Hollow Microspheres Research Articles

Carbon-negative heat-stored limestone calcined clay cement mortar containing form-stable phase change materials

Heat-stored cement-based materials (HSCMs) with form-stable phase change materials (PCMs) have exhibited tremendous opportunities for energy conservation and emission reduction in buildings. In this study, a novel HSCM system was designed by incorporating form-stable PCMs into limestone calcined clay cement (LC3) mortar, in which a highly compatible form-stable PCM was constructed by the three-step method including the synthesis of red mud-based geopolymer hollow microsphere (RMHM), the impregnation of n-Octadecane (ODE) into RMHM and the surface precipitation of CaCO3. The microstructures, phase transition properties, chemical compatibility and thermal stability of the two resulting form-stable PCMs (namely ODE/RMHM and ODE/RMHM@CaCO3) were evaluated. A comparative analysis was conducted to reveal the influence mechanism of ODE/RMHM and ODE/RMHM@CaCO3 on the microstructural evolution, hydration reaction, mechanical and thermal properties of LC3 mortar. Moreover, the numerical model method confirmed the significant role of the prepared LC3-based in temperature control and energy conservation in building. In addition, the obtained LC3-based HSCM could achieve a short dynamic payback period and sequestered huge of carbon emissions for service life. In overall, this work opened up a novel path of economically feasible carbon-negative building materials with form-stable PCM.

3D grape string-like heterostructures enable high-efficiency sodium ion capture in Ti3C2Tx MXene/fungi-derived carbon nanoribbon hybrids.

2D transition metal carbides and carbonitrides (MXenes) have emerged as promising electrode materials for electrochemistry ion capture but always suffer from severe layer-restacking and irreversible oxidation that restrains their electrochemical performance. Here we design a dual strategy of microstructure tailoring and heterostructure construction to synthesize a unique 3D grape string-like heterostructure consisting of Ti3C2Tx MXene hollow microspheres wrapped by fungi-derived N-doping carbon nanoribbons (denoted as GMNC). The 3D grape string-like heterostructure effectively avoids the aggregation of Ti3C2Tx MXene sheets and enhances the stability of MXenes, providing abundant active sites for ion capture, and an interconnected conductive bionic nanofiber network for high-rate electron transport. In consequence, GMNC achieves a superior adsorption capacity for sodium ions (Na+) in capacitive deionization (CDI) (162.37 mg gNaCl-1) with an ultra-high instantaneous adsorption rate (30.52 mg g-1 min-1) at an applied voltage of 1.6 V and satisfactory cycle stability over 100 cycles, which is a strong performer among the state-of-the-art values for MXene-based CDI electrodes. In addition, in situ electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) measurement combined with density functional theory (DFT) reveals the mechanisms of the Na+ capture process in the GMNC heterostructure. This work opens a new avenue for designing high-performance MXenes with a 3D hierarchical heterostructure for advanced electrochemical applications.

Direct evidence of pore structural effects on the compressive strength of lightweight cement slurry containing nano silica fume and hollow glass microspheres

This paper presents the results of an experimental study about the pore structure of 7 kinds of density-controlled lightweight cement slurry (LWCS) containing hollow glass microspheres and nano silica fume. X-ray micro-computed tomography (XCT) was used to characterize the microscopic pore structure of the LWCS specimens blended with nano silica fume (NSF) by 0–30% on the aspects of plane porosity, total porosity, pore size, sphericity, specific surface area, and fractal dimension. Meanwhile, the mineralogical and microstructural characterization of the NSF-affected pastes after the curing regime were tracked analyzed by thermogravimetric analysis (TGA), XCT, and scanning electron microscopy (SEM). Subsequently, the relationship between pore parameters and compressive strength of LWCS specimens was established. The optimum amount of nano silica fume was determined based on compressive strength, pore structure characterization parameters, and weight loss. The results show that the incorporation of NSF into LWCS matrix contributes to the improvement of the compressive strength. The optimal addition content for NSF is 20%, which can maximize the compressive strength at all curing ages. The filling of available space, the promotion of heterogeneous nucleation of cement hydrates and the pozzonlanic reaction of NSF itself, which densifies and homogenizes LWCS microstructures, account for the effects of NSF on the strength and pore characteristics of LWCS. The pore structure characterization parameters of LWCS, including total porosity, large pores (>100 µm) volume, large pores and medium pores (50–100 µm) volume, pore size, fractal dimension, and specific surface area, are all negatively linearly correlated with compressive strength. The harmful effect of large pores and medium pores on compressive strength is more pronounced than that of tiny pores (< 50 µm). There is a good negative ternary linear fitting relationship correlation between the fractal dimension, the large pores volume and the compressive strength (R2 =0.89). In order to prepare LWCS with excellent strength, the pores with size greater than 50 µm should be controlled or eliminated if possible. Fractal dimension is a more accurate quantitative parameter to characterize the compressive strength than the other pore parameters.

