40 °C and 75% humidity, high temperature high humidity (HTHH). The sample bags were pulled out at day 0, 30, 60, and 90 for RT condition and HTHH condition. Therefore, treatments were analyzed as a 2 × 2 × 2 × 3 factorial, with two premix types (vitamin premix vs. VTM), two oil types (MO vs. MCFA), two storage conditions (RT vs. HTHH), and three time points (day 30, 60, and 90). The objective of Exp. 2 was to determine the effect of heat pulse treatment and MCFA addition on water-soluble vitamin (riboflavin, niacin, pantothenic acid, and cobalamin) stability with two premix types. A sample from each treatment was heated at 60 °C and 20% humidity. Therefore, treatments were analyzed as a 2 × 2 factorial, with two premix types (VP vs. VTM) and two oil types (MO vs. MCFA). For Exp. 1, the following effects were significant for riboflavin: main effect of premix type (P < 0.0001), storage condition (P = 0.015), and storage time (P < 0.0001); for pantothenic acid: premix type × storage time × storage condition (P = 0.003) and premix type × oil type (P < 0.0001) interactions; and for cobalamin: premix type × storage condition (P < 0.0001) and storage time × storage condition (P < 0.0001) interactions and main effect of oil type (P = 0.018). The results of Exp. 2 demonstrated that there was an interaction between oil type and premix type for only pantothenic acid (P = 0.021). The oil type did not affect the stability of riboflavin, niacin, or cobalamin and pantothenic acid stability was not different within similar premixes. The only difference in water-soluble vitamin stability between VP and VTM was for pantothenic acid (P < 0.001). The results of this experiment demonstrated that the stability of water soluble vitamins are dependent on the vitamin of interest and the conditions at which it is stored.

A CaCDPK29-CaWRKY27b module promotes CaWRKY40-mediated thermotolerance and immunity to Ralstonia solanacearum in pepper.

CaWRKY40 in pepper (Capsicum annuum) promotes immune responses to Ralstonia solanacearum infection (RSI) and to high-temperature, high-humidity (HTHH) stress, but how it interacts with upstream signalling components remains poorly understood. Here, using approaches of reverse genetics, biochemical and molecular biology we functionally characterised the relationships among the WRKYGMK-containing WRKY protein CaWRKY27b, the calcium-dependent protein kinase CaCDPK29, and CaWRKY40 during pepper response to RSI or HTHH. Our data indicate that CaWRKY27b is upregulated and translocated from the cytoplasm to the nucleus upon phosphorylation of Ser137 in the nuclear localisation signal by CaCDPK29. Using electrophoretic mobility shift assays and microscale thermophoresis, we observed that, due to the replacement of Q by M in the conserved WRKYGQK, CaWRKY27b in the nucleus failed to bind to W-boxes in the promoters of immunity- and thermotolerance-related marker genes. Instead, CaWRKY27b interacted with CaWRKY40 and promoted its binding and positive regulation of the tested marker genes including CaNPR1, CaDEF1 and CaHSP24. Notably, mutation of the WRKYGMK motif in CaWRKY27b to WRKYGQK restored the W-box binding ability. Our data therefore suggest that CaWRKY27b is phosphorylated by CaCDPK29 and acts as a transcriptional activator of CaWRKY40 during the pepper response to RSI and HTHH.

Methylome Patterns of Cattle Adaptation to Heat Stress.

Heat stress has a detrimental impact on cattle health, welfare and productivity by affecting gene expression, metabolism and immune response, but little is known on the epigenetic mechanisms mediating the effect of temperature at the cellular and organism level. In this study, we investigated genome-wide DNA methylation in blood samples collected from 5 bulls of the heat stress resilient Nellore breed and 5 bulls of the Angus that are more heat stress susceptible, exposed to the sun and high temperature-high humidity during the summer season of the Brazilian South-East region. The methylomes were analyzed during and after the exposure by Reduced Representation Bisulfite Sequencing, which provided genome-wide single-base resolution methylation profiles. Significant methylation changes between stressful and recovery periods were observed in 819 genes. Among these, 351 were only seen in Angus, 366 were specific to Nellore, and 102 showed significant changes in methylation patterns in both breeds. KEGG and Gene Ontology (GO) enrichment analyses showed that responses were breed-specific. Interestingly, in Nellore significant genes and pathways were mainly involved in stress responses and cellular defense and were under methylated during heat stress, whereas in Angus the response was less focused. These preliminary results suggest that heat challenge induces changes in methylation patterns in specific loci, which should be further scrutinized to assess their role in heat tolerance.

