Ultrafine Powders Research Articles

Preparation and Characterization of Ultra-Fine Oil Palm Ash Powder by Ultrasonication and Alkaline Treatment for Its Evaluation as Reinforcing Filler in Natural Rubber.

Ultra-fine oil palm ash (OPA) particles were successfully prepared using ultrasonication along with optimal chemical deagglomeration. The influence of chemical treatment by sodium hydroxide (NaOH) solution on the OPA particles was found to be an important factor in enhancing deagglomeration efficiency. The average particle size of the original OPA (41.651 μm) decreased remarkably more than 130 times (0.318 μm) with an obvious increase of Brunauer–Emmet–Teller (BET) surface area after treating the OPA with 3M NaOH, followed by ultrasonication for 30 min. The changes in particle size and surface morphology were investigated using transmission electron microscopy and scanning electron microscopy. Moreover, the chemical functional groups of the untreated and treated OPA showed different patterns of infrared spectra by the presence of sodium carbonate species owing to the effect of NaOH treatment. The incorporation of both untreated and treated OPA in natural rubber by increasing their loading can improve cure characteristics (i.e., reducing optimum cure time and increasing torques) and cure kinetic parameters (i.e., increasing the rate of cure and reducing activation energy). Nevertheless, the strength, degree of reinforcement, and thermal stability of treated OPA as well as wettability between treated OPA particles and NR were greater than that resulting from the untreated OPA.

Effect of nano TiO2particles on the properties of carbon fiber-epoxy composites

A composite material was prepared using epoxy as a matrix, and carbon fiber (20% volume fraction) together with nano titanium dioxide (TiO2) particles in varying weight fractions (0,2,4 and 6%) as hybrid reinforcement. Mechanical tests (impact strength and wear resistance) were carried out, in addition to the study of liquid uptake behavior during immersion in chemical solutions, and inspection with scanning electron microscope imaging to reveal the microscopic details. The results showed that the addition of TiO2have improved the mechanical properties of the composites, as the specimen reinforced with 4% TiO2showed the highest impact strength, in addition to improved wear resistance. The scanning electron images for the specimens showed finely dispersed carbon fibers surrounded by the ultrafine TiO2nano powder, suggesting a uniform distribution of reinforcement throughout the whole matrix for all the prepared specimens. The liquid uptake results showed that the specimen reinforced with 20% carbon fibers and 6% nano TiO2had the highest diffusion rate, especially when immersed in hydrochloric acid. The results show that the prepared composite could be a good alternative to traditional materials whenever good wear resistance is involved, together with impact and chemical resistance, such as in anti-skid flooring applications.

Дослідження впливу ультразвукової обробки на фазовий склад і магнетні властивості високодисперсних порошків стопів Cu–Co і Cu–Fe, одержаних методом електроіскрового диспергування в різних рідинах

Дослідження впливу ультразвукової обробки на фазовий склад і магнетні властивості високодисперсних порошків стопів Cu–Co і Cu–Fe, одержаних методом електроіскрового диспергування в різних рідинах

High efficiency of the NH4H2PO4/Mg(OH)2 composite for guaranteeing safety of wood production

Currently, China's timber industry is in high demand with the development of real estate. However, there is a certain fire hazard in the production process of wood manufacturing. Once a fire occurs, the fire is violent and the spread is rapid. Therefore, to improve the safety of its production process, ammonium dihydrogen phosphate and magnesium hydroxide were selected to prepare a new composite superfine dry powder, which was denoted as the NH4H2PO4/Mg(OH)2 composite. Furthermore, to figure out dry powders' extinction effect on Class A fire, the wood-crib fire suppression effect of the NH4H2PO4/Mg(OH)2 composite was test, and then compared with that of ultrafine dry powder (UDP) and commercial ABC dry powder (C-ABC) in a 1 m³ chamber. Three parameters of the fire extinguishing process, namely flame extinction time, powder consumption and temperature drop were adopted to measure the fire suppression performance. The results demonstrated that UDP and C-ABC both had a larger flame extinction time and powder consumption than the NH4H2PO4/Mg(OH)2 composite. Besides, a fire (wood cribs) can be extinguished by the NH4H2PO4/Mg(OH)2 composite with the fastest temperature drop and a much-improved toxic gas suppression ability. In short, the NH4H2PO4/Mg(OH)2 composite can better guarantee the safety of the wood processing production process. Moreover, the reasons for performance advantages of the NH4H2PO4/Mg(OH)2 composite were discussed.

