Specific Surface Area Of Powders Research Articles

Zinc-ion battery with non-aqueous electrolyte and zinc-manganese spinel positive electrode

Zinc manganite spinel powder specific surface area was found to increase by an order of magnitude via a treatment with sulfuric acid. The specific surface area, determined by nitrogen adsorption, correlates with the specific capacity of zinc manganite spinel positive electrodes. Zinc manganite spinel subjected to a controllable acidic treatment is a promising material for the non-aqueous zinc-ion batteries.

Sintering densification behavior of nano-ITO powder with high oxygen vacancy induced via plasma stimulation

With the growing electronics display industry, indium tin oxide (ITO) powder plays a crucial role in target preparation. To enhance the sintering performance of ITO powder, a high-activity nano ITO powder was prepared using plasma spraying, and compared to a commercial powder. This study aimed to investigate the effects of different preparation methods on powder morphology, dispersibility, oxygen vacancy concentration, and the physical properties of powders on target density, surface morphology, grain size, element distribution, and solid solubility. The results indicate that the plasma spraying high-activity nano ITO powder exhibits better dispersibility, higher oxygen vacancy concentration, and a specific surface area of up to 88.39 m2/g compared to the commercial powder. Under normal pressure sintering conditions, plasma spraying nanoscale ITO powder exhibits higher sintering activity, leading to easier densification of ceramic targets with reduced porosity, more uniform surface grains, and significant stepped growth between surface grains. High-resolution transmission electron microscopy (HRTEM) analysis suggests that targets prepared with high-activity powder have greater tin solubility in indium oxide compared to traditional commercial ceramic targets. This article further explores the relationship between powder specific surface area, oxygen vacancy, and sintering activity, along with the formation mechanism of high oxygen vacancy.

Optimizing liquid phase promotion effect by modifying powder specific surface area in Si4+/Mg2+ co-doped transparent Yb:YAG ceramics

Utilizing the Si4+/Mg2+ co-doping has been considered an effective approach to fabricate highly transparent ceramics. However, the optimum doping concentration has been reported with considerable uncertainties. In this work, highly transparent Yb:YAG ceramics were obtained via the solid-state method and the sintering behavior is discovered to be closely related to both the doping concentration of Si4+/Mg2+ and the specific surface area (SBET) of powders. SBET is effectively modified by setting the ball-milling time, where the maximum SBET (30.914 m2/g) is achieved with 24 h ball-milling time. With increasing SBET, less Mg2+ is required for better optical properties. When SBET equals 30.914 m2/g, the highest in line transmittance @1100 nm of 84.85% is obtained with Si4+/Mg2+ doping concentrations of 0.50 wt.% and 0.05 wt.%, respectively. The relation between SBET and optimum doping concentration is explained by the different magnitudes of liquid phase promotion required for different contact areas between powder particles.

The Impact of Brick Powder Specific Surface Area on Cement Replacement in Mortar Mixes: A Sustainable and Cost-effective Solution for the Construction Industry

This study examined the use of clay brick powder (CBP) as a partial substitute for cement in mortar mixes. Five mixes were tested, each differing by the fineness of the CBP, obtained by grinding brick waste for different durations (30, 60, 90, 120 minutes). Several parameters were evaluated; apparent density, porosity, spread, ultrasonic pulse velocity (UPV), flexural and compressive strength, and the pozzolanic activity index. The results indicate that, when the brick powder is ground for 60 minutes, the spread of the mortar exceeds 95% compared to the reference mortar. The addition of CBP appears to increase the water absorption and porosity of the mortars, without significantly influencing their apparent density. Most samples have a UPV close to 4000m/s, attesting to satisfactory mechanical properties. The use of 20% CBP in replacement of cement leads to a decrease in flexural strength. However, this drop is less when the specific surface area of the CBP is close to that of cement. As for compressive strength, a decrease is also noted with the introduction of CBP, but this decrease can be mitigated by using CBP with a specific surface area similar to that of cement. These factors can significantly influence the pozzolanic activity of the mortar mix. Furthermore, our investigations into environmental and economic analyses show that the use of cement mixes including CBP results in a significant decrease in energy consumption and CO2 emissions. More specifically, the replacement of 20% of cement with CBP of different granulometries has led to promising results.

