Intrinsic Micro Research Articles

Biocompatible optical physically unclonable function hydrogel microparticles for on-dose authentication

On-dose authentication (ODA) enhances security by incorporating customized molecular or micro-tags into each pill, preventing counterfeit products in genuine packages. ODA's security relies on tag non-replication and non-reverse engineering. Combining ODA with graphical Physical Unclonable Functions (PUF) promises maximum security. PUF uses intrinsic micro or nanoscale randomness as a unique ‘fingerprint’. However, current graphical PUFs have limitations like specific illumination requirements and the use of toxic materials, restricting their use in pharmaceuticals.In this study, we propose a novel approach called on-dose PUF. This method involves embedding microspheres randomly within micro biocompatible hydrogel particles. We showcase two distinct types of such on-dose PUFs. The first type utilizes randomly distributed superparamagnetic colloids (SPC) of identical diameters, while the second type utilizes vortexed sunflower oil drops of various diameters. The diameter and coordinates of the microspheres serve as input for generating cryptographic keys. A universal circle identification and binning program is used for extracting this information. One advantage of this approach is that it enables imaging using white light illumination and low-magnification microscopy, as color and signal intensity information are not crucial. This method enables patients to verify their medication by using their mobile phones from home.To assess the performance of the proposed on-dose PUF, we conducted canonical investigations on the single-diameter system. This system can only generate one layer of cryptographic keys, making it potentially more vulnerable than the multiple-diameter system. However, the single-diameter system successfully passed NIST Statistical tests and exhibited sufficient randomness, ideal bit uniformity, Hamming distance, and device uniqueness. Furthermore, we found that the encoding capacity of the single-diameter system was 9.2×1018, providing ample labeling potential.

Reversible switchable wettability of intrinsic micro/nanostructured pollen microcarriers via pH-induce from superhydrophobicity to superhydrophilicity

The wettability of microcarriers is influenced by surface chemistry and surface micro-nanostructure. Reproducible fabrication and precise control of microcarriers with complex structures are expensive and challenging. It is expected that the fabrication of reversible super-wetting carriers without the need for a template or complex winding processing will greatly promote the application of super-wetting materials. Hence, it should be possible to obtain super-wetting microcarriers by regulating intrinsic micro-nanostructured pollen microcarriers’ surface chemistry. A systematic study was performed using different solvents to regulate the wettability of sporopollenin. The changes in surface structure and surface chemistry were studied, and the regulation mechanism of sporopollenin reversible wettability was determined. Tuning pH could induce the wettability transition of sporopollenin, and this wettability transition was reversible. In addition, studies have also shown that the intrinsic micro-/nanostructures of sporopollenin were the basis for the realization of super-wettability, and the protonation and deprotonation of the carboxyl group of the pectin layer were the keys to switching between superhydrophobic and superhydrophilic properties. This is the first report on the fabrication of reversible wetting-regulated microcarriers based on intrinsic micro-nanostructures, indicating that it is possible to use sporopollenin to fabricate reversible wetting-regulated super-wetting microcarriers.

Modern approaches to the application of mathematical modeling methods in biomedical research

This paper presents a brief overview of the main approaches to mathematical modeling of the interaction of optical radiation with biological tissues. In the case of light propagation in tissue, the Monte Carlo method is an approximation of the solution of the radiation transfer equation. This is done by sampling the set of all possible trajectories of light quanta (photon packets) as they pass through the tissue. Such a stochastic model makes it possible to simulate the propagation of light in a turbid (scattering) medium. The main types of interaction between photons and tissue are considered: scattering, absorption, and reflection/refraction at the boundary of the medium. The algorithm of the method is based on the statistical approximation of the estimated parameters instead of using non-linear functional transformations. Efficient methods for modeling the problem of Raman spectroscopy in turbid media are shown, taking into account the parameters of the detector and the sample size. Two fundamental approaches to the numerical simulation of Raman scattering are considered. Based on data from open literary sources, a variant of modeling Raman scattering in normal multilayer human skin in the near infrared wavelength range is shown. The Raman spectra of ex vivo normal skin tissue sections are presented to quantify various intrinsic micro spectral properties of different skin layers. The reconstructed Raman spectrum of the skin is compared with clinically measured skin spectra in vivo. The overall good agreement between the simulated process and experimental data is shown. The possibility of using the sequential Monte Carlo method for data processing in correlation wide-field optical coherence tomography for the study of biological objects is shown.

