Formation Mechanism Of Composite Research Articles

Mechanical properties, thermophysical properties, and long-term ablation behaviours of C/C–ZrC– ZrB2– W–Cu composites

Spacecraft thermal protection materials need to survive long-term exposure to oxygen-containing environments at 2400 °C. In this study, a high-density and low-porosity metal-ceramic-modified composite was prepared at a low temperature (1500 °C) in the presence of W and Cu using combined slurry brushing and reactive melt infiltration methods. An investigation of the composite formation mechanism and the effects of W and Cu indicated that W and ZrB2 were formed via dissolution-precipitation and the external diffusion of C and B, respectively. The low reaction temperature and the metallic phases significantly improved the mechanical properties, thermophysical properties, and long-term ablation behaviours of C/C–ZrC–ZrB2–W–Cu. Compared to traditional C/C–ZrC, the flexural strength and fracture toughness of the composite increased by 71.56 % and 90.05 % to 345.95 MPa and 14.52 MPa m1/2, respectively, and the thermal conductivity increased by 174.93 % to 59.11 W/m·K. In addition, W and Cu effectively lowered the surface temperature by nearly 250 °C during 300 s ablation, and the mass and line ablation rates decreased to −0.272 mg/s and −0.247 μm/s, respectively.

Acid-Extracted Hydrocarbon Anomalies and Significance in the Chaoshan Depression of the Northern South China Sea

To predict the favorable zones and the types of reservoirs, acid extraction has been used in the Chaoshan depression to detect trace amounts of light hydrocarbons, heavy hydrocarbons, and the δ 13C (‰) of methane. As a result, two integration anomalous zones for exploration activity were blocked out in the northeastern and southwestern parts of the Chaoshan Depression, respectively. By analyzing the differentiation law and structural characteristics of hydrocarbon gases, as well as the stable carbon isotope ratio of methane, the underlying reservoirs were predicted to be gas reservoirs, and the seismically interpreted Dongsha-A (DS-A) structure was predicted to be a gas-rich structure. By correlating the seismic profile and geochemical anomalies, it was determined that fault planes and micro-fractures are the main controlling factors for the occurrence of the seabed’s geochemical anomalies. A composite formation mechanism of “lower generation, upper accumulation and micro fractures leaking” is proposed for the control of the underlying petroleum reservoirs, as well as for the micro-fracture control of permeability and surface adsorption control. Acid-extracted hydrocarbon anomalies have favorable indicating significance for exploration activity.

Formation mechanism of nanocomposites between starch and stearic acid via nanoprecipitation

Starch is one of effective host material for encapsulation of hydrophobic compounds using nanoprecipitation. In this study, stearic acid was encapsulated using starch, in which nanoprecipitation consisted of three phases such as the addition of an anti-solvent (ethanol) at 90 °C, the cooling procedure, and the addition of ethanol at an ambient temperature. To investigate the formation mechanism of composites between starch and stearic acid using nanoprecipitation, the changes in the physicochemical properties and crystalline structure of the composites for preparation phases 1, 2, and 3 were evaluated. During phase 1, the stearic acid content and complexation index of the sample mainly increased up to 2.8 mg/g composite and 83.4%, respectively. However, relatively minor changes were observed during the followed phases 2 and 3. The mean diameter of the composite gradually increased to 193.7 nm during phase 1, followed by a dramatic increase to 364.1 nm after phase 2. TEM revealed that individual particles with smaller sizes were mainly generated during phase 1; however, the particles formed larger aggregates by coagulation during phase 2. XRD and 13C NMR spectroscopy revealed that the V-type polymorph, in terms of short- and long-range crystalline structures, was mainly generated during phase 1.