Impact of storage conditions and premix type on fat-soluble vitamin stability.

Feed ingredients and additives could be a potential medium for foreign animal disease entry into the United States. The feed industry has taken active steps to reduce the risk of pathogen entry through ingredients. Medium chain fatty acid (MCFA) and heat pulse treatment could be an opportunity to prevent pathogen contamination. The objective of experiment 1 was to determine the impact of 0, 30, 60, or 90 d storage time on fat-soluble vitamin stability when vitamin premix (VP) and vitamin trace mineral premix (VTM) were blended with 1% inclusion of MCFA (1:1:1 blend of C6:C8:C10) or mineral oil (MO) with different environmental conditions. Samples stored at room temperature (RT) (~22 °C) or in an environmentally controlled chamber set at 40 °C and 75% humidity, high-temperature high humidity (HTHH). The sample bags were pulled out at days 0, 30, 60 and 90 for RT condition and HTHH condition. The objective of experiment 2 was to determine the effect of heat pulse treatment and MCFA addition on fat-soluble vitamin stability with two premix types. A sample from each treatment was heated at 60 °C and 20% humidity. For experiment 1, the following effects were significant for vitamin A: premix type × storage condition (P = 0.031) and storage time × storage condition (P = 0.002) interactions; for vitamin D3: main effect of storage condition (P < 0.001) and storage time (P = 0.002); and for vitamin E: storage time × storage condition interaction (P < 0.001). For experiment 2, oil type did not affect the stability of fat-soluble vitamins (P > 0.732) except for vitamin A (P = 0.030). There were no differences for fat-soluble vitamin stability between VP and VTM (P > 0.074) except for vitamin E (P = 0.016). Therefore, the fat-soluble vitamins were stable when mixed with both vitamin and VTM and stored at 22 °C with 28.4% relative humidity (RH). When premixes were stored at 39.5 °C with 78.8%RH, the vitamin A and D3 were stable up to 30 d while the vitamin E was stable up to 60 d. In addition, MCFA did not influence fat-soluble vitamin degradation during storage up to 90 d and in the heat pulse process. The vitamin stability was decreased by 5% to 10% after the premixes was heated at 60 °C for approximately nine and a half hours. If both chemical treatment (MCFA) and heat pulse treatment have similar efficiency at neutralizing or reducing the target pathogen, the process of chemical treatment could become a more practical practice.

Modification of the functional properties of hard-to-cook cowpea seed flours and cooked prepared pastes by γ-irradiation.

Cowpeas are an inexpensive source of quality protein but their utilisation is limited by long seed cooking time. This is exacerbated by development of the hard-to-cook (HTC) defect, which also adversely affects starch and protein functionality. Gamma-irradiation can eliminate cowpea seed insect infestation and affects seed functional properties, including reducing cooking time. Hence, the potential of γ-irradiation to modify the starch- and protein-related functionalities of HTC cowpeas was investigated. Gamma-irradiation at approximately 11kGy was applied to the seeds of two cowpea varieties, differing in HTC susceptibility, where HTC had been induced by high-temperature, high-humidity (HTHH) storage. HTHH storage increased flour pasting peak viscosity by up to 40% in the less susceptible variety and by more than 100% in the more susceptible variety. Gamma-irradiation at least completely reversed this effect, due to starch depolymerisation and debranching. Gamma-irradiation also positively impacted on some protein-related properties adversely affected by HTC; partially reversing the reduction in flour and cooked paste nitrogen solubility index of the HTC-susceptible cowpea, as a result of protein depolymerisation. The multiple benefits of γ-irradiation: disinfection, cooking time reduction and reversing some adverse effects of HTC on functional properties could make it a viable process for improving HTC cowpea quality.

Laboratory Studies of Questing Behavior in Colonized Nymphal Amblyomma maculatum Ticks (Acari: Ixodidae).

