Microscopic Observations Of Cross Sections Research Articles

Effect of AFP induced triangular gaps on manufacturing quality and stress distribution of composite panels

Automated fiber placement technology still faces some significant challenges in fiber path planning for composite laminates with unconventional geometries. Laying triangular gaps can inevitably result in material geometric discontinuities due to geometric constraints such as turning radius, tow angle deviation, and compaction requirements. How to effectively design the distribution of triangular gaps in the thickness direction to reduce the impact on composite parts has become a key issue. This study focuses on the through-thickness staggered distribution of triangular gaps during the path planning process for composite web panels of I-shaped spars. Through ultrasonic scanning analysis and microscopic observation of cross-sections, the effects of differently distributed triangular gaps on the thickness variation, defect distribution, and local waviness of web panels were thoroughly investigated. Afterwards, a finite element model containing gap defects was established to evaluate the effect of different staggered planning schemes of triangular gaps on the stress concentration of web panels by stress concentration factors. Results show that the trajectory planning scheme of layer-by-layer staggering distribution of triangular gaps has obvious advantages compared with the staggered approach with a specific number of layer intervals in terms of forming quality and stress concentration of composite panels.

Active-type starch synthase (SS) IIa from indica rice partially complements the sugary-1 phenotype in japonica rice endosperm.

Introduction of higher SSIIa activity to mild-type isa1 mutant by crossing results in restoration of crystallinity, starch granule structure, and production of plump seeds. Isoamylase 1 (ISA1) removes improper α-1, 6 glycosidic branches of amylopectin generated by starch branching enzymes and is essential for the formation of proper amylopectin structure. Rice isa1 (sug-1) mutants in japonica cultivar with less-active starch synthase IIa (SSIIa) and low granule-bound SSI (GBSSI) expression display wrinkled seed phenotype by accumulating water-soluble phytoglycogen instead of insoluble amylopectin. Expression of active SSIIa in transgenic rice produced with a severe-type isa1 mutant accumulated some insoluble glucan with weak B-type crystallinity at the periphery of seeds but their seeds remained wrinkled. To see whether introduction of high levels of SSIIa and/or GBSSI can restore the grain filling of the mild-type sug-1 mutant (EM653), new rice lines (SS2a gbss1L isa1, ss2aL GBSS1 isa1, and SS2a GBSS1 isa1) were generated by crossing japonica isa1 mutant (ss2aL gbss1L isa1) with wild type indica rice (SS2a GBSS1 ISA1). The results showed that SS2a gbss1L isa1 and SS2a GBSS1 isa1 lines generated chalky plump seeds accumulating insoluble amylopectin-like glucans with an increase in DP 13-35, while ss2aL GBSS1 isa1 generated wrinkly seeds and accumulated soluble glucans enriched with DP < 13. Scanning electron microscopic observation of cross-section of the seeds showed that SS2a gbss1L isa1 and SS2a GBSS1 isa1 produced wild type-like polygonal starch granules. These starches showed the A-type crystallinity comparable to the wild type, while the japonica isa1 mutant and the transgenic rice do not show any or little crystallinity, respectively. These results indicate that introduction of higher SSIIa activity can mostly complements the mild-type sug-1 phenotype.

Chip formation mechanism in machining of Al/SiCp composites based on analysis of particle damage

Particles cracking and debonding are important damage modes that affect the manufacturing processes of Al/SiCp composites. The study of chip formation is the most effective and cheapest way to understand the machining characteristics of a material. Therefore, a comprehensive investigation of the effects of particle damage on the chip formation is of great significance for optimizing the manufacturing processes of Al/SiCp composites. This paper aims to investigate the forming mechanism of particle damage and the effects of particle damage on the chip formation in machining of Al/SiCp composites. The followings are the contributions of this study: (1) According to microscopic observations of chip roots, the forming mechanism of particle damage was revealed. (2) Based on the microscopic observations of cross-section and fracture surface of chips, the effect of particle damage on chip formation was investigated systematically in machining of Al/SiCp composites with varying particle contents and sizes under different cutting conditions. (3) Based on different degrees of particle damage in the chip formation, three novel conceptual models of the chip formation for various fracture types were proposed to visually describe the forming process of chips in machining of Al/SiCp composites.