Preparation of a novel alginate hydrogel microspheres covered by hollow silica for controlled-release application

Sodium alginate hydrogel has been widely used in the field of controlled-release. In this paper, in order to prevent the negative effect of fast degradation and explosive release of pure sodium alginate hydrogel in the drug delivery process, we developed a novel alginate hydrogel supported by hollow silica microsphere for drug delivery. Briefly, the drugs were fused with sodium alginate and the hollow silica microspheres followed by ion crosslinking to form a composite hydrogel microsphere with a core–shell structure (SA@SiO2). The structure and morphology of the composite hydrogel were characterized by Fourier infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), scanning electron microscope (SEM), transmission electron microscope (TEM) along with fluorescence microscope. On this basis, using three different types of organic compounds (rhodamine B, Indocyanine green and salicylic acid) as model molecules, the controlled-release performance of the SA@SiO2 microspheres were investigated in detail. The research results show that the drug delivery system has broad-spectrum controlled-release performance for different types of molecules, and the controlled-release time can exceed 40 h. At the same time, the pH- responsive property of the sodium alginate hydrogel endows the delivery system with a certain targeting function. This study provides a new strategy for constructing an efficient targeted drug controlled-release system.

Regulating hollow structure of CL-20 microspheres using microjet droplet technology to enhance safety and combustion performance

Hollow energetic microspheres have attracted great attention in the field of materials due to their wide application potential. However, scalable, simple, and low-cost production methods have not been achieved yet. In this study, using nitrocellulose (NC) as a binder, hollow and porous hollow CL-20 microspheres were prepared by the assist of microjet droplet technology. The effects of receiving liquid temperature, solution concentration, and solvent type on the morphology, particle size, shell thickness, and pore size of the CL-20 microspheres were systematically investigated. Furthermore, the influences of shell thickness and pore size on the dispersibility, crystal structure, thermal decomposition, mechanical sensitivity, and combustion behavior of CL-20 microspheres were further studied. The results showed that precise control over the shell thickness and pore size of CL-20 microspheres could be achieved by adjusting the process parameters. Compared to raw CL-20, the CL-20 microspheres exhibited excellent dispersibility and improved thermal and safety performance (raw CL-20 vs CL-20 microspheres, 40.3° vs 27.1° ∼ 29.1°; 240.4℃ vs 241.1 ∼ 246.2℃; 2 J vs 25 ∼ 32.5 J). Ignition experiments demonstrated that the hollow and porous hollow structures significantly enhanced the combustion flame of CL-20, shortened the burning time, and thereby improved energy release efficiency. This preparation method is simple and efficient, providing a new approach for the fabrication of multi-structured hollow energetic microspheres.

Physical and high temperature properties of basalt fiber-reinforced geopolymer foam with hollow microspheres

For ultra-light geopolymer foam, it is challenging to maintain excellent mechanical properties and foaming stability while continuously reducing the density. In this study, basalt fibers (BF) and hollow microspheres (HM) were used to prepare a basalt fiber-reinforced metakaolin (MK)-based geopolymer foam (FRGF) and the workability, microstructure, physical properties, high-temperature performance, and shrinkage characteristics were systematically investigated. Results indicate that incorporating 50% HM into FRGF significantly reduces the fluidity by 31.2% and reaction rate of the geopolymer paste, slows down the decomposition rate of hydrogen peroxide, and enhances the stability of the foaming process. Additionally, the incorporation of HM increases the total porosity of the FRGF from 75.4% to 86.3%, lowers the bulk density from 0.42 g/cm3 to 0.34 g/cm3, and decreases the thermal conductivity to 0.0681 W/(m⋅K). Concurrently, the introduction of BF significantly enhances the mechanical properties of FRGF, with a 28-day compressive strength reaching 2.49 MPa. After treatment at 1000 ℃, the FRGF transformed from an amorphous gel structure to a crystalline structure. The sintering between BF and the matrix notably enhances the performance of interfacial transition zone (ITZ), further increasing the energy absorption capability and decreasing the linear shrinkage of FRGF at high temperatures (1000 °C) by 55.2%. In conclusion, 50% HM and 0.6% BF demonstrated superior mechanical properties, thermal insulation, and high-temperature performance. It offers a strategy to resolve the contradiction between the density, mechanical performance, and stability of geopolymer foams and has potential applications in the field of high-temperature insulation.

