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The effect on point defects of annealing in a phosphorus vapour is studied on GaPN layers grown by vapour phase epitaxy. When the pressure P of the phosphorus (P4) vapour is vaned, the concentration of the deep centre, thermally activated with an activation energy of 0.24 i 0.01 eV given by o m , vacancies. Based on the experimental data obtained, the known models of the nitrogen-related deep centre are analysed and the formation of such a centre is considered in the case when the background Si is the dominant donor impurity. The centre is shown to differ from defects formed with the participation of group VI elements, and a model of the centre is proposed.

A comparative study of wear resistance, hardness and elastic modulus in samples of VT6 titanium alloy with a mineral coating created using low-temperature technological operations (local heating up to 80°C) and without coating was performed. The hardness and elastic modulus in nanoindentation mode were measured by applying a series of indentations with various maximum loads. The load was selected in a way that penetration depth of the tip into the material ranged from 500 nm to 4 μm with an estimated thickness of the modified layer of about 10 μm. The creation of a mineral layer increased the hardness of the surface of the titanium alloy sample by 45 -70 % and also caused a 2 -3 times increase of the roughness parameters of samples. Taking into account the specific features of measuring physical and mechanical properties of thin modified layers, wear resistance was measured using the method of multi-cycle friction with a sapphire sphere, while controlling the clamping force and deepness of the tip penetration into the sample. Wear resistance of the surface of the sample modified by minerals increased by 4 -5 times as compared to the wear resistance of the surface of the VT6 titanium alloy without a modification. By authors' opinion, the results of the studies reveal big potentials of using metal parts from titanium and titanium alloys with mineral coatings in various devices and mechanical assemblies. Проведено сравнительное исследование износостойкости, твердости и модуля упругости образцов из титаново-го сплава ВТ6 с минеральным покрытием, созданным при использовании низкотемпературных технологических операций (с локальным нагревом до 80°С), и без покрытия. Измерения твердости и модуля упругости в режиме наноиндентирования были проведены путем нанесения серии уколов с различной максимальной нагрузкой. Нагруз-ка подбиралась таким образом, чтобы глубина внедрения наконечника в материал составляла от 500 нм до 4 мкм при оценочной толщине модифицированного слоя около 10 мкм. Создание минерального слоя увеличило твердость поверхности образца из титанового сплава на 45 -70 %, а также увеличило параметры шероховатости образцов в 2 -3 раза. Корректность измерения определяется тем, что на малых глубинах влияние подложки на измеряемые величины мала, и поэтому ею можно было пренебречь. Разброс данных сопоставим с измеряемыми величинами, что, возможно, связано с относительно большой шероховатостью образцов. Учитывая особенности измерения фи-зико-механических свойств тонких модифицированных слоев, измерение износостойкости было выполнено мето-дом многоциклового трения сапфировой сферой с контролем силы прижима и углубления наконечника в образец. Использование такой системы измерения особенно важно при испытании тонких слоев, когда толщина слоя со-поставима с параметрами шероховатости поверхности. Износостойкость поверхности образца, модифицирован-ной минералами, увеличилась в 4 -5 раз по сравнению с износостойкостью поверхности титанового сплава ВТ6 без модификации. По мнению авторов, результаты исследования открывают бол...

Improving the wear resistance of the surface of metal parts used in various industries is one of the relevant areas of materials science. The aim of this work was a comparative study of the wear resistance of a sample of an aluminum alloy (EN AW-2024, an aluminum alloy of the Al-Cu-Mg system) modified with ultrafine particles of minerals using the sclerometry method, which makes it possible to measure the physicomechanical properties of the material at the microscale, as well as determining some tribological parameters (hardness and elastic modulus) of a duralumin sample with a mineral coating.Wear resistance was measured using a NanoScan-4D scanning hardness tester using the multi-cycle friction method using a sapphire sphere with control of the pressing force and the deepening of the tip into the sample. The use of such a measurement system is especially important when testing thin modified layers, when the layer thickness is comparable with the surface roughness parameters and the influence of the substrate is excluded.The measurement results showed that the wear resistance of the surface of an aluminum alloy sample modified with ultrafine mineral particles increased by more than 12 times compared to the wear resistance of an aluminum alloy surface without modification. Also, measurements of the hardness and elastic modulus of the surface of the modified sample were performed taking into account the features of measuring the mechanical parameters of thin layers.The obtained parameters of the modified surface of the aluminum alloy can be further used to build models of the processes of friction and wear of the surface modified by ultrafine particles of minerals. The lack of an acceptable explanation of the nature of the special properties of the surface modified by particles of minerals of natural origin does not exclude the use of the observed effects to significantly increase the resource of various parts and mechanisms.

The effects of varying the ammonia flux on the concentrations of background Si and free carriers and on deep traps for majority and minority carriers in n-GaP layers grown by vapour epitaxy have been studied by secondary ion mass spectrometry and deep level transient spectroscopy. The contribution from the background silicon to the free carrier concentration in samples variously doped with nitrogen is discussed. It is shown that the deep centre at E c − 0.24 eV may be attributed to silicon. The model of this centre in the form Si Ga -V P accounts for experimental results obtained in the present work and those already reported. The concentration of the dominant nonradiative recombination centre at E v + 0.75 eV is studied, depending on growth conditions, and its model is proposed in the form of a complex consisting of intrinsic defects.