Selective electrochemical extraction of copper from multi-metal e-waste leaching solution and its enhanced recovery mechanism

Recycling activity for waste electrical and electronic equipment is always accompanied with leaching solution containing copper. Its selective extraction is of environmental and economic significance, and is beneficial for subsequent resource purification procedure. Compared with techniques such as chemical precipitation and solvent extraction, potentiostatic electrodeposition is outstanding with the advantage of high selectivity, electron as clean reagent, and minimal chemical usage. However, key factors affecting copper electrodeposition behavior as well as its kinetic process remain unclear, which blocks its further application. In this study, selective copper electrochemical extraction from multi-metal leaching solution of waste liquid crystal display panels is explored. Copper electrodeposition is analyzed from electrochemical and mass transport point of view, and the main results are summarized: (i) copper can be first electrodeposited due to its higher reduction potential compared with indium; (ii) applied potential and agitation are the most influential factors towards space-time yield and current efficiency; (iii) a semi-empirical kinetic model could quantitatively describe the influence of agitation and the time-current-concentration relationship. The model-predicted extraction rate agreed well with experimental data throughout electrodeposition; (iv) electrodeposition experiments show over 95% of copper can be selectively extracted as ultrafine copper powder (~150 nm) at 0.05 V (vs. SHE).

Influence of ultra-fine steatite powder on the fresh and hardened properties of self-compacting concrete

Being one of the globally used construction material, upgrading in the concrete has always become the cardinal motif for the researchers inducing the advancements in the same. Self compacting concrete being one such special concrete has eased much of the work for the constructors in many aspects. Steatite powder (Hydrated magnesium silicate powder) is introduced as an additive in the self compacting concrete in this experimental study. The fresh properties of self-compacting concrete such passing ability, filling ability flowing ability and segregation resistance along with the hardened concrete studies such as compressive strength as well as split tensile strength were studied. An entire powder content of 530Kg/m3 and a water/powder ratio of 0.43 were adopted throughout the study for the mix proportions. Different percentages of Ultra Fine Natural Steatite Powder (UFNSP) were incorporated to the complete weight of the OPC at 0%, 5%, 10%, 15%, 20% and 25% as an additive. The flow properties of the SCC developed with UFNSP were noted to be within the permissible limits of the European guidelines for SCC. Whereas on the other side, the mechanical properties remain elevated up to 20% of addition of UFNSP by developing optimum strength at 15% of UFNSP owing to the finer particle size of the UFNSP along with the presence of Mg in the SCC mixes thus developed.

Ultrasonic monitoring of variations in dust concentration in a powder classifier

Fine powders are generated in large volumes by industrial activities such as mining, metallurgical processing, energy generation and processing of waste. To meet specifications for further use, powder processing such as comminution and size classification are commonly applied. To optimise the design and operation of air-flow based classification processes, continuous on- line, monitoring of variations in dust particle concentration are an asset. This paper reports on the development of a novel ultrasonic measurement system suitable for robust monitoring of air-borne dust concentration variations during the operation of powder classification installations. The system was tested on a pilot-scale classifier designed for air-borne separation and recovery of ultrafine powders from coal combustion fly ashes. The monitoring method is based on a measurement of ultrasonic wave attenuation by particles suspended in the air-flow of the classifier.

Ultrasound-enhanced preparation and photocatalytic properties of graphene-ZnO nanorod composite

This paper studies the preparation and photocatalytic properties of graphene- ZnO nanorod composite with ultrasonic treatment. Graphene-ZnO nanorod composite photocatalyst with good structure is prepared after ultrasonic treatment for 30 h at 30 kHz in distilled water-ethanol dispersant using ultra-fine zinc powder. The effects of different proportions of zinc powder and expanded graphite on the photocatalytic properties of the composites are investigated. Besides, the prepared Graphene-ZnO nanorod composite photocatalyst is characterized by X-ray diffraction (XRD), laser Raman spectrometer (Ra-man), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet–visible spectroscopy (UV–Vis). It is found that ZnO nanorods in the composite exhibit a hexagonal wurtzite structure and are uniformly coated on the surface of graphene with a diameter of about 20 nm. The degradation efficiency of the composite materials prepared with different proportions of zinc powder and expanded graphite to methyl orange is quite different. When the zinc powder is 1.0 g, the photocatalytic activity of the composite is better than that with the same amount of zinc oxide nanorods. Results prove that the composite materials prepared with the appropriate proportion of raw materials show good photocatalytic performance, and the composite process is simple because it can be completed only under ultrasonic conditions. It breaks through the limitation of high temperature and high pressure in the traditional preparation process and has important reference significance for the development of zinc oxide composite in the field of catalysis.