Surface and Interface Treatments on Wooden Artefacts: Potentialities and Limits of a Non-Invasive Multi-Technique Study

Wooden artefacts embrace wide-ranging types of objects, like paintings on panel, sculptures, musical instruments, and furniture. Generally, in the manufacturing process of an artwork, wood is firstly treated with organic and inorganic materials to make it nonporous and morphologically homogeneous, and, at last, the surface treatment consists of varnishes or coatings applied with the aims of conferring aesthetic properties and protecting wood from biological growth and external degradation agents, as well as mechanical damage. In this work, different wooden mock-ups were prepared by varying some parameters: concentration of filler and pigment, respectively, in the ground and paint layers, thickness of the protective varnish coat, and sequence of the layers. The mock-ups were subsequently exposed to time-varying artificial aging processes. The multi-analytical non-invasive approach involved spectroscopic (reflection FT-IR, Raman, and X-ray fluorescence), tomographic (optical coherence tomography) and colorimetric techniques. Data were interpreted using both univariate and multivariate methods. The aim was to evaluate potential and limits of each non-invasive technique into the study of different stratigraphies of wooden artworks. This approach was supported by microscopic observations of cross-sections obtained from selected mock-ups. The methodological approach proposed here would add valuable technical know-how and information about the non-invasive techniques applied to the study of wooden artworks.

Pharmacognostic Profile of Ageratum conyzoides L Plant and Simplicia

Ageratum conyzoides Linn. is known as billy goat weed, including the family Asteraceae. This plant has been used empirically as a medicine for diarrhea, scratches, antinflammatory, snakebite, insecticide and nemasiticide. This study aims to identify plants based on pharmacognitive profiles including macroscopy, microscopy and non-parametric characters from plant parts of Ageratum conyzoides to determine the standardization of herbs. The results showed that the leaves were ovoid, pale green, soft hairy and purple, bluish or white flowers flowers. Microscopic observations of cross section of stem and leaf showed the presence of parenchyma cells, collenchyma cells and multicellular non-glandular trichomes, upper and lower epidermal cells, stomata in the upper and lower epidermis of the leaf. The highest value of water content was in the radix. The highest value of ash content was in the stem. The highest value of acid soluble ash content was in the radix. The highest value of water-soluble extract was in the folium. The highest value of ethanol-soluble extract was in the flower. The results of this study can be used as authentication of plant parts and a basis for the analysis of the standard pharmacopoeia A. conyzoides.

Performance of composite sandwich structures under thermal cycling

Effect of thermally induced microcracks on mechanical performance of a space grade laminated sandwich panel is investigated. A simple non-contact setup using liquid nitrogen is developed to subject the material to low temperature of −170℃ with cooling rate of 24℃/min. Then the samples are exposed to the elevated temperature of 150℃ inside oven. Microcracks formation and propagation are monitored through microscopic observation of cross-section during the cycling. Flatwise tensile test is performed after a number of cycles. A correlation is made between number of cycles and flatwise mechanical strength after quantifying the microcracks. It is observed that the crack formation gets saturated at about 40 cycles, avoiding the need to conduct more thermal cycles. Microcrack formation both at the free edge and middle of laminate was observed. The crack density at the middle was comparatively less than the ones found on the free edges. Results for non-contact cooling are compared with samples from direct nitrogen contact cooling. Microscopic inspection and flatwise test show differences between contact and non-contact cooled samples. Flatwise tensile strength for non-contact cooled samples shows 15% reduction, while the contact cooled samples have about 30% decrease in bond strength. A 3D finite element analysis is conducted to qualitatively identify the location of stress concentration which can be possible sites of crack formation. Good agreement is observed between the model and experimental results.

Influence of temperature on the progamic phase in Citrus

Temperature in the progamic phase is critical for the success of plant sexual reproduction, and new knowledge is needed to optimise breeding programmes to obtain new varieties that adapt to a climate change scenario. Using three male donors and one female recipient in the genus Citrus, we evaluated the effect of four temperature regimes on each process in the progamic phase. An innovative method based on microscopic observations of cross sections from pollinated pistils collected daily allowed a comprehensive analysis of pollen tube growth (dynamics and kinetics) along the pistil. Pollen grain germination and stigmatic receptivity were evaluated directly on the stigma, which offers more accurate information than previously reported in vitro experiments. Our results showed that warm temperatures reduce the time needed by pollen tubes to reach ovules and accelerate pistil degeneration, while cold temperatures produce the opposite effects. Interestingly, we observed both pollen grain germination and pollen tube growth at 10 °C, which have not been observed in previous studies in citrus. At this temperature, the differences observed in both pollen grain germination and pollen tube growth for different genotypes reflect the adaptation of their sporophytic generation to low temperatures which would enable gametophytic screening to be used as a tool to select better adapted genotypes to different temperature conditions. The differences observed in the growth rates between pollen tubes in each genotype-temperature combination provide an opportunity to explore additional gametophytic selection in this reproductive phase. The capacity to respond to temperature changes in the progamic phase to ensure mating can be useful for breeding programs that focus on obtaining better adapted populations to different temperature conditions.