A General Strategy for the Synthesis of Hierarchically Ordered Metal-Organic Frameworks with Tunable Macro-, Meso-, and Micro-Pores.

Hierarchically ordered porous materials with tailored and inter-connected macro-, meso-, and micro-pores would facilitate the heterogeneous adsorption and catalysis processes for a wide range of applications but remain a challenge for synthetic chemists. Here, a general and efficient strategy for the synthesis of inverse opal metal-organic frameworks (IO MOFs) with a tunable size of macro-, meso-, and micro-pores is reported. The strategy is based on the step-wise template formation, precursor infiltration, solvo-thermal reaction, and chemical etching. As a proof of the general applicability of this strategy, a series of inverse opal zirconium-based MOFs with intrinsic micro- and/or meso-pores, including UiO-66, MOF-808, NU-1200, NU-1000 and PCN-777, and tunable macropores (1µm, 2µm, 3µm, 5µm, and 10µm), have been prepared with outstanding yields. These IO MOFs demonstrate significantly enhanced absorption rates and faster initial hydrolysis rates for organophosphorus (OPs) aggregates compared to those of the pristine MOFs. This work paves the way for the further development of hierarchically ordered MOFs for advanced applications.

Exploring the intrinsic micro-/nanoparticle size on their in vivo fate after lung delivery.

Micro-/nanocarriers due to their significant advantages are widely investigated in pulmonary drug delivery. However, different size carriers have varied drug release rate, concealing the effect of particle size on the fate of drugs in vivo. Therefore, by keeping drug release rate comparable, the objective of this study is to elucidate the influence of particle size itself on drug in vivo fate after intratracheal instillation to mice. Here, using paclitaxel (PTX) as a drug model, 100nm, 300nm, 800nm, and 2500nm poly(lactide-co-glycolide) (PLGA) particles with the same release rate were prepared. It was demonstrated that the in vivo fate of particles after lung delivery was size-dependent. Consistent with most reports of model particles with neglected release kinetics, the mucus penetration capacity in airtifical mucus decreased with increasing particle size and there is no significant difference between 800nm and 2500nm particles. The in vivo airway distribution experiments confirmed the results of the in vitro mucus penetration study, that is, the smaller the particles, the more distributed in the airway. Both in vitro and in vivo macrophage uptake results confirmed that the larger particles were more readily taken up by macrophages. In contrast, the uptake of smaller particles in A549 cells was higher than that of larger particles. Some new findings were disclosed in lung retention, lung absorption and lung targeting. Different from previous reports, this study demonstrated that particles with smaller size had longer lung retention, AUC(0-t) in bronchoalveolar lavage fluid (BALF) of 100nm particles was 1.6, 1.9, 2.5 times higher than that of 300nm, 800nm, and 2500nm particles and 11.7 times of the PTX solution group. The same trend was observed in lung tissue absorption, the AUC(0-t) in the lavaged lung of 100nm particles was 1.8, 2.2, 2.8, 8.6 times higher than that of 300nm, 800nm, 2500nm particles and PTX solution groups, respectively. The lung targeting efficiency was particles size independent. In conclusion, the in vivo fate of particles with the same release kinetics after intratracheal instillation is size-dependent, smaller size particles are conducive for lung retention and lung absorption. Overall, our study provided scientific guidance for the rational design of particle based pulmonary drug delivery system.

Intrinsic Random Optical Features of the Electronic Packages as Physical Unclonable Functions for Internet of Things Security

The increasing security threat is a serious challenge to the internet of things (IoT). Hardware‐based security primitive is an essential and powerful way to protect IoT devices from various attacks. But most of the current security hardwares are based on macrophysical features, which are usually produced by reproducible deterministic processes and can be copied by counterfeiters. Herein, a physical unclonable function (PUF) with high robustness based on the intrinsic random micro‐/nanostructures of the electronic packages is proposed thereby demonstrating a low‐cost and label‐free hardware security solution for IoT. Using the unique surface micropattern and the spatially coded laser scattering, the proposed PUFs can be used as anticounterfeiting labels, authentication tokens and cryptographic key generators. With the help of the proposed PUFs, the safety protection is still effective even when the attacker is able to get access to the database because the secret keys are inherently hidden in the complex microscopic stochastic physical features of the PUFs but not the database. The proposed package‐enabled PUFs provide a promising and practical physical protection solution for IoT security.

