This work was supported by the Natural Science and Engineering Research Council of Canada (Discovery Grant No. 122795-2010) and the program of the Canada Research Chair in Quantum Semiconductors (JJD). The help provided by Xiaohuan Xuang, Mohamed Walid Hassen and technical assistance of Sonia Blais of the Universit&#233; de Sherbrooke Centre de caract&#233;risation de mat&#233;riaux (CCM) in collecting XPS data are greatly appreciated. NL acknowledges the Merit Scholarship Program for Foreign Student, Fonds de recherche du Qu&#233;bec - Nature et technologies, for providing a graduate student scholarship.

Preparação 1. Amostra <ol><li> Use um estilete diamode para clivar um tipo-n (P-dopado) de um lado polido bolacha de Si (resistividade 3.1 ~ 4.8 Ω.m), que é de 3 polegadas de diâmetro, 380 mm de espessura, em amostras de 12 mm x 6 mm; limpar as amostras em OptiClear, acetona e álcool isopropílico (5 minutos para cada etapa). </li><li> Etch amostras em um ~ solução de HF 0,9% durante 1 minuto para gravar distância óxido inicial; enxágüe em água DI e seco em alta pureza (99,999%) de azoto (N2). </li><li> Armazene as amostras preparadas em N 2 saco para conter a sua oxidação no ar. </li></ol> 2. Irradiado Amostras por ArF (λ = 193 nm) e KrF (λ = 248 nm) lasers. <ol><li> Colocar as amostras em uma câmara de altura 0,74 mm e, em seguida, vedar a câmara com uma janela de sílica fundida que tem uma elevada transmissão de UV em (≥90%). Encher a câmara com H 2 O 2 / H 2 O solução na gama de 0,01-0,2% ou com Metha desgaseificadonol usando um canal microfluídico. </li><li> Irradiar amostras homogeneizadas com ARF ou KRF lasers em demagnification de 2,6 e 1,8, respectivamente. Irradiar apenas dois sítios em cada amostra, aumentando pulsos de laser de 100 a 600 no passo 100 de impulsos por meio de uma máscara circular (4 mm de diâmetro). Irradiar as amostras da mesma maneira com uma &quot;folha de bordo&quot; (9 mm x 7,2 milímetros) de máscara. </li><li> Amostras de enxágüe em água DI, secar com N 2 resplendor; Colocar as amostras num recipiente selado, em seguida, encher rapidamente este recipiente com N2, de modo a evitar a exposição ao ar antes de mais experiências. </li></ol> 3. Nanosferas Imobilização de Bio-conjugados <ol><li> Diluir nanosferas de 40 nm de diâmetro conjugado com biotina e fluoresceína corado numa solução salina tamponada com fosfato pH 7,4 a solução 10 12 partículas / ml a temperatura ambiente (PBS 1X) (~ 25 ° C). Mergulhe a laser irradiado amostras ARF ou KRF para 2 &amp;# 160; hr nesta solução à temperatura ambiente. </li><li> Lavar as amostras com PBS para eliminar fluoresceína nanoesferas manchadas fisicamente ligados na superfície. </li></ol> 4. Caracterização de superfície <ol><li> Ângulo de contato de medição (CA) <ol><li> Realizar medições estáticas CA com um goniômetro em um ambiente de RT e umidade do ambiente. </li><li> Empregar alta pureza DI água (resistividade 17,95 mohms · cm) em um micro-seringa; gerar volume similar (~ 5 mL) cai na superfície da amostra através da redução do micro-seringa a uma altura similar para cada medição. </li><li> Capturar e salvar a água cai imagens de perfil por câmera CCD com software. Medir de forma independente 4 locais diferentes com as mesmas condições de irradiação. </li><li> Estimar e calcular a média dos valores da CA no módulo de análise gota de software ImageJ; carregar a imagem e transformá-lo em escala de cinza; lançar o plugin Dropsnake; colocar cerca de poucos nós sobre o contorno de queda (~ 10 nós) da esquerda para adireito de inicializar cobra; aceitar a curva conectando esses nós e evoluir a curva pressionando o botão cobra. Nota: ângulos de contato são exibidas na imagem e tabela. </li></ol></li><li> Medição XPS <ol><li> Investigar superfície modificação química com um espectrômetro de XPS (pressão base de 1x10 -9 Torr) equipado com uma fonte de Al Ka trabalhando a 150 W: <ol><li> Coloque as amostras para dentro da câmara de vácuo. </li><li> Adquirir os dados da pesquisa de superfície em modos de energia constantes de 50 eV passe de energia a partir de uma área de 220 mm x 220 mm. </li><li> Adquirir dados scans de alta resolução a partir da mesma área analisada em 20 eV passar energia. </li></ol></li><li> Processo de dados dos espectros XPS com software de quantificação espectros XPS, como referenciado 25,26. </li></ol></li><li> Microscópio de fluorescência de imagem <ol><li> Excite amostras, que foram irradiados através de &quot;folha de bordo&quot; máscara e expostos a fluoresceína nanoesferas manchadas, usandouma fonte de luz azul (λ = 450 ~ 490 nm). </li><li> Observe imagens fluorescentes, emitindo a 515 nm, com um microscópio invertido de fluorescência em ampliação de 4X. </li><li> Caracterizar a morfologia da superfície destas amostras com a AFM, referenciado como 27. </li></ol></li></ol>