Measurement of specific surface area of barite in drilling fluid and its applications

In the weighting drilling fluid, barite will adsorb the free water and additives in the drilling fluid, which often worsens the performance of the drilling fluid. In order to optimize the performance of drilling fluid, a method for measuring the specific surface area of powder in liquid phase based on low field nuclear magnetic resonance (NMR) relaxation was established to study the occurrence state of barite in drilling fluid. The variation of specific surface area of barite in suspension with different concentrations were measured by particle size calculation and low field NMR, and the experimental results show that the specific surface area obtained by low field NMR can reflect the aggregation state of barite in liquid phase. Through organic carbon adsorption and rheological test, the adsorption law of barite to different drilling fluid additives was obtained. This study can solve the problem of additive addition in drilling fluid and optimize the performance of drilling fluid.

Fabrication of high specific surface area TiO2 nanopowders by anodization of porous titanium

The specific surface area of TiO2 powders is an important factor affecting the performance. In this study, we present a simple and novel method to fabricate TiO2 nanopowders based on electrochemical anodization. TiO2 nanopowders with coral-like structure surface and maximum specific surface area of 280 m2/g were fabricated in an aqueous electrolyte containing 1 M Na2SO4 and 0.5 wt% NaF under applied potential of 10 V. Porous titanium as an anodic substrate enhances the reaction rate and promotes the shedding of nanotube fragments. The reaction yield of powders prepared at high-frequency 10 V is nearly 3.7 times higher than that prepared at constant potential 10 V. The specific surface area of the powder prepared at high-frequency-15 V is 61% higher than that prepared at constant potential 15 V.

Solution combustion synthesis of high surface area Li2TiO3 nanostructure particles: Effect of nitric acid and NaCl addition

Nano/mesoporous-structured Li2TiO3 powders were synthesized by solution combustion method using citric acid as fuel. Effect of nitric acid and NaCl addition on the molecular, structure, microstructure, and the specific surface area of powders was studied. The obtained nanoparticles were characterized with different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET analysis. The XRD patterns showed the formation of monoclinic structure of Li2TiO3, while FTIR spectra confirm the absorption band corresponding to the metal - O stretching vibrations. The SEM micrographs showed that highly agglomerated powders and porous microstructures were formed. Specific surface area, mean pore size, and pore volume of the samples were obtained by BET analysis and confirmed the nano/meso scale of the pores. Moreover, the results showed that nitric acid addition, as a secondary oxidant, up to 9 L per molar fuel helped to complete combustion reaction. Furthermore, adding NaCl increased specific surface area of nanopowders considerably. A mechanism for the role of NaCl during the combustion reaction was suggested.

Spherical Agglomerates of Lactose Reduce Segregation in Powder Blends and Improve Uniformity of Tablet Content at High Drug Loads.

We report here on improved uniformity of blends of micronised active pharmaceutical ingredients (APIs) using addition of spherical agglomerates of lactose and enhanced blend flow to improve tablet content uniformity with higher API loads. Micromeritic properties and intra-particle porosity (using nano-computed X-ray tomography) of recently introduced spherical agglomerates of lactose and two standard lactose grades for the direct compression processes were compared. Powder blends of the individual lactose types and different micronised API drug loads were prepared and subjected to specific conditions that can induce API segregation. Tablet content uniformity during direct compression was related to the lactose material attributes. The distinctive micromeritic properties of the lactose types showed that spherical agglomerates of lactose had high intra-particle porosity and increased specific surface area. The stability of binary blends after intense sieving was governed by the intra-particle porosity and surface roughness of the lactose particles, which determined the retention of the model substance. Greater intra-particle porosity, powder specific surface area, and particle size of the spherical agglomerates provided greater adhesion of micronised particles, compared to granulated and spray-dried lactose. Thus the spherical agglomerates provided enhanced final blend flow and uniformity of tablet content at higher drug loads.

Low cost automated instrumentation for the measurement of the specific surface area of powders by the Brunauer–Emmett–Teller (BET) method

An automated instrument to measure specific surface area (SSA) of powdered materials was designed using the Brunauer–Emmett–Teller (BET) isotherm method. A sample of known SSA was introduced to make the method simple, accurate, and fast. The cost of the instrument was reduced by operating the instrument at a fixed partial pressure. A piezoelectric sensor was introduced to detect the changes in gas flow rates with better sensitivity and low cost. The analyzer was used to analyze the SSA of an unknown sample, to compare the SSA of two samples, and to identify unknowns using the SSA. The error of the instrument was less than 0.1%.