Insights into the micro magnetic loss mechanism of microwave absorption by off-axis electron holography

Abstract High permeability and high saturation magnetization are two key attributes to strong microwave absorption for magnetic loss composites, which depend on the chemical composition, particle size, surface profile, fabrication method, etc. However, it is still a challenge to understand the influences of these properties on micro magnetic behaviors to manipulate microwave absorption performances. In this study, magnetic absorbers with spherical and flaky shapes were adapted to investigate the influences of morphology on magnetic properties via off-axis electron holography. Stray magnetic flux lines were visualized to validate the difference in the forms of magnetic incorporation among spherical and flaked-shaped metallic particles, which then results in reflection loss (RL) up to −53 dB for the flakes and absorption (>99%) bandwidth up to 3 GHz for the spherical types. The micro-field detection using the powerful technique of off-axis electron holography sheds new light on the understanding about intrinsic magnetic micro behaviors for metallic composites.

Nanostructured Functional Hydrogels as an Emerging Platform for Advanced Energy Technologies.

Nanostructured materials are critically important in many areas of technology because of their unusual physical/chemical properties due to confined dimensions. Owing to their intrinsic hierarchical micro-/nanostructures, unique chemical/physical properties, and tailorable functionalities, hydrogels and their derivatives have emerged as an important class of functional materials and receive increasing interest from the scientific community. Bottom-up synthetic strategies to rationally design and modify their molecular architectures enable nanostructured functional hydrogels to address several critical challenges in advanced energy technologies. Integrating the intrinsic or extrinsic properties of various functional materials, nanostructured functional hydrogels hold the promise to break the limitations of current materials, improving the device performance of energy storage and conversion. Here, the focus is on the fundamentals and applications of nanostructured functional hydrogels in energy conversion and storage. Specifically, the recent advances in rational synthesis and modification of various hydrogel-derived functional nanomaterials as core components in batteries, supercapacitors, and catalysts are summarized, and the perspective directions of this emerging class of materials are also discussed.

Collagen Complexity Spatially Defines Microregions of Total Tissue Pressure in Pancreatic Cancer

The poor efficacy of systemic cancer therapeutics in pancreatic ductal adenocarcinoma (PDAC) is partly attributed to deposition of collagen and hyaluronan, leading to interstitial hypertension collapsing blood and lymphatic vessels, limiting drug delivery. The intrinsic micro-regional interactions between hyaluronic acid (HA), collagen and the spatial origins of mechanical stresses that close off blood vessels was investigated here. Multiple localized pressure measurements were analyzed with spatially-matched histochemical images of HA, collagen and vessel perfusion. HA is known to swell, fitting a linear elastic model with total tissue pressure (TTP) increasing above interstitial fluid pressure (IFP) directly with collagen content. However, local TTP appears to originate from collagen area fraction, as well as increased its entropy and fractal dimension, and morphologically appears to be maximized when HA regions are encapsulated by collagen. TTP was inversely correlated with vascular patency and verteporfin uptake, suggesting interstitial hypertension results in vascular compression and decreased molecular delivery in PDAC. Collagenase injection led to acute decreases in total tissue pressure and increased drug perfusion. Large microscopic variations in collagen distributions within PDAC leads to microregional TPP values that vary on the hundred micron distance scale, causing micro-heterogeneous limitations in molecular perfusion, and narrows viable treatment regimes for systemically delivered therapeutics.

Supercapacitive Performances of Activated Highly Microporous Natural Carbon Macrofibers

Activated carbons with high specific surface area (even above 2000 m2 g−1) and pronounced microporosity are prepared in two-stage process involving conventional carbonization of waste hemp fibers and subsequent activation by potassium hydroxide. Samples with considerably different surface and intrinsic micro- and mesoporous properties are obtained at different carbonization and activation conditions. The improvements of the capacitive properties are found upon increase in carbonization temperature, since it considerably influenced the specific surface area and the content of surface oxygen groups. Cyclic voltammetry experiments reveal the dependence of specific capacitance on the sweep rate due to the characteristic porous structure of the samples. The highest measured value in 1 M H2SO4 solution is 122 F g−1. The electrochemical impedance data indicates eight-branch transmission line equivalent electric behavior of activated carbons.

