Sample Shrinkage Research Articles

Application of dilatometric analysis to the study of autoclaved calcium silicate materials

The process of shrinkage of calcium silicate hydrate was investigated by dilatometry up to 350 °C. The properties of this material are based on the formation of C–S–H phases during the reaction at temperatures between 180 and 205 °C and water vapor pressure lower than 16 bars. The main C–S–H phases are 11.3 A tobermorite and xonotlite. 11.3 A tobermorite converts to 9.3 A tobermorite on air at temperatures around 300 °C. The hydrosilicate materials were prepared from quicklime and finely ground sand with different CaO/SiO2 ratios under different hydrothermal conditions. The reaction time was 24 h. Materials based on xonotlite and tobermorite were produced, and the calcium silicate phases were characterized by XRD and TG/DTA methods. Dilatometry measurements were used to study the effect of heating conditions on sample shrinkage. Dehydration of hydrated calcium silicate minerals occurred during heating. The results show that sample shrinkage is dependent on the type and amount of C–S–H phases, the amount of bound water and formation of 9.3 A tobermorite. All samples showed shrinkage after heating up to 350 °C, but this change was not irreversible for all samples after cooling to room temperature.

Fluoropolymer Nanosheet as a Wrapping Mount for High-Quality Tissue Imaging.

In the field of biological microscopy technology, it is still a practical challenge to obtain high-quality tissue images, due to the tissue desiccation that occurs during observations without an effective sample mounting. Inspired by the use of plastic food wrap, this study proposes the use of polymer thin films (also known as nanosheets) to fix the tissue samples. Water-repellent nanosheets composed of the amorphous fluoropolymer CYTOP are prepared with adjustable thicknesses and their hydrophobicity, transparency, and adhesion strength are evaluated. They show excellent water-retention effect and work well for sample fixation. By wrapping cleared mouse brain slices with a 133 nm thick CYTOP nanosheet, this study achieves high spatial resolution neuron images while scanning over a large area for a long period of time. No visible artifacts arising from sample shrinkage can be detected. This study also expects that nanosheet wrapping could be effective over a longer time span by combination with conventional agarose embedding.

Comparative microstructure study of oil palm fruit bunch fibre, mesocarp and kernels after microwave pre-treatment

The implementation of microwave technology in palm oil processing offers numerous advantages; besides elimination of polluted palm oil mill effluent, it also reduces energy consumption, processing time and space. However, microwave exposure could damage a material’s microstructure which affected the quality of fruit that can be related to its physical structure including the texture and appearance. In this work, empty fruit bunches, mesocarp and kernel was microwave dried and their respective microstructures were examined. The microwave pretreatments were conducted at 100W and 200W and the microstructure investigation of both treated and untreated samples were evaluated using scanning electron microscope. The micrographs demonstrated that microwave does not significantly influence kernel and mesocarp but noticeable change was found on the empty fruit bunches where the sizes of the granular starch were reduced and a small portion of the silica bodies were disrupted. From the experimental data, the microwave irradiation was shown to be efficiently applied on empty fruit bunches followed by mesocarp and kernel as significant weight loss and size reduction was observed after the microwave treatments. The current work showed that microwave treatment did not change the physical surfaces of samples but sample shrinkage is observed.

EFFECT OF GRANULATION, MECHANICAL ACTIVATION, THERMOVACUUM TREATMENT AND AMBIENT GAS PRESSURE ON TI–0,5C SYSTEM SYNTHESIS REGULARITIES