Hollow CoSe2-ZnSe microspheres inserted in reduced graphene oxide serving as advanced anodes for sodium ion batteries

Transition metal selenides are promising anode candidates for sodium ion batteries (SIBs) because of their higher theoretical capacity and conductivity than metal oxides. However, the disadvantages of severe capacity degradation and poor magnification performance greatly limit their commercial applications. Herein, we have developed a new hollow bimetallic selenides (CoSe2-ZnSe)@reduced graphene oxide (rGO) composite with abundant heterointerfaces. The rGO could not only alleviate the volume variations of hollow CoSe2-ZnSe microspheres during cycling, but also improve the conductivity of composite. The presence of the heterointerfaces could help to accelerate ionic diffusion kinetics and improve electron transfer, resulting in the improved sodium storage performance. As an advanced anode for SIBs, the CoSe2-ZnSe@rGO exhibits an enhanced initial coulombic efficiency of 75.1% (65.2% of CoSe2@rGO), extraordinary rate capability, and outstanding cycling stability (540.3 mAh/g at 0.2 A/g after 150 cycles, and 395.2 mAh/g at 1 A/g after 600 cycles). The electrochemical mechanism was also studied by kinetic analysis, showing that the charging/discharging process of CoSe2-ZnSe@rGO is mostly related to a capacitive-controlled behavior.

A novel rGO-ZnFe2O4 hollow microsphere composite with excellent microwave absorption properties

In order to develop lightweight, efficient and broadband microwave absorbing materials, rGO-ZnFe2O4 hollow microsphere composites were prepared by the solution method in this paper. The effects of reduced graphene oxide (rGO) content on the microstructure of hollow microspheres and the microwave absorption properties of the material were studied. rGO micropowders and ZnFe2O4(ZFO) particles are uniformly distributed on the hollow microspheres. The rich porous hollow structure is conducive to the multiple reflection and scattering of electromagnetic microwaves. This structure and distribution state enable the composite material to have good impedance and form a synergistic effect of multiple absorption effects. The results show that the minimum reflection loss (RLmin) is −28.83 dB and the effective absorption bandwidth(EAB) is 5.92 GHz (11.04∼16.96 GHz) when the thickness is 2.00 mm and the rGO is 6.3 wt.%. The Radar scattering cross section(RCS) results show that the RCS values of the samples with the rGO is 6.3 wt.% are mostly below −20 dBm2 in the range of microwave incidence angle of −90°< Theta < 90°, which indicates the composites has wide-angle microwave absorption ability. This study provides a new approach to the design and preparation of efficient and lightweight electromagnetic microwave absorbing materials.

Preparation of lightweight polycarbonate composite foams with robust hollow glass microspheres via CO2 foaming

AbstractPolycarbonate (PC) composites are often used in the production of high value‐added products, but it is necessary to improve its environment stress cracking condition in the presence of pre‐strain and soluble solvents. In this work, the effect of weight reduction and strengthening is realized by introducing microstructures and hollow glass microspheres (HGMs) into the PC composites. It is found that the addition of HGMs can reduce the melt viscosity and Tg value of the composite materials, which will change the foaming behavior of PC/HGMs composites. Besides, the effect of different content of HGMS and foaming temperature on the foaming behavior of PC/HGMs composite foams are studied. The PC/HGMs composite foams exhibit a typical structure of both large and small cellular pores, because of the existence of hollow beads and cellular structures. Moreover, compared to the neat PC foam, the tensile strength as well as the flexural strength of the composite foams are significantly increased by 110.9% and 364.7%, respectively. Furthermore, the as‐prepared PC/HGMs composite foams have low thermal conductivity (lower than 0.07 W/mK), which can effectively insulate heat propagation.Highlights Hollow glass microsphere can reduce melt viscosity and Tg of composites. The mechanical properties of composite foams have been greatly improved. Composite foams exhibit excellent thermal stability due to their microstructure.