Synthesis of nano-sized TiC powders by designing chemical vapor deposition system in a fluidized bed reactor

Chemical vapor deposition (CVD) process is an effective way to fabricate highly pure ultra-fine powders; however commercial fabrication of high quality TiC powders through conventional CVD (TiCl4–H2–CH4) system remains a great challenge. The main obstacle is that the conversion of chemically stable TiCl4 to TiC is too low (theoretically 13.3% at 1000 °C) to provide sufficient supersaturation to form powders but only coating. To tackle this problem, relatively unstable TiCl3 was proposed as a novel precursor, which is easier to achieve homogeneous nucleation due to the higher conversion of TiCl3 to TiC in the TiCl3–CH4–H2 system (theoretically 37.7% at 1000 °C). In addition, a fluidized bed reactor (FBR) with fluidized TiC seeds providing local turbulence was employed to boost the homogeneous nucleation. Based on the novel idea, for the first time, high purity nano-sized TiC powders (about 77.1 nm, purity 99.46 at.%) were successfully fabricated by a fluidized bed chemical vapor deposition (FBCVD) process. More importantly, an advanced simple and effective process was successfully developed to activate the common TiCl4 raw material to synthesize nano-sized TiC powders by designing the reactor.

Evolution of nano-scaled lamellae and its effect on strength of Ti–Ta composite

Abstract Introduction of nanoscale lamellae is an efficient way to improve the mechanical performance of alloys/composites. Here, we present a convenient and available approach to introduce nanoscale metallic lamellae into Ti–Ta based composites via spark plasma sintering and subsequent hot rolling. The formed lamellae originate from ultra-fine Ta powder with the particle size of less than 2 μm. Ti–Ta nanoscale lamellae consist of alternating Ti- and Ta-enriched lamellae with a body-centered cubic interface resulting from the effect of partial diffusion, as revealed by transmission electron microscopy. The nanoscale lamellae can significantly impede the motion of dislocations and thus effectively improve the strength of the Ti–Ta composite. The strength enhanced by nanoscale lamellae reaches up to 136.18 MPa when the total deformation degree is 60%. The manufacturing route developed here is versatile, capable of making high performance composites with nanoscale lamellae.

Preparation of sustainable and green cement-based composite binders with high-volume steel slag powder and ultrafine blast furnace slag powder

Abstract The mechanical properties and hydration mechanism of ultrafine ground granulated blast furnace slag powder (UFS)-cement-steel slag powder (SS) ternary cementitious material systems were studied. The chemical effects and contribution ratios of UFS and SS in ternary system at different hydration ages were also investigated. The results show that by adding UFS, the mechanical properties of concrete composites with high-volume SS conforming to the gap-graded particle size distribution are significantly enhanced. The close-packing effect between particles and the pore size distribution of hardened pastes are improved. The strength of cement matrix without any waste is still the highest. The SS has a negative impact on the hydration and strength development of the system at the early hydration ages, but it has a certain promoting effect at later hydration ages. UFS has a visible improvement effect on the hydration and the strength development of the system at both early and later hydration ages. The contribution ratio of UFS was analyzed and was found to be higher than that of SS apparently.