In English

Powders where the γ≈α-Al2O3-nano phases are the priority precursors for catalysts for heterogeneous catalysis with the maximum content of surface 5-coordinated Al centers for Pt attachment. Hydrogenated nano powders (~8 nm) of γ-, γ '-, θ-, κ-Al2O3 soluble in hydrochloric acid were obtained from the processing of aluminum boride powders with an icosahedral structure. Samples, which underwent a step-by-step and single heating of 50-100K heat treatment for 2 hours at temperatures of 570-1470K, were received in quantity of 34. The specific surface area of SВET, m2g-1 was measured by the thermal nitrogen desorption express method of gas chromatography through the GC-1 device. X-ray (phase and coherent), fluorescence and phase chemical-analytical evaluation of the samples were performed. The thermokinetic characteristics of the processes are calculated using the exponential Arrhenius law. Dimensional characteristics of crystallites (10.4-48 nm); specific surface area of powders (213-8.6 m2g-1, SВET); thermokinetic parameters of α-Al2O3 crystallite growth process (V α-Al2O3 - 1.44 10-3 - 6.67 10-3 nm s-1; E α-Al2O3 = 38.7±2.1kJ mol-1; A0 = 0.16±0.0 s-1 along the temperature line 1220-1470K were determined and calculated. The process of dehydration of two OH-groups occurs in the region 570-720K Ea H2O ↑ = 30.5 ± 0.5 kJ mol-1 A0 = 1.33±0.3 s-1. The last group of OH at temperatures of 820 -1070К and a rate of 2.13 10-4 - 4.93 10-4 mol s-1 Ea H2O ↑ = 13.2 ± 0.8 kJ mol-1 A0 = 16.9 ± 0.9 s-1. The activation energy of the phase transition is Ea., γ → α-Al2O3 = 23.9 ± 1.0 kJ mol-1 A0 = 2.01 ± 0.72 s-1 (770-970K) and Ea., γ → α-Al2O3 = 83.5 ± 0.8 kJ mol-1 A0 =(2,05±0,95) 103 s-1 (1070-1170K). It agrees well with the known heat of conversion Eа, γ→α-Al2O3 = 85 kJ mol-1. The TK of γ≈α-Al2O3-nano phases is at 1170K.

Effect of Heat Treatment on the Structure and Phase Composition of the Nanosized Powder Based on a ZrO2 Solid Solution

The nanosized 90 mol.% ZrO2–2 mol.% Y2O3–8 mol.% CeO2 powder was produced by hydrothermal synthesis in an alkaline environment and heat-treated in the range 400–1300°C. The powder properties were examined by X-ray diffraction (XRD), SEM and TEM, petrography, and BET. According to the XRD data, a low-temperature metastable cubic ZrO2 (F-ZrO2) solid solution formed after hydrothermal synthesis. According to the petrography and electron microscopy data, TZrO2 began to form already in the hydrothermal synthesis process. The F-ZrO2 → T-ZrO2 phase transformation was completed in the range 700–850°C. Some T-ZrO2 particles were characterized by a twin substructure. The T-ZrO2 unit cell volume monotonically increased from 133.58 · 10–3 nm3 to 137.09 · 10–3 nm3 and the degree of tetragonality from 1.0033 to 1.0140. No M-ZrO2 was found to form. The powder specific surface area decreased from 94 to 2 m2/g in the heat treatment process. The sizes of primary powder particles (5–10 nm) remained almost unchanged in heat treatment up to 1150°C. The Vickers hardness of the ceramics produced from the powder treated at 850°C was 3.1 GPa and critical fracture toughness factor KIc was 8.4 MPa · m1/2. The preservation of the tetragonal structure (T-ZrO2), which is capable of the martensitic T-ZrO2 → M-ZrO2 transformation, and the strength characteristics determined open ways for microstructural design of smart materials, including shape memory ones, in the ZrO2–Y2O3–CeO2 system.

Development of Sr/Cao catalyst derived from cuttlebone (<i>Sepia officinalis</i>) for biodiesel production

Cuttlebone (Sepia officinalis) was used as a source of calcium oxide for biodiesel catalyst. The objective of this work is to present the bio-based catalyst prepared from cuttlebone. 1, 3, 5 and 10 %wt of strontium was loaded into calcium oxide powder derived from cuttlebone. Structural properties of Sr/CaO catalyst were evaluated by Fourier transform infrared and X-ray diffraction, respectively. There is no change on morphological properties of catalyst between Sr/CaO and pristine CaO. The homogeneous distribution of strontium was confirmed by EDX mapping technique. The specific surface area of powder was estimated to be 10-30 m2·g-1. The thermal stability of catalyst was stable up to 300°C. Preliminary investigation of catalyst for biodiesel was conducted by transesterification from commercial palm olein and methanol. The research work was successfully supported on bio-based economy project.