The authors have nothing to disclose.

Propusemos um protocolo de irradiação com laser UV de uma bolacha de Si na câmara de microfluidos preenchido com baixa concentração de H 2 O 2 a solução para induzir uma superfície Si superhydrophilic, o que é principalmente devido à geração de Si-OH. UV fotólise do laser de H 2 O 2 foi suposto formar carregados negativamente OH - radicais. Além disso, o laser de UV efeito fotoeléctrico conduz à formação de uma superfície carregada positivamente 37.</su...

As notáveis ​​propriedades eletrônicas e químicas, bem como a sua alta resistência mecânica tenha feito de silício (Si) a escolha ideal para dispositivos microeletrônicos e chips biomédicas 1. Controle da superfície do Si selectiva área tem recebido uma atenção significativa para aplicações que envolvem dispositivos de microfluidos e lab-on-chip 2,3 .Este é muitas vezes obtida quer por modificação nano-escala da rugosidade da superfície ou por tratamento químico da superfície 4. A rugosidade da superfície ou padronização para produzir estruturas de superfície desordenadas ou ordenados na superfície do Si incluem fotolitografia 5, litografia por feixe de iões de 6 e 7 técnicas de laser. Comparado com estes métodos, o processo de texturização de superfície do laser é relatado para ser menos complicada com o potencial para produzir microestruturas com uma elevada resolução espacial 8. No entanto, como Si tem um limiar de texturização elevada, requerendo com irradiação de impulsos de fluênciainduzir a texturização de superfície em excesso do seu limiar de ablação (~ 500 mJ / cm 2) 9, a texturização de superfície Si tem sido frequentemente assistida pelo emprego de atmosferas de gases reactivos, tais como a de uma alta pressão SF 6 4,7,8 ambiente. Por conseguinte, para modificar a molhabilidade da superfície do Si, numerosos trabalhos concentraram-se em tratamento químico, depositando orgânicos e inorgânicos 10 filmes 2, ou usando plasma ou feixe de elétron tratamento de superfície 11,12. Reconhece-se que a hidrofilicidade de Si proveniente da existência de grupos OH singulares associados e sobre a sua superfície pode ser conseguida por fervura numa solução de H 2 O 2 a 100 ° C durante vários minutos e 13. No entanto, os estados de superfície hidrofóbicas Si, a maioria dos quais devido à presença de Si-H ou Si-O-CH 3 grupos, podia ser alcançado por tratamento químico molhado envolvendo condicionamento com uma solução de ácido HF ou revestimento com material fotosensitivo 13-15. Para conseguir o controle de molhabilidade de Si seletivo área, medidas de padronização complexos são geralmente necessários, incluindo o tratamento em soluções químicas 16. A alta reactividade química de radiação do laser de UV