Fracture behavior and microstructure of Al2O3–SiO2 castables containing andalusite

To evaluate the andalusite role on the fracture behavior of Al2O3–SiO2 castables and reveal the improvement mechanism of flexibility, Al2O3–SiO2 castables with various andalusite additions (0, 10, 20, 30, 40, and 50 wt%) were prepared adopting homogenized bauxite, andalusite, calcium aluminate cement, microsilica and ultrafine α-Al2O3 powder as raw materials. Wedge splitting test was used to determine fracture behavior of Al2O3–SiO2 castables. The improvement mechanism of toughness was discussed according to the analysis of microstructure. The results show that incorporation of andalusite is an effective way to change fracture behavior and improve the flexibility of the Al2O3–SiO2 castables. The force-displacement curve of the Al2O3–SiO2 castables without andalusite addition is featured with a linear fracture behavior, while the force-displacement curves of the Al2O3–SiO2 castables containing andalusite are characterized by a nonlinear fracture behavior. The flexibility parameter (GF/σNT ratio) rises markedly from 35.3 μm of the castable without andalusite to 197.8 μm of the castables with 40% of andalusite addition, which increases more than twice. Microcracks toughening plays one major role in the improvement of the flexibility of Al2O3–SiO2 castables containing andalusite. The formation of microcracks can be attributed to mismatch of coefficient of thermal expansion between andalusite particles and matrix, caused by anisotropic behavior of andalusite aggregates and mullitized andalusite aggregates. The interlocking microstructure of in situ formed mullite grain in the matrix is the second reason for the toughness improvement of Al2O3–SiO2 castables containing andalusite.

Biomorphic SiC: porous SiC and ultrafine SiC powder formation through biomimicking route

ABSTRACT Natural wood is a ready-to-use template for making porous silicon carbide (SiC) body. Biomorphic β-SiC was synthesised from wood of a mango (Mangifera Indica) tree. Carbon template was made by carbonising this wood at 1000°C in argon gas atmosphere. Thus formed template was repeatedly infiltrated with a mixture of tetraethyl-orthosilicate (TEOS) (in alcohol) and oxalic acid solution (aqueous). Heat treatment at 1600°C for 1 h in vacuum converted the infiltrated template to β-SiC with a complex hierarchical cellular structure- a mimic of the plant structure. To produce phase pure SiC, unreacted carbon (C) and silica (SiO2) (if any) were removed by burning in air followed by treating with hydrofluoric acid. Mono dispersed SiC powder having particle size of ∼225 nm has been obtained by crushing, grinding and milling of thus formed biomorphic SiC body. A grinding limit is reported for the first time in SiC system.

Efficient preparation of ultrafine powder from waste cellulose by physicochemical method

Consumer waste of cotton cellulose is receiving increasing attention. In this study, in order to recycle waste cotton cellulose fibre into ultrafine powder efficiently, a compact process containing sulfuric acid treatment and stone milling was examined. Scanning electronic microscopy (SEM) and atomic force microscope (AFM) were used to study the morphology of the original cellulose fibre, acid modified fibre and milled cellulose powder. The particle size, crystallinity and strength loss were also explored. The results illustrated that the fibre strength can be largely reduced by acid treatment and high temperature and the crystallinity of the fibre decreased after stone milling. Ultimately, the production efficiency and the output of the micron dry cellulose powder were greatly improved. About 1 kg dry ultrafine powder with particle size around 40 μm was achieved in 1.5 h by stone milling in laboratory. This method shows a great potential for industrial application in the future.

The Effect of Matrix and Processed Material Properties on the Performance of Diamond Drills

The results of laboratory tests for drilling of corundum, chamotte, and porcelain with diamond tubular drills in running water, as well as the friction of cylindrical samples of the matrix against these materials, have been described. Bronze containing ultrafine ASM 1/0 diamond powders and molybdenum, as well as bronze without this reinforcement, served as the matrix for the drills and cylindrical samples. The speed of processing corundum, chamotte, and porcelain with diamond drills constantly increased when the concentration of diamond powders raised to 11 wt.%. At the same time, the tool wear significantly reduced, reaching the minimum at 5–9 wt.% of ASM 1/0 concentration (depending on the choice of the test material). The wear of diamond powder increased binsignificantly when the concentration of diamond powders grew to 11 wt.%. Similar results were obtained for the matrix of samples. Thus, the wear of the matrix samples decreased with an increase in the ASM 1/0 concentration. Such a decrease was observed even at 11 wt.% for friction against corundum. During friction against chamotte and porcelain, the wear of the samples reached the minimum at 7 wt.% diamond powders. As in the case with drills, a further increase in the content of ASM 1/0 in the reinforcement led to an increase in wear of the samples. High wear of the drills and samples at a relatively high content (11 wt.%) of ultrafine diamond powders was explained by the porosity that occurred in the matrix. The studies performed allowed concluding that reinforcement containing ultrafine ASM 1/0 diamond and molybdenum powders should be introduced into the matrix of diamond drills to improve their performance and decrease the consumption of abrasive material. The matrix samples containing up to 7 wt.% of ultrafine diamond powders can be successfully used as an abrasive tool for finishing (polishing) a series of nonmetallic materials, in particular, semiprecious and precious stones in jewelry production.

