Synthesis of Spinel-Hydroxyapatite Composite Utilizing Bovine Bone and Beverage Can

Spinel-based hydroxyapatite composite (SHC) has been synthesized utilizing bovine bones as the source of the hydroxyapatite (HAp) and beverage cans as the aluminum (Al) source. The bovine bones were defatted and calcined in the air atmosphere to transform them into hydroxyapatite. The beverage cans were cut and milled to obtain fine Al powder and then sieved to obtain three different particle mesh size fractions: +100#, −140# + 170#, and −170#, or Al particle size of >150, 90–150, and <90 µm, respectively. The SHC was synthesized using the self-propagating intermediate-temperature synthesis (SIS) method at 900 °C for 2 h with (HAp:Al:Mg) ratio of (87:10:3 wt.%) and various compaction pressure of 100, 171, and 200 MPa. It was found that the mechanical properties of the SHC are influenced by the Al particle size and the compaction pressure. Smaller particle size produces the tendency of increasing the hardness and reducing the porosity of the composite. Meanwhile, increasing compaction pressure produces a reduction of the SHC porosity. The increase in the hardness is also observed by increasing the compaction pressure except for the smallest Al particle size (<90 µm), where the hardness instead becomes smaller.

Production of Hydroxypyruvic Acid by Glycerol Oxidation over Pt/CeO2-ZrO2-Bi2O3-PbO/SBA-16 Catalysts

Pt/CeO2-ZrO2-Bi2O3-PbO/SBA-16 (SBA-16: Santa Barbara Amorphous No. 16) catalysts were synthesized to produce hydroxypyruvic acid by glycerol oxidation. In the catalysts, the introduction of PbO into CeO2-ZrO2-Bi2O3 improved the oxygen release and storage abilities owing to the synergistic redox reaction of Pb2+/4+ and Ce3+/4+, which facilitated the oxidation ability of Pt. In addition, the oxidation of the secondary OH group in glycerol might be accelerated by the geometric effects of glycerol, Pt, and Bi3+ or Pb2+/4+. Furthermore, the moderate reaction conditions such as room temperature and open-air atmosphere enabled the suppression of further oxidation of hydroxypyruvic acid. The highest catalytic activity was obtained for 7 wt% Pt/16 wt% Ce0.60Zr0.15Bi0.20Pb0.05O2−δ/SBA-16, which provided a hydroxypyruvic acid yield maximum of 24.6%, after the reaction for 6 h at 30 °C in atmospheric air.

Controllable sites and high-capacity immobilization of uranium in Nd2Zr2O7 pyrochlore

As potential nuclear waste host matrices, two series of uranium-doped Nd2Zr2O7 nanoparticles were successfully synthesized using an optimized molten salt method in an air atmosphere. Our combined X-ray diffraction, Raman and X-ray absorption fine-structure (XAFS) spectroscopy studies reveal that uranium ions can precisely substitute the Nd site to form an Nd2–x U x Zr2O7+δ (0 ≤ x ≤ 0.2) system and the Zr site to form an Nd2Zr2–y U y O7+δ (0 ≤ y ≤ 0.4) system without any impurity phase. With increasing U concentration, there is a phase transition from pyrochlore (Fd 3 m) to defect fluorite (Fm 3 m) structures in both series of U-doped Nd2Zr2O7. The XAFS analysis indicates that uranium exists in the form of high-valent U6+ in all samples. To balance the extra charge for substituting Nd3+ or Zr4+ by U6+, additional oxygen is introduced accompanied by a large structural distortion; however, the Nd2Zr1.6U0.4O7+δ sample with high U loading (20 mol%) still maintains a regular fluorite structure, indicating the good solubility of the Nd2Zr2O7 host for uranium. This study is, to the best of our knowledge, the first systematic study on U-incorporated Nd2Zr2O7 synthesized via the molten salt method and provides convincing evidence for the feasibility of accurately immobilizing U at specific sites.

Optimisation of Propane Production from Hydrothermal Decarboxylation of Butyric Acid Using Pt/C Catalyst: Influence of Gaseous Reaction Atmospheres

The displacement and eventual replacement of fossil-derived fuel gases with biomass-derived alternatives can help the energy sector to achieve net zero by 2050. Decarboxylation of butyric acid, which can be obtained from biomass, can produce high yields of propane, a component of liquefied petroleum gases. The use of different gaseous reaction atmospheres of nitrogen, hydrogen, and compressed air during the catalytic hydrothermal conversion of butyric acid to propane have been investigated in a batch reactor within a temperature range of 200–350 °C. The experimental results were statistically evaluated to find the optimum conditions to produce propane via decarboxylation while minimizing other potential side reactions. The results revealed that nitrogen gas was the most appropriate atmosphere to control propane production under the test conditions between 250 °C and 300 °C, during which the highest hydrocarbon selectivity for propane of up to 97% was achieved. Below this temperature range, butyric acid conversion remained low under the three reaction atmospheres. Above 300 °C, competing reactions became more significant. Under compressed air atmosphere, oxidation to CO2 became dominant, and under nitrogen, thermal cracking of propane became significant, producing both ethane and methane as side products. Interestingly, under a hydrogen atmosphere, hydrogenolytic cracking propane became dominant, leading to multiple C–C bond cleavages to produce methane as the main side product at 350 °C.

New Solid Solution and Phase Equilibria in the Subsolidus Area of the Three-Component CuO–V2O5–Ta2O5 Oxide System

The results of the study of the three-component system of CuO–V2O5–Ta2O5 oxides showed, inter alia, that in the air atmosphere in one of its cross-sections, i.e., in the CuV2O6–CuTa2O6 system, a new substitutional solid solution with the general formula CuTa2−xVxO6 and homogeneity range for x > 0.0 and x ≤ 0.3 is formed. The influence of the degree of incorporation of V5+ ions into the CuTa2O6 crystal lattice in place of Ta5+ ions on the unit cell volume, thermal stability and IR spectra of the obtained solid solution was determined. Moreover, the value of the band gap energy of the CuTa2−xVxO6 solid solution was estimated in the range of 0.0 < x ≤ 0.3, and on this basis, the new solid solution was classified as a semiconductor. On the basis of the research results, the studied system of CuO–V2O5–Ta2O5 oxides was also divided into 12 subsidiary subsystems.

Effect of Atmospheres on Transformation of Heavy Metals during Thermal Treatment of MSWI Fly Ash: By Thermodynamic Equilibrium Calculation

The vaporization behaviors of eight heavy metals (Pb, Zn, Cu, Cd, Cr, Co, Mn, and Ni) in municipal solid wastes incineration (MSWI) fly ash during thermal treatment under air atmosphere (21% O2/79% N2), an inert atmosphere (100% N2), and a reducing atmosphere (50% CO/50% N2) were evaluated based on a thermodynamic equilibrium calculation by FactSage 8.1. The results show that the reducing atmosphere promotes the melting of MSWI fly ash, resulting in a more liquid phase than in air or an inert atmosphere. Except for Cd, the formation of liquids can dissolve heavy metals and reduce their vaporization ratio. In the air and inert atmospheres, Pb, Zn, Cu, Co, Mn, and Ni vaporize mainly in the form of metallic chlorides, while Cd volatilizes in the form of metallic Cd (g) and CdO (g). In the reducing atmosphere, Co, Mn, and Ni still vaporize as chlorides. Zn and Cd mainly vaporize in the form of Zn (g) and Cd (g), respectively. In terms of Pb, in addition to its chlorides, the volatiles of Pb contain some Pb (g) and PbS (g). Cr has a low vaporization ratio, accounting for 2.4% of the air atmosphere. Cr, on the other hand, readily reacts with Ca to form water-soluble CrCaO4, potentially increasing Cr leaching. Except for Cd, the results of this study suggest that the reducing atmosphere is used for the thermal treatment of MSWI fly ash because it promotes the melting of fly ash and thus prevents heavy metal vaporization.

DIFFERENT SCHEMES FOR OBTAINING FRACTAL RELIEF OF NANOSIZED PLATINUM FILMS

В работе исследуется морфология рельефа наноразмерных пленок платины на поверхности слюды с помощью сканирующего зондового (в режиме атомного-силового) и туннельного микроскопов. Пленки платины исследовались непосредственно после их получения на установке магнетронного напыления, а также после отжига в муфельной печи в воздушной атмосфере. Отжиг позволял установить возможные диапазоны изменения фрактальной размерности и высотных параметров, соответствующие деградации нанорельефа. Получены значения фрактальной размерности для пленок разной толщины при двух альтернативных методах исследования на разных исходных масштабах образцов: на основе данных атомносилового микроскопа - D̅=2,17÷2,38 и сканирующего туннельного микроскопа - D̅=2,28÷2,50 в зависимости от последовательности напыления слоев и отжига пленок. Выбор последовательности операций магнетронного напыления и отжига и внешних условий позволяют формулировать рекомендации по развитию технологии «выращивания» структур с заданной морфологией поверхности. The morphology of the relief of nanosized platinum films on the mica surface is investigated using the scanning probe (in the atomic force mode) and tunneling microscopy. Platinum films were investigated immediately after their preparation in a magnetron sputtering facility, as well as after annealing in a muffle furnace in an air atmosphere. Annealing made it possible to establish the possible ranges of variation of the fractal dimension and the altitude parameters corresponding to degradation of the nanorelief. The values of the fractal dimension were obtained for films of different thicknesses using two alternative methods of investigation at different initial scales of samples: based on the data of an atomic force microscope - D̅ = 2,17÷2,38 and a scanning tunneling microscope - D̅ = 2,28÷2,50 depending on the sequence of deposition of layers and annealing of films. For comparison, experimental data of other authors are presented. The choice of the sequence of operations for magnetron sputtering and annealing, and external conditions makes it possible to formulate recommendations for development of the technology for «growing» structures with a given surface morphology.

STUDIES OF PROCESSES OF THE PRECURSOR FORMATION FOR PRODUCTION OF CuAlO NANOCERAMICS AT THE EFFECT OF DOUBLE LASER PULSES ON AD1 AND M2 ALLOYS IN THE AIR ATMOSPHERE

Проведено исследование процессов образования смешанных нанопорошков Al, оксидов меди и алюминия, прекурсоров для получения нанокерамик типа CuAlO и CuAlO при воздействии сдвоенных лазерных импульсов энергией 53 мДж и между импульсным интервалом 10 мкс на мишень, состоящую из пластинок алюминия марки АД1 и меди марки М2, склеенных между собой и помещенную в закрытую стеклянную прямоугольную кювету. Установлено, что последовательное воздействие серий сдвоенных лазерных на мишень из алюминия, а затем на мишень из меди приводит к многократному увеличению выхода субоксидов AlO, ионов и атомов алюминия и меди в лазерном факеле, направляемом на подложку, при напылении пленок, по сравнению с воздействием одиночными лазерными импульсами. Изучены процессы, происходящие на поверхности подложки при напылении пленок. Показана возможность получения прекурсоров для получения нанокерамик типа CuAlO и CuAlO. A study of formation of mixed Al nanopowders, copper and aluminum oxides, and precursors for production of CuAlO and CuAlO nanoceramics under the influence of double laser pulses with energy of 53 mJ and the interpulse interval of 10 microseconds on a target consisting of plates of aluminum grade AD1 and copper grade M2, 0,4 mm thick, glued together and placed in a closed rectangular glass cuvette. It is found that the successive exposure of a series of double laser beams to an aluminum target and then to a copper target leads to a multiple increase in the yield of AlO suboxides, aluminum and copper ions and atoms in the laser torch, compared with the exposure to single laser pulses. To better understand the hidden mechanisms of this dependence, we study the processes occurring both on the surface and in the near-surface laser plasma inside the resulting microchannel when the target is broken by a series of single and double laser pulses. The possibility of obtaining precursors for the production of nanoceramics such as CuAlO, CuAlO is shown.

RESEARCH OF AlO и Al NANOPOWDER FORMATION PROCESSES IN PLASMA UNDER THE INFLUENCE OF DEFOCUSED DUAL LASER PULSES ON ALUMINUM IN THE AIR ATMOSPHERE

