Binder Melt Research Articles

Research on Sol-Gel Synthesis of Low-Temperature Na2O-B2O3-SiO2 Vitrified Bonds and Preparation of High-Strength Stacked Abrasives Using the Molding and Crushing Method.

Currently, the sol-gel technique is employed in the synthesis of high-performance vitrified bonds; however, its application in the fabrication of stacked abrasives has been minimally explored. Furthermore, the methods utilized in the production of abrasive particles for stacked abrasives are technically challenging and incur high costs, which hinders their actual industrial application. Consequently, this study utilizes the sol-gel approach to synthesize a Na2O-B2O3-SiO2 ternary system vitrified bond powder and employs a molding and crushing method, which offers a lower technological barrier and reduced preparation costs, for the production of abrasive particles subsequently fabricating corundum stacked abrasives. Upon setting the binder composition to a molar ratio of n(SiO2):n(B2O3):n(Na2O) = 65:23:12, it was observed that the crystallization within the glass matrix was minimized and the optimal sintering temperature for the synthesized laminate abrasive to be sustained at 820 °C. At the aforementioned temperature, the binder melt is capable of flowing uniformly amongst the abrasive granules, thereby ensuring a robust encapsulation of the particles. The average single particle compressive strength of the prepared corundum stacked abrasive with a grain size of forty mesh can reach the highest of all composition points at 28.56 N and the average single particle compressive strength of the prepared diamond stacked abrasive is 28.14 N.

Binder melt: Composite propellants with RDX**

AbstractThe binder melt on the surface of aluminized composite propellants with RDX has been quantified using experimental and computational approaches. A scanning electron microscope in conjunction with energy dispersive spectroscopy was used to analyze the surface of unburnt and extinguished propellant samples. Rapid depressurization technique was used to obtain the extinguished propellants. Five propellants were prepared, keeping the aluminum and binder fraction constant at 4 % and 16 %, respectively. The RDX fraction in the propellants was varied from 3 % to 12 %. It was found that the melt on the surface of the propellant increased from 36.7 % to 43.9 % when the RDX fraction was changed from 3 % to 12 % in the propellant. For propellants containing 3 % to 9 % RDX, a region of plateau burning was observed in the pressure range of 5–7 MPa, while propellants containing 12 % RDX showed plateau burning between 7–10 MPa.

Dynamic measurement of internal strain on composite solid propellant constituents during laser induced combustion

Binder melt flow and ammonium perchlorate (AP) cracking have been topics for research for a long time. Both impact the burning rate dependence on pressure and the binder flow. Rapid depressurization of the combustion vessel is the most common tool used to study binder melt flow by studying the ripples on the quenched surface. Laminate propellants were used to study fundamental combustion phenomena such as the melt flow over the oxidizer/binder interface AP/hydroxyl-terminated polybutadiene (HTPB). This study starts with thermally induced strain measurements in single crystals of AP with thicknesses 1- to 2.5-mm and neat HTBP slabs then finishes with laminates of AP/HTPB. A CO2 laser ignited and burned samples over a range of heat fluxes. First ever in- situ mapping of the two-dimensional thermally-induced internal strain generated at ignition to steady state combustion were imaged using a high-speed polarization camera. Heating of the surface produced strain fields in the AP, HTPB, and laminate provide information on the thermal diffusion during the ignition and fully developed combustion. This paper demonstrates how using polarized high-speed video, the binder melt flow was more accurately observed and AP cracking mechanisms can be better studied.