This paper studies dependences of combustion velocities and changes in sample relative lengths from ambient pressure and thermovacuum degassing (TVD) time for the Ti + 0,5C mixture. It was shown that Ti + 0,5C mixture TVD significantly (doubly) increase combustion velocity as well as sample shrinkage. Sample shrinkage occurs under the influence of surface tension due the sufficient quantity of a liquid phase in combustion products that ensure their low viscosity. It was not possible before to obtain pressed samples from the mechanically activated (MA) Ti + C mixture because of their low strength, and therefore to investigate their combustion regularities. To solve this problem, the authors used preliminary granulation of the initial Ti + 0,5C mixture before MA. As a result, dependences of combustion velocity and post-combustion changes in sample lengths from MA time were obtained for the first time ever for the Ti + 0,5C preliminary granulated mixture. It was found that mechanical activation decreases mixture combustion velocity and significantly (triply) increases sample elongation after combustion. Combustion velocity after MA mixture TVD reaches combustion velocity of initial mixtures at the same TVD time. The samples of condensed reaction products from the MA mixture retained a slight elongation (within 8 %) after TVD. X-ray phase analysis revealed no reaction products formed during MA. Combustion products of all mixtures (initial, activated mixture and activated granules) contain the Ti2C phase and Ti traces. X-ray analysis of the initial and MA mixtures shows peaks intensity broadening and reduction of peak intensity to the background intensity ratio after MA thus indicating a higher defect rate in the crystal structure of the components of mixtures. This effect intensifies with an increase in activation time. The study results are interpreted based on the conduction – convection model of reaction wave propagation.

Modelling bench-scale fire on engineered wood: Effects of transient flame and physicochemical properties

The engineered wood such as medium density fibreboard (MDF) has been widely used in buildings and constructions, and has the advantages of energy saving, consistent performance, and fine finish. However, its fire hazards have not yet been well studied. In this paper, a one-dimensional pyrolysis model was proposed for fires on the bench-scale MDF sample, and considered four features: (I) four-step non-first-order kinetic model, (II) transient flame heat flux, (III) heterogeneous vertical density profile, and (IV) sample shrinkage. The default modelling scheme including all four features gave excellent agreements with the experimental ignition delay time and mass loss rate of MDF under constant cone irradiations of 35–65 kW/m2. Comparisons showed that assuming one-step kinetics and homogeneous vertical density profile can clearly affect the prediction of ignition delay time. Neglecting the sample shrinkage can significantly impair the prediction of mass loss rate. If multiple simplifications were used together or in different sequences, synergy and compensation effects were discovered in modelling. It is suggested that the influence of these four features as well as their compensation and synergy effects should not be overlooked in modelling fires on engineered wood, even for a bench-scale fire.

Impact of chemical finishing on laser-sintered nylon 12 materials

Additive Manufacturing offers many potential benefits including reduced tooling costs and increased geometric freedom. However, the surface quality of the parts is typically below that of conventionally-processed materials. This paper evaluates a new chemical post-processing method to reduce the roughness of laser-sintered Nylon 12 components. This process is called the PUSh™ process. The treatment reduced the surface roughness of sample parts from 18μm to 5μm Ra and largely eliminated roughness with length scales below 500μm. Treatment did not affect the flexural modulus, flexural strength, or dimensions of 3.2mm thick bending specimens, but it did significantly impact the mechanical properties of thin tensile specimens that are one to eight layers thick. The post processing reduced the breaking force of the samples, but it increased the ultimate tensile strength and elongation at break. The impact was largest on the thinnest parts. Significant sample shrinkage (12–20%) and weight gain (3.7–7%) from treatment was also observed in the tensile specimens. The results show that the PUSh™ process dramatically increases surface smoothness and elongation at break in thin specimens. It decreases the surface strength, but effects are negligible in larger samples.

A Comparative Modeling Study of Quince Infrared Drying and Evaluation of Quality Parameters

Abstract In this research, infrared drying of thin-layer quince slices with thickness of 5±0.24 mm was investigated at four levels of radiation power. The final temperatures of 50, 60, 70 and 80 °C were achieved by regulating the radiation power. A comparative study was performed among adaptive neuro-fuzzy inference system (ANFIS) and 10 well-known empirical models to predict the drying kinetics. The ANFIS modeling results showed an excellent prediction of moisture content value (R 2=0.9998 and RMSE=0.0041). Among the empirical models, Midilli model fitted the experimental data well for the whole range of temperatures (R 2=0.9987–0.9994 and RMSE=0.0068–0.0098). Effect of final drying temperature on the sample color, shrinkage, texture and rehydration ratio was also investigated. Analysis of variance of quality parameters showed that the final drying temperature had a significant effect on the color, shrinkage and texture (p < 0.05). The final drying temperature of 80 °C had a negative effect on the color, shrinkage and texture of samples.