Nonlinear Resonant Ultrasound Spectroscopy for Predicting Sensitivity to Initiation in Granular High Explosives

AbstractNonlinear Resonant Ultrasound Spectroscopy (NRUS) is a technique that can measure bulk nonlinear coefficients of the nonlinear elastic modulus for a material. NRUS has been used to identify damage in a variety of granular materials including rocks and concrete. Some energetic materials, such as Pentaerythritol Tetranitrate (PETN), are commonly fielded as pressed granular compacts. It is well known that the sensitivity to initiation of these materials is heavily dependent on their microstructure, and that microstructure changes naturally (becomes damaged) over time. In this study, we examine the use of NRUS to identify changes in microstructure between pristine and thermally aged PETN pellets. In particular, we examine the relationship between the bulk hysteretic nonlinearity, α, of the pellets and time spent at temperature, powder specific surface area (SSA), and sensitivity to initiation. We find that, in general, α does not increase uniformly for all pellets within a single thermal aging condition. However, when the pellets are test fired to determine sensitivity to initiation, there is a strong correlation between α and firing voltage threshold. NRUS‐measured α has the added benefit that the measurements can be made in situ and on benchtop scales.

Properties of Ceramics Obtained Based on Mechanically Mixed Powders of Zirconium Hydroxide and a Dopant

The results of studies of the structure, phase composition and specific surface area of powders based on zirconium dioxide obtained by the method of thermal decomposition of a mechanical mixture of hydroxide and a stabilizing additive are presented. The forming and sintering of ceramic samples obtained from calcined powders were studied, as well as some properties of the ceramics. It has been shown that fine-grained dense high-strength ceramics with a flexural strength of 860 MPa and microhardness up to 12 – 13 GPa can be obtained from the synthesized powders.

Influence of Particle Size Distribution of Limestone Powder on Fluidity and Harden Performance of the Cement Paste

Based on the particle size distribution test of 6 kinds of limestone powder, the fractal dimension of particle size distribution was calculated, and its influence on the surface area, median grain diameter and RR-B value was studied. In addition, 20% of the total mass of cement was replaced with limestone powder, and the effect of fractal dimension on fluidity of cement paste and 3, 7, 28d strength of mortar was investigated. The results showed that fractal dimension for limestone powder specific surface area has a good linear relationship with median grain diameter and RR-B value. The fractal dimension showed a quadratic function with the degree of the fluidity, and the maximum value was between 2.1-2.2. Mortar strength at the age of 3, 7, 28d value displayed a linear relationship with fractal dimension L4 had the greatest effect on strength. L1-L4 had more influence on the strength at the age of 3d and 7d than that of 28d. While the influence of L5-L7 on the strength at 3d, 7d and 28d was essentially similar to each other.

3D defective graphenes with subnanometric porosity obtained by soft-templating following zeolite procedures.

By applying the well-known templating mechanism employed for the synthesis of mesoporous silicas to the structuration of sodium alginate, a novel defective 3D tubular graphene material (graphenolite) with hierarchical macro/meso/micro-porous structure, very high powder specific surface area (1820 m2 g−1) and regular micropore size (0.6 nm) has been obtained. The key feature of the process is the filmogenic property of alginate that is able to replicate the liquid crystal rods formed by the CTAC template in the aqueous phase. The 3D graphene exhibits 2.5 times higher capacitance using Li+ electrolyte compared to K+, indicating that Li+ can ingress to the ultramicropores which, in contrast, are not accessible to K+. Electrochemical impedance measurements also indicate much lower resistance for Li+ in comparison to K+ electrolyte, confirming the benefits of controlled microporosity of 3D graphene granting selective access to Li+, but not to K+. The present report opens the door for the synthesis of a wide range of 3D graphene materials that could be prepared following similar strategies to those employed for the preparation of zeolites and periodic mesoporous aluminosilicates.