DETERMINATION OF THE COEFFICIENT SLIDING FRICTION VALUE IN THE CONTACT THE CUTTING TOOL-COMPOSITE

One of the most important characteristics in calculating the cutting tool wear in contact with the processed composite is the friction coefficient. In most calculations, including the finite element method, the friction coefficient is traditionally set as a constant, the value of which is often taken from experience without any reason. However, when machining reinforced composites, there are too many mechanical and technological factors that have a very strong effect on the friction coefficient value. This influence is associated not only with the initial heterogeneity of the composite, but also with the constant actual change in the contact conditions over time, caused by the wear of the tool cutting part. The friction coefficient value in real conditions of contact interaction has a very complex physical content due to the presence of products of fibers and binder destruction in the contact, partial a binder melting at a temperature in contact, and the unevenness of the cut fibers presence.
 This article presents a formulation that allows you to calculate the value of the friction coefficient depending on the volumetric content and the inclination angle of the reinforcing elements. It is proposed to calculate the friction coefficient value as the product of two factors, one of which is responsible for the filler volumetric content, and the other for the reinforcing elements orientation. The calculations use the mixtures theory relations .The presented expressions for calculations are based on the use of limited experimental information presented by various authors. The available data are often contradictory and relate, as a rule, to predicting the processed surface quality of unidirectional glass and carbon fiber reinforced plastics. At the same time, the friction coefficient value in the calculations has a significant impact on the representation of tool wear and life. The model does not take into account the contact pressure effect, mutual sliding velocity and temperature on the friction coefficient value, which will be the subject of further research in this direction.

Observation of aluminum interaction with the binder melt layer using high-speed synchrotron-based phase contrast imaging

Particle interactions with the binder melt layer are a major factor in the combustion efficiency and stability of the propellant in a solid rocket motor. Metal particles tend to agglomerate on the surface of burning solid propellants, inhibiting the combustion process. Therefore, reduction of molten aluminum agglomeration in a solid rocket motor is vital to the improvement of solid rocket propulsion system performance. In other work, quenched samples have been used to study the impact of how metal particles alter the flow properties of the molten propellant surface. In-situ optical measurements have also been attempted for these particle-condensed phase interactions, but with little success due to the opacity and strong gradients within the flame. This study expanded on previous work using synchrotron–based x-rays to directly image these aluminum agglomerates as they interacted with the binder. X-ray absorption and phase contrast in the images allowed for the direct measurement of the particle size in combusting propellants in-situ at typical rocket pressures. Particle size distributions were collected in an optically accessible combustion vessel over a pressure range of 1.4- to 6.9-MPa (200- to 1000-psig). This investigation measured the aggregate sizes ranging from 300-to 650-µm at a 6.9 MPa chamber pressure. Interestingly, the lowest binder melting temperature produced the longest aluminum chaining at 1.1 mm and the highest binder melting temperature produced the second longest chain at 524 µm long. The study observed aluminum interactions with the binder melt layer on the propellant surface that may be a contributing factor in a plateau propellant. Additionally, data pointed to possible relationships between binder viscosity, burning rate, aluminum clusters, and chain formation in a solid propellant. The study concluded with collecting data on the molten aluminum volumetric changes in a propellant environment, thus defining a starting particle diameter for particle regression rates. Collecting the regression rates also provided information on the evaporation rate of aluminum, which burned in the propellant flame. All of these data are critical for understanding the combustion of aluminum-based solid rocket propellants and outlines knowledge gaps that need additional data.

Cracking features of asphalt mixtures under induced heating-healing

This research presents effects of induced heating-healing process on fracture properties and life extension of asphalt mixtures. Induced heating-healing technique is an innovative technique to repair damages and heal cracks in asphalt mixtures, implementing an external electromagnetic field to raise temperature of asphalt mixture. Temperature rising results in melting and flowing of asphalt binder between crack edges, healing cracks, and recovering internal strength of asphalt mixture lost during service life. Previous researchers considered different criteria to quantify induced healing efficiency in asphalt concrete, resulting in substantial differences. Nevertheless, conclusions presented by previous researchers are not comparable due to different materials, heating, healing, and testing conditions. Hence, a further study is needed to identify induced healing effectiveness based on asphalt mixtures form different binder grades. In this study, activated carbon modified and unmodified asphalt binders were utilized to prepare asphalt mixtures. Then, a cyclic heating-healing scenario under semi-circular bending (SCB) test was conducted at intermediate and low temperatures. Values of the fracture criteria (i.e., peak load, stress intensity factor, stiffness, strain energy, critical strain energy release rate, and fracture energy) were quantified at each cycle. Besides, extensions of fatigue and thermal fatigue lives obtained via induced healing process were characterized. Comparing results of modified and unmodified mixtures indicates that activated carbon significantly improves efficacy of induced healing. Additionally, induced healing process leads to different effects on different crack features. Moreover, induced healing efficiencies obtained based on fatigue and thermal fatigue extensions are approximately similar to that of peak load criterion. This study indicates that to evaluate effects of induced heating-healing process on improvement of different mechanical behaviors in asphalt mixtures over service life, corresponding crack property (criteria) needs to be considered.