também foi utilizada para substratos sólidos revestidos com película orgânica área processo selectivo e modificar a sua capacidade de humedecimento 17. No entanto, uma quantidade limitada de dados disponíveis sobre a modificação assistida por laser de Si molhabilidade por irradiação das amostras imersas em soluções químicas diferentes. Em nossa pesquisa anterior, UV irradiação do laser de semicondutores III-V no ar 18-20 e NH 3 21 foi utilizado com sucesso para alterar a composição química da superfície do GaAs, InGaAs e InP. Determinou-se que a irradiação com laser de UV de semicondutores III-V em água desionizada (DI) de água diminui óxidos superficiais e carbonetos, enquanto que a água adsorvida sobre a superfície de semicondutor 22 aumenta. Uma superfície fortemente hidrofóbico Si (CA 10 ~3 °) foi obtido por irradiação com laser ArF amostras de Si em metanol na nossa recente trabalho 23. Tal como indicado por espectroscopia de fotoelectrão de raios-X (XPS), isto é principalmente devido à capacidade de o laser ArF para photodissociate CH3OH. Temos também utilizado KrF e lasers de ArF para irradiar de Si (001) em um 0,01% de H 2 O 2 em água Dl. Isto permitiu-nos alcançar formação de superfície superhydrophilic de Si (001), caracterizado pelo CA de perto de 15 ° seletivo área. Os resultados sugerem que esta XPS é devido à geração de ligações Si-OH na superfície irradiada 24. Uma descrição detalhada desta nova técnica utilizando KrF e lasers de ArF para a área de modificação selectiva in situ da superfície hidrófila / hidrófoba de Si superfície em baixa concentração de H 2 O 2 / H 2 O e soluções de metanol é demonstrado neste artigo. Os detalhes fornecidos aqui deve ser suficientepara permitir que experiências semelhantes para ser realizada por investigadores interessados.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>fluorescein stained nanospheres</td>
			<td>Invitrogen</td>
			<td>F8795</td>
			<td></td>
		</tr>
		<tr>
			<td>OptiClear</td>
			<td>National Diagnostics</td>
			<td>OE-101</td>
			<td></td>
		</tr>
		<tr>
			<td>ArF laser (&#955;=193 nm)</td>
			<td>Lumonics</td>
			<td>pulse master 800</td>
			<td></td>
		</tr>
		<tr>
			<td>KrF laser (&#955;=248 nm)</td>
			<td>Lumonics</td>
			<td>pulse master 800</td>
			<td></td>
		</tr>
		<tr>
			<td>XPS</td>
			<td>Kratos Analytical</td>
			<td>AXIS Ultra DLD</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescence microscope</td>
			<td>Olympus</td>
			<td>IX71</td>
			<td></td>
		</tr>
		<tr>
			<td>XPS quantitification software</td>
			<td>CasaXPS</td>
			<td>2.3.15</td>
			<td></td>
		</tr>
	</tbody>
</table>

selective area modification of silicon surface wettability by pulsed uv laser irradiation in liquid environment