Physico-mechanical characterization and thermal property evaluation of polyester composites filled with walnut shell powder

This paper reports on the processing and overall characterization of walnut shell powder (WSP) filled polyester composite. The effects of this filler on the properties of polyester resin are studied by conducting various characterization tests under controlled laboratory conditions. The composite formation mechanism has been explained by the interpretation of Fourier transform infrared (FTIR) spectroscopic and X-ray Diffraction (XRD) analysis. The study reveals that the incorporation of WSP particles modifies the density and porosity of the composites along with their tensile, compressive, flexural, and impact strengths. Thermo-gravimetric analysis (TGA) is done on the samples to get an insight into their thermal stability. Measurement of thermal conductivity is carried out on samples of different compositions, and it is found that the inclusion of walnut shell powder leads to significant improvement in the thermal insulation capability of polyester resin. It is recorded that with an increase in the WSP content from 0 to 20 wt. % in polyester, the value of the effective thermal conductivity ( K eff) drops by about 42%. It is further seen that with the incorporation of WSP, the coefficient of thermal expansion (CTE) of polyester is substantially lowered.

Application of Nanosilicon to the Sintering of Mg-Mg2Si Interpenetrating Phases Composite.

The new in situ fabrication process for Mg-Mg2Si composites composed of interpenetrating metal/intermetallic phases via powder metallurgy was characterized. To obtain the designed composite microstructure, variable nanosilicon ((n)Si) (i.e., 2, 4, and 6 vol.% (n)Si) concentrations were mixed with magnesium powders. The mixture was ordered using a sonic method. The powder mixture morphologies were characterized using scanning electron microscopy (SEM), and heating and cooling-induced thermal effects were characterized using differential scanning calorimetry (DSC). Composite sinters were fabricated by hot-pressing the powders under a vacuum of 2.8 Pa. Shifts in the sintering temperature resulted in two observable microstructures: (1) the presence of Mg2Si and MgO intermetallic phases in α-Mg (580 °C); and (2) Mg2Si intermetallic phases in the α-Mg matrix enriched with bands of refined MgO (640 °C). Materials were characterized by light microscopy (LM) with quantitative metallography, X-ray diffraction (XRD), open porosity measurements, hardness testing, microhardness testing, and nanoindentation. The results revealed that (n)Si in applied sintering conditions ensured the formation of globular and very fine Mg2Si particles. The particles bonded with each other to form an intermetallic network. The volume fraction of this network increased with (n)Si concentration but was dependent on sintering temperature. Increasing sintering temperature intensified magnesium vaporization, affecting the composite formation mechanism and increasing the volume fraction of silicide.

Synthesis of Inorganic Compounds in the Matrix of Polysaccharide Chitosan.

Data related to the fabrication of hybrid materials based on the polysaccharide chitosan were systematized and reviewed. The possibility of using chitosan as a “host” matrix for in situ synthesis of inorganic compounds for the preparation of various types of composite materials were investigated. Coprecipitation of metal oxides/hydroxides (Fe, Ni, Al, Zr, Cu and Mn) with chitosan was carried out through the alkalinization of solutions containing metal salts and chitosan, with the addition of ammonia or alkali solutions, homogeneous hydrolysis of urea, or electrophoretic deposition on the cathode. The synthesis of transition metal ferrocyanides and hydroxyapatite was achieved from precursor salts in a chitosan solution with simultaneous alkalinization. The mechanism of composite formation during the coprecipitation process of inorganic compounds with chitosan is discussed. Composite materials are of interest as sorbents, coatings, sensors, and precursors for the production of ceramic and electrode materials.

Effect of Ni on the formation mechanism of TiC/Ni composites fabricated by reactive sintering

The TiC/Ni composites with 0 wt%, 55 wt% and 70 wt% Ni contents were fabricated by pressureless reactive sintering to study the effect of Ni on the formation mechanism of composites. The results show that the solid reaction between Ti and graphite is controlled by the diffusion of C through TiC layer, and the morphology of TiC layer is similar to the graphite sheet in sample without Ni. By contrast, graphite would dissolve into Ni in samples with Ni, and Ni particles would form continuous skeleton around Ti particles by solid phase sintering. Meanwhile, Ni diffuses into Ti particles to form NiTi compound. Therefore, graphite and C in Ni skeleton reacts with Ti to form TiC layer on whole surface of NiTi particles, resulted in the similar morphology of TiC layers to original Ti particles. Moreover, Ni plays one key role in the liquid phase sintering of TiC/Ni composites by forming NiTiC eutectic phase. The relative density of TiC/Ni composites are higher than 96%, while the samples without Ni shows no obvious shrinkage. The increase of Ni also contributes to the decrease of sintering temperature by enhancing the solution-precipitation process.