Обоснование технологических параметров при производстве композитной ленты на основе полифениленсульфида

The purpose of the study was to select technological parameters of the production line of unidirectional thermoplastic polyphenylene sulfide-based tapes. The selection was made relying on the variation of the tape speed, the temperature of the sub-melting furnace, and the calendering module in the simulation of heat transfer processes. Modeling of heat transfer was based on the results of tests to determine the temperatures of phase transitions of a thermoplastic polymer in the composition of composite material and the dependence of the heat capacity of the composite on temperature. The indicated properties of the material were determined by analyzing the dependences obtained during differential scanning calorimetry and thermogravimetric analysis. As a result, the allowable range of distances between the polymer binder melting furnace and the calendering module was determined, which provides the necessary tape temperatures at the stages under consideration and the manufacturability of production. The permissible range of distances between the calendering module and the coiling module was also determined.

Formation of Plasma Powder Coatings from Cermet with Subsequent High-Energy Modification

The paper presents research on the effect of technological parameters of high-energy processing on the performance properties of powder coatings made of cermet. The use of pulse-plasma treatment is considered as an example of high-energy modification of coatings. As used powder coating materials, various versions of carbide-containing ceramics with the addition of a solid lubricant in an iron-based metal matrix have been selected in the paper. Coatings of carbide-containing ceramics with the addition of a solid lubricant in an iron-based metal matrix on are being developed to replace those of a nickel-based matrix. Such factors as crack resistance, wear resistance, workability, brittleness, as well as economic components often limit the use of powder materials based on carbide ceramics with the addition of solid lubricant in the matrix based on nickel. When only the wear process determines the service life of a part, such powder materials should be replaced with cheaper powder materials based on carbide ceramics with the addition of solid lubricant in an iron-based matrix. The proposed developments increase the wear resistance of the plasma coating due to the introduction of high-chromium steel and molybdenum into the material. Optimum porosity is formed in the initial powder mixture during the synthesis of FeCrMo–MoS 2 –TiC composite materials, there is an improvement in the technological parameters of powder materials, their utilization rate in plasma spraying increases, and the technology of applying wear-resistant plasma coatings becomes cheaper. The addition of the Mo element to the FeCr binder increases the wetting of titanium carbides by the binder melt during self-propagating high-temperature synthesis of the developed composite powder. Subsequent layer-by-layer processing of plasma-sprayed coatings from powders of the developed ceramics using repetitive pulses of plasma flows using different energy levels makes it possible to create strictly defined structures with necessary and controlled porosity, which decreases in a certain sequence from the outer treated layers to the base. Such treatment contributes to a significant increase in the wear resistance of the treated friction surfaces, increases the oil holding capacity, in addition, an increased adhesive and cohesive strength of the formed layers bordering the substrate is formed. Processing distances, the total number of impacts have been varied in accordance with the methodological developments, when changing the applied technological characteristics of pulse-plasma effects. The total number of plasma pulses influences on the created thickness of the plasma coating layers after treatment and contributes to the melting with compaction of the coatings obtained by the plasma treatment and the creation of a structure with hardened characteristics.