Effect of Heat Treatment on the Physicochemical Properties of Ultrafine ZrO2–Y2O3–CeO2–Al2O3–CoO Powders

Variations in the phase composition, specific surface area, and morphology of structural components in the ultrafine powder of composition (wt.%) 70 (90 ZrO2 (3 Y2O3, 2 CeO2)–10 Al2O3)–30 CoAl2O4 (70ZA30CoA), produced by hydrothermal synthesis combined with mechanical mixing, were studied in the heat treatment process up to 1300°C. The study employed Xray diffraction, scanning and transmission electron microscopy, petrography, and BET. The formation of CoAl2O4 in the 70ZA30CoA powder in the heat treatment process was accompanied by reversible phase transformations: T-ZrO2 → M-ZrO2 → T-ZrO2. The M-ZrO2 content increased from 15% to 46% in the temperature range 850–1000°C and decreased to 13% after heat treatment to 1150°C. The process involved slight coarsening of the primary T-ZrO2 particles, while the size of the primary M-ZrO2 particles remained practically unchanged. The phase transformation was due to a decrease in the free energy of the ultrafine 70ZA30CoA powder, representing a thermodynamically nonequilibrium system. The phase composition changed color of the 70ZA30CoA powder in the following sequence: gray → gray blue → dark cyan → bright blue. Morphological analysis of the structural components showed that the CoAl2O4 formation and reversible T-ZrO2 → M-ZrO2 phase transformation were accompanied by shape change, loosening, and subsequent sintering of the agglomerates. The chain-like agglomerates of various shapes and sizes indicate that the 70ZA30CoA powder sinters actively at 1300°C. The decrease in the specific surface area from 46 to 1 m2/g depending on the heat treatment temperature was determined by the development of three structural transformation processes: formation of CoAl2O4, phase transition of the ZrO2 solid solution, and sintering of the 70ZA30CoA powder. The established regularities are of fundamental importance for the microstructural design of ZrO2 composites such as ZrO2–Y2O3–CeO2–Al2O3–CoO materials of blue and other colors for various applied purposes.

Adsorption and Structural Properties of ASD-4 Powder after Surface Modification with Mn, Fe, Co, and Ni Formates

Low-temperature nitrogen adsorption, X-ray phase analysis (XRD), and electron microscopy are used to analyze the physicochemical properties (morphology, texture, phase composition, specific surface area, and porosity) of ASD-4 ultrafine powder and the products of the reaction between ASD-4 nanopowder and Mn, Fe, Co, and Ni formates. Results from studying the morphology and phase composition of oxidation products are presented, and the specific surfaces and porosities of the powders are calculated. Features of the adsorption isotherms of the studied samples after modifying them with formates are discussed in terms of their conformity to a specific type, according to the recommendations of the International Union of Pure and Applied Chemistry (IUPAC), and to certain types of porosity. The data show that the ASD-4 + 2% Mn and ASD-4 + 2% Ni samples are the ones with the highest adsorption activity. The specific surface area is 19.7907 m2/g for ASD-4 + 2% Mn and 10.1244 m2/g for ASD-4 + 2% Ni. The ASD-4 + 2% Mn and ASD‑4 + 2% Ni samples have more pores of mixed shape (slit-like and cylindrical) with widths of around 48.7234 and 44.2675 A, respectively. The pore volumes are 0.028250 and 0.012156 cm3/g for the ASD-4 + 2% Mn and ASD-4 + 2% Ni, respectively.

The immunomodulatory effects of Carapax Trionycis ultrafine powder on cyclophosphamide-induced immunosuppression in Balb/c mice.