Preparation and performance of intumescent water-based coatings with both thermal insulation and flame retardant functions

Functional flame retardant polymer materials are of great strategic relevance in reducing energy consumption in the wake of accelerated advances in materials science. In this paper, boehmite sol was employed to modify the surface of hollow glass microspheres (HGMs), self-designed a new type of intumescent flame retardant with melamine polyphosphate and starch (M-S system), which subsequently achieved synergistic flame retardant effects and produced high-performance water-based HGMs@Al2O3/M-S composite coatings that could be successively manufactured. As revealed from findings, HGMs@Al2O3 retained the fundamental structure and characteristics of HGMs and enhanced the interfacial compatibility with the water-based polymer matrix. The thermal conductivity of 0.097 W/(m·K) was achieved at 7 wt% HGMs@Al2O3, which notably strengthened the fire resistance of the coating when compounded with 20 wt% M-S. HGMs@Al2O3 also acted as a catalyst for carbon formation and achieves self-extinguishing off fire when the LOI value reached 36 % and UL94 passed the V-0 test. The maximum pyrolysis temperature of the HGMs@Al2O3/M-S composite coatings was 410.1 °C. The results of conical calorimetry indicate that the HRR were reduced by 76.9 % and the THR by 83.8 %, the superior smoke suppression performance of the material. FPI and FGI were 0.21 m2s/kW and 3.02 kW/m2/s separately, indicating a significant improvement in the fire performance of the material, with high residual carbon strength. When burned, HGMs@Al2O3 migrates to the surface of the material and acts as a flame retardant. It demonstrates that the material is superior to previous resemble products and has tremendous potential for application and further industrialization.

Performance of Si3N4 hollow microspheres prepared by spray drying and carbothermal reduction nitridation

A simple and scalable approach to fabricate monodispersed Si3N4 hollow microspheres (Si3N4 HMs) with uniform spherical structures is proposed in this study. This approach involves spray drying of Si3N4 precursor, followed by carbothermal reduction nitridation. The homogeneous Si3N4 precursor was first obtained by mixing phenolic resins and silicon resins, which are carbon and silicon sources, respectively. The spray drying process was then tuned by regulating the viscosity of the precursor by adding polyvinyl butyral in an appropriate ratio. Next, the hollow precursor microspheres were pyrolyzed at 1500 °C for 6 h, while ensuring that the shells of the obtained Si3N4 HMs remained intact. Porous Si3N4 ceramics with different contents of Si3N4 HMs were then prepared using the gel-casting method. It was observed that the densities and dielectric constants of the porous Si3N4 ceramics decreased with an increasing Si3N4 HMs content. Thus, the proposed approach can be used for the synthesis of Si3N4 HMs, that can be further processed into ceramic materials with both low densities and dielectric constants.

Porous hollow CaO microsphere synthesized by the template-assisted approach for enhanced CO2 capture

The development of cheap, environmentally friendly adsorbents with high adsorption capacity and good cycle stability is of great significance for reducing excessive CO2 emissions. However, the CaO-based adsorbents with low prices and high theoretical adsorption capacity suffer from serious sintering problems and poor cyclic stability. Herein, we synthesized porous hollow CaO microspheres for enhanced CO2 capture by the template-assisted approach, in which the carbon sphere template with different carbon chain lengths were prepared by hydrothermal method. The interaction between carbon chain lengths, morphologies, and properties of CaO-based adsorbents was systematically investigated. The results show that the porous hollow CaO microsphere prepared with a sucrose carbon template possesses a higher initial CO2 adsorption capacity (15.3 mmol g−1) and better cyclic stability after 20 cycles by reducing the mass transfer length of CO2 and buffering the volume expansion. In addition, the kinetics study reveals that the porous hollow spherical morphology can significantly improve the CO2 adsorption kinetics, especially in the chemical control stage, which provides theoretical guidance for the further understanding of the carbonization process. The systematic study marks the significance of precise tailoring of porous hollow CaO microsphere to achieve the desired performance of CO2 adsorption.