Combustion behaviour of composite sandwich propellants containing RDX

Addition of nitramine particles (RDX) to composite solid propellants are promoted in advanced propulsion systems for better performances, high energy, high specific impulse, and environmentally benign combustion products. This study is performed for understanding the combustion mechanism of RDX based matrices and sandwich propellants. Four types of fine AP/Al/binder matrix mixtures are considered, two samples contain 5% and 20% RDX while another two mixtures are without RDX, for comparison. Burning rate experiments are carried out on sandwich propellants and matrices in the pressure range of 2–10 MPa. The condensed phase behaviour of RDX decomposition and RDX melt flow, their influence on the matrix flame and interaction with leading edge flames (LEFs) located over lamina interfaces of sandwich propellants are assessed from quenched surface profiles and SEM micrographs. The effect of middle lamina thickness and pressure on burning rates of sandwich propellants are investigated. It is noticed that different levels of addition of RDX to matrix induces either an increase or decrease in burning rates depending upon the composition and fine AP/binder ratio. The binder melt flow effect is reduced in RDX containing matrix lamina due to presence of near-surface premixed flame. The effect of middle lamina thickness on burning rates of RDX containing sandwich propellants is significant. The overall burning rates of RDX sandwich propellants are relatively high when compared to their corresponding non-RDX counterparts. This is due to the existence of RDX assisted matrix flame that re-establishes the interaction between the LEFs anchored over lamina interfaces. Such matrix flames that are located over the regions of matrix in inter-particle spaces of the propellant microstructure would have a positive effect on the LEFs and outer diffusion flames over coarse AP particles.

Tailoring Binder Melting Temperature to Study the Binder Melt Layer Flow in Ammonium Perchlorate Composite Propellants

ABSTRACT Understanding the melt layer of composite solid propellants is crucial to theoretically model the combustion mechanism. Numerous studies on the melt layer flow have determined that the melting temperatures of the binder govern the burning rate dependence on pressure. Previous investigations discovered that using curatives and using different binders alter the binder melting temperature. The authors have developed a process to tailor the melting temperature through a functionalization process on the hydroxyl-terminated polybutadiene (HTPB) polymer. This study presents the analysis on the impacts of the melt layer dynamics of an ammonium perchlorate (AP)/HTPB-based propellant with tailorable melting temperatures. Pyrolysis measurements observed increased binder melt layer flow, resulting in lower pyrolysis rates. Propellants made with similar melting temperatures to the traditional R45M had similar burning rates but introduced more scatter due to the hardness of the propellant. Additional propellant samples containing 17 wt% aluminum (Al) and 70 wt% AP were made with a range of melting temperatures to study the impact of melting temperature on the melt layer. A rheological study on the cured propellant mixtures with tailored melting properties identified the melting temperatures for the level of HTPB functionalization. Those mixtures were burned, and the burning rates varied based on the melting temperature. The results suggested that a lower melting temperature produces a plateau propellant.

Binder melt: Quantification using SEM/EDS and its effects on composite solid propellant combustion

The present study reports the development of a novel technique to quantify binder melt on the surface of the propellant. Non-aluminized AP-HTPB propellants of 86% particulate loading are used to illustrate the technique. Elemental maps of unburnt and extinguished propellant surface are obtained using EDS (Energy Dispersive Spectroscopy). Overlap between the elements is identified and the elemental maps are processed to calculate AP and binder area exposed in unburnt and extinguished samples. The AP area exposed is found to be around 72.3% and 63.3% for unburnt and extinguished samples, respectively, indicating a reduction in AP exposed area with extinguished samples. This has been attributed to the binder melt discussed in literature but never quantified. Simulations have been carried out to analyze and understand the effects of this binder melt. A random packing algorithm is used to simulate propellant packs. Also, a methodology to account for binder melt layer is introduced and is used to capture AP exposed areas. Effect of binder melt in propellants with different solid loading and varying particle size is discussed. It is shown that fine AP particles are more prone to being covered by binder melt than the coarse AP particles. A possible explanation to the behavior of plateau burning propellants observed in literature has been provided through this analysis.