The influence of heat treatment on the structure and thermal properties of metallic glasses

This paper presents the structure and chosen properties of Fe-based ribbons with specified composition, after casting and heat treating. The aim of this work was to produce amorphous ribbons and study the influence of heat treatment on the structure and thermal properties before and after annealing. The base alloy ingot was prepared by induction melting of pure Fe, Co, B, Si and Nb elements in argon atmosphere. Then, the station for ultra-fast cooling of molten alloy with high vacuum pumps, designed for the production of metallic glasses in the form of ribbons by Buhler Melt Spinner SC was used. Also, the X-ray diffraction analysis system PANalytical X’Pert PRO was used. As-cast ribbons and metallic glasses after annealing were examined by differential scanning calorimetry (DSC) method, with the use of DSC822 Mettler Toledo. Annealing was done at different temperature. On the basis of obtained dependence, the glass transition temperature (Tg), onset crystallization temperature (onset—Tx) and peak crystallization temperature (peak—Tp) were determined. The supercooled liquid region (ΔTx), specific heat and the crystallization enthalpy (ΔH) were calculated as well. The microscopic observation of cross section of ribbons was carried out by means of the Zeiss Supra 35 scanning electron microscope. Based on experimental data, the discussion on the correlation between thermal properties, structure, annealing and future application was carried out.

A class II KNOX gene, KNOX4, controls seed physical dormancy

Physical dormancy of seed is an adaptive trait that widely exists in higher plants. This kind of dormancy is caused by a water-impermeable layer that blocks water and oxygen from the surrounding environment and keeps embryos in a viable status for a long time. Most of the work on hardseededness has focused on morphological structure and phenolic content of seed coat. The molecular mechanism underlying physical dormancy remains largely elusive. By screening a large number of Tnt1 retrotransposon-tagged Medicago truncatula lines, we identified nondormant seed mutants from this model legume species. Unlike wild-type hard seeds exhibiting physical dormancy, the mature mutant seeds imbibed water quickly and germinated easily, without the need for scarification. Microscopic observations of cross sections showed that the mutant phenotype was caused by a dysfunctional palisade cuticle layer in the seed coat. Chemical analysis found differences in lipid monomer composition between the wild-type and mutant seed coats. Genetic and molecular analyses revealed that a class II KNOTTED-like homeobox (KNOXII) gene, KNOX4, was responsible for the loss of physical dormancy in the seeds of the mutants. Microarray and chromatin immunoprecipitation analyses identified CYP86A, a gene associated with cutin biosynthesis, as one of the downstream target genes of KNOX4 This study elucidated a novel molecular mechanism of physical dormancy and revealed a new role of class II KNOX genes. Furthermore, KNOX4-like genes exist widely in seed plants but are lacking in nonseed species, indicating that KNOX4 may have diverged from the other KNOXII genes during the evolution of seed plants.

Characterization of Handsheets Prepared from TEMPO-Oxidized Pulps with De-bonder

A hardwood bleached kraft pulp was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation, and two TEMPO-oxidized pulps with different carboxylate but similar aldehyde contents were prepared. Handsheets were prepared from the reference and TEMPO-oxidized pulps with di(oleamidoethyl)ammonium formic acid salt (DOFAS) used as a de-bonder in handsheet-making. Density, DOFAS content and tensile strength of the handsheets were measured, and these properties were compared between the reference and TEMPO-oxidized pulps. When the TEMPO-oxidized pulps were used, sheet density was effectively decreased, but degrees of tensile strength reduction of the handsheets were diminished to some extent, in comparison with the reference pulp. Sheet density can be decreased by partial prevention of interfiber hydrogen bonds with DOFAS molecules added, although interfiber bonds are still present when TEMPO-oxidized pulps are used. Scanning electron microscopic observations of cross sections of the handsheets also supported the above hypothesis. TEMPO-oxidized pulps had significant amounts of aldehyde groups so that hemiacetal linkages are probably formed with hydroxyl groups at the interfiber bonding areas, thus resulting in higher tensile strength of the handsheets prepared thereof. Hence, an effective decrease in sheet density can be achieved with less reduction of tensile strength by preparation of handsheets from TEMPO-oxidized pulps with DOFAS. Aldehyde groups formed by the TEMPO-mediated oxidation and present on the pulp fiber surfaces are likely to contribute to higher tensile strength of the handsheets.