Thermal and Wettability Properties of Nanoclay-Filled Epoxy-Based Foam Composite as Lightweight Material

Abstract Epoxy-based foam composite (EBFC) materials have received considerable attention recently because of their wide range of applications in the aerospace and marine industries. EBFC materials made from hybrid fillers are materials generated to have improved thermal properties. This work focuses on improving the thermal properties and wettability of EBFC materials with hybridized fillers by infusing hollow glass microspheres (HGM) and clay. The HGM content varied between 1 weight percent (wt.%) and 5 wt.% in foam composite materials while clay content varied between 1 wt.% and 5 wt.% in each of the HGM-filled series of foam composite materials. These foam composite materials were fabricated using a conventional resin casting method. The thermal properties, such as thermal conductivity, thermal expansion, coefficient of thermal expansion, as well as specific heat capacity, water contact angles, and percentage of water absorption of hybrid-filled foam composite materials were investigated and compared with neat epoxy and epoxy foam materials. It was found that hybrid-filled foam composite materials exhibited improved thermal properties over neat epoxy material because of good chemical reactions and excellent interfacial adhesion between the fillers and matrix. These improved thermal properties may suggest that this material may be suitable for application in industries where lightweight materials with good thermal properties are required. This reveals a new area in foam composite manufacturing research by enhancing thermal properties with hybrid fillers.

Fabrication and characterization of polyvinyl alcohol/sodium alginate loaded carvacrol/silica hollow microspheres composite hydrogel as a colourimetric freshness indicator

A hybrid hydrogel consisting of anthocyanin (ATH), sodium alginate (SA), polyvinyl alcohol (PVA) and carvacrol (CA) loaded silica hollow microspheres (SC) was designed and fabricated as a colorimetric freshness indicator with antibacterial activity for monitoring meat spoilage. The microstructure and physicochemical properties of the hybrid hydrogels were investigated. The carvacrol could be loaded into silica microspheres, and the maximum degradation temperature raised to 179.6 °C due to the formation of hydrogen bonds between carvacrol and SiO2 microspheres. ATH and SC composite were well compatible with PVA/SA hydrogel with intramolecular hydrogen bond interactions. The three-dimensional network structure of the PVA/SA hydrogel was disrupted with increasing SC content, resulting in a gradual decrease in thermal stability, swelling capacity and tensile strength of the hydrogel. The SC-PVA/SA-ATH hydrogels exhibited satisfactory antibacterial ability against E. coli and S. aureus due to the effective release of CA from the hybrid hydrogel, and the inhibition ratio of SC3-PVA/SA-ATH was over 95%. The meat preservation experiment revealed that the hydrogel indicators exhibited distinctive color changes during the process of meat spoilage quality changes, indicating its promising application prospect in food preservation packaging.

Preliminary Investigation on Mechanical Properties of Hollow Glass Spheres

Hollow glass microspheres (HGM) have been employed in a wide range of applications such as thermal insulating coatings for construction and transportation applications and for acoustic insulation coatings. As such, it is expected for the HGM to exhibit an extremely high pressure tolerance in order to endure the harsh environment. In this present study, an effort has been made to investigate the mechanical properties of hollow glass microsphere. The glass sphere with diameters between 5-30 µm, 50-90 µm and 90-125 µm were used for this investigation. This study's objectives are to investigate the strength of HGM and gain an in-depth understanding of the mechanical characteristics of the sintered spheres.

Direct-writing assembly of high-strength hierarchical porous mullite-based lattices with a multiscale reinforcing strategy

High-strength mullite-based lattices with a hierarchical porous structure were assembled using waste fly ash hollow microspheres (FAHMs) as the main raw material by a direct ink writing (DIW) technique. The hollow microspheres were uniformly distributed in the strut matrix, creating a pore structure with a size ranging from 54 μm to 97 μm. Wet printed lattices were solidified by a protein gelling technique to further inhibit the shape deformation. Hollow microspheres, together with the dense matrix formed by aluminum silicate powder, formed the three-dimensional skeleton of struts in the mullite-based lattices. The lattice with a porosity of 84.3 % exhibited a high compressive strength of 2.74 MPa, along with a low thermal conductivity of 0.191 W m−1 K−1. Compared to most reported lattices with the same density, such as conventional mullite lattices, the stretching-bending dominated hierarchical porous mullite-based lattice exhibited superior mechanical properties. These lattices with both high porosity and high strength are cost-effective, flexible, scalable, and can facilitate the application of porous ceramics in emerging fields.