Experimental Study on Airtightness of Cement Sheath Under Alternating Stress

The airtightness of cement sheath under alternating loading and unloading was studied using self-developed experiment facilities, and the mechanism of airtightness failure of cement sheath under alternating loading and unloading was understood based on the experimental results. Under the action of lower alternating pressure inside the casing, the time for the cement sheath to fail can be long; the action of high alternating pressure, on the other hand, will soon break down the airtightness of the cement sheath. This indicates that low pressure inside the casing string imposes low force on cement sheath which still retains its elasticity, and elastic deformation takes place in the cement sheath under alternating loading and unloading. Under the action of high stresses, on the other hand, the intrinsic micro fractures and deficiencies inside the cement sheath begin to connect with each other, and both elastic deformation and plastic deformation take place inside the cement sheath. As the alternating goes on, the plastic deformation becomes accumulated, to the extent that the plastic deformation does not vanish after unloading. Differences in the deformations of casing string and cement sheath at the interface result in a tensile stress, which, when exceeding the cementation strength at the interface, will cause the airtightness of the cement sheath to fail. This is the so-called low cycle fatigue failure of the airtightness of cement sheath under the action of alternating loading and unloading. Higher internal pressure in the casing string results in higher induced stress inside the cement sheath, larger plastic deformation, higher residual strain and tensile stress at the interface after unloading, and, the less of the number of cycles required to cause the airtightness of the cement sheath to fail.

Site specific bone loss induced by spaceflight in mice: a multiscale evaluation of trabecular and cortical structure and quality

Intrinsic quality, micro and nano structure of bone after 1 month of spaceflight and during 1 week of recovery had never been investigated. The aim was to explore these properties in appendicular and axial skeleton of mature mice.Ten C57/Bl6 male mice flew on the 30-day space Russian BION-M1 high-orbit satellite mission (Biomedical Ethics Commission of IBMP, n°319). Five were euthanized 12 h after landing, the others 8 days later. A ground control group was kept in the same conditions as in flight (housing, food and climate).Body weight, soleus muscle mass, and femur length were not significantly different between groups.In the femur, microgravity significantly decreased trabecular BV/TV (−65% vs Ctr) (micro-CT), increased trabecular and periosteal TRAP+ osteoclast surfaces and marrow adiposity (X22 vs Ctr), and decreased Ct.Th (−5.4% vs Ctr). Nano-indentation analysis indicated that cortical modulus, hardness and working energy were significantly decreased whereas the degree of mineralization (micro radiography) was not affected by microgravity. Microgravity did not affect cortical osteocyte lacuna density but decreased their mean 3D volume (Synchrotron Radiation nanotomography, n>8000 lacunae per sample). Eight days after landing, osteoclast cell surface were restored but trabecular BV/TV and Ct.Th remained lower than Ctr group.In vertebrae, microgravity significantly decreased BV/TV (−36% vs Ctr) and the modulus in the younger mineralized matrix which tended to increase after recovery. Degree of mineralization, mineral and collagen intrinsic quality (infra-red spectroscopy) were not changed by microgravity.To summarize, microgravity severely decreased bone mass, altered bone structure and intrinsic mechanical properties in both sites and increased femoral marrow adiposity. One week after landing, these properties tended to be rescued in vertebrae but remained altered in the femur despite normalized osteoclastic cell surfaces. The decrease of osteocyte lacunar volume suggests the existence of an intra-cortical bone preservation mechanism in absence of mechanical loading.

Neurovascular Coupling Response Dysfunction after Ischemic Stroke: The Possible Mechanism in Cognition Impairment

One of the cardinal aspects of post-ischemic stroke disabilities is cognitive decline correlated with higher long-term mortality rate. There are various hypotheses about cognition impairment after ischemic stroke, but lately, neurovascular coupling (NVC) response impairment and neurovascular unit (NVU) disruption have been proposed as causes for cognitive decline. The NVC mechanism, a feature of the brain’s intrinsic micro circulation, regulates local cerebral blood flow (CBF) in accordance with the underlying neuronal activity. It seems that, cerebral ischemia triggers several molecular and cellular cascades including excitotoxicity, neuroinflammation, oxidative stress and blood brain barrier (BBB) disruption which eventually leads to NVU malfunction and NVC response impairment which results in cognitive dysfunction in many stroke patients. This review tries to focus on the factors involved in NVC response that might affect cognition after ischemic stroke.