ポリマー含浸焼成回数の異なる三次元織ＳｉＣ／ＳｉＣ複合材料のＡＥ法による曲げ破壊挙動の評価

The effect of the porosity on the fracture behavior of 3D-woven SiC/SiC composites fabricated by multiple polymer impregnation pyrolysis (PIP) process was focused in this paper. The number of PIP cycles was varied as two, four and nine which yielded various porosities from 13 to 30%. The fracture behavior was examined by 4-point bending tests with the aid of acoustic emission (AE) monitoring. The microscopic observations of cross section after loading showed that the critical stress for the onset of crack formation on the tensile surface was increased with the decrease in porosity. However, the AE analysis indicated that the composite with the lowest porosity showed the earliest crack propagation in the rich PIP-SiC matrix region. The composite with intermediate porosity exhibited the most delayed onset of microdamage accumulation. Regardless of the porosity, the large pores located between fiber bundles did not arrest the crack growth from tensile side along thickness. The effect of the porosity on bending fracture process was explained by both the several crack propagation paths and the stress levels for the initiation of the cracks.

Effect of aluminum content on mechanical properties of hydrogenated Mg–Al magnesium alloys

Abstract The mechanical properties of hydrogenated Mg–Al magnesium alloys with various aluminum content were investigated. The ductility, yield strength (YS) and ultimate tensile strength (UTS) of the hydrogenated material decreased while the hardness increased with increasing the aluminum content. Microscopic observations of cross-sections of hydrogenated specimens with various Al content revealed that hydrogen cracks extended deeply as the Al content in the Mg–Al alloys increased. Moreover, X-ray diffraction (XRD) analysis revealed that MgH 2 and AlH 3 hydrides are formed during hydrogenation and were found to contribute to hydrogen embrittlement of Mg–Al alloys. However, the embrittled zone was observed to be larger at the fracture surface of Mg–15Al alloy than that of Mg–5Al alloy. Moreover, the fracture surface of Mg–30Al alloy exhibited completely brittle fracture after hydrogenation.

Mg-Doped Sapphire Crystal Fibers Grown by Laser-Heated Pedestal Growth Method

We grew sapphire crystal fibers doped with various Mg concentrations from 0.5 to 4 mol % by the laser-heated pedestal growth method. It was easy to grow defect-free 0.5 mol % Mg-doped sapphire crystal fibers longer than 50 mm; however, the length of the defect-free region decreased as the amount of MgO doping increased. The growth rates also influenced the quality of the fibers. Microscopic observations of cross sections of the grown fibers revealed that the defects were always concentrated in the central regions of the fibers. Using an electron probe X-ray microanalyzer, we also found Mg in the central regions of the fibers. We discuss the influence of thermocapillary convection and the growth rate on the Mg distribution, and the reason for the formation of defects by constitutional supercooling is described. Using thermomechanical analyzer measurements, we suggest that the strength of the sapphire can be enhanced by MgO doping, which increases Young's modulus.

Evaluation of Corrosion and Wear Resistance of Hard Cermet Coatings Sprayed by Using an Improved HVOF Process

Research for alternatives of hard chrome plating has been widely carried out in the world. High-velocity oxygen-fuel (HVOF)-sprayed cermet coating is one of such alternative candidates. Depending on the cermet powder for spraying, however, sometimes the density of the sprayed coatings is not sufficient for desired corrosion resistance. A gas-shroud (GS) attachment for use with commercial HVOF, which is effective in suppressing oxidation of sprayed particles while raising the velocity of sprayed particles, has been developed. The GS-HVOF spray has been successfully applied to corrosion resistant alloys such as HastelloyC. In this study, a WC cermet system with corrosion and wear resistance was sprayed using a gas-shroud attachment. Porosity in the coatings was observed by the microscopic observation of cross sections. Corrosion and wear resistance was evaluated by alternating current corrosion monitoring in artificial seawater and abrasive wear-tester, respectively. Coatings deposited by the gas-shroud HVOF were superior in terms of both corrosion and wear resistance to coatings formed by the conventional HVOF. The density of the sprayed coatings was improved using the gas-shroud attachment, resulting in superior corrosion and wear resistance.