Effect of binder melt flow on the leading edge flames of solid propellant sandwiches

This study reports the effect of binder melt flow on the burning behaviour, specifically the burning rate controlling sites referred to as the leading edge flames (LEFs), of different types of sandwich propellants, namely, pure, micro-aluminized and nano-aluminized binder. The distance between the LEFs anchored over the lamina interface edges of sandwiches is measured from the combustion images captured under high spatio-temporal resolution. Similarly, the extent of binder melt flow is also measured from the quenched surfaces of sandwiches. The burning rate experiments are performed as well on sandwiches with different middle lamina contents and thicknesses at pressures of 2, 4 and 7 MPa. Two different curing agents are considered to examine the melt flow behaviour of the binder. The curing agent significantly influences the inter-LEF distance mainly in the case of pure binder sandwiches, however, its effect is negligible in aluminized binder sandwiches because of the presence of Al particles that impedes the flow to appreciable extent. Substantial protrusion of the middle lamina relative to the lamina interfaces is observed in micro-aluminized binder sandwiches due to significant accumulation of Al particles on the burning surface. In the case of nano-aluminized binder sandwiches, such protrusion is relatively marginal since nano-Al particles burn quickly, which enables the gas phase flame to locate close to the burning surface, although the extent of Al accumulation is considerably more than in the former case. This causes the nano-aluminized binder sandwiches as a whole to burn significantly faster than the other two cases in the pressure range (<7 MPa) where the LEFs predominantly control the sandwich burning rates.

Heat assisted twin screw dry granulation

A new “assisted” dry granulation method has been devised for the twin‐screw granulator. The method may be beneficial to drug preparation as it limits heat exposure to only one barrel zone, much shorter than melt granulation. Its mechanism was investigated using four placebo formulations, each containing a polymer binder with a glass transition temperature lower than 130°C. Variables of study included screw configuration, screw speed, barrel zone temperature, and moisture content. Granulated samples were characterized for size and porosity while feed powders were examined for their thermal transitions, interparticle friction, cohesion, and sintering rate. Results indicated that granule coalescence relied on melting of polymer binder in the kneading blocks by a combination of heat conducted from barrel and generated from screw speed friction. Successful granulation was possible with minimal addition of water, although varying the moisture content showed the relevance of the polymer's glass transition temperature and sintering progress. © 2017 American Institute of Chemical Engineers AIChE J, 2017

A novel approach to composite propellant combustion modeling with a new Heterogeneous Quasi One-dimensional (HeQu1-D) framework

This paper is concerned with a new and novel approach to modeling composite propellant burn rate behavior. It is founded on the fact that composite propellant combustion is largely boxed between the premixed limits – of pure AP and fine AP-binder (HTPB, here) whose burn behaviors are taken as known. The current strategy accounts for particle size distribution using the burn time averaging approach. The diffusional effects are accounted for through a calibrated heterogeneous quasi-one-dimensional model (HeQu1-D for short) that allows for the flame temperature dependence on the local AP size-binder thickness geometry. Fine AP-binder homogenization is adopted as in recent models with refinement on the particle size as a function of pressure. The specialty of the present approach is that it invokes local extinction for fuel rich conditions for specific particle sizes when the heat balance causes the surface temperature to drop below the low pressure deflagration limit of AP; this feature allows for the prediction of extinction of propellant combustion. Combining these ideas into a MATLAB® calculation framework that uses a single dataset on properties of AP and binder consistent with burn rate vs. pressure of pure AP and fine AP-binder system allows for making the predictions of propellants with multiple particle sizes and different fractions. Comparisons of burn rate data over nearly thirty compositions from different sources appear excellent to good. It is found that it is important to treat the full particle size distribution to achieve better predictions. Low burn rate index (∼0.25) observed with addition of SrCO3 is captured by extending the model to include the effect of binder melt; the gas phase effect is accounted for by calibration against catalytic effect on the fine AP-binder propellant. An interesting deduction from the model is that the temperature sensitivity of propellants should not exceed that of AP. The robustness of the current model and speed of determining the burn rate behavior allow for the possibility of determining the particle size distribution required to meet the burn rate specifications of a specific propellant for practical applications before actually embarking on making the propellant.