There are abundant resources of Carapax Trionycis from soft-shelled turtle processing wastes each year in China. Our preliminary work showed that Carapax Trionycis ultrafine powder (CTUP) obtained using ball-milling with a particle size of 2.24 μm (D0.025) contained more active ingredients. The CTUP D0.025 has a good bioaccessibility, but there has been no report about the immunomodulatory function of CTUP. Therefore, using a cyclophosphamide-induced immunosuppression mice model, we investigated the immunomodulatory effects of CTUP D0.025. The results indicated that CTUP D0.025 administration significantly improved the immune organ (bone marrow, thymus and spleen) indices, ameliorated spleen tissue morphology and increased the capacity of splenocyte proliferation and the activity of macrophage phagocytosis. CTUP D0.025 also significantly promoted the secretion of cytokines (IL-2, IL-4, IL-10, IFN-γ and TNF-α), improved the related mRNA expression levels of IL2, IFN-γ, T-bet and GATA3 in immunosuppressed mice and increased the production of serum hemolysin and the levels of IgG, IgM as well as complement C3 . Moreover, CTUP D0.025 administration enhanced the antioxidant capacity of mice, exhibited a moderating effect on the damage of bone and skeletal muscle and improved the recovery of bone mineral density and calcium metabolism. These findings demonstrated that CTUP D0.025 had an effective immune-enhancing function in immunosuppressive Balb/c mice and also exhibited anti-osteoporosis properties. © 2020 Society of Chemical Industry.

Anisotropic Nd-Fe Ultrafine Particles with Stable and Metastable Phases Prepared by Induction Thermal Plasma

Both stable Th2Zn17-type and metastable TbCu7-type phases of anisotropic Nd-Fe ultrafine particles are prepared selectively by controlling the cooling rate using the low-oxygen induction thermal plasma (LO-ITP) process. The cooling rate is controlled by introducing the additional Ar gas at the end of the plasma flame. Moreover, numerical calculations based on a binary aerosol formation-growth model clarifies the alloying mechanism during rapid cooling wherein Nd-Fe vapor solidifies. The metastable Nd-Fe alloy ultrafine particle is formed in the cooling rate of 5×105 K/sec via the alloy droplet which is formed after the Fe and Nd vapors convert simultaneously into the liquid phase. The mean particle sizes of obtained ultrafine alloy powders without and with quenching are 76.3 ± 24.2 nm and 37.0 ± 12.5 nm, respectively. Electron microscopy observation reveals that the obtained particles are single crystalline. The Nd concentration of Nd-Fe particles shows a distribution in the range of 10.1–12.6 at%. X-ray diffraction and magnetic measurement demonstrate that the obtained particles are anisotropic and can be aligned by external magnetic field. Therefore, this process paves the way to achieve a new-generation anisotropic permanent magnet.

FUNCTIONAL AND TECHNOLOGICAL PROPERTIES OF THE FOOD ADDITIVE MAGNETOFOOD IN THE PRODUCTION OF MARSHMALLOWS

Production of whipped confectionery (marshmallows, pressed fruit paste, sweets with light-textured centres) is a complex process difficult to control. To expand and modernise their production, it is necessary to find simpler technologies, both resource- and energy- saving, to increase the stability of the heterogeneous dispersed system, and to improve the quality of finished products. In this respect, applying food additives of the nanometer range in technology looks very promising due to their unique physicochemical parameters and their many functional and technological properties. In the paper, it is suggested to solve the problem of stabilising the polyphase structure of whipped confectionery products and to form their quality by using the food additive Magnetofood based on ferrous and ferric oxides (FeO×Fe2O3). Magnetofood is ultrafine powder with a particle size of
 ~80 nm. It has a high functional and technological potential: large specific surface and a set of useful properties (the additive is surface- active, with complex-forming, sorption, and stabilising properties). This allows us to recommend Magnetofood as an additive with a complex action to improve the quality and extend the shelf life of sugar confections like fruit paste and fruit jelly products, in particular, white and pink marshmallows. It has been found that addition of Magnetofood in the form of an aqueous suspension at the stage of swelling and dissolution of the gelling agent improves the shape and consistency, reduces the density of the foam structure by 1.12–1.15 times, reduces the amount of gelling agent by 10–12% for agar and by 7–9% for pectin, increases the mechanical strength of marshmallows by 11.5–12.6% for agar and by 8.2-9.1% for pectin. Besides, the foaming ability of egg white increases by 1.14-1.4 times (with constant foam stability (99±1)% due to the stabilising effect of Magnetofood nanoparticles), and the thixotropic property of the gel structure becomes 1.4–1.5 times as much