Combustion of cylindrical Ti + 0.5C compacts: Influence of mechanical activation, thermovacuum degassing, and ambient pressure

We explored the influence of mechanical activation (MA), thermovacuum degassing (TVD), and ambient pressure on burning velocity and sample shrinkage/elongation for SHS reactions in cylindrical Ti + 0.5C powder compacts. Thermovacuum degassing of Ti + 0.5C mixtures was found to increase the burning velocity (2-fold) and sample shrinkage. Mechanical alloying decreased the burning velocity and gave large (3-fold) sample elongation. The results can be readily rationalized in terms of conduction-convection combustion theory.

Optimal Contrast Agent Staining of Ligaments and Tendons for X-Ray Computed Tomography.

X-ray computed tomography has become an important tool for studying the microstructures of biological soft tissues, such as ligaments and tendons. Due to the low X-ray attenuation of such tissues, chemical contrast agents are often necessary to enhance contrast during scanning. In this article, the effects of using three different contrast agents—iodine potassium iodide solution, phosphotungstic acid and phosphomolybdic acid—are evaluated and compared. Porcine anterior cruciate ligaments, patellar tendons, medial collateral ligaments and lateral collateral ligaments were used as the basis of the study. Three samples of each of the four ligament/tendon types were each assigned a different contrast agent (giving a total of twelve samples), and the progression of that agent through the tissue was monitored by performing a scan every day for a total period of five days (giving a total of sixty scans). Since the samples were unstained on day one, they had been stained for a total of four days by the time of the final scans. The relative contrast enhancement and tissue deformation were measured. It was observed that the iodine potassium iodide solution penetrated the samples fastest and caused the least sample shrinkage on average (although significant deformation was observed by the time of the final scans), whereas the phosphomolybdic acid caused the greatest sample shrinkage. Equations describing the observed behaviour of the contrast agents, which can be used to predict optimal staining times for ligament and tendon X-ray computed tomography, are presented.

Calibration of two filter papers at different temperatures and its application to GMZ bentonite

It is worth to study the hydro-mechanical behavior of unsaturated soils at different temperatures since non-isothermal conditions are inevitable in the practice of geotechnical engineering, e.g., unsaturated buffer/backfill materials in the nuclear waste disposal repository experience increasing temperature due to the dissipation of the radioactive energy. Suction is the key variable in predicting unsaturated soil’s hydro-mechanical responses, and the filter paper method is a simple, but effective method to measure the suction of unsaturated soils. This study presents the results of a series of tests examining the effect of temperature on the calibration curves of Whatman No. 42 and Double Circle No. 203 filter papers, and the application of these curves to the measurement of the total suction of compacted unsaturated bentonite at different temperatures. The calibration curves between the suction and water content for the two filter papers were determined at temperatures of 20, 40, 60 and 80 °C by the vapor equilibrium technique using fifteen types of saturated salt solutions. The test results show that calibration curves decreases with increasing temperature. The calibration equations for the filter papers are proposed at temperatures of 20, 40, 60 and 80 °C. The calibration curves were used to determine the soil–water characteristic curve (SWCC) of Gaomiaozi calcium bentonite, a possible buffer material for the deep geological disposal of high level radioactive waste in Chinese repositories, at these temperatures. It is found that the SWCCs of the bentonite are similar between the two filter papers, and decrease clearly with temperature, especially above 60 °C. Not only does the bentonite show a lower soil–water characteristic curve at higher temperature, but the volume of the soil sample shrinkage was also more significant.

Control of Y-211 content in bulk YBCO superconductors fabricated by a buffer-aided, top seeded infiltration and growth melt process