Effect of TiO2 content on Ni/TiO2 composites electrodeposited on SS316L for hydrogen evolution reaction

Composite Ni/TiO2 catalysts have gained enormous interest in recent years in both electrocatalysis and photoelectrocatalysis for the generation of hydrogen. However, there are no systematic studies of the synthesis and characterization of these materials for applications in energy storage.In this work, three Ni/TiO2 catalysts were synthesized starting from nickel electrodeposition on AISI 316 L stainless steel with a modified Ni Watts bath, where different TiO2 contents have been added (0.1, 0.3, and 0.5% w/v). The mechanism of composite formation was studied at different electrodeposition times, in order to analyze the early periods of synthesis, reaching a chemically and structurally stable material after 45 min. It was found that all Ni/TiO2 catalysts present catalytic activity towards hydrogen generation, higher than that found by plating with a conventional Ni Watts. Particularly, the Ni/TiO2(0.3) catalyst presents increases in hydrogen formation efficiency of 75.3% and 67.8% at 298 K and 323 K, respectively.

Effects of Raw Material Molar Ratio and Addition of Mg on Titanium Aluminide–Alumina Composite Formation Mechanism

In this study, the effects of molar ratio of the raw materials (TiO2 and Al) and the addition of Mg on the titanium aluminide–alumina composite formation mechanism were investigated. To do this, in the first step, three molar ratios of 1.5 : 6.5, 1.5 : 3.5, and 3 : 5 of TiO2 : Al, with no presence of Mg and, in the second step, the same molar ratios with 2 wt.% Mg were used. Differential thermal analysis was applied to determine the critical temperatures of each ratio. Based on DTA results, the heat treatment was performed. It is found that with increasing the aluminum content, the reactions accelerate due to merge of the sub-reactions, and subsequently this causes the transient phase number to decrease. In the second step of the experiments, Mg was added to the previously mentioned molar ratios of TiO and Al. Mg reduced the reaction temperatures and accelerated the reaction processes as a result of low melting point eutectic formation.

Effect of micropores on the microstructure and mechanical properties of porous Cu-Sn-Ti composites

The porous Cu-Sn-Ti composites were fabricated by using a sintering-dissolution process with carbamide particles as space holders. The macroporosity of the composites was consistently controlled. The micropores among the pore-walls and wall intersections were quantitatively analyzed by using 2D micrographs and 3D X-ray tomographic reconstruction technique. The size, shape and distribution of the micropores and their effect on the mechanical properties of the composites (compressive strength, Young's modulus, and flexural strength) were investigated in relation to the composite formation mechanism and micropores evolution. It was found that the amount of graphite particles has a significant impact on the micropores formation and further on the mechanical properties of the bulk material. The rapid increase in the number of micropores as well as the gradual decrease in the compressive and flexural strengths were found to be caused by the increase of the graphite particle concentration. The mechanical performance could be improved by optimizing the alloy composition content and arranging the distribution of carbamide particles.

Microwave-Assisted Synthesis of C/SiO2 Composite with Controllable Silica Nanoparticle Size.

A C/SiO2 composite was produced from 3-aminophenol and tetraethyl orthosilicate (TEOS) by a synthesis protocol that involved microwave irradiation. This protocol featured simultaneous 3-aminophenol polymerization and TEOS hydrolysis and condensation, which were achieved rapidly in a microwave reactor. The SiO2 component was formed from low-concentration TEOS confined in cetyltrimethylammonium bromide micelles. We demonstrated a control of the SiO2 particle size, ranging from 20 to 90 nm, by varying the 3-aminophenol concentration. The carbon component provided a microporous structure that greatly contributed to the high specific surface area, 375 m2/g, and served as a host for the nitrogen functional groups with a content of 5.34%, 74% of which were pyridinic type. The composite formation mechanism was clarified from time-series scanning electron microscopy images and dynamic light scattering analysis. An understanding of the composite formation mechanism in this protocol will enable the design of composite morphologies for specific applications.

Binary Complex Based on Zein and Propylene Glycol Alginate for Delivery of Quercetagetin.