Environmental factors affect host-seeking behavior in ticks. In this study, 80 nymphal Amblyomma maculatum Koch were released in an observation arena containing four different heights of broomsedge stems (Andropogon virginicus L.) anchored in sand. Observations were made over three days as to proportion of ticks questing, questing height, and stem height distribution This scenario was replicated three times with different cohorts of ticks (n = 80 per replicate) for each of three treatment combinations of temperature and humidity: High temperature/high humidity (HTHH), high temperature/low humidity (HTLH), and low temperature/high humidity (LTHH). A fourth treatment utilizing the same size cohort and number of replicates included Wind (HTHHW+/-) by alternating days of wind and no-wind conditions over four days. Mean questing height for ticks under HTHH, HTLH, and LTHH conditions ranged from 4.45 to 6.03 cm with ticks questing significantly higher in HTHH. A significantly lower proportion ticks quested in HTLH (8.64%) than HTHH (14.06%) and LTHH (15.33%). In HTHH and LTHH, a significantly higher proportion of ticks were observed questing on 5-cm stems. Wind significantly reduced average questing height, and when absent, ticks on 20- and 30-cm stems quested significantly higher. These data indicate that A. macuatum nymphs randomly select stems to quest upon and climb upward until environmental conditions are prohibitive/ideal. Conditions with reduced vapor pressure deficit (VPD) led to higher questing frequency and height. Relatively low questing heights observed correspond with size of preferred hosts and may explain infrequency of collection by dragcloth in the field.

Elucidating Molecular- and Particle-Level Changes during the Annealing of a Micronized Crystalline Drug

Micronization of crystalline active pharmaceutical ingredients can lead to formation of a thermodynamically unstable material with surface disorder. This material undergoes structural stabilization and particle-level changes over time that, in turn, alters the surface properties and interparticle interactions of the micronized drug. The unstable nature of the micronized drug can lead to variability in the performance of dry powder inhaler drug products. To improve the physicochemical stability of the micronized drug, an annealing step is often introduced. However, there is limited understanding of changes in the micronized drug under different annealing conditions. In this study, we examine the molecular- and particle-level changes occurring in a micronized drug during annealing under varying temperature and humidity conditions using orthogonal techniques. We demonstrate the use of surface free energy (SFE) measured by inverse gas chromatography (IGC) to monitor surface-specific changes. Micronization led to an increase in SFE, which progressively reduced during annealing. SFE trends correlated with the molecular-level surface disorder patterns measured by relative humidity perfusion microcalorimetry. The interparticle interactions tracked using IGC and atomic force microscopy show that as the micronized drug stabilized, there was a transition from dominant drug-drug cohesive forces to drug-lactose adhesive forces. For the nonhygroscopic model compound, combined high temperature-high humidity conditions showed fastest annealing kinetics. Further, the SFE descriptor enabled us to differentiate the extent of mechanical activation of the neat micronized drug and co-micronized drug-magnesium stearate blends. The study identifies tools for characterizing postmicronization material changes that can help develop materials with consistent quality.

Influence of gene regulation on rice quality: Impact of storage temperature and humidity on flavor profile

Effects of high temperature-high humidity (HT-HH) storage on the flavor profile of rice were investigated. Volatile compounds such as aldehydes, ketones, and furans increased when rice was stored under HT-HH conditions, leading to a pronounced deterioration in rice quality. Correspondingly, the fatty acid content of the rice significantly increased during storage. Lipid oxidation was also accelerated under HT-HH conditions leading to the formation of peroxides. However, catalase activity was reduced under these conditions promoting the accumulation of peroxides. For the first time, insights into the genetic mechanisms responsible for these changes were obtained using RNA-sequencing to establish the flavor metabolic pathways in rice. Under HT-HH conditions, gene expression of lipase increased while that of catalase decreased, leading to faster hydrolysis and oxidation of the rice lipids. As a result, a series of lipid degradation products was formed (such as fatty acids, aldehydes, and ketones) that decreased the rice flavor quality.

Experimental and numerical analysis on total heat recovery performance of an enthalpy wheel under high temperature high humidity working conditions

Enthalpy wheels (EWs) have been extensively used for total heat recovery from ventilation air. Despite there being many studies reporting on their performances under common working conditions with a small temperature and humidity ratio difference (ΔT < 20 °C, Δω < 15 g kg−1), there are few studies reporting on their performances under high temperature high humidity (HTHH) working conditions. This study aims to investigate the total heat recovery performance of an EW under HTHH working conditions. A mathematical model is established and validated to predict the performance. The effects of rotation speed, air inlet velocity, air inlet temperature, and air inlet humidity ratio on the total heat recovery performance are numericallyinvestigated, and performance comparisons between HTHH working conditions and other common working conditions are also carried out. The comparison results show that the EW performs better for total heat recovery under HTHH working conditions, with εtotal improving by 6% compared to common working conditions. The reasons behind the discrepancies are revealed by analyzing the distributions of temperature and humidity in the EW. This study is expected to be beneficial to design EWs to recover total heat from HTHH waste gas.