Bulk (RE)–Ba–Cu–O ((RE)BCO, where RE stands for rare-earth), single grain superconductors can trap magnetic fields of several tesla at low temperatures and therefore can function potentially as high field magnets. Although top seeded melt growth (TSMG) is an established process for fabricating relatively high quality single grains of (RE)BCO for high field applications, this technique suffers from inherent problems such as sample shrinkage, a large intrinsic porosity and the presence of (RE)2BaCuO5 (RE-211)-free regions in the single grain microstructure. Seeded infiltration and growth (SIG), therefore, has emerged as a practical alternative to TSMG that overcomes many of these problems. Until now, however, the superconducting properties of bulk materials processed by SIG have been inferior to those fabricated using the TSMG technique. In this study, we identify that the inferior properties of SIG processed bulk superconductors are related to the presence of a relatively large Y-211 content (∼41.8%) in the single grain microstructure. Controlling the RE-211 content in SIG bulk samples is particularly challenging because it is difficult to regulate the entry of the liquid phase into the solid RE-211 preform during the infiltration process. In an attempt to solve this issue, we have investigated the effect of careful control of both the infiltration temperature and the quantity of liquid phase powder present in the sample preforms prior to processing. We conclude that careful control of the infiltration temperature is the most promising of these two process variables. Using this knowledge, we have fabricated successfully a YBCO bulk single grain using the SIG process of diameter 25 mm that exhibits a trapped field of 0.69 T at 77 K, which is the largest value reported to date for a sample fabricated by the SIG technique.

Predicting the drying properties of sludge based on hydrothermal treatment under subcritical conditions

The effects of hydrothermal treatment on the drying properties of sludge were determined. Sludge was hydrothermally treated at 180–260 °C for 0.5–5 h using NaOH and HCl as additives to influence reaction conditions. Untreated sludge and attained hydrochar samples were then dried under identical conditions with a laboratory microdryer and an X-ray microtomograph was used to follow changes in sample dimensions. The effective moisture diffusivities of sludge and hydrochar samples were determined and the effect of process conditions on respective mean diffusivities evaluated using multiple linear regression. Based on the results the drying time of untreated sludge decreased from approximately 80 min to 37–59 min for sludge hydrochar. Drying of untreated sludge was governed by the falling rate period where drying flux decreased continuously as a function of sludge moisture content due to heat and mass transfer limitations and sample shrinkage. Hydrothermal treatment increased the drying flux of sludge hydrochar and decreased the effect of internal heat and mass transfer limitations and sample shrinkage especially at higher treatment temperatures. The determined effective moisture diffusivities of sludge and hydrochar increased as a function of decreasing moisture content and the mean diffusivity of untreated sludge (8.56·10−9 m2 s−1) and sludge hydrochar (12.7–27.5·10−9 m2 s−1) were found statistically different. The attained regression model indicated that treatment temperature governed the mean diffusivity of hydrochar, as the effects of NaOH and HCl were statistically insignificant. The attained results enabled prediction of sludge drying properties through mean moisture diffusivity based on hydrothermal treatment conditions.

Effect of freezing pretreatment on the drying characteristics and volume change of carrots immersed in a fluidized bed of inert particles under reduced pressure

A drying method with a low drying temperature and a high drying rate that induces small volume change in biological samples was developed for drying heat-sensitive foods and agricultural products. Freezing pretreatment was combined with fluidized-bed drying under reduced pressure. Cylindrical carrot samples were frozen and then immersed in a fluidized bed of inert particles under reduced pressure without thawing. A higher drying rate was achieved for carrots subjected to freezing pretreatment than for the untreated counterparts. The drying rate was higher at 12 kPa than at atmospheric pressure. The volume change induced during the drying process was smaller for carrots subjected to freezing pretreatment than for the untreated congeners. A high drying rate at a low temperature with minimal sample shrinkage was achieved via the combined freezing pretreatment and fluidized-bed drying under reduced pressure. This method can be applied for drying heat-sensitive materials such as food and agricultural products.

An improved top seeded infiltration growth method for the fabrication of Y–Ba–Cu–O bulk superconductors

Buffer-aided top seeded infiltration and growth (TSIG) with a suitable liquid phase reservoir has been compared with the top seeded melt growth (TSMG) process and applied successfully to fabricate single grain YBa2Cu3O7-δ​(YBCO) bulk superconductors. A Yb-based liquid phase has been observed to yield the homogeneous, high density YBCO single grains by the TSIG technique. Sintering the Y2BaCuO5(Y-211) preform prior to TSIG has been found to be critical in retaining the shape of the sample during the infiltration and growth process. A number of advantages of the TSIG process have been demonstrated, including a dramatic reduction in sample shrinkage and a general improvement in bulk microstructure. TSIG processed samples also exhibit a fine and even distribution of unreacted, embedded Y-211 inclusions that play a key role in flux pinning in the fully processed bulk material. A YBCO sample of diameter 25mm fabricated by the optimised buffer-aided TSIG process was able to trap a field of 0.63T at 77K, which is the highest value of trapped field ever reported for a YBCO sample fabricated by the TSIG process. The technique reported here has the potential to improve further the microstructural and superconducting properties of single grain bulk YBCO, which enhances further the applications potential of these materials.