Propylene glycol alginate (PGA) was found to be able to dissolve in aqueous ethanol solution and applied to interact with zein to form a noncovalent binary complex by the antisolvent coprecipitation method at pH 4.0. Quercetagetin (Q) was employed to explore the Q-delivery potential of Zein-PGA binary complex. A fruit tree-like microstructure was observed for Zein-PGA binary complex as its "branches" were closely adsorbed by zein particles. A solid sponge-like entity was formed after lyophilization of Zein-PGA binary complex colloidal dispersion. A synergistic effect was found between zein and PGA on improving the entrapment efficiency and loading capacity of Q. The incorporation of Q at a high concentration induced a significant effect on the tertiary structure of zein. Electrostatic attraction, hydrogen bond, and hydrophobic effects were mainly involved in the interactions between zein and PGA. Schematics with four possible structures were proposed to explain the formation mechanism of composites.

Fabrication of W-Cu alloy via combustion synthesis infiltration under an ultra-gravity field

Tungsten copper alloy with a tungsten concentrate of 70 vol% was prepared by self-propagating high-temperature synthesis in an ultra-gravity field. The phase structures and components of the W-Cu alloy fabricated via this approach were the same as those via traditional sintering methods. The temperature and stress distributions during this process were simulated using a new scheme of the finite element method. The results indicated that nonequilibrium crystallization conditions can be created for combustion synthesis infiltration in an ultra-gravity field by the rapid infiltration of the liquid copper product into the tungsten compact at high temperature and low viscosity. The cooling rate can be above 100,000 K/s and high stresses in tungsten (~5 GPa) and copper (~2.6 GPa) were developed, which passivates the tungsten particle surface, resulting in easy sintering and densifying the W-Cu alloy. The reliability of the simulation was verified through temperature measurement and investigation of the microstructure. The W-Cu composite-formation mechanism was also analyzed and discussed with the simulation results.

Research on the formation mechanism of composites from lignocelluloses and CaCO3

The purpose of this work is to explore the formation mechanism of lignocellulose composites in ionic liquids, which is very important for the potential applications of lignocellulose composites. In this study, the lignocellulose/CaCO3 composites have been synthesized using different concentrations of CaCO3 by a rapid and green microwave-ionic liquid method. In view of the experimental results and literature, the formation mechanism of the composites from lignocelluloses and CaCO3 was proposed. It is suggested that lignocelluloses accumulated Ca2+ ions due to the complexation of the Ca2+ ions and the highly anionic polysaccharide groups of lignocelluloses, and CaCO3 was obtained by the strong electrostatic interactions between carbonate anions and calcium cations. When the content of CaCO3 reached a certain level, the activity of CaCO3 in the composites was mainly as aggregation. Using lignocelluloses instead of cellulose as a template to synthesize the organic–inorganic composites was a facile method, which does not need to separate the lignocelluloses and can utilize all the main components of lignocelluloses.

Synthesis, characterization and formation mechanism of SiC/spinel nanocomposite

This paper reports the successful synthesis of SiC/spinel (MgAl2O4) nanocomposite from talc, aluminum and graphite powders. The initial powders were mixed to obtain stoichiometric spinel containing 27.26wt.% SiC. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques were utilized to characterize the synthesized powders. SiC/spinel nanocomposite was obtained after 6h ball milling of initial materials in argon atmosphere with subsequent annealing at 1200°C for 1h in vacuum. The obtained nanocomposite had crystallites size between 1 and 15nm with the mean diameter of 9nm. The SiC/spinel composite formation mechanism was scrutinized. The results showed that SiC/spinel nanocomposite was not produced directly and the formation of some intermediate compounds is unavoidable during the synthesis procedure. The SiC/spinel nanocomposite powder may be a potential nanocomposite for high temperature applications with self-crack-healing capability.