Unstructured finite element modeling thermally sprayed cermet coatings post-treatment by pulsed high-energy fluxes

Thermal spraying of cermet coatings made of composite powders which particles consist of ultrafine carbide inclusions in metal or metal alloy matrix gives wide opportunities of creation of coatings for extreme application conditions. However, the high content of carbide inclusions in the cermet particles is the reason of their low level deformation at impact with substrate or coating surface that results in porosity of plasma as-sprayed layer. Decrease in coating porosity at simultaneous increase of its bond strength with substrate is possible by means of subsequent pulsed high-energy treatment. The problem consists in binder melting at minimum impact on carbide inclusions and substrate. Because the experimental development of this technology is rather multivariate procedure, a preliminary computer optimization is very perspective. The computing experiments were carried out, which allowed to optimize power density in a single pulse and its duration depending on thickness and porosity of the deposited TiC-NiCr layers.

Theoretical analysis of cermet splats formation under porous quasi-liquid particle ‘melted binder – suspended ultrafine refractory inclusions’ impacting with substrate

The use of composite powders with particles formed by very hard ultrafine inclusions suspended in a metal/metal alloy binder (WC–Co, Cr3C2–NiCr, TiC–NiCr, etc.) in thermal spray process presents a promising strategy in formation of wear-, abrasive- and corrosion resistant coatings. The high volume content of carbide phase inclusions in the cermet powder particles (50–80%) provides high effective viscosity of the binder melt with high-melting solid inclusions suspended in it. That is why takes place a low value of deformation of quasi-liquid particles “melted binder – suspended solid ultrafine inclusions” impinging onto the substrate or onto previously deposited coating layer. All these explain why plasma-sprayed cermet coatings have a comparatively high porosity at the interfaces between individual splats and at the coating–substrate interface. Theoretical analysis of splat formation from porous cermet particle upon its impingement onto substrate was carried out taking into consideration the key physical parameters (KPPs) of particle–substrate interaction: temperature, velocity and size of cermet particle, substrate temperature, volume concentration of ultrafine solid refractory inclusions uniformly distributed in a liquid metal binder.

Activated charcoal: as burn rate modifier and its mechanism of action in non-metalized composite solid propellants

Modification of composite solid propellant burning rates becomes a requirement based on the necessities of a mission. Literature discusses about various burn rate modifiers which can modify the burning rates effectively. This paper attempts to understand the behavior and mechanism of (dry) activated charcoal (a recently reported burn rate modifier) in composite solid propellant combustion. Extensive experimental studies are performed to achieve this objective. Effects of activated charcoal are studied on the individual components (fuel and oxidizer) of a composite solid propellant. Its behavior when present at various locations in a sandwich propellant and the quenched surface structures these sandwich propellants is also studied. These studies are further extended to composite propellants as well. From these studies, it is concluded that activated charcoal acts on the primary diffusion flame and enhances the binder melt flow over the surface. The unique features observed with activated charcoal (enhancement in burning the rates is observed only at low pressures and burn rate pressure index reduced) are justified with the proposed mechanism and site of its action. Understanding the mechanism of activated charcoal provided an opportunity to tailor a propellant composition, with activated charcoal coated on ammonium perchlorate, which exhibited very high burning rates (17.34 mm/s at 70 bar) and a near plateau burning (n ~0.08) in the pressure range of 20–70 bar. Also, this paper proposes a mechanism, as to what causes a propellant to have a relatively larger binder melt flow and consequently lower n has been answered.

Studies on the role of iron oxide and copper chromite in solid propellant combustion

Iron oxide and copper chromite are the known burn rate enhancers used in a composite solid propellant. Lot of research has been carried out to understand the mechanism or location of action of the burn rate modifiers so as to better tailor the burning rate of a composite propellant. The literature is still very confusing in affirming the mechanism. Here, a systematic study has been carried out, by undertaking experiments at varying levels of combinations of the individual components (ammonium perchlorate, which is oxidizer and hydroxyl terminated poly butadiene, which is both fuel and binder) of composite solid propellant. Firstly, thermal gravimetric analysis, differential scanning calorimetry and burning rate measurements on the individual components are carried out to study the effect of iron oxide and copper chromite on the components themselves. It has been noticed that though both iron oxide and copper chromite are effective on ammonium perchlorate, iron oxide is slightly more effective than copper chromite. Also, copper chromite enhanced the binder melt flow, while iron oxide reduced it. These are followed-up by experiments on sandwich propellants, which give greater insight and enables better understanding of the behavior of iron oxide and copper chromite in composite propellants, as these are simple two-dimensional analogue of the composite solid propellants. Finally, experiments are carried out on the composite solid propellants to obtain a holistic understanding of the behavior/location of action of iron oxide and copper chromite in them. These studies are used to explain certain unexplained but observed phenomena, at the same time elucidating the location of action of these burn rate modifiers in composite solid propellant combustion. Based on these observations, it has been proposed that both iron oxide and copper chromite are primarily acting on the condensed phase. These studies are further complimented with experiments to analyze the thermal conductivity measurements of various propellant samples. This is pursued to understand the reason for the differences in burn rate pressure index for the composite propellants with iron oxide and with copper chromite. It has been understood from these studies that the thermal conductivity of a composite propellant is a key parameter, which affects the burn rate pressure index. Literature has never addressed it from this perspective.