Low-cost fabrication of multicomponent silicate microspheres with tailored crystallization and morphology

This study presents a cost-effective method using sol-emulsion-gel approach to prepare micron-sized multicomponent silicate microspheres (SMs). SMs were obtained via rotary evaporation using water glass or silica sol as the silicon source. Results revealed that two-stage heating drying or two-step ion exchange treatment effectively suppressed crystallization in water glass-based SMs. The size and concentration of silicon sources and the rotary evaporation temperature dominated the sphericity and surface wrinkling of SMs. Smaller silicon sources like water glass or 5 nm silica sol with relatively high concentration, along with a suitable evaporation temperature like 65 °C, contributed to higher sphericity and smoother surfaces. The formation mechanism of microsphere crystallization and methods for its suppression were analyzed based on emulsion drying theory. Formation principles of microspheres with different morphologies were explained using wet-shell and dry-shell drying models. This method enables low-cost, large-scale fabrication of high-performance hollow glass microspheres (HGMs) with high quality SMs.

Preparation and Compression Resistance of Lightweight Concrete Filled with Lightweight Calcium Carbonate Reinforced Expanded Polystyrene Foam.

Lightweight concrete is widely used in the construction industry due to its low density and high strength. In this paper, lightweight concrete was prepared by a simple two-step method. Firstly, the light calcium carbonate reinforced epoxy macrospheres (LCR-EMS) material was obtained by adhering calcium lighter carbonate powder to the expanded polystyrene foam spheres (EPS) material using the "balling method". In the second step, the LCR-EMS was mixed with water, cement, and the hollow glass microspheres (HGMS) material using the "molding method" to obtain lightweight concrete. The combination of macroscopic photographs and microscopic morphology shows that the LCR-EMS material itself is uniformly encapsulated and well bonded to the matrix. Test results show that the density of the lightweight concrete decreases with an increase in the volume fraction of stacked LCR-EMS, the diameter, and the proportion of HGMS in the matrix, but it decreases with a decrease in the number of layers of LCR-EMS. The compressive strength of lightweight concrete exhibits a completely opposite trend. When three layers of LCR-EMS were used as filler material, the density and compressive strength of the concrete were 1.246 g/cm3 and 8.19 MPa, respectively. The density and maximum compressive strength of lightweight concrete were 1.146 g/cm3 and 6.37 Mpa, respectively, when filled with 8-9 mm-2L-90 svol% of LCR-EMS and 40 wt% of HGMS in the matrix. Compared with lightweight concrete filled with 90% EPS, the density increased by 20% while the compressive strength increased by 300%.

Constructing Interconnected Hollow Mesopore Sn-Si Mixed Oxide Microspheres by Aerosol-Assisted Alkali Treatment with Enhanced Catalytic Performance in Baeyer-Villiger Oxidation

In this work, Sn-Si mixed oxide microspheres with concave hollow morphologies were first synthesized by a simple aerosol method using the very common commercial surfactant cetyl trimethyl ammonium bromide (CTAB) as a template, and then highly interconnected mesoporous and hollow Sn-Si mixed oxide microspheres were synthesized via an alkali (NaOH) treatment in the presence of CTAB. The results show that CTAB plays a crucial role not only in forming hollow morphologies during the aerosol process, but also protecting the amorphous framework and thus preventing the excessive loss of Sn species during the NaOH treatment. More importantly, it widens mesoporous distribution and forms interconnected mesoporous channels. The catalytic performance of Baeyer–Villiger oxidation on the interconnected mesoporous and hollow Sn-Si mixed oxide microspheres with 2-adamantanone and hydrogen peroxide was 9.4 times higher than that of the sample synthesized without the addition of CTAB; 2.3 times that of the untreated parent, which was due to the excellent diffusion properties derived from the hollow and interconnected mesopore structure. This method is mild, simple, low-cost, and can be continuously produced, which has the prospect of industrial application. Furthermore, the fundamentals of this study provide new insights for the rational design and preparation of highly interlinked mesoporous and hollow metal-oxides with unique catalytic performances.

Preparation and Characteristics of High-Performance, Low-Density Metallo-Ceramics Composite.

By applying the physical vapour deposition method, hollow ceramic microspheres were coated with titanium, and subsequently, they were sintered using the spark plasma sintering technique to create a porous ceramic material that is lightweight and devoid of a matrix. The sintering process was carried out at temperatures ranging from 1050 to 1200 °C, with a holding time of 2 min. The samples were subjected to conventional thermal analyses (differential scanning calorimetry, thermogravimetry, dilatometry), oxidation resistance tests, and thermal diffusivity measurements. Phase analysis of the samples was performed using the XRD and the microstructure of the prepared specimens was examined using electron microscopy. The titanium coating on the microspheres increased the compressive strength and density of the resulting ceramic material as the sintering temperature increased. The morphology of the samples was carefully examined, and phase transitions were also identified during the analysis of the samples.