Mechanism and optimization of titanium carbide-reinforced iron composite formation through carbothermal reduction of hematite and anatase

This study investigated an optimization of titanium carbide-reinforced iron composite fabricated using a combination of powder metallurgy and carbothermal reduction of hematite-anatase mixture using 2k factorial design. The composite formation mechanism is described as well. Powders of hematite, anatase and graphite with mole ratio of 1:1:6 were mixed for 1h together with 0wt%, 1wt% and 5wt% FeCl3. The mixture was pressed at 5MPa, calcined for 1h at 1000°C, 1100°C or 1200°C and sintered at 1200°C. X-ray diffraction of the calcined powder showed that with increasing temperature TiO2 was reduced to TiC through formation of various suboxides (Ti3O5 and Ti2O3). Scanning electron microscope observation of the sintered composite indicated that addition of FeCl3 enhanced the formation of TiC in iron matrix. Consequently, microhardness and density of the sintered composite improved noticeably. Based on microhardness, green density and sintered density measurements, design of experiment analysis suggested that an increase in both FeCl3 content and calcination temperature increased the percentage of hematite and anatase reduction.

High energy ball milling (HEBM) of high volume fraction hard-phase composite powder: Production and characterisation of Al4C3–27 vol.%NiCrAlY composite powder

Abstract This work characterises the microstructural development of an Al 4 C 3 based composite powder containing 27 vol.%NiCrAlY by high energy ball milling for up to 35 h in air. The observed mechanism of microstructural development was distinctly different to the traditional composite formation mechanism in which hard particles are folded into a ductile metal binder. During milling the isolated NiCrAlY particles were surrounded by a thick dense layer of Al 4 C 3 particles, preventing cold welding of the ductile phase. With continued milling the consolidated carbide particles acted as the effective binder through which the NiCrAlY particles were dispersed. It was only after 15–20 h of milling that the NiCrAlY phase became distributed sufficiently to act as a binder in the traditional sense. The microstructural and compositional development of the composite powder as a function of milling time is discussed through analysis by scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy.

Synthesis and characterization of poly(o-methoxyaniline)–lignosulfonate composites

Poly(o-methoxyaniline)–lignosulfonate (POMA–LGS) composites were synthesized through oxidative chemical polymerization of o-methoxyaniline by ammonium persulfate (APS) in the presence of sodium lignosulfonate (NaLGS). The structure of the composites was investigated using FTIR, UV–vis spectroscopies and SEM. The AC conductivity and free radical scavenging of the composites were also tested. The LGS content was found to have a strong influence on the structure and properties of the composites. A higher LGS content led to composites with a higher AC conductivity, a higher specific surface area, as well as a greater radical scavenging capacity. A new composite formation mechanism was proposed, with the sulfate group dissociated from the oxidant of APS as the main dopant, POMA particles as adsorbate and LGS as the adsorbent.

Electrical properties of ceria/carbonate nanocomposites

Ceria-based composites are developed as potential electrolytes for intermediate solid oxide fuel cell applications and a better understanding of the ionic conduction mechanism serves this purpose. Ceria-based composites were produced by several processing routes using a ceria-based ceramic host (Sm, Gd doped ceria) and various Na and Li carbonates. Simple ceria/carbonate two-phase nanocomposites were synthesized by the carbonate precipitation method followed by a thermal treatment. The decomposition course of the precursor, the thermal stability, morphology and the composite formation mechanism were studied by thermogravimetric–differential thermal analyses (TG–DTA), IR, UV, SEM and XRD analyses. The conductivity temperature dependence in the 300–800°C temperature range, performed on composite pellets, exhibits conductivity values one-two higher magnitude order and a lower activation energy of 0.809±0.001eV, with respect to 1.693±0.005eV for pure ceria obtained under the same conditions. This enhancement of the composite conductivity, corroborated with the blue shift of the gap energy, as deduced from the UV spectra, was attributed to the oxygen ion transport through an interface mechanism between the two phases of the ceria/carbonate composite.

Spectroscopic investigation of structure and mechanism of proton conductivity CsHSO4 and composites CsHSO4/SiO2

IR and RS spectra, structural, thermodynamical and transport properties of CsHSO4 and CsHSO4/SiO2 composites have been investigated. It is shown that CsHSO4 is stabilized in composites in phase II (monoclinic modification), which turns into amorphous state with increasing silicon dioxide content. A formation of disordered highly conducting states of CsHSO4 in composites at the temperatures noticeably lower than superionic phase transition was stated. Bond length equalization in sulfate-ions, weakening of hydrogen bond system, and as a result easier proton transfer in composites in comparison with pure salt take place in these conducting states. Mechanism for formation of composites and their proton conductivity is proposed.