(활성탄/고분자바인더)복합성형체의 압출온도에 따르는 응집구조 및 유량 상관성에 관한 연구

정수처리 방식에 있어서 소형화의 필요성이 증대됨에 따라 복합적인 기능을 갖는 단일구조 여과재 개발이 절실히 요구되고 있다. 본 연구에서는 단일구조를 가지는 필터개발을 위하여 활성탄과 고분자 바인더로 구성된 성형체를 압출소결방식으로 제조하여, 제조된 성형체의 밀도, 공극률 및 유량을 평가하여, 최대유량을 가지는 성형체의 최적 압출온도를 결정하였다. 또한 성형체의 공극률 평가에 있어서 전체 공극률뿐만 아니라 관통형 기공의 공극률을 추가로 평가하여 유량과의 상관성을 평가하였다. 압출온도가 고분자 바인더의 Melting point인 <TEX>$133^{\circ}C$</TEX> 이상인 <TEX>$140{\sim}230^{\circ}C$</TEX>에서 단일구조 복합 활성탄 성형체 구성이 가능하였으며, 압출온도 <TEX>$170^{\circ}C$</TEX>가 복합성형체의 밀도가 낮고, 관통기공의 공극률이 높아, 최대유량을 가지는 복합성형체의 제조가 가능한 최적 압출온도로 확인되었다. 또한 복합성형체를 통해 흐르는 물의 유량은 성형체의 전체 공극률 보다 관통형기공의 공극률에 크게 의존함을 알 수 있었다. As the need for miniaturization in water purification filter increases, the development of filter media for single filtration with multiple function was strongly required. In this study, the molded activated carbon composed of single unit was manufactured by extrusion-sintering process, and then the flow rate, density and porosity were investigated using the molded activated carbon manufactured at various extrusion temperature. We confirmed that it was possible to manufacture the single unit-molded activated carbon when the extrusion temperature was <TEX>$140{\sim}230^{\circ}C$</TEX> more than <TEX>$133^{\circ}C$</TEX> being of polymer binder melting point, and the optimal extrusion temperature for the molded activated carbon with maximum flow rate was <TEX>$170^{\circ}C$</TEX> since the molded activated carbon had low density and high through porosity. Also we confirmed that the flow rate through the molded activated carbon was strongly dependent upon through pore porosity compared to total porosity for the molded activated carbon.

Investigations on Activated Charcoal, a Burn-Rate Enhancer in Composite Solid Propellant

Through careful experimentation, this paper establishes that moisture trapped inside the pores of activated charcoal was the reason for the burn-rate enhancement of composite solid propellant observed in literature. This paper demonstrates that, even with the presence of moisture in activated charcoal, the propellants can not only be cured to be free from blow holes and voids but also have good mechanical properties. Experiments were also carried out to examine the possible mechanism for high burn rates and burn-rate pressure index observed in composite propellants when moisture was present in activated charcoal. Scanning-electron-microscope images show that moisture in activated charcoal reduces the binder melt flow. It is noticed that formation of the bubbly layer is more when moisture is present in the binder. This bubbly layer might be exploding near the surface of the propellant and taking away the binder melt layer. This could be the cause for the observed increase in the burn rate and burn-rate pressure index of aluminized composite propellants.