A molhabilidade de silício (Si) é um dos parâmetros importantes na tecnologia de funcionalização de superfície deste material e de fabrico de biosensores. Nós relatamos em um protocolo de usar KRF e Arf lasers irradiação Si (001) amostras imersas em um ambiente líquido com baixo número de pulsos e operando a fluências moderadamente baixos de pulso para induzir Si modificação molhabilidade. Wafers imerso por até 4 horas em um 0,01% H 2 O 2 / H 2 O solução não mostrou mudança mensurável em seu ângulo de contato inicial (CA) ~ 75 °. No entanto, o 500-pulso KrF e lasers de ArF irradiação de tais bolachas numa microcâmara cheio com 0,01% de H 2 O 2 / H 2 O solução a 250 e 65 mJ / cm2, respectivamente, diminuiu a AC a perto de 15 °, indicando a formação de uma superfície superhydrophilic. A formação de Si-OH terminada (001), sem alteração mensurável da morfologia da superfície da bolacha, temfoi confirmada por espectroscopia de fotoelétrons de raios-X e medidas de microscopia de força atômica. As amostras foram irradiadas a área selectivo, em seguida, imersas em solução de nanoesferas coradas com fluoresceina conjugado com biotina durante 2 horas, resultando em uma imobilização bem sucedida das nanoesferas na área não irradiado. Isto ilustra o potencial do método para biofunctionalization área selectiva e fabricação de arquitecturas baseadas biosensoriamento-Si avançada. Também descrevemos um protocolo similar de irradiação de bolachas imersos em metanol (CH3OH), utilizando a laser ArF operando em pulso de fluência de 65 mJ / cm 2 e a formação in situ de uma superfície fortemente hidrofóbico de Si (001) com o CA de 103 °. Os resultados indicam XPS induzida por laser ArF formação de Si- (OCH 3) x compostos responsáveis ​​pela hidrofobicidade observada. No entanto, nenhum desses compostos foram encontrados por XPS Si na superfície irradiada pelo laser KrF metanol, demonstrandoa incapacidade de o laser KrF a photodissociate metanol e criar -OCH3 radicais.

Estes resultados representativos tenham sido apresentados no nosso anterior trabalho publicado 23,24. A Figura 1 mostra a AC vs. n (número de impulsos) em sítios irradiado por laser de KrF a 250 mJ / cm 2 em DI H2O para diferentes concentrações de H 2 O 2 / H2O soluções (por exemplo,., 0,01, 0,02, 0,05 e 0,2%). A CA diminui com o aumento de número de impulsos para todo o H 2 O 2 soluções. A CA mínima (~ 15 °) para o H 2 O 2<...

Watch this Scientific Journal Video about Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment at JoVE.com

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

Relatamos uma alteração no processo de HF tratado in situ de Si (001) para um estado de superfície hidrófilo ou hidrófobo por irradiação de amostras em câmaras de microfluidos cheios com H 2 O 2 / H 2 O solução (0,01% -0,5%) ou soluções de metanol usando laser UV pulsado de baixa fluência de pulso relativa.

Seletiva Área Modificação de Superfície Wettability Silicon por Pulsed Laser irradiação UV em meio líquido

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

selective-area-modification-silicon-surface-wettability-pulsed-uv

Research

JoVE Journal

Engineering

8.2K visualizações.  Université de Sherbrooke.  Relatamos uma alteração no processo de HF tratado in situ de Si (001) para um estado de superfície hidrófilo ou hidrófobo por irradiação de amostras em câmaras de microfluidos cheios com H 2 O 2 / H 2 O solução (0,01% -0,5%) ou soluções de metanol usando laser UV pulsado de baixa fluência de pulso relativa. 

Vídeo: Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11.
Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps).
Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators.

An experimental method to examine the early plasma evolution induced by ultrashort laser pulses is described. Using this method, high quality images of early plasma are obtained with high temporal and spatial resolutions. A novel integrated atomistic model is used to simulate and explain the mechanisms of early plasma.

Investigação da Evolução Plasma Precoce Induzida por Pulsos ultracurtos de laser

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a ...