Detection and formation mechanism of micro-defects in ultrafine pitch Cu—Cu direct bonding*Project supported by the National Natural Science Foundation of China (Grant No. 61274111) and the National Basic Research Program of China (Grant No. 2015CB057205).

In this paper, Cu–Cu interconnects with ultrafine pad pitches of 6 μm, 8 μm, and 15 μm are implemented on the 12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive (NDT) c-mode scanning acoustic microscopy (c-SAM). However, cross sectional observation of bonding interfaces reveals that micro-defects such as micro seams are located at SiO2 bonding interfaces. In order to examine the micro-defects in the ultra-fine pitch direct bonding process by the NDT technology, a novel “defect-enlarged approach” is proposed. The bonded dies are first annealed in an N2 oven at 300 °C for a few hours and then cooled quickly in air. The c-SAM scanning images show large defects at the place where nothing can be detected by c-SAM before this treatment. Cross sectional observation of the bonding interfaces indicates that these defects consist of large size micro seams at the SiO2 bonding interface, especially near Cu pads with an ultrafine pitch of 6 μm. However, these large defects disappear after several hours at room temperature, observed by c-SAM. It is inferred that the disappearance of these defects inspected by the “defect-enlarged approach” results from the combination of intrinsic micro seams and “weak” bonds in the silicon oxide layer. Then the underlying physical mechanism of these micro-defects is proposed, which is influenced by Cu pad surface topology and bonding models.

Analytical modelling of a refractive index sensor based on an intrinsic micro Fabry-Perot interferometer.

In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10−4 RIU can be implemented by using a couple of standard and low cost photodetectors.

PH-Manipulated Underwater-Oil Adhesion Wettability Behavior on the Micro/Nanoscale Semicircular Structure and Related Thermodynamic Analysis.

Controlling oil of wettability behavior in response to the underwater out stimulation has shown promising applications in understanding and designing novel micro- or nanofluidic devices. In this article, the pH-manipulated underwater-oil adhesion wetting phenomenon and superoleophobicity on the micro- and nanotexture copper mesh films (CMF) were investigated. It should be noted that the surface exhibits underwater superoleophobicity under different pH values of the solution; however, the underwater-oil adhesion behavior on the surface is dramatically influenced by the pH value of the solution. On the basis of the thermodynamic analysis, a plausible mechanism to explain the pH-controllable underwater-oil adhesion and superoleophobic wetting behavior observed on a micro- and nanoscale semicircular structure has been revealed. Furthermore, variation of chemistry (intrinsic oil contact angle (OCA)) of the responsive surface that due to the carboxylic acid groups is protonated or deprotonated by the acidic or basic solution on free energy (FE) with its barrier (FEB) and equilibrium oil contact angle (EOCA) with it hysteresis (OCAH) are discussed. The result shows that a critical intrinsic OCA on the micro- and nano- semicircular texture is necessary for conversion from the oil Cassie impregnating to oil Cassie wetting state. In a water/oil/solid system, the mechanism reveals that the differences between the underwater OCA and oil adhesive force of the responsive copper mesh film under different pH values of solution are ascribed to the different oil wetting state that results from combining the changing intrinsic OCA and micro-/nanosemicircular structures. These results are well in agreement with the experiment.

Wide-angle spectral imaging using a Fabry-Pérot interferometer

In this work, a refractive index sensor setup based on a biconically tapered fiber (BTF) concatenated to an intrinsic all-fiber micro Fabry-Perot interferometer (MFPI) is presented. Here, the power of the MFPI spectral fringes decreases as the refractive index interacts with the evanescent field of the BTF segment. Furthermore, it is demonstrated that the RI sensitivity can be enhanced by bending the BTF segment. Finally, it is shown that by using this sensing arrangement, at ∼1.53 μm wavelength, it is possible to detect refractive index changes within the measurement range of 1.3 to 1.7 RIU, with a sensitivity of 39.92 dB/RIU and a RI resolution of 2.5 ⋅ 10−3 RIU with a curvature of C = 18.02 m−1.