Drying and Shrinkage Kinetics of Solid Waste of Olive Oil Processing

The problems created in managing olive mill wastewater (OMW) have been extensively investigated during the last few years. In most cases, dehydration of olive mill wastes is a first step before developing further applications. The subject of this study was to determine the drying behavior of OMW solid fraction (OMWS). Drying (moisture vs time) and shrinkage (image vs time) data were obtained on slabs of OMWS in an air dryer operated at 60–80°C. The effective diffusivity was determined using (a) the simplified solution of Fick's second law and (b) the method of slopes of the drying curve, taking into account the effect of moisture content on diffusivity and sample shrinkage. The combined effect of moisture content and temperature on effective diffusivity was expressed by an empirical model. In addition, each moisture loss and shrinkage curve was fit to 10 simplified drying models. The dependence of the best descriptive model constants on drying temperature was expressed by an appropriate type of model.

制备大尺寸单畴YBCO超导块材的新方法

The top seed melt-textured growth method (TSMTG) is a most effective method for the preparation of large size single domain YBCO bulk superconductors, but suffers from sample shrinkage and serious sample deformation problems during the TSMTG process; the top-seeded infiltration growth method (TSIG) was invented to overcome these problems. However, three different powders, comprising Y2BaCuO5 (Y211), YBa2Cu3O y (Y123), and BaCuO2, must be prepared before fabrication of single domain YBCO bulk superconductors by the traditional TSIG method. This process is complicated, time-consuming, energy-consuming, and leads to atmospheric pollution, and it is also impossible to control the density and the distribution of the Y211 particles in the samples. To solve these important technical problems, we have invented a new TSIG method whereby a mixture of Y2O3 + 1.2 BaCuO2 powder is used as a new solid phase to replace the traditional solid-phase Y211, and a mixture of Y2O3, BaCuO2 and CuO powder is used as a new liquid phase rather than the traditional (Y123 + 3 BaCuO2 + 2 CuO) phase. Using this new solid phase and liquid phase, single domain YBCO bulk superconductors with diameters of 59 mm and 93 mm have been successfully prepared by the proposed TSIG process. We found that: (1) the crystal growth rate of the single domain YBCO bulks prepared by the new TSIG process is approximately 1.7 times higher than that of similar samples prepared by the traditional TSIG method; (2) the levitation force of single domain YBCO bulks prepared by the new TSIG process is 1.65 times higher than that of samples prepared by the traditional TSIG method; (3) the Y211 particles prepared by the new TSIG process are much smaller in size and have a more reasonable distribution than in the samples prepared by the traditional TSIG method, and this can effectively improve the flux pinning force of the sample. These results indicate that the new TSIG process that was developed in our laboratory is a very important and highly practical method for the fabrication of low-cost, large size, high-quality single domain rare earth BCO (REBCO)-type bulk superconductors.

Changes in structure and in mechanical properties during the pyrolysis conversion of crosslinked polymethylsiloxane and polymethylphenylsiloxane resins to silicon oxycarbide glass

The subject of this study is the thermally induced conversion of cross-linked polymethylsiloxane and polymethylphenylsiloxane resins into inorganic silicon oxycarbide glass. This topic is studied in view of the changes in the chemical structure of the precursor and in the context of the changes in hardness and elasticity, pyrolysis weight losses, density changes, and sample shrinkage. Two aspects of the pyrolysis process were studied: i) the effect of the pyrolysis temperature (tested from 400 to 1000°C) and ii) the effect of pyrolysis time in cases of isothermal pyrolyses (at 520°C and 650°C). The mechanical properties were evaluated by means of micro-indentation tests, while the characterisation of the chemical structure was performed via FTIR spectroscopy, combustion analysis and EDS. The results of these experiments are discussed in the context of the use of examined materials as a precursor for the composite matrix or the sandwich core.