Mechanical Property of SAC305 Ball-Grid Array and Epoxy Sn-58Bi Solder Joints with 85 °C/85% Relative Humidity Environmental Conditions.

The ball-grid array (BGA) is widely used to reduce component size and it had advantages such as high I/O pins and fine pitch. Typical Sn-Ag-Cu (SAC) solder alloys are used for formation of BGA because SAC solder has excellent characteristics among lead-free solders. However, the electronic components assembled by SAC solder were easily damaged by heat during manufacture process because SAC solder had high melting point of 220 °C. To prevent these thermal damages, SAC305 BGA component assembled by Sn-58Bi solder paste has been studied because Sn-58Bi solder had low melting point of 139 °C. In generally, Sn-58Bi solder was improved by additional elements or polymer such as epoxy because Sn-58Bi had a brittle property. However, the epoxy Sn-58Bi solder did not guaranteed high environmental reliability such as high-temperature high-humidity (HTHH) test. Thus, we evaluated the shear strength of solder joints assembled by SAC305 BGA components with Sn-58Bi solder paste and epoxy Sn-58Bi solder paste. The shear strength of solder joints was evaluated by die shear test after HTHH test at the 85 °C/85% RH conditions. The Cu6Sn5 intermetallic-compound (IMC) at the interface of solder joints was observed by scanning electron microscope (SEM). The IMC thickness of Sn-58Bi solder joints was smaller than that of epoxy Sn-58Bi solder. The shear strength was improved up to 20% by epoxy addition. The shear strength of epoxy Sn-58Bi solder joints dramatically decreased after HTHH test for 100 h.

Preparation and reliability of flexible phosphor film for warm white LED

The flexible phosphor film consists of green Y3Al5O12: Ce3+ phosphors, red CaAlSiN3: Eu2+ phosphor and common silicone by spin coating method. The phosphor film was aged by xenon lamp ageing, high temperature-high humidity, the intensity of the emission peak decreased by 2·23, 5·21% and the colour temperature decreased by 1, 20 K, respectively. So the experiment results indicated that the reliability of phosphor film after xenon lamp ageing is better than that after high-temperature and high-humidity. Phosphor powders in the film are homogeneous without precipitation, and it can be seen from the SEM images of the film. The colour temperature of the phosphor film is 2813 K and the flexible phosphor film is practical and useful. Moreover uniform warm white light could be obtained by packing flexible phosphor film with InGaN/GaN LED chips.

Pepper CabZIP63 acts as a positive regulator during Ralstonia solanacearum or high temperature-high humidity challenge in a positive feedback loop with CaWRKY40.

CaWRKY40 is known to act as a positive regulator in the response of pepper (Capsicum annuum) to Ralstonia solanacearum inoculation (RSI) or high temperature-high humidity (HTHH), but the underlying mechanism remains elusive. Herein, we report that CabZIP63, a pepper bZIP family member, participates in this process by regulating the expression of CaWRKY40. CabZIP63 was found to localize in the nuclei, be up-regulated by RSI or HTHH, bind to promoters of both CabZIP63(pCabZIP63) and CaWRKY40(pCaWRKY40), and activate pCabZIP63- and pCaWRKY40-driven β-glucuronidase expression in a C- or G-box-dependent manner. Silencing of CabZIP63 by virus-induced gene silencing (VIGS) in pepper plants significantly attenuated their resistance to RSI and tolerance to HTHH, accompanied by down-regulation of immunity- or thermotolerance-associated CaPR1, CaNPR1, CaDEF1, and CaHSP24. Hypersensitive response-mediated cell death and expression of the tested immunity- and thermotolerance-associated marker genes were induced by transient overexpression (TOE) of CabZIP63, but decreased by that of CabZIP63-SRDX. Additionally, binding of CabZIP63 to pCaWRKY40 was up-regulated by RSI or HTHH, and the transcript level of CaWRKY40 and binding of CaWRKY40 to the promoters of CaPR1, CaNPR1, CaDEF1 and CaHSP24 were up-regulated by TOE of CabZIP63. On the other hand, CabZIP63 was also up-regulated transcriptionally by TOE of CaWRKY40. The data suggest collectively that CabZIP63 directly or indirectly regulates the expression of CaWRKY40 at both the transcriptional and post-transcriptional level, forming a positive feedback loop with CaWRKY40 during pepper's response to RSI or HTHH. Altogether, our data will help to elucidate the underlying mechanism of crosstalk between pepper's response to RSI and HTHH.