MECHANOCHEMICAL SYNTHESIS OF CALCIUM TITANATE AND RESEARCH OF ITS PHOTOCATALYTIC ACTIVITY

Recently much attention is paid to the synthesis and study of the properties of inorganic materials, based on alkaline earth titanates with a perovskite structure that have various polymorphic forms depending on the temperature. Calcium titatanat (CaTiO3) can be selected from the variety of perovskites because of its relatively high dielectric constant, unique photochemical properties, chemical stability, and compatibility with biological tissues, which leads to its application in microelectronics, photocatalysis and biomedicine as bone implants. In this paper, a solid-phase synthesis of calcium titanate was carried out by ceramic technology using mechanochemistry methods. This method allows to obtain calcium titanate directly by mechanochemical activation from the initial mixture of Ca (OH)2 and TiO2, which significantly reduces the energy consumption for its production. Structural changes in the synthesized material during calcination at 120 °C, 200 °C, 400 °C, 600 °C, and 800 °C were studied. The particle size and specific surface area of powders synthesized and calcined at 800 °C was measured by laser diffraction ("Analysette 22") and the low temperature (77K) nitrogen adsorption-desorption vapor, respectively. The phase composition of the obtained materials was studied by X-ray diffraction. It was found on the basis of studies of the particle size distribution that synthesized and calcined powders contain nanoparticles with sizes of 377 and 422 nm. The samples of CaTiO3 calcined at 120 °C and 800 °C have a mesoporous structure, the specific surface area was 46 and 7 m2/g, respectively, and average pore size in powders was 4 nm. It was found by the X-ray diffraction technique that the uncalcined sample contains admixtures of CaCO3 and TiO2 that can be removed completely at 600 °C.The photocatalytic activity of the synthesized material has been studied by the example of Rhodamine B dye decoloration on the calcium titanate calcined at 800°C. It was found that the decomposition degree of dye in solution was 77% for 80 min at a 6.7% shadow adsorption.

Synthesis and Physico-Chemical Characterization of Different Mesoporous Bioactive Glass Nanopowders: in-vitro SBF Activity and Cytotoxicity

ABSTRACTMesoporous bioactive glass (MBG) nanopowders from SiO2-CaO-P2O5 system have been prepared by three different variations using different structure directing agents: (1) through wet chemical method (MBWC650) using non-ionic surfactant, PEG; (2) using Pluronic P123, another non-ionic surfactant via hydrothermal process (MBHM650); and (3) using ionic surfactant CTAB, via wet chemical process (MBCTAB650). Comparative study of phase, morphology and textural properties of all M BG nanopowders were accomplished by different characterization techniques. Specific surface area of powders was found to be 52.2, 169.3 and 473.2 m2.g–1 for MBWC650, MBHM650 and MBCTAB650, respectively. Kinetic SBF immersion study was carried out to examine hydroxyapatite forming ability of the powders. Supernatant analyses showed high dissolution of Ca2+ and PO43– ions in MBCTAB650 while MBHM650 showed initial level of HAp formation ability over its surface in contrast with MBWC650. Other characterizations confirmed formation of Ca-P over MBG nanopowders. Cell viability of 117% for MBWC650, 90% for MBHM650 and 89% for MBCTAB650 after seven days were noted. MBHM650 and MBWC650 could be suitable candidate as dental/orthopedic bone filler material whereas high surface area of MBCTAB650 powder can be useful for delivering pharmaceutical agents in-vitro / in-vivo.

Heat Treatment of Tantalum and Niobium Powders Prepared by Magnesium-Thermic Reduction

Changes in the specific surface area and porous structure of tantalum and niobium powders, which were prepared by magnesium-thermic reduction of Ta2O5, Mg4Ta2O9, and Mg4Nb2O9 oxide compounds and subjected to heat treatments at temperatures of 600–1500°C, have been studied. It is noted that, owing to the mesoporous structure of the magnesium-thermic powders, the decrease in the surface area during heat treatment, first of all, is related to a decrease in the amount of pores less than 10 nm in size. The heat treatment of a reacting mass is shown to allow us to correct the specific surface area of the powder without any increase in the oxygen content in it. Data on the effect of heat treatment conditions on the specific charge of capacitor anodes are reported.

Estimation of specific surface area of particles based on size distribution curve

Workability in the fresh state is one of the most important factors in design and production of concrete and can be related to the water demand of the mixture, which in addition to other factors is a function of the particle shape of aggregates and binders and their specific surface area. While it is known that the shape of fine particles has a significant effect on the water demand, there are uncertainties regarding how the various shape parameters would affect the specific surface area, mainly because up to now many of the shape parameters have not yet been clearly defined and there are no commonly accepted methods for their measurement and/or estimation. In this research, the actual particle shapes were replaced with regular convex polyhedrons to calculate the total specific surface area using the size distribution curves of the samples. The obtained results indicate that while, in some cases, the assumption of a spherical particle shape leads to an acceptable estimation of the specific surface area when compared with Blaine test results, the specific surface area of powders with more angular particles could be calculated more accurately with the assumption of a polyhedron shape rather than a sphere.