Engenharia

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

Caracterização de modificações superficiais por interferometria de luz branca: Aplicações em Ion Sputtering, ablação por laser, e as experiências Tribologia

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Fabricação de Nano-engenharia transparentes Óxidos Realização por deposição por laser pulsado

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

Visualização de alta velocidade líquido Jet impactação sobre uma superfície móvel

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

Integration of Light Trapping Silver Nanostructures in Hydrogenated Microcrystalline Silicon Solar Cells by Transfer Printing

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly known as plasmonic effects, play an important role. Research in this field has, however, been impeded owing to the difficulty of fabricating devices containing the desired functional metal nanostructures. In order to provide a viable strategy to this issue, we herein show a transfer printing-based approach that allows the quick and low-cost integration of designed metal nanostructures with a variety of device architectures, including solar cells. Nanopillar poly(dimethylsiloxane) (PDMS) stamps were fabricated from a commercially available nanohole plastic film as a master mold. On this nanopatterned PDMS stamps, Ag films were deposited, which were then transfer-printed onto block copolymer (binding layer)-coated hydrogenated microcrystalline Si (&#181;c-Si:H) surface to afford ordered Ag nanodisk structures. It was confirmed that the resulting Ag nanodisk-incorporated &#181;c-Si:H solar cells show higher performances compared to a cell without the transfer-printed Ag nanodisks, thanks to plasmonic light trapping effect derived from the Ag nanodisks. Because of the simplicity and versatility, further device application would also be feasible thorough this approach.

A viable transfer printing-based methodology to introduce plasmonic metal nanostructures in solar cells is described. Using nanopillar poly(dimethylsiloxane) stamps, an Ag-based ordered nanodisk array was integrated with standard hydrogenated microcrystalline Si solar cells, which led to improved device performances due to plasmonic light trapping.

Integração da luz Interceptação de prata Nanoestruturas em células solares de silício hidrogenado microcristalina por Transferência de impressão

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

Automação de Modo de bloqueio em uma rotação do laser da fibra não-linear de polarização através de medidas de polarização de saída

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Emissão espectroscópica Boundary Investigation Camada durante ablativo Teste de material em Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

Fabricação de alta temperatura de nanoestruturado ria-Stabilized Zirconia-Scaffolds (ZEI) pela<em&gt; In Situ</em&gt; Carbono Templating xerogéis

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

Preparação das redes de cristal líquido para macroscópica movimento oscilatório induzido pela luz

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves several steps, include drawing samples, cooling, cutting, transport to the laboratory, and analysis. The whole analysis process requires more than 30 minutes, which hinders on-line process control. Laser-induced breakdown spectroscopy is an excellent on-line analysis method that can satisfy the requirements of vacuum induction melting because it is fast and noncontact and does not require sample preparation. The experimental facility uses a lamp-pumped Q-switched laser to ablate melted liquid steel with an output energy of 80 mJ, a frequency of 5 Hz, a FWHM pulse width of 20 ns, and a working wavelength of 1,064 nm. A multi-channel linear charge coupled device (CCD) spectrometer is used to measure the emission spectrum in real time, with a spectral range from 190 to 600 nm and a resolution of 0.06 nm at a wavelength of 200 nm. The protocol includes several steps: standard alloy sample preparation and an ingredient test, smelting of standard samples and determination of the laser breakdown spectrum, and construction of the elements concentration quantitative analysis curve of each element. To realize the concentration analysis of unknown samples, the spectrum of a sample also needs to be measured and disposed with the same process. The composition of all main elements in the melted alloy can be quantitatively analyzed with an internal standard method. The calibration curve shows that the limit of detection of most metal elements ranges from 20-250 ppm. The concentration of elements, such as Ti, Mo, Nb, V, and Cu, can be lower than 100 ppm, and the concentrations of Cr, Al, Co, Fe, Mn, C, and Si range from 100-200 ppm. The R2 of some calibration curves can exceed 0.94.

During vacuum induction melting, laser-induced breakdown spectroscopy is used to perform real-time quantitative analysis of the main-ingredient elements of a molten alloy.

Análise quantitativa de indução a vácuo de fusão por espectroscopia de degradação induzida por laser

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves ...