Thermal effects of carbonated hydroxyapatite modified by glycine and albumin

In this work calcium phosphate powders were obtained by precipitation method from simulated solutions of synovial fluid containing glycine and albumin. X-ray diffraction and IR spectroscopy determined that all samples are single-phase and are presented by carbonate containing hydroxyapatite (CHA). The thermograms of solid phases of CHA were obtained and analyzed; five stages of transformation in the temperature range of 25-1000°C were marked. It is shown that in this temperature range dehydration, decarboxylation and thermal degradation of amino acid and protein connected to the surface of solid phase occur. The tendency of temperature lowering of the decomposition of powders synthesized from a medium containing organic substances was determined. Results demonstrate a direct dependence between the concentration of the amino acid in a model solution and its content in the solid phase

Milk-containing product with milk fat replacer, manufactured using sour cream technology with an extended shelf life

The authors proposed a milk-containing product with a substitute for milk fat, produced according to the technology of sour cream using a protective culture in order to prolong the shelf life. The use of protective starter cultures does not require additional equipment or changes in technological parameters. The protective culture is introduced along with the main sourdough and works according to the traditional principle of fermentation, as well as through competitive exclusion, i.e. taking up space and reducing the possibility for the growth of yeast, molds and BGKP. Two developments of a milk-containing product were carried out - the first using a protective culture (experimental sample), the second without using a protective culture (control sample). The products are stored for 40 days at a temperature of 4 ± 2 °C. In the control sample, on day 30, yeast growth, deterioration in organoleptic indices, increase in titratable acidity were observed, on day 40, the product was considered spoiled. In the experimental sample, organoleptic, physicochemical and microbiological parameters during storage were within normal limits. The shelf life of a milk-containing product with a milk fat substitute produced using the technology of sour cream is determined using a protective culture taking into account a safety factor of 30 days. An increase in the shelf life of the latter by 30% was established in comparison with the control sample

Гетерофазная керамика в системе Hf–Si–Mo–B, полученная сочетанием методов СВС и горячего прессования

The paper focuses on obtaining heterophase powder ceramics and consolidated ceramics based on borides and silicides of hafnium and molybdenum by combining the methods of self-propagating high-temperature synthesis (SHS) and hot pressing (HP). Composite ceramic SHS powders HfB2–HfSi2–MoSi2 were obtained according to the scheme of magnesium-thermal reduction from oxide raw materials where the combustion wave is characterized by temperatures of 1750–2119 K and high mass combustion rates of 8,4– 9,3 g/s. The structure of synthesized SHS powders consists of relatively large MoSi2 grains up to 10 μm in size and submicron elongated HfB2 grains located mainly inside the MoSi2 grains and rounded Si precipitates. The composition with a lower concentration of boron contains a large number of polyhedral HfSi2 grains with a size of less than 10 μm. The resulting powders are characterized by an average particle size of ~6 μm with a maximum size up to 26 μm. Phase compositions of ceramics consolidated by the HP method and SHS synthesized powders are identical. The microstructure of compact samples consists of faceted HfB2 elongated grains 0,5– 10,0 μm in size, polyhedral HfSi2 and MoSi2 grains up to 8–10 μm in size and silicon interlayers. Consolidated ceramics has a high structural and chemical homogeneity, low residual porosity of 1,1–1,7 %, high hardness of 11,7–12,6 GPa and thermal conductivity of 62–87 W/(m·K).Работа посвящена получению гетерофазной порошковой и консолидированной керамики на основе боридов и силицидов гафния и молибдена путем комбинирования методов самораспространяющегося высокотемпературного синтеза (СВС) и горячего прессования (ГП). Композиционные керамические СВС-порошки HfB2–HfSi2–MoSi2 получали по схеме магнийтермического восстановления из оксидного сырья, при котором волна горения характеризуется температурами 1750–2119 К и довольно высокими значениями массовых скоростей горения 8,4–9,3 г/с. Структура синтезированных СВС-порошков состоит из относительно крупных зерен MoSi2 размером до 10 мкм и субмикронных вытянутых зерен HfB2, преимущественно расположенных внутри зерен MoSi2, а также округлых выделений Si. Состав с меньшей концентрацией бора содержит большое количество полиэдрических зерен HfSi2 размером менее 10 мкм. Полученные порошки характеризуются средним размером частиц ~6 мкм при максимальном размере до 26 мкм. Фазовые составы консолидированной методом ГП керамики и синтезированных СВС-порошков идентичны. Микроструктура компактных образцов состоит из ограненных вытянутых зерен HfB2 размером 0,5–10,0 мкм, полиэдрических зерен HfSi2 и MoSi2 размером до 8–10 мкм и прослоек кремния. Консолидированная керамика обладает высокой структурной и химической однородностью, низкой остаточной пористостью 1,1–1,7 %, высокой твердостью 11,7–12,6 ГПа и теплопроводностью 62–87 Вт/(м·К)