Computer Vision System (CVS) for In-Line Monitoring of Visual Texture Kinetics During Shrimp (Penaeus Spp.) Drying

In this study, the effects of drying medium temperature and velocity were surveyed on the image texture features of shrimp (Penaeus spp.) batches in a dryer equipped with a perpendicular dual-view computer vision system (CVS). This was carried out by applying an innovative rotation- and scale-invariant image texture processing approach with the capability of eliminating the effects of sample shrinkage on the visual textural features. Moreover, the variations in image texture parameters were investigated with moisture ratio, color, and geometrical characteristics of the shrimp samples. Drying experiments were conducted at hot air drying (HAD) temperatures of 50–90°C and superheated steam drying (SSD) temperatures of 110–120°C with drying medium velocities of 1–2 m/s. Several configurations of a multilayer perceptron artificial neural network (MLP-ANN) were also used to predict the moisture ratio and the geometrical characteristics of the shrimp batch using the image texture parameters. Generally, the image texture features were significantly affected by drying medium temperatures (p < 0.01), and the effects of drying medium velocities on the textural properties were nonsignificant (p > 0.05). Additionally, the higher drying temperatures generated products with uniform and regular texture patterns. The SSD produced samples with somewhat nonuniform and irregular texture patterns compared with HAD at 90°C. Finally, selected MLP-ANN topologies successfully predicted the moisture ratio and the geometrical characteristics of the shrimp batch using the textural properties with correlation coefficients higher than 0.99.

Effects of sample site and size, skin tension lines, surgeon, and formalin fixation on shrinkage of skin samples excised from canine cadavers.

To assess the effects of sample size and location, skin tension lines, surgeon, and formalin fixation on the extent of shrinkage that occurs in excised canine skin samples. Cadavers of 4 adult purpose-bred mixed-breed hound dogs with grossly normal skin. 54 circular areas of skin (2-, 4-, and 6-cm-diameter samples from each of 9 body regions on each side) were excised by 1 of 2 surgeons from each cadaver. The diameter of each sample was measured in 4 orientations (parallel to previously reported tension lines, perpendicular to tension lines, in a dorsoventral orientation, and in a craniocaudal [or rostrocaudal] orientation) at 3 time points (before and immediately after excision and after 24 hours of formalin fixation). 216 samples were measured in all 4 orientations at all 3 time points. For all samples, mean ± SE decrease in diameter after fixation, compared with pre-excision findings, was 6.2 ± 0.7 mm. No significant correlations were found between percentage of skin shrinkage and surgeon, body side or region, or measurement orientation in relation to skin tension lines. The mean sample diameter immediately after excision differed significantly from that before excision (mean diameter decrease, 5.5 ± 0.7 mm). Overall, sample diameter immediately after excision and after formalin fixation did not differ. The extent of shrinkage of skin samples from hound cadavers that occurred immediately after excision was notable. A better understanding of the effectors of excised skin sample shrinkage is needed, especially when histopathologic findings provide guidelines for surgical margins.

Application and assessment of optical clearing methods for imaging of tissue-engineered neural stem cell spheres.

Three-dimensional (3D) cell culture is an important tool that facilitates biological discoveries by bridging the divide between standard two-dimensional cell culture and the complex, high-cell-density in vivo environment. Typically, the internal structures of 3D tissue-engineered samples are visualized through an involved process of physical sectioning, immunostaining, imaging, and computational reconstruction. However, recent progress in tissue-clearing methods has improved optical-imaging-depth capabilities in whole embryos and brains by reducing tissue opacity and light scattering, thus decreasing the need for physical sectioning. In this study, we assessed the application of the recently published clearing techniques Clear(T2), Scale, and SeeDB to tissue-engineered neural spheres. We found that scaffold-free self-assembled adult hippocampal neural stem cell spheres of 100-μm diameter could be optically cleared and imaged using either Clear(T2) or Scale, while SeeDB only marginally improved imaging depth. The Clear(T2) protocol maintained sphere size, while Scale led to sample expansion, and SeeDB led to sample shrinkage. Additionally, using Clear(T2) we cleared and successfully imaged spheres of C6 glioma cells and spheres of primary cortical neurons. We conclude that Clear(T2) is the most effective protocol of those tested at clearing neural spheres of various cell types and could be applied to better understand neural cell interactions in 3D tissue-engineered samples.