Изучено влияние величины и типа расфокусировки сдвоенных лазерных импульсов на целенаправленное формирование компонентного и зарядового состава лазерной плазмы при воздействии сдвоенных лазерных импульсов на мишень из алюминиевого сплава АД1 (спектрометр LSS-1). Показано, что при расфокусировке более +1 мм интенсивность линии ионов Al III увеличивается в несколько раз в сравнении с нулевой расфокусировкой, интенсивность линий ионов Al II, N II также более менее монотонно увеличивается. Одновременно с этим интенсивность полос AlO практически становится равным нулю. При значении величины расфокусировки 1 мм проведены исследование процессов образования смешанных нанопорошков AlO и Al при воздействии последовательных серий сдвоенных лазерных импульсов энергией 53 мДж и меж-импульсным интервалом 10 мкс на алюминиевую мишень, помещенную в закрытую стеклянную прямоугольную кювету. Размер первичных частиц AlOоцененный с помощью электронной микроскопии высокого разрешения, преимущественно составил 30 - 40 нм, а Al - 45 - 60 нм. Частицы собраны в агломераты. The influence of the magnitude and type of defocusing of twin laser pulses on the purposeful formation of the component and charge composition of laser plasma under the influence of twin laser pulses on a target made of aluminum alloy AD1 (LSS-1 spectrometer) has been studied. It is shown that when defocusing is more than 1 mm, the intensity of the ion line Al III increases several times in comparison with zero defocusing, the intensity of the ion lines Al II, N II also increases more or less monotonously. At the same time, the intensity of the bands AlO practically becomes zero. At the 1 mm defocusing value, the processes of formation of mixed nanopowders were studied and, under the influence of successive series of double laser pulses with the energy of 53 mJ and the inter-pulse interval of the iss on an aluminum target placed in a closed rectangular glass cuvette, the size of primary Al Oparticles estimated using high-resolution electron microscopy was mainly 30 - 40 nm, and Al -45 - 60 nm. The particles are collected into agglomerates.

DYNAMICS OF RESPONSE OF A SENSOR BASED ON A NANOSTRUCTURED TIN DIOXIDE LAYER EXPOSED TO THE ISOPROPANOL VAPORS

С помощью золь-гель технологии синтезированы наноструктурированные газочувствительные пленки диоксида олова. Исследовано влияние температуры на проводимость сенсора в атмосфере очищенного воздуха, на величину отклика сенсора при воздействии паров изопропанола различной концентрации. На температурной зависимости проводимости плёнки диоксида олова в атмосфере чистого воздуха наблюдается локальный минимум. Уменьшение проводимости с ростом температуры в диапазоне 300...350С может быть связано с диссоциацией молекулярной формы адсорбированного кислорода. При температурах выше 350 °С проводимость возрастает из-за десорбции атомарной формы адсорбированного кислорода с поверхности газочувствительного слоя диоксида олова. Обнаружено, что наибольший отклик к газовым пробам достигается при рабочей температуре сенсора порядка 350°С. Предполагается, что это обусловлено наличием на поверхности атомарной формы хемосорбированного кислорода. Проведен анализ концентрационных и температурных зависимостей времени отклика сенсора при воздействии паров изопропанола. Время отклика сенсора монотонно уменьшается с повышением содержания примеси в газовых пробах, по-видимому, из-за увеличения скорости адсорбции частиц примеси из газовой фазы на поверхность газочувствительного слоя. Установлено, что зависимость времени отклика от рабочей температуры имеет аррениусовский вид, что может быть связано с термоактивированными адсорбционно-десорбционными и гетерогенными химическими процессами на поверхности активного слоя сенсора. Nanostructured gas-sensitive tin dioxide films have been synthesized by sol-gel technology. A conductivity vs temperature dependence of a gas sensor into atmosphere of synthetic air has been investigated. A response vs temperature dependence of a gas sensor into atmosphere of isopropanol vapors with various concentrations has been investigated. Local minimum on the temperature dependence of the tin dioxide film conductivity in clean air atmosphere were observed. A decrease in conductivity with increase temperature in the range of 300...350 °C can be associated with a dissociation molecular form of the adsorbed oxygen. At temperatures above 350 °C, conductivity increases because of desorption of the atomic form of the adsorbed oxygen on the surface of gas-sensitive tin dioxide film. The greatest response value is achieved at a sensor temperature equal to 350 °C. It is proposed that the reason is a domination of the atomic form of the chemisorbed oxygen on the surface. The analysis of response time vs concentration and response time vs temperature of gas sensor has been carried out. Sensor response time decreases monotonically with increase admixture substance in gas-probes, apparently because of increase in adsorption rate admixture particles on the surface of gas-sensitive film. It was found that the dependence of the response time on the operating temperature has an Arrhenius form. This may be associated with thermally activated adsorption-desorption processes and heterogeneous chemical reactions on the surface of sensor active layer.