SrO- and MgO-doped microwave sintered 3D printed tricalcium phosphate scaffolds: mechanical properties and in vivo osteogenesis in a rabbit model.

The presence of interconnected macro pores allows guided tissue regeneration in tissue engineering scaffolds. However, highly porous scaffolds suffer from having poor mechanical strength. Previously, we showed that microwave sintering could successfully be used to improve mechanical strength of macro porous tricalcium phosphate (TCP) scaffolds. This study reports the presence of SrO and MgO as dopants in TCP scaffolds improves mechanical and in vivo biological performance. We have used direct three dimensional printing (3DP) technology for scaffold fabrication. These 3DP scaffolds possessed multiscale porosity, that is, 3D interconnected designed macro pores along with intrinsic micro pores. A significant increase in mechanical strength, between 37 and 41%, was achieved due to SrO and MgO doping in TCP as compared with pure TCP. Maximum compressive strengths of 9.38 ± 1.86 MPa and 12.01 ± 1.56 MPa were achieved by conventional and microwave sintering, respectively, for SrO-MgO-doped 3DP scaffolds with 500 μm designed pores. Histomorphological and histomorphometric analysis revealed a significantly higher osteoid, bone and haversian canal formation induced by the presence of SrO and MgO dopants in 3DP TCP as compared with pure TCP scaffolds when tested in rabbit femoral condyle defect model. Increased osteon and thus enhanced network of blood vessel formation, and osteocalcin expression were observed in the doped TCP scaffolds. Our results show that these 3DP SrO-MgO-doped TCP scaffolds have the potential for early wound healing through accelerated osteogenesis and vasculogenesis.

3D printed tricalcium phosphate scaffolds: Effect of SrO and MgO doping on in vivo osteogenesis in a rat distal femoral defect model.

The presence of interconnected macro pores is important in tissue engineering scaffolds for guided tissue regeneration. This study reports in vivo biological performance of interconnected macro porous tricalcium phosphate (TCP) scaffolds due to the addition of SrO and MgO as dopants in TCP. We have used direct three dimensional printing (3DP) technology for scaffold fabrication followed by microwave sintering. Mechanical strength was evaluated by scaffolds with 500 µm, 750 µm, and 1000 µm interconnected designed pore sizes. Maximum compressive strength of 12.01 ± 1.56 MPa was achieved for 500 µm interconnected designed pore size Sr-Mg doped scaffold. In vivo biological performance of the microwave sintered pure TCP and Sr-Mg doped TCP scaffolds was assessed by implanting 350 µm designed interconnected macro porous scaffolds in rat distal femoral defect. Sintered pore size of these 3D printed scaffolds were 311 ± 5.9 µm and 245 ± 7.5 µm for pure and SrO-MgO doped TCP scaffolds, respectively. These 3D printed scaffolds possessed multiscale porosity, i.e., 3D interconnected designed macro pores along with intrinsic micro pores. Histomorphology and histomorphometric analysis revealed a significant increase in osteoid like new bone formation, and accelerated mineralization inside SrO and MgO doped 3D printed TCP scaffolds as compared to pure TCP scaffolds. An increase in osteocalcin and type I collagen level was also observed in rat blood serum with SrO and MgO doped TCP scaffolds compared to pure TCP scaffolds. Our results show that these 3D printed SrO and MgO doped TCP scaffolds with multiscale porosity contributed to early healing through accelerated osteogenesis.

Synthesis and characterization of laminated Si/SiC composites

Laminated Si/SiC ceramics were synthesized from porous preforms of biogenous carbon impregnated with Si slurry at a temperature of 1500°C for 2h. Due to the capillarity infiltration with Si, both intrinsic micro- and macrostructure in the carbon preform were retained within the final ceramics. The SEM micrographs indicate that the final material exhibits a distinguished laminar structure with successive Si/SiC layers. The produced composites show weight gain of ≈5% after heat treatment in air at 1300°C for 50h. The produced bodies could be used as high temperature gas filters as indicated from the permeability results.