Corrosion barriers for silver-based telescope mirrors comparing PEALD and PVD of AlOx

ABSTRACTAstronomical telescopes continue to demand high-endurance high-reflectivity silver mirrors that can withstand years of exposure in earth-based observatory environments. The University of California Observatories Astronomical Coatings Lab has undertaken development of protected silver coatings suitable for telescope mirrors that maintain high reflectivity at wavelengths from 340 nm through the mid-infrared spectrum. We present promising results of enhanced corrosion barriers using plasma-enhanced atomic layer deposition (PEALD) of aluminum oxide (AlOx) as a top barrier layer. Novel coating recipes developed with ion-assisted electron beam deposition (IAEBD) of materials including yttrium fluoride and oxides of yttrium, tantalum, and silicon are used to compare the endurance of physical vapor deposition-grown barriers with PEALD-grown barriers of similar thickness. Samples of these mirror coatings were covered with conformal layers of AlOx deposited by PEALD using trimethylaluminum as a metal precursor and plasma-activated oxygen as an oxidant gas. Samples of coating recipes with and without PEALD oxide undergo aggressive high temperature/high humidity (HTHH) environmental testing in which samples are exposed to an environment of 80% humidity at 80°C for ten days in a simple test set-up. HTHH testing show visible results suggesting that the PEALD oxide offers enhanced robust protection against chemical corrosion and moisture from an accelerated aging environment. Mirror samples are further characterized by reflectivity/absorption before and after deposition of oxide coatings. AlOx is suitable for many applications and has been the initial material choice for this study.

Development of an in-situ High Temperature-High Humidity TEM Observation Technique and Its Application to the Analysis of Catalyst Degradation Mechanism

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Solution-Processed Photosensitive Passivation Layer for an a-Si TFT for LCDs with a Low Dielectric Constant

A solution-processed photosensitive passivation layer with a low dielectric constant (PPLD) has been developed for an a-Si thin film transistor. The PPLD has three highly important properties: a low leakage current, low water absorption, and high-transparency. In addition to providing passivation, the PPLD doubles as a planarization layer. The photoactive property of the PPLD is convenient for its adaption to LCD manufacturing process. A photoactive compound contained in the PPLD enables the formation of contact holes and patterns via a photolithography process. Meanwhile, the PPLD requires ITO workability and strong adhesion property on metal and glass substrates. Apart from the above features, an a-Si TFT must perform with extremely high reliability if it is to replace the conventional inorganic passivation layer (SiNx:H). This reliability has been achieved by an a-Si TFT and LCD panel coated with the PPLD. A reliability test was conducted under a high-temperature, high-humidity (HH) condition to examine how resistant the electronic characteristics were to change. The PPLD-coated LCD panel display view showed no defects for a test duration of HH200 hours. This high reliability was presumed to be at least partly attributable to the low water absorption rate of the passivation layer and the suppression of the increase of the TFT off-leakage current by the PPLD, a passivation layer designed to be non-polar as possible. Judging from the results of these experiments, this solution-processed passivation layer seems to be a viable substitute for the conventional inorganic passivation layer. For a larger screen LCD and higher drive frequency, the problem of RC delay has been emerged. The low dielectric constant of the PPLD will suppress the RC delay of the signal and realize both a higher pixel and a higher drive frequency. key words: passivation, a-Si, solution-processed, reliability

Electrical and Mechanical Properties of Carbon Aerogels / Phenolic Resin for Nanocomposites

This study used carbon aerogels (CA) and phenolic resin in fixed proportations to produce nano high polymer resin, and used poly ehtylene oxide (PEO) as the modifying agent for phenolic resin to improve the mechanical properties of phenolic resin and promote the surface conductivity. The prepared nano high polymer resin and carbon cloth were made into nano-prepreg by using ultrasonic impregnation method, and a nano-prepreg composite material was prepared by using hot compacting and cut to test pieces to measure its mechanical properties and surface conductivity as well as the influence of temperature-humidity environment (85°C/168hr and 85°C/85%RH/168hr) on mechanical properties. The result showed that the surface conductivity increased by 64.55%, the tensile strength at room temperature increased by 35.7%, the flexural strength increased by 18.4%, and the impact strength increased by 101%. In hot environment (85°C/168hr), the tensile strength decreased by 23.8%, the flexural strength increased by 3.1%, and the impact strength increased by 84.6%. In high temperature-high humidity environment (85°C/85% RH/168hr), the tensile strength decreased by 29.6%, the flexural strength decreased by 17%, and the impact strength increased by 95.7%.Introduction