섬유의 적층각과 금속판의 특성에 따른 섬유 금속 적층판의 충격 손상 거동

Impact tests were conducted to study the effect of angle ply and metal laminate on impact damage<br/> characteristics of Fiber Metal laminates (FML). Impact tests were conducted using drop weight impact machine and damage behavior were analyzed by comparing with load-displacement curve and surface observation and microscopic observation of cross sections. The effect of angle ply on impact characteristics of FML are influenced by property of metal laminate. i.e., when the metal laminate is not enough to strong to prevent fiber debonding, Angle ply FML is superior to singly oriented ply (SOP) FML because angle ply enhance the stiffness by fiber supports and prevent crack propagation. However, when the metal laminate is<br/> enough to strong to prevent fiber debonding. SOP FML is superior to Angle ply FML because the fiber of lower ply in Angle ply FML are more stressed than that of SOP FML.

N&lt;SUB&gt;2&lt;/SUB&gt;&lt;SUP&gt;+&lt;/SUP&gt;イオン注入した純チタンの大気中および水蒸気中での高温酸化挙動

N2+ ions were implanted into specimens of commercially supplied pure titanium at 1.5 MeV with different doses ranging from 5×1020 to 2×1021 ions per m2, and the oxidation behavior of specimens was investigated in air and water vapor at 823 K and 1073 K.The mass gain of the specimen increases with increasing holding time and it is much larger in water vapor than in air. The mass gain of the implanted specimen is less than that of unimplanted specimen in both environments, and the amount of oxidation decreases with increasing implantation doses. According to X-ray diffraction analysis, TiH2 is detected in the substrate after oxidation in water vapor. The X-ray analysis and the microscopic observation of cross section indicate that the oxidation in water vapor occurs from the interface between the oxidation film and the substrate by the inner transfer of water vapor. The reason for the reduction of oxidation by N2+ ion implantation can be that the Ti2N or TiN precipitates decrease the effective surface area for oxide formation and the soluted nitrogen atoms prevent the ingress of oxygen atoms into the surface region.

Effects of pH and ionic strength on microfiltration of C. glutamicum

The effects of pH and ionic strength on microfiltration of Corynebacterium glutamicum ( C. glutamicum) were evaluated. The filtration performance was characterized by the specific cake resistance ( α) calculated from measurement of dead-end filtration flux using Ruth's equation. When the pH of the cell slurry was adjusted from 6.3 to 2.0, α decreased by a factor of 5 which meant that the total flux was improved five times; the effect of ionic strength was much less. Measurements of zeta potential and hydrophobicity showed the cells to be more hydrophobic and have lower surface charge at pH 2 than at neutral pH. Microscopic observation of cross-sections of the cell cake layer showed cells aggregated at pH 2, but not at pH 5. The aggregation behavior is consistent with the reduction of surface repulsion at pH 2 and the larger voids between aggregates account for the larger flux.

Interfacial diffusion in layered polyesters

Microscopic observations of cross sections of laminates of unsaturated polyesters revealed a birefringent zone (interphase) at the interface. Several observations associated with this interphase were made that predicted either beneficial or detrimental effects of the presence of the interphase in the laminate. A study was conducted to identify the origin and to characterize the properties of the interphase. It was proven that the interfacial diffusion of uncured liquid resin into the previously cured resin formed the interphase. The significant effect of the curing of the second layer on the thickness of the interphase was evident. The diffusion kinetics was dependent on the laminate preparation conditions. A correlation was developed that predicts the properties of the interphase based on crosslinking density of layer I and gel time of the resin of layer II.

Interfacial diffusion in layered polyesters

Microscopic observations of cross sections of laminates of unsaturated polyesters revealed a birefringent zone (interphase) at the interface. Several observations associated with this interphase were made that predicted either beneficial or detrimental effects of the presence of the interphase in the laminate. A study was conducted to identify the origin and to characterize the properties of the interphase. It was proven that the interfacial diffusion of uncured liquid resin into the previously cured resin formed the interphase. The significant effect of the curing of the second layer on the thickness of the interphase was evident. The diffusion kinetics was dependent on the laminate preparation conditions. A correlation was developed that predicts the properties of the interphase based on crosslinking density of layer I and gel time of the resin of layer II. © 1996 John Wiley & Sons, Inc.

Microscopic Observation of Cross-Section of Dyed Wool and Nylon 6 Fibers after Treatment with Low-Temperature Plasma.

Wool and nylon 6 fibers were treated with O2, CF4, and atmospheric He/Ar low-temperature plasmas and then dyed with acid and basic dyes respectively. The cross-sections of dyed fibers were observed with optical microscope. The diffusion of both acid and basic dyes for wool was increased by O2 plasma treatment, whereas for the O2 plasma-treated nylon 6 fiber the diffusion of acid dye was restrained and that of basic dye was increased.